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Muscle strength cutoff-points for men with SCI Muscle strength cutoff-points for functional independence and wheelchair ability in men with spinal cord injury
Journal Pre-proof Muscle strength cutoff-points for men with SCI Muscle strength cutoff-points for functional independence and wheelchair ability in men with spinal cord injury Frederico Ribeiro Neto, PhD, Rodrigo Rodrigues Gomes Costa, MSc, Ricardo Antônio Tanhoffer, PhD, Josevan Cerqueira Leal, PhD, Martim Bottaro, PhD, Rodrigo Luiz Carregaro, PhD PII:
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https://doi.org/10.1016/j.apmr.2020.01.010
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ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION
Received Date: 15 March 2019 Revised Date:
18 November 2019
Accepted Date: 8 January 2020
Please cite this article as: Neto FR, Gomes Costa RR, Tanhoffer RA, Leal JC, Bottaro M, Carregaro RL, Muscle strength cutoff-points for men with SCI Muscle strength cutoff-points for functional independence and wheelchair ability in men with spinal cord injury ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION (2020), doi: https://doi.org/10.1016/j.apmr.2020.01.010. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Inc. on behalf of the American Congress of Rehabilitation Medicine
Muscle strength cutoff-points for men with SCI
Muscle strength cutoff-points for functional independence and wheelchair ability in men with spinal cord injury
Authors: Frederico Ribeiro Neto, PhD1,2,* Rodrigo Rodrigues Gomes Costa, MSc2 Ricardo Antônio Tanhoffer, PhD3 Josevan Cerqueira Leal, PhD1,4 Martim Bottaro, PhD1 Rodrigo Luiz Carregaro, PhD1,4
1. College of Physical Education, Universidade de Brasilia (UnB), Brasilia, Brazil. 2. SARAH Network of Rehabilitation Hospitals, Brasilia, Brazil. 3. Physiology Department, Metabolism Laboratory, Universidade Federal do Paraná (UFPR), Setor de Ciências Biológicas, Curitiba, Brazil. 4. School of Physical Therapy, Universidade de Brasilia (UnB), Brasilia, Brazil.
We certify that no party having a direct interest in the results of the research supporting this article has or will confer a benefit on us or on any organization with which we are associated.
*Corresponding author: Frederico Ribeiro Neto Department: Spinal Cord Injury Program Institution: SARAH Rehabilitation Hospital Network/SARAH Brasilia Country: Brazil Tel: 55 61 3319-1831 Mob: 55 61 99184-1550 Fax: 55 61 3319-1538 Email: [email protected]
1
MUSCLE STRENGTH CUTOFF-POINTS FOR FUNCTIONAL INDEPENDENCE AND
2
WHEELCHAIR ABILITY IN MEN WITH SPINAL CORD INJURY
3 4
ABSTRACT
5
Objective: Determine trunk and shoulder muscle strength cutoff-points for functional independence
6
and wheelchair skills, and verify the predictive capacity of relative and absolute peak torque in men
7
with spinal cord injury (SCI).
8
Design: Cross-sectional study.
9
Setting: Rehabilitation Hospital Setting.
10
Participants: Fifty-four men with SCI were recruited and stratified into high and low paraplegia
11
groups.
12
Interventions: All subjects performed maximum strength tests for shoulder abduction/adduction
13
(isokinetic) and trunk flexion/extension (isometric) to determine relative and absolute peak torque
14
cutoff-points for the Spinal Cord Independence Measure (SCIM-III) and Adapted Manual
15
Wheelchair Circuit (AMWC).
16
Main outcomes: The primary outcomes were SCIM-III, AMWC-Brazil test, and strength variables
17
(peak torques). Demographic characteristics obtained from participants’ electronic medical records
18
were the secondary outcomes used as predictor variables of functional independence.
19
Results: The best predictive model for SCIM-III (R=0.78, P≤0.05) used the sum of trunk flexion
20
and extension relative peak torque values to determine the cutoff-points (1.42 N.m/kg for a score of
21
70). Relative shoulder abduction peak torque was used in the predictive models for AMWC
22
outcomes: performance score (R=0.77, P≤0.05 and cutoff-points of 0.97 N.m/kg for 300.0 meters)
23
and 3-minute overground wheeling (R=0.72, P≤0.05 and cutoff-points of 0.96 N.m/kg for 18.5
24
seconds).
25
Conclusions: Relative peak torque showed better predictive capacity compared to absolute peak
26
torque. Cutoff-points were established for relative muscle strength and could help health
1
27
professionals set appropriate goals for individuals with SCI to achieve high functional independence
28
and wheelchair ability.
29 30
Keywords: muscle strength dynamometer; rehabilitation; resistance training; test taking skills;
31
reference values.
32 33
Abbreviations: AMWC: Adapted Manual Wheelchair Circuit; BMI: body mass index; HP: high
34
paraplegia group; LP: low paraplegia group; MVIC: maximum voluntary isometric contraction;
35
OMNI-RES: perceived exertion scale for resistance exercises; SCI: spinal cord injury; SCIM-III:
36
Spinal Cord Independence Measure; TSI: time since injury; 1RM: one maximum repetition test.
37
2
38
INTRODUCTION
39 40 41
Functional independence is one of the main goals of individuals with spinal cord injury
42
(SCI).1 Improvements in walking speed, transfers, and upper limb strength are relevant outcomes
43
targeted by a wide range of interventions.1-3 Wheelchair ability is a major determinant of functional
44
independence,1 since it governs the autonomy of this population.4 Additionally, it has long been
45
recognized that age,5, 6 age at the SCI event,6 level and severity of injury,1, 7 time since injury,5, 7
46
initial SCI level6, 7 and length of hospital stay1, 7 are good predictors of functional independence.
47
However, these variables are not influenced by exercise, whereas muscle strength and power,1, 8
48
aerobic fitness,1 musculoskeletal pain,1 physical activity level,5 body composition,8 and spasticity1
49
are directly affected by interventions such as strength training.
50 51
Muscle strength is deemed essential for individuals with SCI9, and reduced strength has
52
been associated with a decline in physical function.10 Nevertheless, the relationship between
53
strength and independence remains a challenging topic, since predicting functional independence
54
based on strength measurements has yet to be clearly defined.11, 12 However, to the best of our
55
knowledge, only one study has used the one repetition maximum (1RM) bench press performance
56
to establish reference values for strength in individuals with SCI.8 Although cutoff-points to achieve
57
a higher level of independence (absolute and relative strength of 51.0 kg and 0.77 kg.kg-1,
58
respectively) have been reported,8 the 1RM bench press is not a gold standard for strength
59
assessment,13, 14 assesses only fully preserved muscles and it could not differentiate high and low
60
paraplegia.8 Although, evidence suggests a positive relationship between strength and functional
61
independence based on fully preserved muscles of individuals with paraplegia,5, 8 optimal functional
62
independence may also be affected by partially compromised muscles (e.g., trunk muscles),15 which
63
are not traditionally assessed in individuals with SCI16 and unfeasible to evaluate in 1RM bench
64
press test. 3
65 66
The adoption of absolute or relative strength can influence functional independence
67
assessment, and absolute values are considered a good predictor for different functional
68
independence instruments.8 Likewise, relative strength is the best mobility predictor. However,
69
using absolute values as a reference can be misleading.17 Relative strength is increasingly
70
recognized as a good health predictor in other populations and has proved useful in strength
71
research. While reduced strength may limit transfer agility and wheelchair propulsion regardless of
72
body mass,11 strong obese individuals may exhibit further complications. Although cross-sectional
73
muscle area (muscle thickness) is a major determinant of strength, strong overweight individuals do
74
not necessarily perform better in endurance activities.18 Similarly, increased body mass associated
75
with decreased strength may result in poor functional independence.8
76 77
Thus, the present study aimed to: (1) determine optimal trunk and shoulder strength cutoff-
78
points for greater functional independence and wheelchair skills in men with SCI; (2) establish
79
predictive equations for functional independence in men with SCI, based on relative and absolute
80
strength and wheelchair skills; and (3) compare strength between high and low paraplegia
81
(exhibiting fully and partially preserved muscles).
82 83
METHODS
84 85 86
Participants
87 88
Fifty-four men with SCI were consecutively recruited from the rehabilitation program of a
89
Network Centre of Rehabilitation Hospitals until the calculated sample size for each group was
90
achieved. Data were collected from September 2016 to February 2017. The study was approved by 4
91
the institutional Ethics Committee (protocol n. 2.447.149), and all participants were outpatients and
92
provided written informed consent.
93 94
Inclusion criteria were: 1) male, 2) diagnosed with traumatic SCI paraplegia, 3) at least six
95
months of time since injury, 4) complete motor lesion (ASIA Impairment Scale A or B)19 and 5)
96
manual wheelchair user. Participants were excluded if they had a history of metabolic disorders,
97
cardiovascular, cardiac, or orthopedic surgery that would hamper performance in functional tests or
98
an adequate exercise technique and were a user of walking equipment (e.g., braces or crutches) for
99
daily life activities.
100 101 102
Subjects were sequentially assigned to a high (HP, T1 to T6) or low paraplegia group (LP, T7 to L3) until reaching the estimated sample size.
103 104
Procedures
105 106
On day one, the participants were advised of the procedures, received instructions, and
107
underwent clinical, functional independence, and wheelchair ability assessments. Wheelchair mass,
108
frames, and ownership were recorded for intergroup comparison since these variables can affect
109
wheelchair skills.20 Strength assessments were conducted after a 24 to 72-hour interval.
110 111
Clinical Assessment
112 113
Body mass was assessed, and height was calculated based on Rufino et al.,21 who
114
determined the height multiplying the half arm span by two and dividing the result by 1.06. Two
115
physiotherapists evaluated the muscle tone of hips and knees (flexion and extension) with the
5
116
Modified Ashworth Scale,22 The total score for the left and right limbs was used in analyses, and
117
item 1+ was set to 1.5.
118 119
Functional Independence and Wheelchair Ability (SCIM-III and AMWC-Brazil)
120 121
Functional independence was assessed using the Spinal Cord Independence Measure
122
version III (SCIM-III)23, 24. The SCIM-III scale items are graded by difficulty level according to the
123
individual’s skill level.24 The total score ranges from 0 to 100, with high scores indicating greater
124
skill and independence. The three subscales assess self-care (20 points, 4 items), respiratory and
125
sphincter management (40 points, 4 items), and mobility (40 points, 9 items).23
126 127
Wheelchair ability was determined using the Adapted Manual Wheelchair Circuit (AMWC-
128
Brazil).25 Participants were allowed to adjust the hand rims and gloves to match their normal
129
propulsion conditions. Subjects used their own manual wheelchairs or those provided by the
130
rehabilitation center. Fourteen standard AMWC items were performed with fixed order and two
131
minutes’ rest between them. Before the execution of each item, the assessor explained how it should
132
be performed and the required time to complete the task. The item performed within the estimated
133
time was marked as ‘1’ point. Half point was available to the doorstep, platform, and transfer
134
items.25 The outcomes provided by the AMWC-Brazil were: (1) ability score (sum of the scores for
135
all fourteen items); (2) performance score (total time, in seconds, of the three items that should be
136
performed in the shortest possible time: Figure-of-eight, 15-m sprint and 4-m artificial grass); (3) 3-
137
minute overground wheeling (meters): the highest distance covered in 3 minutes during wheelchair
138
propulsion; (4) total time of thirteen items (in seconds, excluding item 14, the 3-minute overground
139
wheeling).25
140
6
141
Strength Assessment
142 143
Three maximum strength tests were carried out in a fixed order on an isokinetic
144
dynamometer (Biodex System 4), with 5-minute rest between them, as follows: (1) Concentric
145
shoulder abduction and adduction at 60°/s; (2) Maximum voluntary isometric contraction (MVIC)
146
of trunk flexion and; (3) MVIC of trunk extension. The same assessor conducted all the tests and
147
gave standardized verbal encouragement.
148 149
Concentric shoulder abduction and adduction: participants were allowed to hold the handle
150
with their non-involved limb to increase trunk stabilization (Figure 1A and 1B). Familiarization
151
consisted of two sets of 10 submaximal concentric and reciprocal repetitions, at 60°/s, with a 1-
152
minute rest between sets and level 2 on the perceived exertion scale for resistance exercises
153
(OMNI-RES).26 This was followed by shoulder abduction and adduction assessments (5 maximal
154
concentric and reciprocal contractions, at 60°/s).
155 156
FIGURE 1
157 158
MVIC of trunk flexion and extension: in a pilot study, 80º trunk flexion was the position of
159
balance for individuals with SCI in the sitting position, without assistance. Due to reduced trunk
160
muscle strength in subjects with a high-level injury, tests were performed at 55º and 105º in the
161
sagittal plane for hip flexion and extension, respectively. The participants were unbalanced in the
162
direction of the movement being tested and stabilized by straps and belts to allow low torque values
163
to be detected (Figure 1C and 1D).
164 165 166
Strength assessment consisted of 2 familiarization sets and two 6-second MVIC sets separated by 1-minute intervals. The familiarization sets were submaximal (level 2 on the OMNI7
167
RES).26 For the two MVIC sets, participants were instructed to execute a continuous maximum
168
contraction and avoid bouncing movements. The highest peak torque between the two MVIC sets
169
was used for analysis. Participants performed the trunk flexion test with their arms relaxed and for
170
trunk extension were instructed to rest their hands on the belts (Figure 1C and 1D).
171 172
The highest absolute and relative peak torque in each movement, as well as the sum of peak
173
torque values for shoulder abduction and adduction and trunk flexion and extension were used in
174
analyses. For inter-group comparison, peak torque was normalized by body mass and expressed in
175
newton-meters per kilogram (N.m/kg).
176 177
Outcomes
178 179
The primary outcomes were SCIM-III scale (total score), AMWC-Brazil (ability score,
180
performance score, total time of thirteen items and 3-minute overground wheeling), and strength
181
variables (absolute and relative peak torque for shoulder abduction and adduction and trunk flexion
182
and extension, sum of shoulder abduction and adduction peak torque [relative and absolute] and
183
trunk flexion and extension peak torque values [relative and absolute]).
184 185
Demographic characteristics (birth date, time since injury, etiology, and neurological level
186
of injury), obtained from participants’ electronic medical records, were the secondary outcomes
187
used as predictor variables of functional independence.
188 189
Statistical analysis
190 191
The sample size was calculated based on fixed linear multiple regression model,
192
considering an effect size of 0.30, α of 5%, power (1 - β) of 90%, and three predictors out of a total
193
of 19 possible variables (absolute and relative peak torque for shoulder abduction and adduction and 8
194
trunk flexion and extension; sum of shoulder abduction and adduction peak torques; sum of trunk
195
flexion and extension peak torques; age; age at injury; time since injury; injury level; body mass;
196
body mass index; and spasticity), resulting in a sample of 54 individuals with SCI.
197 198
The Kolmogorov-Smirnov normality test was used to assess the data distribution.
199
Descriptive data were presented as mean and standard deviation or median and interquartile (25th
200
and 75th percentiles) for the outcomes defined as parametric or nonparametric, respectively. An
201
independent t-test was used to compare group means when normality assumptions were met and the
202
Mann-Whitney U test for independent samples to compare non-parametric variables.
203 204
Stepwise starting from linear to cubic fitting regression was used to generate equations for
205
predicting SCIM-III total score and AMWC-Brazil outcomes (ability score, performance score, 3-
206
minute overground wheeling, and total time of thirteen items). To avoid collinearity, Spearman’s
207
test was applied to correlate all the predictor variables. The correlation matrix was analyzed, and
208
variables that exhibited a high or very high correlation were considered collinear.1 Correlation
209
coefficient values were classified as very weak (below 0.20); weak (0.20 to 0.39); moderate (0.40 to
210
0.69); high (0.70 to 0.90) and very high (> 0.90).27 All strength variables were inserted in the
211
regression analysis separately to improve collinearity control. Injury level was considered a dummy
212
variable, indicating which group was used for specific observations.
213 214
Based on percentiles (10, 25, 50, 75, and 90), the cutoff-points for absolute and relative
215
peak torque for the independence scales (SCIM-III and AMWC-Brazil) were established using a
216
ROC (receiver operating characteristic) curve. The highest statistically significant percentile for an
217
area under the curve was considered for analysis. Based on the SCIM-III and AMWC-Brazil cutoff-
218
points, subjects were classified as having high or low functional independence.
219 9
220
The outlier labeling rule was used to detect outliers, and discrepancies.28 Outlier values
221
were calculated by the difference between the 25th and 75th percentiles multiplied by a factor (2.2).
222
The result is then subtracted from the 25th percentile and added to the 75th percentile.
223 224
The IBM SPSS Statistics package (version 22.0; SPSS Inc, Armonk, NY), Matlab
225
(R2014.A) and G*Power statistical power analysis software (version 3.1.9.2; Universität Kiel,
226
Germany) were used. Statistical significance was set at 5% (P≤0.05; two-tailed).
227 228
RESULTS
229 230 231
Participant characteristics
232 233 234
There were no dropouts in this study, and no significant differences were found in wheelchair mass or distribution between SCI groups (Table 1).
235 236
TABLE 1
237 238
Strength comparisons
239 240
Relative peak torque for shoulder adduction and abduction and the sum of these values
241
were significantly higher in the LP compared to HP. Relative peak torque for trunk flexion and
242
extension MVIC was higher in the LP than HP (P≤0.05) (Table 2).
243 244
TABLE 2
245 10
246
Functional independence and wheelchair skills comparisons
247 248
All the SCIM-III results were significantly higher for the LP when compared to the HP.
249
With respect to the AMWC-Brazil outcomes, only the inter-group ability score did not differ
250
between groups (P>0.05) (Table 3).
251 252
TABLE 3
253 254
Functional independence prediction
255 256
The cubic equation models produced the highest significant correlations (R2) for the
257
outcomes (supplementary data No. 1-A, No. 1-B and No. 1-C). All the regression equations were
258
significant, except for the AMWC-Brazil ability score. The total time of thirteen items equations
259
exhibited the lowest correlation and was classified as moderate (R=0.69). Both HP and LP obtained
260
the maximum result (14.0) for ability score and this outcome was removed from equation model
261
and cutoff points analysis. The correlation matrix of 19 predictor variables has been shown in
262
supplemental data No. 2.
263 264
The sum of relative peak torque values for trunk flexion and extension showed the greatest
265
predictive capacity for the SCIM-III scale (R=0.78, P≤0.05; β=0.34, P≤0.01) (Table 4), while the
266
sum of shoulder abduction and adduction relative peak torques had the highest predictive capacity
267
for the AMWC-Brazil total time of thirteen items (β=-0.57 and P=0.02) (Table 4). Relative peak
268
torque of shoulder abduction was used in the equation models for the 3-minute overground
269
wheeling and performance scores (β=0.18, β=-0.27, respectively, P≤0.05).
270 271
TABLE 4 11
272 273
Regression models associated with functional independence and wheelchair skills were
274
better for relative than absolute peak torque. Injury level, time since injury, and age were also
275
significant predictors included in regression models (Table 4 and supplementary data No. 3).
276 277
Strength cutoff-points for functional independence and wheelchair skills
278 279
The sum of relative peak torque values for trunk flexion and extension showed a cutoff
280
point of 1.42 N.m/kg to achieve a score of 70 in the SCIM-III (Table 5), while the cutoff point for
281
the sum of shoulder abduction and adduction relative peak torques was 2.35 N.m/kg, associated
282
with a total time of thirteen items of 111.90 sec (Table 5). The cutoff-points for relative peak torque
283
of shoulder abduction to obtain a 3-minute overground wheeling time of 300 m and performance
284
score of 18.5 sec were 0.96 and 0.97 N.m/kg, respectively (Table 5 and supplementary data No. 4).
285 286
TABLE 5
287 288
DISCUSSION
289 290 291
Relative and absolute peak torque from partially preserved muscles were better able to
292
discriminate between SCI levels, considering that absolute peak torque of shoulder adduction did
293
not show a significant difference between HP and LP. However, relative peak torque was a better
294
predictor of functional independence when compared to absolute strength. Although time since
295
injury, age and injury level exhibited were more important than muscle strength in the predictive
296
equations (considering the SCIM-III and three out of four AMWC-Brazil outcomes), the
297
implications of strength are significant because it is influenced by exercise interventions.
298 12
299
Our findings indicated significant differences in trunk strength (flexion and extension)
300
between the HP and LP. Trunk flexion/extension MVIC on an isokinetic dynamometer has not been
301
previously adopted in the context of SCI and was, therefore, a suitable assessment. The abdominal
302
muscles are innervated by the intercostal nerves (T7 to T11) and the erector spinae by spinal nerves,
303
with both muscle groups determinant to trunk balance. The paraplegia groups were stratified
304
considering these characteristics and significant intergroup differences in peak trunk
305
flexion/extension torque were expected. Identifying differences in trunk flexion/extension strength
306
between SCI levels is important in functional independence assessments because impaired trunk
307
balance can compromise performance in activities of daily living.29 Moreover, the trunk
308
flexion/extension peak torques of the present study were obtained at 55º and 105º in the sagittal
309
plane for hip flexion and extension, respectively. This positioning was based on a pilot study to
310
ensure that all participants could perform the test, independently of their injury level.26
311
Nevertheless, it is necessary to consider that the trunk flexion/extension isometric peak torque could
312
be achieved in other angles of trunk flexion/extension.
313 314
The regression equation model containing the sum of relative peak torque values for trunk
315
flexion and extension explained 61% of functional independence (SCIM-III). In this respect, our
316
findings corroborate those of previous studies,30, 31 in which the trunk muscles were considered vital
317
to postural balance.29 We demonstrated that a cutoff point of 1.42 N.m/kg was required for
318
isometric trunk flexion and extension to achieve 70 points on the SCIM-III scale. Prior
319
investigations have reported SCIM-III values ranging from 29 to 51 in individuals with acute SCI
320
and shorter rehabilitation times.23, 32 These studies used heterogeneous samples and broader
321
inclusion criteria, which could affect interpretations of an optimal SCIM-III score associated with
322
higher degrees of independence.32 Aidinoff et al.37 recorded SCIM-III scores between 64 and 78 for
323
individuals with thoracic and lumbar SCI at hospital discharge, with a mean stay of 5 months.33 A
324
Brazilian study reported SCIM-III scores of 68 and 65 for individuals with HP and LP, 13
325
respectively.8 As such, a score of 70 on the SCIM-III can be considered a suitable and plausible
326
goal for functional independence in individuals with thoracic and lumbar SCI.
327 328
In the present study, both trunk flexion/extension and shoulder abduction/adduction
329
provided suitable cutoff-points for outcomes related to better functional independence and
330
wheelchair skills. The strength variables with the highest predictive capacity for wheelchair skills
331
were the sum of relative peak torque values for shoulder abduction and adduction and shoulder
332
abduction relative peak torque. Wheelchair ability was assessed based on four AMWC-Brazil
333
outcomes, and only the ability score showed no significant difference between the HP and LP. This
334
outcome had a ceiling effect in studies by Kilkens et al.,4, 34 Cowan et al.35 and Ribeiro Neto et al.,25
335
albeit without paraplegic subgroup stratification. However, significant differences were observed
336
between the paraplegia groups for 3-minute overground wheeling, performance score and total time
337
of thirteen items, and the models explained 52%, 59%, and 48% of wheelchair skills, respectively.
338 339
The shoulder muscle’s strength training is traditionally excluded or present a reduced
340
workload of abduction exercises, mostly because of a high prevalence of shoulder injury in the daily
341
life of individuals with SCI.36, 37. The overall idea is to minimize the occurrence of injuries in this
342
joint during rehabilitation.36, 37 Previous studies proposed interventions based on strength training
343
mainly focused on the anterior and posterior muscles of the trunk.36, 37 However, both shoulder
344
abduction and adduction are rather important for wheelchair propulsion and activities of daily
345
living.5, 30, 38 Our findings corroborate this statement since the shoulder abduction was correlated to
346
a better performance in three of the AMWC-Brazil outcomes. Therefore, there is a paradox between
347
the risk of injury by overuse and the importance of shoulder abduction for daily life activities. It is
348
suggested that not only the prime shoulder adduction muscles should be emphasized during a
349
rehabilitation and strength training program, but also exercises focusing on synergistic and
350
stabilizing muscles. 14
351 352
In addition to relative and absolute peak torque, the covariates injury level, time since
353
injury and age were also predictors in the regression models. Only age and time since injury were
354
significantly correlated with the independence outcomes and simultaneously entered in the
355
regression equation. However, the correlation value was low (0.28), minimizing the risk of
356
collinearity (supplemental data No. 2) and presented the collinearity statistics tolerance ranging
357
from 0.95 to 0.99 for regression equation using absolute strength. In contrast to other studies that
358
found reduced β values for age and time since injury,7, 8 these predictors had the greatest influence
359
on SCIM-III and AMWC-Brazil performance scores, respectively. The equation models explained
360
48% to 61% of functional independence and the wheelchair skills assessed. Thus, our findings
361
suggest that further studies are needed to elucidate whether other predictors (such as body
362
composition, length of hospital stay and sex) affect the functional independence and wheelchair
363
ability of individuals with SCI. Moreover, further studies focusing on the feasibility of clinical tests
364
(e.g., handgrip dynamometry or 1RM tests) on the assessment of the strength of partially
365
compromised muscles are warranted and might help to establish the strength cutoff points in clinical
366
practice.
367 368
Study Limitations
369 370
Wheelchair data were recorded and similar group distribution confirmed, but many of the
371
wheelchairs were old and had minor bearings defects. Although this variable improves the external
372
validity of our study, the low socioeconomic status of the participants precluded routine or
373
necessary repairs, which might have affected performance in the AMWC-Brazil. Another limitation
374
was a possible ceiling effect in the SCIM-III, reported in previous studies.8 Trunk or shoulder
375
strength measures may be misleading, since a large section of the SCIM-III is related to respiration,
376
the bowel and bladder, which may have influenced our findings and the cutoff point determination. 15
377
In addition, it is worth noting that the weight differences of the item scores might have affected the
378
equation model. Finally, because the shoulder is a three-dimensional joint, the role of synergists and
379
assessments within a broader combination of gestures, such as specific tasks and activities of daily
380
living, may also be associated with predicting functional independence.
381 382
CONCLUSION
383 384 385
In the present study, relative peak shoulder abduction torque, the sum of relative peak
386
torques for trunk flexion/extension and shoulder abduction/adduction showed the highest predictive
387
capacity for functional independence and wheelchair ability. The cutoff-points established could be
388
adopted as a parameter for optimal functional independence and wheelchair skills.
389 390
CONFLICT OF INTEREST
391 392
The authors declare no conflict of interest.
393
16
394
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20
TABLES AND FIGURES LEGENDS
Tables Table 1: Participant demographic data, considering the injury level groups. Variables are presented as median (25th and 75th percentiles). Body mass index (BMI) is expressed as mean (standard deviation). Etiology is expressed in absolute values (frequency in each group) and wheelchair characteristics as frequency (%) and mean (standard deviation).
* Significant difference in relation to the HP (P≤0.05); † Significant difference in relation to the LP (P≤0.05); ‡ Significant difference compared to rigid frame (P≤0.05). HP: high paraplegia; LP: low paraplegia. na: not applicable.
Table 2: Descriptive data for absolute (abs, N.m) and relative muscle strength (rel, N.m/kg) in the high (HP) and low paraplegia (LP) groups. Relative peak torque values for shoulder adduction and abduction as well as the sum of these values for shoulder exercises are expressed as mean (standard deviation). The other variables are expressed as median (25th and 75th percentiles).
* Significant difference compared to the HP (P≤0.05). ABD: abduction; ADD: adduction; EXT: extension; FLX: flexion; PT: peak torque; PTabs: absolute peak torque; PTrel: relative peak torque; SAAsum: shoulder abduction and adduction peak torque; TFEsum: sum of trunk flexion and extension peak torques.
21
Table 3: Descriptive data of functional independence and wheelchair ability outcomes (SCIM-III and AMWC-Brazil) in the high paraplegia (HP) and low paraplegia (LP) groups. The performance score and 3-minute overground wheeling test are expressed as mean (standard deviation) and the other variables as median (25th and 75th percentiles).
* Significant difference compared to the HP (P≤0.05). 3MinTest: 3-minute overground wheeling test; AMWC-Brazil: Adapted Manual Wheelchair Circuit - Brazilian version PS: performance score; Resp.: respiration; SCIM-III: Spinal Cord Independence Measure version III; SM: sphincter management; TT: total time of thirteen items.
Table 4: Stepwise regression (R and R2 values) for the independence scale (SCIM-III) and wheelchair skills (AMWC-Brazil), beta weights (β) and probability values (P) of the predictor variables.
* Statistical significance (P≤0.05). 3MinTest: 3-minute overground wheeling test; ABD: abduction; PS: performance score; PTabs: absolute peak torque; PTrel: relative peak torque; SAAsum: sum of shoulder abduction and adduction peak torques; TFEsum: sum of trunk flexion and extension peak torques; TSI: time since injury; TT: total time of thirteen items.
22
Table 5: Results of the ROC curve for strength variables with the best predictive values for the independence scale (SCIM-III) and wheelchair skills (AMWC-Brazil) at the highest percentile and with statistical significance for the area under curve.
Area under the curve (AUC) was statistically different from the ROC curve reference line for all strength variables (P≤0.05). 3MinTet: 3-minute overground wheeling test; ABD: abduction; CP: cutoff point for strength variables (N.m/kg); PTrel: relative peak torque; SAAsum: sum of shoulder abduction and adduction peak torques; SENS: sensitivity; SPEC: specificity; TFEsum: sum of trunk flexion and extension peak torques; TR: test result.
Figure Figure 1: Illustration of the position adopted for shoulder abduction and adduction (A and B) and trunk flexion (C) and extension (D) in maximum strength testing on an isokinetic dynamometer. A: initial shoulder abduction position in the isokinetic test, at an angle of 15º; B: initial shoulder adduction position in the isokinetic test, at an angle of 90º; C: trunk flexion position in the isometric test, at a hip angle of 55º and, D: initial trunk extension position in the isometric test, at a hip angle of 105º.
23
Table 1: Participant demographic data, considering the injury level groups. Variables are presented as median th
(25
th
and 75
percentiles). Body mass index (BMI) is expressed as mean (standard deviation). Etiology is
expressed in absolute values (frequency in each group) and wheelchair characteristics as frequency (%) and mean (standard deviation). n Age (years) 26.9 Time since injury (months) 37.4 Age at injury (years) 23.7 Body mass (kg) 68.2 Height (cm) 170.2 2 BMI (kg/m ) 23.8 Ashworth spasticity scale 3.0 Etiology (n) Auto accident 3 Diving 1 Falls 2 Gunshot wound 18 Hit by falling object 1 Knife wound 0 Motorcycle accident 2 Wheelchair frame (kg) Rigid 48.1% Folding 22.2% Double Folding 29.6% Wheelchair owner (kg) Participant 42.6% Hospital 7.4% * Significant difference in relation to the
HP 27 (22.9 - 36.8) (16.8 - 53.2) (18.8 - 34.9) (56.6 - 76.2) (167.9 - 174.5) (4.9) (2.0 - 4.0) (5.6%) (1.9%) (3.7%) (33.3%) (1.9%) (0.0%) (3.7%) 13.9 (2.4) 16.2 (2.4) 17.9‡ (1.5)
29.3 50.1 22.4 67.8 170.2 22.9 0.0* 4 0 2 19 0 1 1 59.3% 40.7% 0.0%
LP 27 (22.4 - 37.9) (21.5 - 104.8) (19.0 - 32.5) (56.5 - 77.7) (167.0 - 176.4) (4.4) (0.0 - 3.0) (7.4%) (0.0%) (3.7%) (35.2%) (0.0%) (1.9%) (1.9%) 13.8 (2.0) 16.1‡ (1.8) -
28.8 39.8 23.1 68.0 170.2 23.3 2.0 7 1 4 37 1 1 3 53.7% 31.5% 14.8%
TOTAL 54 (22.9 - 37.1) (19.4 - 82.2) (19.0 - 33.0) (56.6 – 77.2) (167.0 – 174.5) (4.7) (0.0 - 4.0) (12.9%) (1.9%) (7.4%) (68.4%) (1.9%) (1.9%) (5.6%) 13.8 (2.2) 16.1‡ (2.0) 17.9‡ (1.5)
15.5 (0.9) 37.0% 14.5 (2.5) 79.6% 15.1 (2.7) 15.7 (2.4) 13.0% 15.5 (0.9) 20.4% 15.6 (1.5) HP (P≤0.05); † Significant difference in relation to the LP (P≤0.05); ‡
Significant difference compared to rigid frame (P≤0.05). HP: high paraplegia; LP: low paraplegia. na: not applicable.
Table 2: Descriptive data for absolute (abs, N.m) and relative muscle strength (rel, N.m/kg) in the high (HP) and low paraplegia (LP) groups. Relative peak torque values for shoulder adduction and abduction as well as the sum of these values for shoulder exercises are expressed as mean (standard deviation). The other variables are th
th
expressed as median (25 and 75 percentiles).
n
HP
LP
27
27
Shoulder ABD PTabs
58.20
ABD PTrel
0.86
(0.15)
1.05*
(0.16)
ADD PTabs
82.91
(16.13)
98.83
(22.61)
ADD PTrel
1.28
(0.26)
1.48*
(0.27)
SAAsum absolute
144.31
SAAsum relative
2.14
(0.38)
ABD/ADD PT index
0.65
(0.60 – 0.74)
(49.20 – 61.70)
(25.62)
71.30*
169.73* 2.53* 0.72
(60.00 – 80.20)
(37.72) (0.41) (0.68 – 0.77)
Trunk FLX PTabs
37.10
FLX PTrel
0.53
EXT PTabs
42.10
EXT PTrel
0.65
TFEsum absolute
76.00
TFEsum relative
1.18
(25.80 – 47.90) (0.38 – 0.67) (32.30 – 47.20) (0.53 – 0.76) (62.60 – 94.50) (1.05 – 1.30)
FLX/EXT PT index 0.87 (0.70 – 1.18) * Significant difference compared to the HP (P≤0.05).
64.30* 0.93* 56.30* 0.83* 119.00*
(52.30 – 82.00) (0.78 – 1.17) (39.60 – 67.00) (0.59 – 1.00) (91.70 – 146.30)
1.71*
(1.53 – 2.10)
1.28*
(0.91 – 1.73)
ABD: abduction; ADD: adduction; EXT: extension; FLX: flexion; PT: peak torque; PTabs: absolute peak torque; PTrel: relative peak torque; SAAsum: shoulder abduction and adduction peak torque; TFEsum: sum of trunk flexion and extension peak torques.
Table 3: Descriptive data of functional independence and wheelchair ability outcomes (SCIM-III and AMWCBrazil) in the high paraplegia (HP) and low paraplegia (LP) groups. The performance score and 3-minute overground wheeling test are expressed as mean (standard deviation) and the other variables as median th
th
(25 and 75 percentiles). HP n 27 SCIM-III Self-Care 18 (17 – 18) 18* Resp. & SM 33 (33 – 33) 33* Mobility 17 (16 – 18) 19* Total 67 (66 – 68) 70* AMWC-Brazil Ability Score 14.0 (14.0 – 14.0) 14.0 PS (sec) 21.65 (2.86) 19.06* TT (sec) 130.73 (107.63 – 167.7) 92.44* 3MinTest (m) 253.6 (32.6) 291.6* * Significant difference compared to the HP (P≤0.05).
LP 27 (18 – 18) (33 – 34) (17 – 19) (68 – 71) (14.0 – 14.0) (2.17) (77.91 – 116.54) (35.3)
TOTAL 54 18 33 17 68 14.0 20.35 111.90 272.6
(18 – 18) (33 – 33) (16 – 19) (66 – 70) (14.0 – 14.0) (2.84) (90.18 – 138.39) (38.8)
3MinTest: 3-minute overground wheeling test; AMWC-Brazil: Adapted Manual Wheelchair Circuit - Brazilian version PS: performance score; Resp.: respiration; SCIM-III: Spinal Cord Independence Measure version III; SM: sphincter management; TT: total time of thirteen items.
2
Table 4: Stepwise regression (R and R values) for the independence scale (SCIM-III) and wheelchair skills (AMWC-Brazil), beta weights (β) and probability values (P) of the predictor variables. SCIM-III R 2 R
0.78* 0.61
TFEsum relative
AMWC-Brazil TT 0.69* 0.48
PS 0.77* 0.59
3MinTest 0.72* 0.52
β
p
β
p
β
p
β
p
0.34
<0.01
-
-
-
-
-
-
(TFEsum relative)
2
0.07
0.50
-
-
-
-
-
-
(TFEsum relative) Injury Level 2 (Injury Level) 3 (Injury Level) TSI 2 (TSI) 3 (TSI)
3
0.01 0.40 0.05 -0.10 0.59 -0.03 -0.06
0.71 <0.01 0.71 0.44 <0.01 0.88 0.40
-0.28 0.14 -0.02
<0.01 0.48 0.72
-0.40 -0.18 0.07 -0.11 0.20 -0.06
0.19 0.21 0.65 0.62 0.40 0.43
0.50 -0.12 -0.08 0.19 -0.14 -0.61
0.08 0.36 0.56 0.29 0.52 0.42
SAAsum relative
-
-
-
-
-0.57
0.02
-
-
(SAAsum relative)
2
-
-
-
-
0.17
0.07
-
-
(SAAsum relative)
3
-
-
-
-
0.07
0.36
-
-
-
-
-0.27
<0.01
-
-
0.18
0.04
-
-
0.03
0.75
-
-
-0.01
0.92
-
-0.11 0.42 0.14 -0.12
0.09 <0.01 0.40 0.20
-
-
0.09 -
0.18 -
ABD PTrel (ABD PTrel)
2 3
(ABD PTrel) Age 2 Age 3 Age * Statistical significance (P≤0.05).
3MinTest: 3-minute overground wheeling test; ABD: abduction; PS: performance score; PTabs: absolute peak torque; PTrel: relative peak torque; SAAsum: sum of shoulder abduction and adduction peak torques; TFEsum: sum of trunk flexion and extension peak torques; TSI: time since injury; TT: total time of thirteen items.
Table 5: Results of the ROC curve for strength variables with the best predictive values for the independence scale (SCIM-III) and wheelchair skills (AMWC-Brazil) at the highest percentile and with statistical significance for the area under curve. TR
AUC
95%CI
SENS
SPEC
CP
70
0.77
0.63 – 0.91
0.64
0.80
1.42
111.90
0.76
0.62 – 0.90
0.73
0.79
2.35
18.5
0.80
0.66 – 0.94
0.85
0.68
0.97
TFEsum relative (N.m/kg) SCIM-III SAAsum relative (N.m/kg) Total Time of Thirteen Items (sec) Shoulder ABD PTrel (N.m/kg) Performance Score (sec)
3-MinTest (m) 300.0 0.74 0.58 – 0.89 0.65 0.86 0.96 Area under the curve (AUC) was statistically different from the ROC curve reference line for all strength variables (P≤0.05). 3MinTet: 3-minute overground wheeling test; ABD: abduction; CP: cutoff point for strength variables (N.m/kg); PTrel: relative peak torque; SAAsum: sum of shoulder abduction and adduction peak torques; SENS: sensitivity; SPEC: specificity; TFEsum: sum of trunk flexion and extension peak torques; TR: test result.
S0003-9993(20)30085-X
DOI:
https://doi.org/10.1016/j.apmr.2020.01.010
Reference:
YAPMR 57769
To appear in:
ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION
Received Date: 15 March 2019 Revised Date:
18 November 2019
Accepted Date: 8 January 2020
Please cite this article as: Neto FR, Gomes Costa RR, Tanhoffer RA, Leal JC, Bottaro M, Carregaro RL, Muscle strength cutoff-points for men with SCI Muscle strength cutoff-points for functional independence and wheelchair ability in men with spinal cord injury ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION (2020), doi: https://doi.org/10.1016/j.apmr.2020.01.010. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Inc. on behalf of the American Congress of Rehabilitation Medicine
Muscle strength cutoff-points for men with SCI
Muscle strength cutoff-points for functional independence and wheelchair ability in men with spinal cord injury
Authors: Frederico Ribeiro Neto, PhD1,2,* Rodrigo Rodrigues Gomes Costa, MSc2 Ricardo Antônio Tanhoffer, PhD3 Josevan Cerqueira Leal, PhD1,4 Martim Bottaro, PhD1 Rodrigo Luiz Carregaro, PhD1,4
1. College of Physical Education, Universidade de Brasilia (UnB), Brasilia, Brazil. 2. SARAH Network of Rehabilitation Hospitals, Brasilia, Brazil. 3. Physiology Department, Metabolism Laboratory, Universidade Federal do Paraná (UFPR), Setor de Ciências Biológicas, Curitiba, Brazil. 4. School of Physical Therapy, Universidade de Brasilia (UnB), Brasilia, Brazil.
We certify that no party having a direct interest in the results of the research supporting this article has or will confer a benefit on us or on any organization with which we are associated.
*Corresponding author: Frederico Ribeiro Neto Department: Spinal Cord Injury Program Institution: SARAH Rehabilitation Hospital Network/SARAH Brasilia Country: Brazil Tel: 55 61 3319-1831 Mob: 55 61 99184-1550 Fax: 55 61 3319-1538 Email: [email protected]
1
MUSCLE STRENGTH CUTOFF-POINTS FOR FUNCTIONAL INDEPENDENCE AND
2
WHEELCHAIR ABILITY IN MEN WITH SPINAL CORD INJURY
3 4
ABSTRACT
5
Objective: Determine trunk and shoulder muscle strength cutoff-points for functional independence
6
and wheelchair skills, and verify the predictive capacity of relative and absolute peak torque in men
7
with spinal cord injury (SCI).
8
Design: Cross-sectional study.
9
Setting: Rehabilitation Hospital Setting.
10
Participants: Fifty-four men with SCI were recruited and stratified into high and low paraplegia
11
groups.
12
Interventions: All subjects performed maximum strength tests for shoulder abduction/adduction
13
(isokinetic) and trunk flexion/extension (isometric) to determine relative and absolute peak torque
14
cutoff-points for the Spinal Cord Independence Measure (SCIM-III) and Adapted Manual
15
Wheelchair Circuit (AMWC).
16
Main outcomes: The primary outcomes were SCIM-III, AMWC-Brazil test, and strength variables
17
(peak torques). Demographic characteristics obtained from participants’ electronic medical records
18
were the secondary outcomes used as predictor variables of functional independence.
19
Results: The best predictive model for SCIM-III (R=0.78, P≤0.05) used the sum of trunk flexion
20
and extension relative peak torque values to determine the cutoff-points (1.42 N.m/kg for a score of
21
70). Relative shoulder abduction peak torque was used in the predictive models for AMWC
22
outcomes: performance score (R=0.77, P≤0.05 and cutoff-points of 0.97 N.m/kg for 300.0 meters)
23
and 3-minute overground wheeling (R=0.72, P≤0.05 and cutoff-points of 0.96 N.m/kg for 18.5
24
seconds).
25
Conclusions: Relative peak torque showed better predictive capacity compared to absolute peak
26
torque. Cutoff-points were established for relative muscle strength and could help health
1
27
professionals set appropriate goals for individuals with SCI to achieve high functional independence
28
and wheelchair ability.
29 30
Keywords: muscle strength dynamometer; rehabilitation; resistance training; test taking skills;
31
reference values.
32 33
Abbreviations: AMWC: Adapted Manual Wheelchair Circuit; BMI: body mass index; HP: high
34
paraplegia group; LP: low paraplegia group; MVIC: maximum voluntary isometric contraction;
35
OMNI-RES: perceived exertion scale for resistance exercises; SCI: spinal cord injury; SCIM-III:
36
Spinal Cord Independence Measure; TSI: time since injury; 1RM: one maximum repetition test.
37
2
38
INTRODUCTION
39 40 41
Functional independence is one of the main goals of individuals with spinal cord injury
42
(SCI).1 Improvements in walking speed, transfers, and upper limb strength are relevant outcomes
43
targeted by a wide range of interventions.1-3 Wheelchair ability is a major determinant of functional
44
independence,1 since it governs the autonomy of this population.4 Additionally, it has long been
45
recognized that age,5, 6 age at the SCI event,6 level and severity of injury,1, 7 time since injury,5, 7
46
initial SCI level6, 7 and length of hospital stay1, 7 are good predictors of functional independence.
47
However, these variables are not influenced by exercise, whereas muscle strength and power,1, 8
48
aerobic fitness,1 musculoskeletal pain,1 physical activity level,5 body composition,8 and spasticity1
49
are directly affected by interventions such as strength training.
50 51
Muscle strength is deemed essential for individuals with SCI9, and reduced strength has
52
been associated with a decline in physical function.10 Nevertheless, the relationship between
53
strength and independence remains a challenging topic, since predicting functional independence
54
based on strength measurements has yet to be clearly defined.11, 12 However, to the best of our
55
knowledge, only one study has used the one repetition maximum (1RM) bench press performance
56
to establish reference values for strength in individuals with SCI.8 Although cutoff-points to achieve
57
a higher level of independence (absolute and relative strength of 51.0 kg and 0.77 kg.kg-1,
58
respectively) have been reported,8 the 1RM bench press is not a gold standard for strength
59
assessment,13, 14 assesses only fully preserved muscles and it could not differentiate high and low
60
paraplegia.8 Although, evidence suggests a positive relationship between strength and functional
61
independence based on fully preserved muscles of individuals with paraplegia,5, 8 optimal functional
62
independence may also be affected by partially compromised muscles (e.g., trunk muscles),15 which
63
are not traditionally assessed in individuals with SCI16 and unfeasible to evaluate in 1RM bench
64
press test. 3
65 66
The adoption of absolute or relative strength can influence functional independence
67
assessment, and absolute values are considered a good predictor for different functional
68
independence instruments.8 Likewise, relative strength is the best mobility predictor. However,
69
using absolute values as a reference can be misleading.17 Relative strength is increasingly
70
recognized as a good health predictor in other populations and has proved useful in strength
71
research. While reduced strength may limit transfer agility and wheelchair propulsion regardless of
72
body mass,11 strong obese individuals may exhibit further complications. Although cross-sectional
73
muscle area (muscle thickness) is a major determinant of strength, strong overweight individuals do
74
not necessarily perform better in endurance activities.18 Similarly, increased body mass associated
75
with decreased strength may result in poor functional independence.8
76 77
Thus, the present study aimed to: (1) determine optimal trunk and shoulder strength cutoff-
78
points for greater functional independence and wheelchair skills in men with SCI; (2) establish
79
predictive equations for functional independence in men with SCI, based on relative and absolute
80
strength and wheelchair skills; and (3) compare strength between high and low paraplegia
81
(exhibiting fully and partially preserved muscles).
82 83
METHODS
84 85 86
Participants
87 88
Fifty-four men with SCI were consecutively recruited from the rehabilitation program of a
89
Network Centre of Rehabilitation Hospitals until the calculated sample size for each group was
90
achieved. Data were collected from September 2016 to February 2017. The study was approved by 4
91
the institutional Ethics Committee (protocol n. 2.447.149), and all participants were outpatients and
92
provided written informed consent.
93 94
Inclusion criteria were: 1) male, 2) diagnosed with traumatic SCI paraplegia, 3) at least six
95
months of time since injury, 4) complete motor lesion (ASIA Impairment Scale A or B)19 and 5)
96
manual wheelchair user. Participants were excluded if they had a history of metabolic disorders,
97
cardiovascular, cardiac, or orthopedic surgery that would hamper performance in functional tests or
98
an adequate exercise technique and were a user of walking equipment (e.g., braces or crutches) for
99
daily life activities.
100 101 102
Subjects were sequentially assigned to a high (HP, T1 to T6) or low paraplegia group (LP, T7 to L3) until reaching the estimated sample size.
103 104
Procedures
105 106
On day one, the participants were advised of the procedures, received instructions, and
107
underwent clinical, functional independence, and wheelchair ability assessments. Wheelchair mass,
108
frames, and ownership were recorded for intergroup comparison since these variables can affect
109
wheelchair skills.20 Strength assessments were conducted after a 24 to 72-hour interval.
110 111
Clinical Assessment
112 113
Body mass was assessed, and height was calculated based on Rufino et al.,21 who
114
determined the height multiplying the half arm span by two and dividing the result by 1.06. Two
115
physiotherapists evaluated the muscle tone of hips and knees (flexion and extension) with the
5
116
Modified Ashworth Scale,22 The total score for the left and right limbs was used in analyses, and
117
item 1+ was set to 1.5.
118 119
Functional Independence and Wheelchair Ability (SCIM-III and AMWC-Brazil)
120 121
Functional independence was assessed using the Spinal Cord Independence Measure
122
version III (SCIM-III)23, 24. The SCIM-III scale items are graded by difficulty level according to the
123
individual’s skill level.24 The total score ranges from 0 to 100, with high scores indicating greater
124
skill and independence. The three subscales assess self-care (20 points, 4 items), respiratory and
125
sphincter management (40 points, 4 items), and mobility (40 points, 9 items).23
126 127
Wheelchair ability was determined using the Adapted Manual Wheelchair Circuit (AMWC-
128
Brazil).25 Participants were allowed to adjust the hand rims and gloves to match their normal
129
propulsion conditions. Subjects used their own manual wheelchairs or those provided by the
130
rehabilitation center. Fourteen standard AMWC items were performed with fixed order and two
131
minutes’ rest between them. Before the execution of each item, the assessor explained how it should
132
be performed and the required time to complete the task. The item performed within the estimated
133
time was marked as ‘1’ point. Half point was available to the doorstep, platform, and transfer
134
items.25 The outcomes provided by the AMWC-Brazil were: (1) ability score (sum of the scores for
135
all fourteen items); (2) performance score (total time, in seconds, of the three items that should be
136
performed in the shortest possible time: Figure-of-eight, 15-m sprint and 4-m artificial grass); (3) 3-
137
minute overground wheeling (meters): the highest distance covered in 3 minutes during wheelchair
138
propulsion; (4) total time of thirteen items (in seconds, excluding item 14, the 3-minute overground
139
wheeling).25
140
6
141
Strength Assessment
142 143
Three maximum strength tests were carried out in a fixed order on an isokinetic
144
dynamometer (Biodex System 4), with 5-minute rest between them, as follows: (1) Concentric
145
shoulder abduction and adduction at 60°/s; (2) Maximum voluntary isometric contraction (MVIC)
146
of trunk flexion and; (3) MVIC of trunk extension. The same assessor conducted all the tests and
147
gave standardized verbal encouragement.
148 149
Concentric shoulder abduction and adduction: participants were allowed to hold the handle
150
with their non-involved limb to increase trunk stabilization (Figure 1A and 1B). Familiarization
151
consisted of two sets of 10 submaximal concentric and reciprocal repetitions, at 60°/s, with a 1-
152
minute rest between sets and level 2 on the perceived exertion scale for resistance exercises
153
(OMNI-RES).26 This was followed by shoulder abduction and adduction assessments (5 maximal
154
concentric and reciprocal contractions, at 60°/s).
155 156
FIGURE 1
157 158
MVIC of trunk flexion and extension: in a pilot study, 80º trunk flexion was the position of
159
balance for individuals with SCI in the sitting position, without assistance. Due to reduced trunk
160
muscle strength in subjects with a high-level injury, tests were performed at 55º and 105º in the
161
sagittal plane for hip flexion and extension, respectively. The participants were unbalanced in the
162
direction of the movement being tested and stabilized by straps and belts to allow low torque values
163
to be detected (Figure 1C and 1D).
164 165 166
Strength assessment consisted of 2 familiarization sets and two 6-second MVIC sets separated by 1-minute intervals. The familiarization sets were submaximal (level 2 on the OMNI7
167
RES).26 For the two MVIC sets, participants were instructed to execute a continuous maximum
168
contraction and avoid bouncing movements. The highest peak torque between the two MVIC sets
169
was used for analysis. Participants performed the trunk flexion test with their arms relaxed and for
170
trunk extension were instructed to rest their hands on the belts (Figure 1C and 1D).
171 172
The highest absolute and relative peak torque in each movement, as well as the sum of peak
173
torque values for shoulder abduction and adduction and trunk flexion and extension were used in
174
analyses. For inter-group comparison, peak torque was normalized by body mass and expressed in
175
newton-meters per kilogram (N.m/kg).
176 177
Outcomes
178 179
The primary outcomes were SCIM-III scale (total score), AMWC-Brazil (ability score,
180
performance score, total time of thirteen items and 3-minute overground wheeling), and strength
181
variables (absolute and relative peak torque for shoulder abduction and adduction and trunk flexion
182
and extension, sum of shoulder abduction and adduction peak torque [relative and absolute] and
183
trunk flexion and extension peak torque values [relative and absolute]).
184 185
Demographic characteristics (birth date, time since injury, etiology, and neurological level
186
of injury), obtained from participants’ electronic medical records, were the secondary outcomes
187
used as predictor variables of functional independence.
188 189
Statistical analysis
190 191
The sample size was calculated based on fixed linear multiple regression model,
192
considering an effect size of 0.30, α of 5%, power (1 - β) of 90%, and three predictors out of a total
193
of 19 possible variables (absolute and relative peak torque for shoulder abduction and adduction and 8
194
trunk flexion and extension; sum of shoulder abduction and adduction peak torques; sum of trunk
195
flexion and extension peak torques; age; age at injury; time since injury; injury level; body mass;
196
body mass index; and spasticity), resulting in a sample of 54 individuals with SCI.
197 198
The Kolmogorov-Smirnov normality test was used to assess the data distribution.
199
Descriptive data were presented as mean and standard deviation or median and interquartile (25th
200
and 75th percentiles) for the outcomes defined as parametric or nonparametric, respectively. An
201
independent t-test was used to compare group means when normality assumptions were met and the
202
Mann-Whitney U test for independent samples to compare non-parametric variables.
203 204
Stepwise starting from linear to cubic fitting regression was used to generate equations for
205
predicting SCIM-III total score and AMWC-Brazil outcomes (ability score, performance score, 3-
206
minute overground wheeling, and total time of thirteen items). To avoid collinearity, Spearman’s
207
test was applied to correlate all the predictor variables. The correlation matrix was analyzed, and
208
variables that exhibited a high or very high correlation were considered collinear.1 Correlation
209
coefficient values were classified as very weak (below 0.20); weak (0.20 to 0.39); moderate (0.40 to
210
0.69); high (0.70 to 0.90) and very high (> 0.90).27 All strength variables were inserted in the
211
regression analysis separately to improve collinearity control. Injury level was considered a dummy
212
variable, indicating which group was used for specific observations.
213 214
Based on percentiles (10, 25, 50, 75, and 90), the cutoff-points for absolute and relative
215
peak torque for the independence scales (SCIM-III and AMWC-Brazil) were established using a
216
ROC (receiver operating characteristic) curve. The highest statistically significant percentile for an
217
area under the curve was considered for analysis. Based on the SCIM-III and AMWC-Brazil cutoff-
218
points, subjects were classified as having high or low functional independence.
219 9
220
The outlier labeling rule was used to detect outliers, and discrepancies.28 Outlier values
221
were calculated by the difference between the 25th and 75th percentiles multiplied by a factor (2.2).
222
The result is then subtracted from the 25th percentile and added to the 75th percentile.
223 224
The IBM SPSS Statistics package (version 22.0; SPSS Inc, Armonk, NY), Matlab
225
(R2014.A) and G*Power statistical power analysis software (version 3.1.9.2; Universität Kiel,
226
Germany) were used. Statistical significance was set at 5% (P≤0.05; two-tailed).
227 228
RESULTS
229 230 231
Participant characteristics
232 233 234
There were no dropouts in this study, and no significant differences were found in wheelchair mass or distribution between SCI groups (Table 1).
235 236
TABLE 1
237 238
Strength comparisons
239 240
Relative peak torque for shoulder adduction and abduction and the sum of these values
241
were significantly higher in the LP compared to HP. Relative peak torque for trunk flexion and
242
extension MVIC was higher in the LP than HP (P≤0.05) (Table 2).
243 244
TABLE 2
245 10
246
Functional independence and wheelchair skills comparisons
247 248
All the SCIM-III results were significantly higher for the LP when compared to the HP.
249
With respect to the AMWC-Brazil outcomes, only the inter-group ability score did not differ
250
between groups (P>0.05) (Table 3).
251 252
TABLE 3
253 254
Functional independence prediction
255 256
The cubic equation models produced the highest significant correlations (R2) for the
257
outcomes (supplementary data No. 1-A, No. 1-B and No. 1-C). All the regression equations were
258
significant, except for the AMWC-Brazil ability score. The total time of thirteen items equations
259
exhibited the lowest correlation and was classified as moderate (R=0.69). Both HP and LP obtained
260
the maximum result (14.0) for ability score and this outcome was removed from equation model
261
and cutoff points analysis. The correlation matrix of 19 predictor variables has been shown in
262
supplemental data No. 2.
263 264
The sum of relative peak torque values for trunk flexion and extension showed the greatest
265
predictive capacity for the SCIM-III scale (R=0.78, P≤0.05; β=0.34, P≤0.01) (Table 4), while the
266
sum of shoulder abduction and adduction relative peak torques had the highest predictive capacity
267
for the AMWC-Brazil total time of thirteen items (β=-0.57 and P=0.02) (Table 4). Relative peak
268
torque of shoulder abduction was used in the equation models for the 3-minute overground
269
wheeling and performance scores (β=0.18, β=-0.27, respectively, P≤0.05).
270 271
TABLE 4 11
272 273
Regression models associated with functional independence and wheelchair skills were
274
better for relative than absolute peak torque. Injury level, time since injury, and age were also
275
significant predictors included in regression models (Table 4 and supplementary data No. 3).
276 277
Strength cutoff-points for functional independence and wheelchair skills
278 279
The sum of relative peak torque values for trunk flexion and extension showed a cutoff
280
point of 1.42 N.m/kg to achieve a score of 70 in the SCIM-III (Table 5), while the cutoff point for
281
the sum of shoulder abduction and adduction relative peak torques was 2.35 N.m/kg, associated
282
with a total time of thirteen items of 111.90 sec (Table 5). The cutoff-points for relative peak torque
283
of shoulder abduction to obtain a 3-minute overground wheeling time of 300 m and performance
284
score of 18.5 sec were 0.96 and 0.97 N.m/kg, respectively (Table 5 and supplementary data No. 4).
285 286
TABLE 5
287 288
DISCUSSION
289 290 291
Relative and absolute peak torque from partially preserved muscles were better able to
292
discriminate between SCI levels, considering that absolute peak torque of shoulder adduction did
293
not show a significant difference between HP and LP. However, relative peak torque was a better
294
predictor of functional independence when compared to absolute strength. Although time since
295
injury, age and injury level exhibited were more important than muscle strength in the predictive
296
equations (considering the SCIM-III and three out of four AMWC-Brazil outcomes), the
297
implications of strength are significant because it is influenced by exercise interventions.
298 12
299
Our findings indicated significant differences in trunk strength (flexion and extension)
300
between the HP and LP. Trunk flexion/extension MVIC on an isokinetic dynamometer has not been
301
previously adopted in the context of SCI and was, therefore, a suitable assessment. The abdominal
302
muscles are innervated by the intercostal nerves (T7 to T11) and the erector spinae by spinal nerves,
303
with both muscle groups determinant to trunk balance. The paraplegia groups were stratified
304
considering these characteristics and significant intergroup differences in peak trunk
305
flexion/extension torque were expected. Identifying differences in trunk flexion/extension strength
306
between SCI levels is important in functional independence assessments because impaired trunk
307
balance can compromise performance in activities of daily living.29 Moreover, the trunk
308
flexion/extension peak torques of the present study were obtained at 55º and 105º in the sagittal
309
plane for hip flexion and extension, respectively. This positioning was based on a pilot study to
310
ensure that all participants could perform the test, independently of their injury level.26
311
Nevertheless, it is necessary to consider that the trunk flexion/extension isometric peak torque could
312
be achieved in other angles of trunk flexion/extension.
313 314
The regression equation model containing the sum of relative peak torque values for trunk
315
flexion and extension explained 61% of functional independence (SCIM-III). In this respect, our
316
findings corroborate those of previous studies,30, 31 in which the trunk muscles were considered vital
317
to postural balance.29 We demonstrated that a cutoff point of 1.42 N.m/kg was required for
318
isometric trunk flexion and extension to achieve 70 points on the SCIM-III scale. Prior
319
investigations have reported SCIM-III values ranging from 29 to 51 in individuals with acute SCI
320
and shorter rehabilitation times.23, 32 These studies used heterogeneous samples and broader
321
inclusion criteria, which could affect interpretations of an optimal SCIM-III score associated with
322
higher degrees of independence.32 Aidinoff et al.37 recorded SCIM-III scores between 64 and 78 for
323
individuals with thoracic and lumbar SCI at hospital discharge, with a mean stay of 5 months.33 A
324
Brazilian study reported SCIM-III scores of 68 and 65 for individuals with HP and LP, 13
325
respectively.8 As such, a score of 70 on the SCIM-III can be considered a suitable and plausible
326
goal for functional independence in individuals with thoracic and lumbar SCI.
327 328
In the present study, both trunk flexion/extension and shoulder abduction/adduction
329
provided suitable cutoff-points for outcomes related to better functional independence and
330
wheelchair skills. The strength variables with the highest predictive capacity for wheelchair skills
331
were the sum of relative peak torque values for shoulder abduction and adduction and shoulder
332
abduction relative peak torque. Wheelchair ability was assessed based on four AMWC-Brazil
333
outcomes, and only the ability score showed no significant difference between the HP and LP. This
334
outcome had a ceiling effect in studies by Kilkens et al.,4, 34 Cowan et al.35 and Ribeiro Neto et al.,25
335
albeit without paraplegic subgroup stratification. However, significant differences were observed
336
between the paraplegia groups for 3-minute overground wheeling, performance score and total time
337
of thirteen items, and the models explained 52%, 59%, and 48% of wheelchair skills, respectively.
338 339
The shoulder muscle’s strength training is traditionally excluded or present a reduced
340
workload of abduction exercises, mostly because of a high prevalence of shoulder injury in the daily
341
life of individuals with SCI.36, 37. The overall idea is to minimize the occurrence of injuries in this
342
joint during rehabilitation.36, 37 Previous studies proposed interventions based on strength training
343
mainly focused on the anterior and posterior muscles of the trunk.36, 37 However, both shoulder
344
abduction and adduction are rather important for wheelchair propulsion and activities of daily
345
living.5, 30, 38 Our findings corroborate this statement since the shoulder abduction was correlated to
346
a better performance in three of the AMWC-Brazil outcomes. Therefore, there is a paradox between
347
the risk of injury by overuse and the importance of shoulder abduction for daily life activities. It is
348
suggested that not only the prime shoulder adduction muscles should be emphasized during a
349
rehabilitation and strength training program, but also exercises focusing on synergistic and
350
stabilizing muscles. 14
351 352
In addition to relative and absolute peak torque, the covariates injury level, time since
353
injury and age were also predictors in the regression models. Only age and time since injury were
354
significantly correlated with the independence outcomes and simultaneously entered in the
355
regression equation. However, the correlation value was low (0.28), minimizing the risk of
356
collinearity (supplemental data No. 2) and presented the collinearity statistics tolerance ranging
357
from 0.95 to 0.99 for regression equation using absolute strength. In contrast to other studies that
358
found reduced β values for age and time since injury,7, 8 these predictors had the greatest influence
359
on SCIM-III and AMWC-Brazil performance scores, respectively. The equation models explained
360
48% to 61% of functional independence and the wheelchair skills assessed. Thus, our findings
361
suggest that further studies are needed to elucidate whether other predictors (such as body
362
composition, length of hospital stay and sex) affect the functional independence and wheelchair
363
ability of individuals with SCI. Moreover, further studies focusing on the feasibility of clinical tests
364
(e.g., handgrip dynamometry or 1RM tests) on the assessment of the strength of partially
365
compromised muscles are warranted and might help to establish the strength cutoff points in clinical
366
practice.
367 368
Study Limitations
369 370
Wheelchair data were recorded and similar group distribution confirmed, but many of the
371
wheelchairs were old and had minor bearings defects. Although this variable improves the external
372
validity of our study, the low socioeconomic status of the participants precluded routine or
373
necessary repairs, which might have affected performance in the AMWC-Brazil. Another limitation
374
was a possible ceiling effect in the SCIM-III, reported in previous studies.8 Trunk or shoulder
375
strength measures may be misleading, since a large section of the SCIM-III is related to respiration,
376
the bowel and bladder, which may have influenced our findings and the cutoff point determination. 15
377
In addition, it is worth noting that the weight differences of the item scores might have affected the
378
equation model. Finally, because the shoulder is a three-dimensional joint, the role of synergists and
379
assessments within a broader combination of gestures, such as specific tasks and activities of daily
380
living, may also be associated with predicting functional independence.
381 382
CONCLUSION
383 384 385
In the present study, relative peak shoulder abduction torque, the sum of relative peak
386
torques for trunk flexion/extension and shoulder abduction/adduction showed the highest predictive
387
capacity for functional independence and wheelchair ability. The cutoff-points established could be
388
adopted as a parameter for optimal functional independence and wheelchair skills.
389 390
CONFLICT OF INTEREST
391 392
The authors declare no conflict of interest.
393
16
394
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TABLES AND FIGURES LEGENDS
Tables Table 1: Participant demographic data, considering the injury level groups. Variables are presented as median (25th and 75th percentiles). Body mass index (BMI) is expressed as mean (standard deviation). Etiology is expressed in absolute values (frequency in each group) and wheelchair characteristics as frequency (%) and mean (standard deviation).
* Significant difference in relation to the HP (P≤0.05); † Significant difference in relation to the LP (P≤0.05); ‡ Significant difference compared to rigid frame (P≤0.05). HP: high paraplegia; LP: low paraplegia. na: not applicable.
Table 2: Descriptive data for absolute (abs, N.m) and relative muscle strength (rel, N.m/kg) in the high (HP) and low paraplegia (LP) groups. Relative peak torque values for shoulder adduction and abduction as well as the sum of these values for shoulder exercises are expressed as mean (standard deviation). The other variables are expressed as median (25th and 75th percentiles).
* Significant difference compared to the HP (P≤0.05). ABD: abduction; ADD: adduction; EXT: extension; FLX: flexion; PT: peak torque; PTabs: absolute peak torque; PTrel: relative peak torque; SAAsum: shoulder abduction and adduction peak torque; TFEsum: sum of trunk flexion and extension peak torques.
21
Table 3: Descriptive data of functional independence and wheelchair ability outcomes (SCIM-III and AMWC-Brazil) in the high paraplegia (HP) and low paraplegia (LP) groups. The performance score and 3-minute overground wheeling test are expressed as mean (standard deviation) and the other variables as median (25th and 75th percentiles).
* Significant difference compared to the HP (P≤0.05). 3MinTest: 3-minute overground wheeling test; AMWC-Brazil: Adapted Manual Wheelchair Circuit - Brazilian version PS: performance score; Resp.: respiration; SCIM-III: Spinal Cord Independence Measure version III; SM: sphincter management; TT: total time of thirteen items.
Table 4: Stepwise regression (R and R2 values) for the independence scale (SCIM-III) and wheelchair skills (AMWC-Brazil), beta weights (β) and probability values (P) of the predictor variables.
* Statistical significance (P≤0.05). 3MinTest: 3-minute overground wheeling test; ABD: abduction; PS: performance score; PTabs: absolute peak torque; PTrel: relative peak torque; SAAsum: sum of shoulder abduction and adduction peak torques; TFEsum: sum of trunk flexion and extension peak torques; TSI: time since injury; TT: total time of thirteen items.
22
Table 5: Results of the ROC curve for strength variables with the best predictive values for the independence scale (SCIM-III) and wheelchair skills (AMWC-Brazil) at the highest percentile and with statistical significance for the area under curve.
Area under the curve (AUC) was statistically different from the ROC curve reference line for all strength variables (P≤0.05). 3MinTet: 3-minute overground wheeling test; ABD: abduction; CP: cutoff point for strength variables (N.m/kg); PTrel: relative peak torque; SAAsum: sum of shoulder abduction and adduction peak torques; SENS: sensitivity; SPEC: specificity; TFEsum: sum of trunk flexion and extension peak torques; TR: test result.
Figure Figure 1: Illustration of the position adopted for shoulder abduction and adduction (A and B) and trunk flexion (C) and extension (D) in maximum strength testing on an isokinetic dynamometer. A: initial shoulder abduction position in the isokinetic test, at an angle of 15º; B: initial shoulder adduction position in the isokinetic test, at an angle of 90º; C: trunk flexion position in the isometric test, at a hip angle of 55º and, D: initial trunk extension position in the isometric test, at a hip angle of 105º.
23
Table 1: Participant demographic data, considering the injury level groups. Variables are presented as median th
(25
th
and 75
percentiles). Body mass index (BMI) is expressed as mean (standard deviation). Etiology is
expressed in absolute values (frequency in each group) and wheelchair characteristics as frequency (%) and mean (standard deviation). n Age (years) 26.9 Time since injury (months) 37.4 Age at injury (years) 23.7 Body mass (kg) 68.2 Height (cm) 170.2 2 BMI (kg/m ) 23.8 Ashworth spasticity scale 3.0 Etiology (n) Auto accident 3 Diving 1 Falls 2 Gunshot wound 18 Hit by falling object 1 Knife wound 0 Motorcycle accident 2 Wheelchair frame (kg) Rigid 48.1% Folding 22.2% Double Folding 29.6% Wheelchair owner (kg) Participant 42.6% Hospital 7.4% * Significant difference in relation to the
HP 27 (22.9 - 36.8) (16.8 - 53.2) (18.8 - 34.9) (56.6 - 76.2) (167.9 - 174.5) (4.9) (2.0 - 4.0) (5.6%) (1.9%) (3.7%) (33.3%) (1.9%) (0.0%) (3.7%) 13.9 (2.4) 16.2 (2.4) 17.9‡ (1.5)
29.3 50.1 22.4 67.8 170.2 22.9 0.0* 4 0 2 19 0 1 1 59.3% 40.7% 0.0%
LP 27 (22.4 - 37.9) (21.5 - 104.8) (19.0 - 32.5) (56.5 - 77.7) (167.0 - 176.4) (4.4) (0.0 - 3.0) (7.4%) (0.0%) (3.7%) (35.2%) (0.0%) (1.9%) (1.9%) 13.8 (2.0) 16.1‡ (1.8) -
28.8 39.8 23.1 68.0 170.2 23.3 2.0 7 1 4 37 1 1 3 53.7% 31.5% 14.8%
TOTAL 54 (22.9 - 37.1) (19.4 - 82.2) (19.0 - 33.0) (56.6 – 77.2) (167.0 – 174.5) (4.7) (0.0 - 4.0) (12.9%) (1.9%) (7.4%) (68.4%) (1.9%) (1.9%) (5.6%) 13.8 (2.2) 16.1‡ (2.0) 17.9‡ (1.5)
15.5 (0.9) 37.0% 14.5 (2.5) 79.6% 15.1 (2.7) 15.7 (2.4) 13.0% 15.5 (0.9) 20.4% 15.6 (1.5) HP (P≤0.05); † Significant difference in relation to the LP (P≤0.05); ‡
Significant difference compared to rigid frame (P≤0.05). HP: high paraplegia; LP: low paraplegia. na: not applicable.
Table 2: Descriptive data for absolute (abs, N.m) and relative muscle strength (rel, N.m/kg) in the high (HP) and low paraplegia (LP) groups. Relative peak torque values for shoulder adduction and abduction as well as the sum of these values for shoulder exercises are expressed as mean (standard deviation). The other variables are th
th
expressed as median (25 and 75 percentiles).
n
HP
LP
27
27
Shoulder ABD PTabs
58.20
ABD PTrel
0.86
(0.15)
1.05*
(0.16)
ADD PTabs
82.91
(16.13)
98.83
(22.61)
ADD PTrel
1.28
(0.26)
1.48*
(0.27)
SAAsum absolute
144.31
SAAsum relative
2.14
(0.38)
ABD/ADD PT index
0.65
(0.60 – 0.74)
(49.20 – 61.70)
(25.62)
71.30*
169.73* 2.53* 0.72
(60.00 – 80.20)
(37.72) (0.41) (0.68 – 0.77)
Trunk FLX PTabs
37.10
FLX PTrel
0.53
EXT PTabs
42.10
EXT PTrel
0.65
TFEsum absolute
76.00
TFEsum relative
1.18
(25.80 – 47.90) (0.38 – 0.67) (32.30 – 47.20) (0.53 – 0.76) (62.60 – 94.50) (1.05 – 1.30)
FLX/EXT PT index 0.87 (0.70 – 1.18) * Significant difference compared to the HP (P≤0.05).
64.30* 0.93* 56.30* 0.83* 119.00*
(52.30 – 82.00) (0.78 – 1.17) (39.60 – 67.00) (0.59 – 1.00) (91.70 – 146.30)
1.71*
(1.53 – 2.10)
1.28*
(0.91 – 1.73)
ABD: abduction; ADD: adduction; EXT: extension; FLX: flexion; PT: peak torque; PTabs: absolute peak torque; PTrel: relative peak torque; SAAsum: shoulder abduction and adduction peak torque; TFEsum: sum of trunk flexion and extension peak torques.
Table 3: Descriptive data of functional independence and wheelchair ability outcomes (SCIM-III and AMWCBrazil) in the high paraplegia (HP) and low paraplegia (LP) groups. The performance score and 3-minute overground wheeling test are expressed as mean (standard deviation) and the other variables as median th
th
(25 and 75 percentiles). HP n 27 SCIM-III Self-Care 18 (17 – 18) 18* Resp. & SM 33 (33 – 33) 33* Mobility 17 (16 – 18) 19* Total 67 (66 – 68) 70* AMWC-Brazil Ability Score 14.0 (14.0 – 14.0) 14.0 PS (sec) 21.65 (2.86) 19.06* TT (sec) 130.73 (107.63 – 167.7) 92.44* 3MinTest (m) 253.6 (32.6) 291.6* * Significant difference compared to the HP (P≤0.05).
LP 27 (18 – 18) (33 – 34) (17 – 19) (68 – 71) (14.0 – 14.0) (2.17) (77.91 – 116.54) (35.3)
TOTAL 54 18 33 17 68 14.0 20.35 111.90 272.6
(18 – 18) (33 – 33) (16 – 19) (66 – 70) (14.0 – 14.0) (2.84) (90.18 – 138.39) (38.8)
3MinTest: 3-minute overground wheeling test; AMWC-Brazil: Adapted Manual Wheelchair Circuit - Brazilian version PS: performance score; Resp.: respiration; SCIM-III: Spinal Cord Independence Measure version III; SM: sphincter management; TT: total time of thirteen items.
2
Table 4: Stepwise regression (R and R values) for the independence scale (SCIM-III) and wheelchair skills (AMWC-Brazil), beta weights (β) and probability values (P) of the predictor variables. SCIM-III R 2 R
0.78* 0.61
TFEsum relative
AMWC-Brazil TT 0.69* 0.48
PS 0.77* 0.59
3MinTest 0.72* 0.52
β
p
β
p
β
p
β
p
0.34
<0.01
-
-
-
-
-
-
(TFEsum relative)
2
0.07
0.50
-
-
-
-
-
-
(TFEsum relative) Injury Level 2 (Injury Level) 3 (Injury Level) TSI 2 (TSI) 3 (TSI)
3
0.01 0.40 0.05 -0.10 0.59 -0.03 -0.06
0.71 <0.01 0.71 0.44 <0.01 0.88 0.40
-0.28 0.14 -0.02
<0.01 0.48 0.72
-0.40 -0.18 0.07 -0.11 0.20 -0.06
0.19 0.21 0.65 0.62 0.40 0.43
0.50 -0.12 -0.08 0.19 -0.14 -0.61
0.08 0.36 0.56 0.29 0.52 0.42
SAAsum relative
-
-
-
-
-0.57
0.02
-
-
(SAAsum relative)
2
-
-
-
-
0.17
0.07
-
-
(SAAsum relative)
3
-
-
-
-
0.07
0.36
-
-
-
-
-0.27
<0.01
-
-
0.18
0.04
-
-
0.03
0.75
-
-
-0.01
0.92
-
-0.11 0.42 0.14 -0.12
0.09 <0.01 0.40 0.20
-
-
0.09 -
0.18 -
ABD PTrel (ABD PTrel)
2 3
(ABD PTrel) Age 2 Age 3 Age * Statistical significance (P≤0.05).
3MinTest: 3-minute overground wheeling test; ABD: abduction; PS: performance score; PTabs: absolute peak torque; PTrel: relative peak torque; SAAsum: sum of shoulder abduction and adduction peak torques; TFEsum: sum of trunk flexion and extension peak torques; TSI: time since injury; TT: total time of thirteen items.
Table 5: Results of the ROC curve for strength variables with the best predictive values for the independence scale (SCIM-III) and wheelchair skills (AMWC-Brazil) at the highest percentile and with statistical significance for the area under curve. TR
AUC
95%CI
SENS
SPEC
CP
70
0.77
0.63 – 0.91
0.64
0.80
1.42
111.90
0.76
0.62 – 0.90
0.73
0.79
2.35
18.5
0.80
0.66 – 0.94
0.85
0.68
0.97
TFEsum relative (N.m/kg) SCIM-III SAAsum relative (N.m/kg) Total Time of Thirteen Items (sec) Shoulder ABD PTrel (N.m/kg) Performance Score (sec)
3-MinTest (m) 300.0 0.74 0.58 – 0.89 0.65 0.86 0.96 Area under the curve (AUC) was statistically different from the ROC curve reference line for all strength variables (P≤0.05). 3MinTet: 3-minute overground wheeling test; ABD: abduction; CP: cutoff point for strength variables (N.m/kg); PTrel: relative peak torque; SAAsum: sum of shoulder abduction and adduction peak torques; SENS: sensitivity; SPEC: specificity; TFEsum: sum of trunk flexion and extension peak torques; TR: test result.