- Email: [email protected]
Muscle strength in individuals with healed burns
155
Muscle Strength in Individuals Diane M.M. St-Pierre, PhD, Manon
With Healed Burns
ChoiniBre, PhD, Robert Forget, PhD, Dominique
ABSTRACT. St-Pierre DMM, Choiniere M, Forget R, Garrel DR. Muscle strength in individuals with healed burns. Arch Phys Med Rehabil 1998;79:155-61. Objective: To quantify the long-term effects of bums on muscle strength and to investigate the impact of the initial severity of the trauma on muscle strength. Design: Cross-sectional study comparing individuals with healed bums to nonbumed control individuals matched for age, gender, body mass index, and physical activity level. Setting: Subjects were selected from the data bank of a bum center of a large Montreal teaching hospital and tested in a university laboratory. Patients: Thirty subjects (mean age, 36.3 t 11.5yrs) with second- and third-degree bums covering 15% to 75% of total body surface area (TBSA) (mean, 35.5% -t 15.9%) were evaluated more than 1 year after discharge (mean, 37.3 ? 20.4 months; range, 15 to 92 months). Thirty unburned subjects were recruited from the community at large Main Outcome Measure: Maximal torque, work, and power developed by the elbow and knee flexors and extensors. Results: Subjects with burns of >30% of TBSA produced significantly less torque, work, and power in the quadriceps than control subjects (15.2% to 20.5% depending on velocity @ < ,051). The ability to develop muscle power at the elbow was also compromised in the severely burned subjects (19.2% in extension and 18.7% in flexion [p = .07]) at the faster velocities. No differences were observed between controls and patients with small burn injuries (TBSA of <30%). Conclusion: Patients who had severe bums (TBSA of >30%) had weaker muscles even years after the trauma, suggesting either an inability to fully recover or insufficient rehabilitation. 0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
B
URN INJURIES are common, affecting approximately 1% of the population of the United States each year,‘*’ and are classified as the second major cause of accidental deaths after motor vehicle accidents.‘,3 The survival of the patient is the paramount concern in the acute stage of treatment of major bums, and survival rates have improved considerably over the past couple of decades.‘,3,4 From the School of Physical & Occupational Therapy, McGill University (Dr. St-Pierre); Centre des Grands BriWs, Hate1 Dieu Hospital of Montreal (Drs. Choir&e, Garrel); and the Departments of Surgery and Anesthesia (Dr. Choin&e). Ecole de Rkadaotation (Dr. Forget). and Deoartment of Nutrition (Dr. Garr&, University of hiontreal,‘Montre$ &ebec, danada. Submit for publication February 14, 1997. Accepted in revised form July 25, 1997. Research supported by R&au-Fonds des Pompiers du Qukbec pour les Grands Br%Bs (FPQGB) and Fonds de la Recherche en Sante du Qubbbec. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Diane St-Pierre, PhD, Associate Professor, School of Physical & Occupational Therapy, McGill University, 3654 Drummond Street, Mont&11, QuCbec, Canada H3GlY5. 0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003-9993/98/7902-4386$3.00/O
R. Garrel, MD
Rehabilitation is fundamental for the overall recovery of the patient. The long-term goal of therapy is to return the patient back into society in as near to the patient’s normal prebum functional capacity as possible.5-7To this end it is important to prevent soft-tissue deformity or bum scar contractures, protect the healing skin graft, maintain or restore cardiopulmonary, respiratory, and musculoskeletal function; and promote rapid return to independence in self-care and preburn lifestyle functions.5,7.8Good therapeutic positioning is important to reduce swelling and prevent contracturesg Exercise can help to control edema and attenuate tendon adherence, joint stiffness, capsular shortening, muscle atrophy, and deconditioning.7~8~‘o Splinting may be required to protect the healing graft or help prevent deformities.” Treatments often extend over months after discharge from the hospital, and in many cases full return to a prior level of functioning is not achieved.‘2.‘3Persistent muscle weakness has been reported 8 to 9 months after second- to third-degree bums to an extremity in a small group of patients.’ Blalock and colleagues’* observed that many people with burn injuries reported problems more than 1 year later involving the skin (sensitivity, irritation, scartissue), appearance, ability to work, mobility, and psychological well-being. Impairments in home management and leisure roles have also been reported.r3 Limited range of motion, poor dexterity, loss of mobility, and intolerance for standing and walking, as well as pain and decreased strength and endurance, have been cited as major underlying factors precluding the individual from becoming fully independent in self-care, home management, work, and leisure.r3 In a study with more than 400 patients, Malenfant et alI4reported that more than 30% of bum patients developed chronic pain problems that could affect their daily functioning. Little information is available on the time course of recovery of muscle size and strength following a major bum or on the impact of the severity of the initial trauma on outcome. Some observations suggest that the final functional outcome may depend on the initial extent of the injury.15 Indeed, burn severity affects the magnitude and duration of the hyper metabolic response that is initiated by the injury. The basal metabolic rate can increase up to twice normal values in patients with burns greater than 50% of total body surface area (TBSA).r6,i7Skeletal muscle proteins are particularly vulnerable, undergoing proteolysis to provide amino acids for hepatic gluconeogenesis, wound repair, and acute-phase protein synthesis.‘* This process affects not only the involved musclesbut also those not directly involved with the thermal trauma.‘9.20Therefore, because muscle strength is proportional to muscle cross-sectionalarea’i and the extent of muscle atrophy is dependent on the severity of the initial thermal injury, the ultimate recovery of muscle size and strength may be influenced by the extent of the initial burn injury. The objective of this study was twofold: (1) to quantify the long-term effects of bums on muscle strength; and (2) to investigate the impact of the initial severity of the trauma on muscle strength. METHODOLOGY Subjects Burn subjects. To be included in the study, subjects had to meet the following inclusion criteria: (1) men or women between 18 to 70 years of age who had sustained burn injuries to Arch
Phys Med
Rehabil
Vol79,
February
1998
156
STRENGTH
Table
Subjects
1: Subject
Burn
Control
IN PEOPLE
WITH
Characteristics:
BUWl
HEALED
BURNS,
Age, Sex, Weight,
St-Pierre
and Height
Control
Burn
COlltd
BWll
Control
TBSA of 530% 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Mean 2 SD TBSA of >30% 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Mean ? SD
38 33 27 27 39 40 54 45 25 58 40 53 27 54 40.0 t 11.4
44 30 29 27 40 48 59 47 24 61 38 46 28 47 40.6 -c 11.8
M M M M M M F M M M M M M F -
M M M M M M F M M M M M M F -
88.6 64.0 68.2 87.7 65.9 59.1 62.0 72.7 67.3 84.1 63.6 93.2 75.0 61.4 72.3 2 11.5
95.5 75.0 70.5 88.2 70.5 61.4 63.6 77.3 65.9 88.6 70.5 86.4 74.1 65.9 75.2 k 10.6
172.5 165.0 172.5 175.0 170.0 167.5 165.0 167.5 177.5 177.5 165.0 172.5 172.5 157.5 169.8 2 5.6
172.5 165.0 170.0 177.5 170.0 167.5 165.0 165.0 177.5 177.5 162.5 170.0 175.0 160.0 169.6 -c 5.8
44 30 37 25 31 51 29 25 29 54 64 51 42 30 47 48 39.8 t 11.9
46 25 37 28 23 45 27 33 30 52 69 51 39 31 41 47 39.0 -t 12.3
M M F M M M M M F M M F M F M M
M M F M M M M M F M M F M F M M
78.6 90.9 53.6 59.1 95.5 93.2 90.9 59.1 47.3 97.3 83.2 61.4 88.6 58.6 86.4 84.1 76.7 i- 17.1
74.1 90.9 56.8 57.3 90.9 90.0 97.7 60.0 51.8 102.3 79.6 58.6 84.1 59.1 84.6 82.7 76.3 t 16.6
177.5 177.5 157.5 165.0 190.0 167.5 175.0 157.5 155.0 180.0 180.0 167.5 185.0 150.0 175.0 170.0 170.6 2 11.4
150.0 182.5 155.0 165.0 185.0 172.5 180.0 162.5 160.0 182.5 175.0 165.0 180.0 152.5 172.5 170.0 169.4 -t 11.3
Grand
39.9 ? 11.5
39.7 2 11.9
-
-
74.7 t 14.7
75.8 k 13.9
170.3 i- 9.0
169.5 2 9.0
mean
F SD
the upper extremities; (2) presence of second- to third-degree bums covering at least 15% of TBSA; (3) elapsed time since injury longer than 12 months; and (4) consent to participate. Upper extremity bums were required because subjects in this study took part concurrently in another study evaluating cutaneous sensitivity in the hand and arm areas. Excluded were subjects whose bums covered less than 15% of TBSA, because generalized muscle weakness would be minimal with this severity of bum.” Also excluded were patients with a history of alcohol abuse, diabetes, or other predisposing causes of neuropathy. Patients with psychiatric and neurologic disorders documented in their medical files were excluded along with those unable to communicate because of language. Thirty bum patients, who had been hospitalized at a hospital bum center in Montreal took part in the study. The study was approved by the Ethics Committees of the hospital and university. Control healthy subjects. The bum patients were pairmatched to control unburned individuals who were recruited from the community at large through personal contacts and advertising. They were paired as closely as possible to the bum subjects for age, stature (height and weight), and physical activity level. The fitness level of the control subjects was assessed initially by phone. The subject was asked to rate his or her perceived level of fitness (sedentary, moderately fit, or very fit). If a possible match was found, a more detailed pairing was done by administering a 7-day physical activity recall questionnaire,” administered by an interviewer (approximately 15 to 20 min). The subject is asked for a total activity recall that includes, home, work, and leisure activities. The subject is initially asked to recall the number of hours slept during the week days and weekend, then is asked to recall how many hours were spent
Arch
Phys
Med Rehabil
Vol 79, February
1998
doing moderate, hard, or very hard activities. Examples of activities in each category (house work, work, and leisure) are provided in the questionnaire. For activities not listed in the questionnaire, clarification of activity intensity was achieved by consulting the compendium of physical activity classification of energy costs of human activities.23 Light activities were calculated by subtraction. Evaluation of Muscle Strength Strength of the knee and elbow flexors and extensors were evaluated bilaterally with a Cybex isokinetic dynamometer,” linked to an IBM PC-AT computerh with commercially available software.’ For the knee measurements, the individual was sitting with stabilizing straps around the chest, pelvis, and thigh. Knee torque measurements were corrected for the effects of gravity. For the elbow measurements, the individual was supine with the shoulder abducted to 1.57radian (rad). Stabilizing straps were secured to the chest, pelvis, and arm. The axis of rotation of the dynamometer was visually aligned to the axis of rotation of either the knee or elbow joints. Subjects were familiarized with the Cybex and tested at 1.05 and 3.14rad/sec. The speeds were not randomized. Four maximal contractions were recorded at each speed with a 2-min rest period between each set. Averages were calculated on the best three of four contractions. In addition, the values of both limbs were combined and averaged. Peak torques and those developed at knee angles of .79 and 1.05rad and elbow angles of 1.57rad were retained for further analysis. Total work and average power were also calculated. Reliability of the above measurements was established by testing nine bum subjects and nine control subjects on two different occasions within a 2-week period.
STRENGTH
Table
2: Subject
Characteristics: Burn
Subjects
TBSA (%) Burn
TBSA of ~30% 1 2 3 4 5
6 7 8
9 IO 11 12 13 14
Mean + SD TBSA of >30% 1
23.4
2 3 4 5 6 7
8 9 10 11 12 13 14 15
16 Mean + SD Grand mean + SD
46.1
Occupation, TBSA
Occupation Burn
Control
15 16 16 20 20 23 25 25 25 26 26 30 30 30
FTW U
u
FTW FTW
s
31 32 33 35 35 37 40 40 42 43 43 60 60 62 70 75
FTW FTW FTW M FTW FTW S U FTW PTW U FTW M FTW FTW PTW
FlW FTW PTW FTW S FTW FTW FTW FTW U U FTW FTW FTW FTW FTW
-
-
+-5.2
2
FTW U FTW PTW U FTW PTW FTW FTW FTW PTW
PTW FTW FTW F-i-W FTW FTW FTW U FTW FTW FTW
14.3
35.5 ? 15.9
Abbreviations: FTW, full-time work; PTW, part-time M, missing data.
Physical
IN PEOPLE
Activity,
Weekly Physical Activity Burn 384.3 266.5 345.5 474.0 256.8 281.3 285.0 228.0 255.8 327.8 508.5 292.8 528.8 256.0 335.1 + 100.6 280.0 578.0 246.5 316.8 316.0 356.0 286.5
and (METS)
559.3 297.3 266.3 325.0 245.5 235.3 270.0 239.3 258.0 296.0 269.5 298.5 381.3 363.8 307.5 1. 84.1
288.0 233.0 323.5 313.3 i 79.1 323.4 2 88.8
324.6 i- 94.1
270.0 302.8 322.0 248.0
HEALED
BURNS,
157
St-Pierre
or her perceived level of pain during testing by tracing a vertical mark on a lo-cm horizontal line with the ends marked by the expressions “no pain” and “unbearable pain.“31
Control
238.5 308.8 288.5 398.5 300.8 337.0 425.0 398.8 268.8 397.0 272.5 285.0 653.5 260.8 336.5 263.3 339.6 i 102.0
292.0
WITH
work; S, studies; U, unemployed;
Data Analysis Baseline characteristics (age, height, weight, weekly energy expenditure, perceived general fatigue) between control and burn subjects were compared with t tests. Analysis of variance (ANOVA) for repeated measures was used to determine significant strength differences between group (bum patients and controls), extent of injury (burned more or less than 30% TBSA), speed (1.05 and 3.14rad/sec) and muscle group (flexion and extension), as well as possible interactions between these factors. Analysis was done on the average response obtained from the bilateral measurements and expressed in either absolute values or relative to body mass index. If significant group interactions were found, simple main effects were calculated to bring out differences between bum patients and controls. To test the homogeneity of the various strength measures, Cronbath’s alpha was calculated for control (a! = .98) and burn subjects (a = .99). Because of this high level of homogeneity, strength measurements were converted into z scores (to account for differences in unit of measurement) and averaged to obtain a global strength score. Pearson correlation coefficients were determined between the global strength score and variables susceptible of influencing strength (age, activity level, length of time since injury, fatigue score). Test-retest reliability was determined with the intraclass correlation coefficient (ICC) applied to the repeated measures ANOVA analysis. Possible differences in fatigue perception between control and bum subjects were determined by t tests. RESULTS
Other Measures Fitness level. A 7-day activity recall questionnaire was used to quantify the average weekly energy expenditure.22 The questionnaire has been shown to be reliable, with Y values ranging from .75 to .84.24It has been validated against a daily selfreport log24,25and an ambulatory solid-state minicomputer that measures continuous heart rate and motion.” The questionnaire has also been observed to be sensitive to changes in physical activity status with training.26 Weekly energy expenditures were calculated in metabolic equivalents (METS) based on the information obtained using the questionnaire. Sleep was estimated as lMET, light activity as l.SMETS, moderate activity as 4METS, hard activity as 6METS, and very hard activity as lOMETS.” MET values were multiplied by the number of hours spent in each of the five categories and the products summed to give total number of METS per week. Fatigue. General daily fatigue was measured subjectively with the Fatigue Severity Scale and a visual analogue scale (VAS). The Fatigue Severity Scale was originally designed to measure fatigue in people with multiple sclerosis.” It comprises a list of nine statements, rated on a scale of 1 to 7. The scale has been shown to have internal consistency, stability over time, and sensitivity to clinically significant change.27It has been used to evaluate fatigue in postpolio and chronic fatigue syndromes.** Each participant was also asked to rate his or her general level of fatigue with a VAS marked with the expressions “no fatigue” and “extreme fatigue.” Pain. Pain can influence the measurement of muscle strength.29,30Therefore, to control for the possible confounding effects of pain during testing, a VAS scale was administered. Presence of pain during testing was evaluated by asking the subject immediately after each set of measurement to rate his
Subject Characteristics The characteristics of the subjects are presented in tables 1 and 2. The sample of bum subjects was comprised of 6 women and 24 men who had sustained their burn injuries a mean of 37.7 ? 20.4 months before testing (range 15 to 92 months). The average extent of their bums was 35.5% ? 15.9% of TBSA (range, 15% to 75%). Sixteen subjects had burns covering more than 30% of TBSA, and 62% of these patients had both upper and lower extremity burns. Similarly, 64% of patients whose bums covered less than 30% TBSA had both upper and lower Table
3: ICCs for Strength Measures of Knee Extensors Control and Burn Subjects Extensors
and Flexors
in
Flexors
Burn
Control
BLIrn
Control
1.05Rad Peak torque 1.05Rad .79Rad Work Power 3.14Rad Peak torque 1.05Rad .79Rad Work Power
.81 .68 .78 .a8 .78
.92 .93 .87 .98 .95
.a9 .90 .90 .93 .91
.93 .91 .92 .98 .96
.a7 .86 .82 .92 .85
.93 .91 .93 .96 .90
.92 .81 .76 .93 .90
.a4 .72 .67 .91 .86
Average
.82
.93
.aa
.a7
In each burn and control group, n = 9. 1.05 and 0.79rad represent the torque developed at the corresponding angles. Work represents the total work performed during the contractions, and power represents the average power developed.
Arch
Phys Med
Rehabil
Vol79,
February
1998
158
STRENGTH
IN PEOPLE
WITH
HEALED
Table
4: ICCs for Strength Measures of Elbow Extensors Control and Burn Subjects
and Flexors
in
taken at the knee (table 3). Good reliability (ICC between 0.6 and 0.8) was observed for most measurements taken at the elbow (table 4). The average pain perceived during testing was below 0.5 on the VAS in all burn (n = 30) and control subjects (0.3 2 1.1, II = 30). For comparison between groups, only absolute peak torques, total work, and average power values are reported, as similar information was gained from joint-specific torques and from torque, work, and power values normalized to body mass index. No statistically significant difference in strength was observed between subjects with bums less than 30% TBSA and their matched controls (tables 5 through 8). Similarly, no difference in knee flexor torques were observed between control subjects and those burned more than 30% of TBSA (table 6). In contrast, knee extensor muscle strength was not completely recovered in subjects burned 30% or more of TBSA. Differences in peak torque (100 - bum value/control value X 100) at 3.14rad/sec (16.0% [p < .05]) and total work produced at 1.05 (15.2% [p < .OOl]) and 3.14rad/sec (20.5% [p < .OOl]), as well as the average power developed at 3.14rad/sec (17.8% [p < .002]), were observed between severely burned subjects and their matching controls (table 5). The ability to develop muscle power at the elbow was also compromised in the severely burned subjects (19.2% in extension and 18.7% in flexion [p = .07]), at the faster velocities (tables 7 and 8).
FleXlrs
EXtMWXS
Burn
Control
Bllrn
Control
.a5
l.OSRad Peak torque 1.57Rad Work Power 3.14Rad Peak torque 1.57Rad Work Power
.86 .93 .75
.75 .72 .80 .74
.82 .77 .91 .74
.77 .81 .81 .76
.77 .77 .92 .79
.71 .69 .68 .64
.76 .79 .90 .76
.73 .75 .77 .75
Average
.83
In each burn and control described in table 3.
group,
.72
.81
n = 9. Rad values,
work,
.77 and power
as
extremity bums. All patients had received skin grafting (partial thickness skin grafting) under general anesthesia. All except two patients had a thermal injury. One subject had a chemical bum, and another had an electrical bum. Both of these subjects were among those whose bums covered less than 30% TBSA. There was no significant age difference between subjects burnt more or less than 30% of TBSA. The average length of hospitalization was 46.6 2 28.7 days. Patients burned more than 30% of TBSA stayed in the hospital significantly longer than those with less severe bums (58.6 +- 30.6 vs 32.8 ? 19.2 days, respectively). Physiotherapy was provided to both groups of patients on a daily basis. Initial treatment focused on range of motion exercises. If patients were alert and could collaborate, they were given an exercise program to do on their own. After skin grafting or wound healing, prolonged progressive stretching, strength, and endurance exercises were added to the program. Upon discharge from the acute care facility, four patients were sent to a rehabilitation center, where they received daily treatment. Three of these patients belonged to the group with bums of less than 30% of TBSA. The other patients were discharged home and were seen in an outpatient clinic up to four times per week. The length of time between injury and testing was similar in both groups of patients (35.2 + 13.8 vs 40.6 5 26.3 months, respectively [p > .OS]). Bum and control subjects did not differ significantly in age, body stature, laterality, or weekly energy expenditure (tables 1 and 2). Measures were similar in bum and control groups on the Fatigue Severity Scale (4.6 ? 1.2 and 4.7 ? 1.1, respectively) and the VAS measuring fatigue (3.3 2 2.4 and 3.4 ? 2.2, respectively).
For the burned subjects, significant correlations were observed between knee strength and current weekly energy expenditure (Y = .38, p = .02) and generalized fatigue perception, as measured by the Fatigue Severity Scale (1. = .32, p = .04) and the VAS (I = -.34, p = .03). There was no significant relationship between the knee strength measures and the length of time between trauma and testing. For control subjects, significant correlations were observed between physical activity level and knee strength (I = .30, p = .05). No other significant correlations were observed.
DISCUSSION The most important finding in this study was the persistence of muscle weakness in people burned more than 30% of TBSA. Indeed, muscle weakness (15% to 20%) was still present a mean of 35 months after injury. In contrast, the muscle strength of subjects with less severe bums was comparable to that of healthy controls. The difference in the extent of recovery between the two groups could not be attributed to age because both groups of patients were of similar age. There are, however, other differences between the two groups of patients that may have contributed to these results. There may
Strength testing was found to be reliable and painless. Excellent reliability (ICC > .80) was found for most measurements 5: Knee Extensor
Torque,
Work,
and Power
in Subjects
St-Pierre
Source of Variation in the Strength Measures
Muscle Strength
Table
BURNS,
With
Burns
of 530%
or >30%
of TBSA
and Their
TBSA of 530% (n = 141
1.05Rad Peak torque (Nm) Work (Nm) Power (watts) 3.14Rad Peak torque Work Power Values reported l p < .05. + p < ,002. *p < .OOl.
Arch
Phys Med
as mean
Rehabil
February
Controls
In = 16)
Burn
Control
Burn
Control
151.1 + 41.3 850.0 t 165.6 120.3 + 25.1
149.8 -t 33.9 792.4 z 178.8 115.9 2 26.6
136.6 i- 40.0 715.5 2 248.3 107.7 2 40.4
152.8 + 40.2 843.5 + 271.4* 119.7 + 39.7
116.0 & 36.2 661.4 k 160.6 224.8 ? 59.1
116.8 ? 30.7 618.2 +- 136.3 214.3 + 46.9
103.8 t 38.1 542.0 2 226.6 190.6 I 85.0
123.6 -c 40.7* 681.7 ? 232.6* 232.0 2 81.9’
5 SD.
Vol79,
Matching TBSA of >30%
1998
STRENGTH
Table
6: Knee
Flexor
Torque,
Work,
and Power
IN PEOPLE
WITH
in Subjects
With
HEALED
Burns
BURNS,
of 530%
159
St-Pierre
or >30%
of TBSA
and Their
TBSAofr30%
Matching TBSAof>30%
(n = 14)
(n = 16) Control
Burn
Control
86.5 2 25.5 492.4 i 105.6 70.2 2 17.2
82.9 t 22.8 443.2 + 120.9 64.2 I 17.4
77.9 t 26.0 409.4 F 148.9 60.6 f 23.6
79.8 2 31.9 456.1 t 198.6 63.6 i 27.2
64.8 2 19.9 380.2 + 103.2 224.8 + 59.1
59.5 t 16.8 324.6 t 99.8 214.3 t 46.9
59.6 2 26.1 311.0 ? 143.0 190.6 k 85.0
59.9 2 24.6 328.8 2 171.4 232.0 + 81.9
BUi-fl
1.05Rad Peaktorque (Nm) Work(Nm) Power (watts) 3.14Rad Peaktorque Work Power Values
reported
as mean
t SD.
have been a greater degree of muscle atrophy in patients with more severe burns. The severity of the injury could have influenced the initial degree of associated muscle atrophy both directly and indirectly: directly because of the detrimental effect of burn severity on muscle protein catabolism,1g*20and indirectly because subjects with severe burns may have been confined to bed for long periods of time or may have experienced more pain. Indeed, chronic nociceptive stimulation has been shown to induce muscle atrophy (reflex muscular atrophy).32,33Bed rest (deconditioning) is also associated with a loss of muscle mass and strength.34-3gThese changes are significant after only 2 weeks of bed rest3’ and affect predominantly the antigravity muscles of the lower extremity.38 The combined effect of protein catabolism and bed rest may have contributed to the observation that differences in muscle strength between burn and control subjects were more predominant in the lower extremities. Indeed, subjects who were burnt more than 30% of TBSA were hospitalized for longer periods of time than subjects with less severe burns (59 vs 33 days). The fact that strength deficits were more marked at the faster velocities suggests a preferential atrophy of fast-twitch fibers. The ability to torque at the fast velocities has been found to be correlated to the percent area occupied by fast-twitch fibers.40,41 It has been suggested that burn-induced muscle proteolysis may be mediated by glucocorticoids.42 Fast-twitch fibers are more sensitive to the catabolic effect of glucocorticosteroids on protein turnover than slow-twitch fibers.43 Myofibrillar protein breakdown was reported to be more severe in the rat extensor digitomm longus than in the soleus, in animals burned 30% of TBSA.42Furthermore, a glucocorticoid receptor antagonist (RU 38486) was able to prevent the increase in muscle proteolysis4’ Persistent muscle weakness may also have resulted from incomplete rehabilitation. Follow-up of these subjects after discharge from the acute care setting was often not optimal, yet they may still have had substantial muscle atrophy and weakness. All patients were seen daily by a physiotherapist while in Table
7: Elbow
Extensor
Torque,
Work,
and Power
in Subjects
With
the acute care facility. Only four patients were transferred to a rehabilitation facility for further intense rehabilitation. The other patients were discharged home and seen up to four times a week in outpatient clinics. The fact that only four patients were transferred to a rehabilitation unit may seem surprising at first glance; however, the length of stay in the acute care facility was long. More protracted rehabilitation may be required for further recovery of muscle function after discharge, but few studies have investigated the effects of additional exercise programs on patient outcome. Cronan and colleagues’ reported less muscle weakness in bum subjects, who, in addition to a treatment program consisting of splinting, stretching, and isometric and isotonic work loads, participated in a cardiovascular training program and a velocity-spectrum isokinetic protocol. Their study, however, had severalmethodologic limitations. They compared the outcome of a small number of nonrandomized subjects who were treated at two different centers. In addition, the length of follow-up was not standardized. Zeller and associates44have advocated the benefits of a work hardening program, but such a program has not yet been subjected to randomized clinical trials. According to the activity recall questionnaire, subjects in this study could be classified as sedentary to moderately active.45 Many, however, reported that they were unable to achieve the same level of activity in comparison to their preburn status. Significant correlations were observed between current weekly energy expenditure and knee strength, suggesting that part of the persistent muscle weakness could have resulted from deconditioning. It is not known at this time whether a longer outpatient rehabilitation program would have permitted the patients to achieve a greater fitness level and, thus, permitted them to return to their prior level of physical activity. To determine if further recovery is possible in this patient population, we are presently conducting a randomized clinical trial investigating the effects of high-resistance strength training on muscle strength and size and quality of life in individuals with major bums. Burns
of 530%
or >30%
of TBSA
and Their
TBSA of ~30% (n = 14)
1.05Rad Peaktorque (Nm) Work(Nm) Power (watts) 3.14Rad Peaktorque Work Power Values reported *p = .07.
as mean
Controls
Matching
TBSAof
Controls
>30%
(n = 16)
Burn
Control
Burn
Control
41.3 i- 14.4 334.4 ? 89.1 36.9 t 11.1
41.6 2 16.2 311.8 i 79.4 34.7 2 11.2
37.0 f 15.4 267.3 ir 131.0 30.1 k 15.1
39.5 2 14.6 320.6 F 148.2 35.1 2 17.1
29.8 t 11.7 246.7 k 76.9 68.7 i- 24.3
32.4 f 15.7 207.5 + 86.5 57.3 ?I 25.3
28.9 i 13.6 190.4 i- 118.0 53.3 t 33.8
29.7 i 12.3 233.2 '- 154.6 66.0 i 43.8"
f SD.
Arch
Phys
Med
Rehabil
Vol79,
February
1998
160
STRENGTH
Table
8: Elbow
Flexor
Torque,
Work,
and Power
IN PEOPLE
WITH
in Subjects
With
HEALED
Burns
BURNS,
of 530%
St-Pierre
or >30%
of TBSA
and Their
TBSA of ~30% (II = 14) BWll
1.05Rad Peak torque (Nm) Work (Nm) Power (watts) 3.14Rad Peak torque Work Power Values reported * p = .07.
as mean
Control
45.3 2 16.7 374.1 + 126.4 41.1 + 15.2
43.9 t 325.8 t 36.7 t
32.4 2 13.6 271.0 + 109.4 15.8 2 33.9
35.0 2 16.4 243.2 2 93.5 68.2 t- 28.4
rehabilitation after discharge from the acute care limits in the degree of muscle plasticity may underlie muscle weakness in individuals with burn injuries more than 30% of TBSA. More research will be shed additional light on the cause of persistent muscle after major bums.
Acknowledgments: The authors thank Jocelyne Fortin for contacting and screening eligible candidates, Rachel Marquis for her assistance in data collection, Mike Dispirit0 and Marc Dumont for data analysis, and Debby Knuutila for her editorial comments. Sincere thanks are extended to all the subjects who participated in the study. References 1. Deitch EA. The management of bums. N Engl J Med 1990;323: 1249-53. 2. Helm PA. Bum rehabilitation: dimentions of the problem. Clin Plast Surg 1992; 19:551-9. 3. Curreri PW, Luterman A, Braun DW, Shires GT. Bum injury: analysis of survival and hospitalization time for 937 patients. Ann Surg 1980; 192:472-7. 4. Muller MJ, Hemdon DN. The challenge of bums. Lancet 1994; 343:216-20. 5. Cronan T, Hammond J, Ward CG. The value of isokinetic exercise and testing in bum rehabilitation and determination of back-to-work status. J Bum Care Rehabil 1990; 11:224-7. 6. Helm PA, Kevorkian CG, Lushbaugh M, Pullium G, Heas MD, Cromes GF. Bum injury: rehabilitation management in 1982. Arch Phys Med Rehabil 1982;63:6-16. 7. Richard RL, Staley MJ. Bum patient evaluation and treatment planning. In: Richard RL, Staley MJ, editors. Bum care and rehabilitation: principles and practice. Philadelphia: F.A. Davis; 1994. p. 201. 20. 8. Harden NG, Luster SH. Rehabitilation consideration in the care of the acute bum patient. Crit Care Nurs Clin North Am 1991; 3:24553. 9. Apfel LM, Irwin CP, Staley MJ, Richard RL. Approaches to positioning the bum patient. In: Richard RL, Staley MJ, editors. Bum care and rehabilitation: principles and practice. Philadelphia: F.A. Davis; 1994. p. 221-41. 10. Humphrey CN, Richard RL, Staley MJ. Soft tissue management and exercise. In: Richard RL, Staley MJ, editors. Bum care and rehabilitation: principles and practice. Philadelphia: F.A. Davis; 1994. p. 324-60. 11. Daugherty MB, Carr-Collins JA. Splinting techniques for the bum patient. In: Richard RL, Staley MJ, editors. Bum care and rehabilitation: principles and practice. Philadelphia: F.A. Davis; 1994. p. 242323. 12. Blalock SJ, Bunker BJ, Moore JD, Foreman N, Walsh JF. The impact of bum injury: a preliminary investigation. J Bum Care Rehabil 1992; 13:487-92. 13. Cheng S, Rogers JC. Changes in occupational role performance after a severe bum: a retrospective study. Am J Occup Ther 1989; 43: 17.24.
Arch
Phys Med
Rehabil
Controls
17.3 101.6 14.6
Burn
Control
40.4 t 17.0 300.4 it 148.5 34.2 t 17.4
41.2 +- 17.1 339.4 t 175.5 37.3 -c 20.2
30.3 t 14.8 213.6 t 136.2 60.3 t 38.8
32.4 t 15.4 259.2 t 173.4 74.2 2 49.6*
-t SD.
CONCLUSION Insufficient setting or persistent involving needed to weakness
Matching
TBSA of 130% (n = 16)
Vol79,
February
1998
14. Malenfant D, Forget R, Papillon J, Amsel R, Frigon J-Y, Choiniere M. Prevalence and characteristics of chronic sensory problems in bum patients. Pain 1996;67:493-500. 15. Helm PA, Walker SC. Return to work after bum injury. J Bum Care Rehabil 1992; 13:53-7. 16. Cunningham JJ. Factors contributing to increased energy expenditure in thermal injury: a review of studies exploring indirect calorimetry. J Parenteral Enteral Nutr 1990; 14:649-56. 17. Garrel DG, de Jonge L. Thermogenic response to feeding in severely burned patients: relation to resting metabolic rate. Bums 1993; 19: 467-72. 18. Wood RR. Metabolic response to bum injury: nutritional implications. Semin Nephrol 1993; 13:359-70. 19. Tomera JF, Martyn J, Hoaglin DC. Neuromuscular dysfunction in bums and its relationship to bum size, hypermetabolism, and immunosuppression. J Trauma 1988;28:1499-504. 20. Odessey R, Parr B. Effect of insulin and leucine on protein turnover in rat soleus muscle after bum injury. Metabolism 1982;31:82-7. 21. Schantz P, Randall-Fox E, Hutchison W, Tyden A, Astrand P-A. Muscle fibre type distribution, muscle cross-sectional area and maximal voluntary strength in humans. Acta Physiol Stand 1983; 117:219-26. 22. Sallis JF, William HL, Wood PD, Fortmann SP, Rogers T, Blair SN, et al. Physical activity assessment methodology in the five-city project. Am J Epidemiol 1985;121:91-106. 23. Ainsworth BE, Haskell WL, Leon AS, Jacobs DR, Montoye HJ, Sallis JF, et al. Compendium of physical activities-classification of energy costs of human physical activities. Med Sci Sports Exert 1993;25:71-80. 24. Dishman RK, Steinhardt M. Reliability and concurrent validity for a 7-d re-call of physical activity in college students. Med Sci Sports Exert 1988;20:14-25. R, Casey K, Haskell WL. 25. Taylor CB, Coffey T, Berra K, Iaffaldano Seven-day activity and self-report compared to a direct measure of physical activity. Am J Epidemiol 1984; 120:818-24. 26. Blair SN, Haskell WL, Ho P, Paffenbarger RS, Vranizan KM, Farquhar JW, et al. Assessment of habitual physical activity by a sevenday recall in a community survey and controlled experiments. Am J Epidemiol 1985; 122:794-804. 27. Krupp LB, LaRocca NG, Muir-Nash J, Steinberg AD. The fatigue severity scale: Application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol 1989;46: 1121-3. 28. Packer TL, Sauriol A, Brouwer B. Fatigue secondary to chronic illness-postpolio syndrome, chronic fatigue syndrome, and multiple sclerosis. Arch Phys Med Rehabil 1994;75:1122-6. 29. Arvidsson I, Eriksson E, Knutsson E, Amer S. Reduction of pain inhibition on voluntary muscle activation by epidural analgesia. Orthopedics 1986;9:1415-9. 30. Stokes M, Young A. The contribution of reflex inhibition to arthrogenous muscle weakness. Clin Sci 1984;67:7-14. 31. Scott J, Huskisson EC. Graphic representation of pain. Pain 1976; 2: 175-84. 32. Hnik P, Holas M, Payne R. Reflex muscle atrophy induced by chronic peripheral nociceptive stimualtion. J Physiol 1977;73:24150. 33. Urbancova H, Hnik P, Vejsada R. Bone fracture induces reflex
STRENGTH
34.
35.
36. 37.
38. 39.
IN PEOPLE
WITH
muscle atrophy which Is sex-dependent. Physiol Res 1993;42:3540. Duvoisin MR, Convertino VA, Buchanan P, Gollnick PD, Dudley GA. Characteristics and preliminary observations of the influence of electromyostimulation on the size and function of human skeletal muscle during 30 days of simulated microgravity. Aviat Space Environ Med 1989;60:671-8. Ellis S, Kirby LC, Greenleaf JE. Lower extremity muscle thickness during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training. Aviat Space Environ Med 1993;64: 1011-5. Greenleaf JE, Bernauer EM, Ertl AC, Trowbridge TS, Wade CE. Work capacity during 30 days of bed rest with isotonic and isokinetic exercise training. J Appl Physiol 1989; 67: 1820-6. Greenleaf JE, Bernauer EM, Ertl AC, Bulbulian R, Bond M. Isokinetic strength and endurance during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training. Aviat Space Environ Med 1994;65:45-50. Leblanc AD, Schneider VS, Evans HJ, Pientok C, Rowe R, Spector E. Regional changes in muscle mass following 17 weeks of bed rest. J Appl Physiol 1992;73:2172-8. Suzuki Y, Murakami T, Haruna Y, Kawakubo K, Goto S, Makita Y, et al. Effects of 10 and 20 days bed rest on leg muscle mass and strength in young subjects. Acta Physiol Stand 1994; 150 Suppl 616:5-18.
HEALED
BURNS,
161
St-Pierre
40. Gregor RJ, Edgerton VR, Perrine JJ, Campion DS, DeBus C. Torque-velocity relationships and muscle fiber composition in elite female athletes. J Appl Physiol 1979;47:388-92. 4 1. Thorstensson A, Grimby G, Karlsson J. Force-velocity relations and fiber composition in human knee extensor muscles. J Appl Physiol 1976;40:12-6. 42. Fang CH, James HJ, Ogle C, Fischer JE, Hasselgren PO. Influence of bum injury on protein metabolism in different types of skeletal muscle and the role of glucocorticoids. J Am Co11 Surg 1995; 180: 33-42. 43. Falduto MT, Czerwinski SM, Hickson RC. Glucocorticoid-induced muscle atrophy prevention by exercise in fast-twitch fibers. J Appl Physiol 1990;69:1058-62. 44. Zeller J, Sturm G, Cruse CW. Patients with burns are successful in work hardening programs. J Burn Care Rehabil 1993; 14:189-96. 45. Dishman RK, Darracott CR, Lambert LT. Failure to generalize determinants of self-reported physical activity to a motion sensor. Med Sci Sports Exert 1992;24:904-10. Suppliers a. Cybex, 10 Trotter Drive, Medway, MA 02053. b. Gold Tech, 135 Dufresne, St.-Basil Le Grand, Quebec J3W lB6, Canada. c. Flex-0-Calc; Electrosport, Inc., Box 413; Stn “A” Weston, Ontario M9N 3N1, Canada.
Arch
Phys
Med Rehabil
Vol79,
February
1998
Muscle Strength in Individuals Diane M.M. St-Pierre, PhD, Manon
With Healed Burns
ChoiniBre, PhD, Robert Forget, PhD, Dominique
ABSTRACT. St-Pierre DMM, Choiniere M, Forget R, Garrel DR. Muscle strength in individuals with healed burns. Arch Phys Med Rehabil 1998;79:155-61. Objective: To quantify the long-term effects of bums on muscle strength and to investigate the impact of the initial severity of the trauma on muscle strength. Design: Cross-sectional study comparing individuals with healed bums to nonbumed control individuals matched for age, gender, body mass index, and physical activity level. Setting: Subjects were selected from the data bank of a bum center of a large Montreal teaching hospital and tested in a university laboratory. Patients: Thirty subjects (mean age, 36.3 t 11.5yrs) with second- and third-degree bums covering 15% to 75% of total body surface area (TBSA) (mean, 35.5% -t 15.9%) were evaluated more than 1 year after discharge (mean, 37.3 ? 20.4 months; range, 15 to 92 months). Thirty unburned subjects were recruited from the community at large Main Outcome Measure: Maximal torque, work, and power developed by the elbow and knee flexors and extensors. Results: Subjects with burns of >30% of TBSA produced significantly less torque, work, and power in the quadriceps than control subjects (15.2% to 20.5% depending on velocity @ < ,051). The ability to develop muscle power at the elbow was also compromised in the severely burned subjects (19.2% in extension and 18.7% in flexion [p = .07]) at the faster velocities. No differences were observed between controls and patients with small burn injuries (TBSA of <30%). Conclusion: Patients who had severe bums (TBSA of >30%) had weaker muscles even years after the trauma, suggesting either an inability to fully recover or insufficient rehabilitation. 0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
B
URN INJURIES are common, affecting approximately 1% of the population of the United States each year,‘*’ and are classified as the second major cause of accidental deaths after motor vehicle accidents.‘,3 The survival of the patient is the paramount concern in the acute stage of treatment of major bums, and survival rates have improved considerably over the past couple of decades.‘,3,4 From the School of Physical & Occupational Therapy, McGill University (Dr. St-Pierre); Centre des Grands BriWs, Hate1 Dieu Hospital of Montreal (Drs. Choir&e, Garrel); and the Departments of Surgery and Anesthesia (Dr. Choin&e). Ecole de Rkadaotation (Dr. Forget). and Deoartment of Nutrition (Dr. Garr&, University of hiontreal,‘Montre$ &ebec, danada. Submit for publication February 14, 1997. Accepted in revised form July 25, 1997. Research supported by R&au-Fonds des Pompiers du Qukbec pour les Grands Br%Bs (FPQGB) and Fonds de la Recherche en Sante du Qubbbec. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Diane St-Pierre, PhD, Associate Professor, School of Physical & Occupational Therapy, McGill University, 3654 Drummond Street, Mont&11, QuCbec, Canada H3GlY5. 0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003-9993/98/7902-4386$3.00/O
R. Garrel, MD
Rehabilitation is fundamental for the overall recovery of the patient. The long-term goal of therapy is to return the patient back into society in as near to the patient’s normal prebum functional capacity as possible.5-7To this end it is important to prevent soft-tissue deformity or bum scar contractures, protect the healing skin graft, maintain or restore cardiopulmonary, respiratory, and musculoskeletal function; and promote rapid return to independence in self-care and preburn lifestyle functions.5,7.8Good therapeutic positioning is important to reduce swelling and prevent contracturesg Exercise can help to control edema and attenuate tendon adherence, joint stiffness, capsular shortening, muscle atrophy, and deconditioning.7~8~‘o Splinting may be required to protect the healing graft or help prevent deformities.” Treatments often extend over months after discharge from the hospital, and in many cases full return to a prior level of functioning is not achieved.‘2.‘3Persistent muscle weakness has been reported 8 to 9 months after second- to third-degree bums to an extremity in a small group of patients.’ Blalock and colleagues’* observed that many people with burn injuries reported problems more than 1 year later involving the skin (sensitivity, irritation, scartissue), appearance, ability to work, mobility, and psychological well-being. Impairments in home management and leisure roles have also been reported.r3 Limited range of motion, poor dexterity, loss of mobility, and intolerance for standing and walking, as well as pain and decreased strength and endurance, have been cited as major underlying factors precluding the individual from becoming fully independent in self-care, home management, work, and leisure.r3 In a study with more than 400 patients, Malenfant et alI4reported that more than 30% of bum patients developed chronic pain problems that could affect their daily functioning. Little information is available on the time course of recovery of muscle size and strength following a major bum or on the impact of the severity of the initial trauma on outcome. Some observations suggest that the final functional outcome may depend on the initial extent of the injury.15 Indeed, burn severity affects the magnitude and duration of the hyper metabolic response that is initiated by the injury. The basal metabolic rate can increase up to twice normal values in patients with burns greater than 50% of total body surface area (TBSA).r6,i7Skeletal muscle proteins are particularly vulnerable, undergoing proteolysis to provide amino acids for hepatic gluconeogenesis, wound repair, and acute-phase protein synthesis.‘* This process affects not only the involved musclesbut also those not directly involved with the thermal trauma.‘9.20Therefore, because muscle strength is proportional to muscle cross-sectionalarea’i and the extent of muscle atrophy is dependent on the severity of the initial thermal injury, the ultimate recovery of muscle size and strength may be influenced by the extent of the initial burn injury. The objective of this study was twofold: (1) to quantify the long-term effects of bums on muscle strength; and (2) to investigate the impact of the initial severity of the trauma on muscle strength. METHODOLOGY Subjects Burn subjects. To be included in the study, subjects had to meet the following inclusion criteria: (1) men or women between 18 to 70 years of age who had sustained burn injuries to Arch
Phys Med
Rehabil
Vol79,
February
1998
156
STRENGTH
Table
Subjects
1: Subject
Burn
Control
IN PEOPLE
WITH
Characteristics:
BUWl
HEALED
BURNS,
Age, Sex, Weight,
St-Pierre
and Height
Control
Burn
COlltd
BWll
Control
TBSA of 530% 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Mean 2 SD TBSA of >30% 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Mean ? SD
38 33 27 27 39 40 54 45 25 58 40 53 27 54 40.0 t 11.4
44 30 29 27 40 48 59 47 24 61 38 46 28 47 40.6 -c 11.8
M M M M M M F M M M M M M F -
M M M M M M F M M M M M M F -
88.6 64.0 68.2 87.7 65.9 59.1 62.0 72.7 67.3 84.1 63.6 93.2 75.0 61.4 72.3 2 11.5
95.5 75.0 70.5 88.2 70.5 61.4 63.6 77.3 65.9 88.6 70.5 86.4 74.1 65.9 75.2 k 10.6
172.5 165.0 172.5 175.0 170.0 167.5 165.0 167.5 177.5 177.5 165.0 172.5 172.5 157.5 169.8 2 5.6
172.5 165.0 170.0 177.5 170.0 167.5 165.0 165.0 177.5 177.5 162.5 170.0 175.0 160.0 169.6 -c 5.8
44 30 37 25 31 51 29 25 29 54 64 51 42 30 47 48 39.8 t 11.9
46 25 37 28 23 45 27 33 30 52 69 51 39 31 41 47 39.0 -t 12.3
M M F M M M M M F M M F M F M M
M M F M M M M M F M M F M F M M
78.6 90.9 53.6 59.1 95.5 93.2 90.9 59.1 47.3 97.3 83.2 61.4 88.6 58.6 86.4 84.1 76.7 i- 17.1
74.1 90.9 56.8 57.3 90.9 90.0 97.7 60.0 51.8 102.3 79.6 58.6 84.1 59.1 84.6 82.7 76.3 t 16.6
177.5 177.5 157.5 165.0 190.0 167.5 175.0 157.5 155.0 180.0 180.0 167.5 185.0 150.0 175.0 170.0 170.6 2 11.4
150.0 182.5 155.0 165.0 185.0 172.5 180.0 162.5 160.0 182.5 175.0 165.0 180.0 152.5 172.5 170.0 169.4 -t 11.3
Grand
39.9 ? 11.5
39.7 2 11.9
-
-
74.7 t 14.7
75.8 k 13.9
170.3 i- 9.0
169.5 2 9.0
mean
F SD
the upper extremities; (2) presence of second- to third-degree bums covering at least 15% of TBSA; (3) elapsed time since injury longer than 12 months; and (4) consent to participate. Upper extremity bums were required because subjects in this study took part concurrently in another study evaluating cutaneous sensitivity in the hand and arm areas. Excluded were subjects whose bums covered less than 15% of TBSA, because generalized muscle weakness would be minimal with this severity of bum.” Also excluded were patients with a history of alcohol abuse, diabetes, or other predisposing causes of neuropathy. Patients with psychiatric and neurologic disorders documented in their medical files were excluded along with those unable to communicate because of language. Thirty bum patients, who had been hospitalized at a hospital bum center in Montreal took part in the study. The study was approved by the Ethics Committees of the hospital and university. Control healthy subjects. The bum patients were pairmatched to control unburned individuals who were recruited from the community at large through personal contacts and advertising. They were paired as closely as possible to the bum subjects for age, stature (height and weight), and physical activity level. The fitness level of the control subjects was assessed initially by phone. The subject was asked to rate his or her perceived level of fitness (sedentary, moderately fit, or very fit). If a possible match was found, a more detailed pairing was done by administering a 7-day physical activity recall questionnaire,” administered by an interviewer (approximately 15 to 20 min). The subject is asked for a total activity recall that includes, home, work, and leisure activities. The subject is initially asked to recall the number of hours slept during the week days and weekend, then is asked to recall how many hours were spent
Arch
Phys
Med Rehabil
Vol 79, February
1998
doing moderate, hard, or very hard activities. Examples of activities in each category (house work, work, and leisure) are provided in the questionnaire. For activities not listed in the questionnaire, clarification of activity intensity was achieved by consulting the compendium of physical activity classification of energy costs of human activities.23 Light activities were calculated by subtraction. Evaluation of Muscle Strength Strength of the knee and elbow flexors and extensors were evaluated bilaterally with a Cybex isokinetic dynamometer,” linked to an IBM PC-AT computerh with commercially available software.’ For the knee measurements, the individual was sitting with stabilizing straps around the chest, pelvis, and thigh. Knee torque measurements were corrected for the effects of gravity. For the elbow measurements, the individual was supine with the shoulder abducted to 1.57radian (rad). Stabilizing straps were secured to the chest, pelvis, and arm. The axis of rotation of the dynamometer was visually aligned to the axis of rotation of either the knee or elbow joints. Subjects were familiarized with the Cybex and tested at 1.05 and 3.14rad/sec. The speeds were not randomized. Four maximal contractions were recorded at each speed with a 2-min rest period between each set. Averages were calculated on the best three of four contractions. In addition, the values of both limbs were combined and averaged. Peak torques and those developed at knee angles of .79 and 1.05rad and elbow angles of 1.57rad were retained for further analysis. Total work and average power were also calculated. Reliability of the above measurements was established by testing nine bum subjects and nine control subjects on two different occasions within a 2-week period.
STRENGTH
Table
2: Subject
Characteristics: Burn
Subjects
TBSA (%) Burn
TBSA of ~30% 1 2 3 4 5
6 7 8
9 IO 11 12 13 14
Mean + SD TBSA of >30% 1
23.4
2 3 4 5 6 7
8 9 10 11 12 13 14 15
16 Mean + SD Grand mean + SD
46.1
Occupation, TBSA
Occupation Burn
Control
15 16 16 20 20 23 25 25 25 26 26 30 30 30
FTW U
u
FTW FTW
s
31 32 33 35 35 37 40 40 42 43 43 60 60 62 70 75
FTW FTW FTW M FTW FTW S U FTW PTW U FTW M FTW FTW PTW
FlW FTW PTW FTW S FTW FTW FTW FTW U U FTW FTW FTW FTW FTW
-
-
+-5.2
2
FTW U FTW PTW U FTW PTW FTW FTW FTW PTW
PTW FTW FTW F-i-W FTW FTW FTW U FTW FTW FTW
14.3
35.5 ? 15.9
Abbreviations: FTW, full-time work; PTW, part-time M, missing data.
Physical
IN PEOPLE
Activity,
Weekly Physical Activity Burn 384.3 266.5 345.5 474.0 256.8 281.3 285.0 228.0 255.8 327.8 508.5 292.8 528.8 256.0 335.1 + 100.6 280.0 578.0 246.5 316.8 316.0 356.0 286.5
and (METS)
559.3 297.3 266.3 325.0 245.5 235.3 270.0 239.3 258.0 296.0 269.5 298.5 381.3 363.8 307.5 1. 84.1
288.0 233.0 323.5 313.3 i 79.1 323.4 2 88.8
324.6 i- 94.1
270.0 302.8 322.0 248.0
HEALED
BURNS,
157
St-Pierre
or her perceived level of pain during testing by tracing a vertical mark on a lo-cm horizontal line with the ends marked by the expressions “no pain” and “unbearable pain.“31
Control
238.5 308.8 288.5 398.5 300.8 337.0 425.0 398.8 268.8 397.0 272.5 285.0 653.5 260.8 336.5 263.3 339.6 i 102.0
292.0
WITH
work; S, studies; U, unemployed;
Data Analysis Baseline characteristics (age, height, weight, weekly energy expenditure, perceived general fatigue) between control and burn subjects were compared with t tests. Analysis of variance (ANOVA) for repeated measures was used to determine significant strength differences between group (bum patients and controls), extent of injury (burned more or less than 30% TBSA), speed (1.05 and 3.14rad/sec) and muscle group (flexion and extension), as well as possible interactions between these factors. Analysis was done on the average response obtained from the bilateral measurements and expressed in either absolute values or relative to body mass index. If significant group interactions were found, simple main effects were calculated to bring out differences between bum patients and controls. To test the homogeneity of the various strength measures, Cronbath’s alpha was calculated for control (a! = .98) and burn subjects (a = .99). Because of this high level of homogeneity, strength measurements were converted into z scores (to account for differences in unit of measurement) and averaged to obtain a global strength score. Pearson correlation coefficients were determined between the global strength score and variables susceptible of influencing strength (age, activity level, length of time since injury, fatigue score). Test-retest reliability was determined with the intraclass correlation coefficient (ICC) applied to the repeated measures ANOVA analysis. Possible differences in fatigue perception between control and bum subjects were determined by t tests. RESULTS
Other Measures Fitness level. A 7-day activity recall questionnaire was used to quantify the average weekly energy expenditure.22 The questionnaire has been shown to be reliable, with Y values ranging from .75 to .84.24It has been validated against a daily selfreport log24,25and an ambulatory solid-state minicomputer that measures continuous heart rate and motion.” The questionnaire has also been observed to be sensitive to changes in physical activity status with training.26 Weekly energy expenditures were calculated in metabolic equivalents (METS) based on the information obtained using the questionnaire. Sleep was estimated as lMET, light activity as l.SMETS, moderate activity as 4METS, hard activity as 6METS, and very hard activity as lOMETS.” MET values were multiplied by the number of hours spent in each of the five categories and the products summed to give total number of METS per week. Fatigue. General daily fatigue was measured subjectively with the Fatigue Severity Scale and a visual analogue scale (VAS). The Fatigue Severity Scale was originally designed to measure fatigue in people with multiple sclerosis.” It comprises a list of nine statements, rated on a scale of 1 to 7. The scale has been shown to have internal consistency, stability over time, and sensitivity to clinically significant change.27It has been used to evaluate fatigue in postpolio and chronic fatigue syndromes.** Each participant was also asked to rate his or her general level of fatigue with a VAS marked with the expressions “no fatigue” and “extreme fatigue.” Pain. Pain can influence the measurement of muscle strength.29,30Therefore, to control for the possible confounding effects of pain during testing, a VAS scale was administered. Presence of pain during testing was evaluated by asking the subject immediately after each set of measurement to rate his
Subject Characteristics The characteristics of the subjects are presented in tables 1 and 2. The sample of bum subjects was comprised of 6 women and 24 men who had sustained their burn injuries a mean of 37.7 ? 20.4 months before testing (range 15 to 92 months). The average extent of their bums was 35.5% ? 15.9% of TBSA (range, 15% to 75%). Sixteen subjects had burns covering more than 30% of TBSA, and 62% of these patients had both upper and lower extremity burns. Similarly, 64% of patients whose bums covered less than 30% TBSA had both upper and lower Table
3: ICCs for Strength Measures of Knee Extensors Control and Burn Subjects Extensors
and Flexors
in
Flexors
Burn
Control
BLIrn
Control
1.05Rad Peak torque 1.05Rad .79Rad Work Power 3.14Rad Peak torque 1.05Rad .79Rad Work Power
.81 .68 .78 .a8 .78
.92 .93 .87 .98 .95
.a9 .90 .90 .93 .91
.93 .91 .92 .98 .96
.a7 .86 .82 .92 .85
.93 .91 .93 .96 .90
.92 .81 .76 .93 .90
.a4 .72 .67 .91 .86
Average
.82
.93
.aa
.a7
In each burn and control group, n = 9. 1.05 and 0.79rad represent the torque developed at the corresponding angles. Work represents the total work performed during the contractions, and power represents the average power developed.
Arch
Phys Med
Rehabil
Vol79,
February
1998
158
STRENGTH
IN PEOPLE
WITH
HEALED
Table
4: ICCs for Strength Measures of Elbow Extensors Control and Burn Subjects
and Flexors
in
taken at the knee (table 3). Good reliability (ICC between 0.6 and 0.8) was observed for most measurements taken at the elbow (table 4). The average pain perceived during testing was below 0.5 on the VAS in all burn (n = 30) and control subjects (0.3 2 1.1, II = 30). For comparison between groups, only absolute peak torques, total work, and average power values are reported, as similar information was gained from joint-specific torques and from torque, work, and power values normalized to body mass index. No statistically significant difference in strength was observed between subjects with bums less than 30% TBSA and their matched controls (tables 5 through 8). Similarly, no difference in knee flexor torques were observed between control subjects and those burned more than 30% of TBSA (table 6). In contrast, knee extensor muscle strength was not completely recovered in subjects burned 30% or more of TBSA. Differences in peak torque (100 - bum value/control value X 100) at 3.14rad/sec (16.0% [p < .05]) and total work produced at 1.05 (15.2% [p < .OOl]) and 3.14rad/sec (20.5% [p < .OOl]), as well as the average power developed at 3.14rad/sec (17.8% [p < .002]), were observed between severely burned subjects and their matching controls (table 5). The ability to develop muscle power at the elbow was also compromised in the severely burned subjects (19.2% in extension and 18.7% in flexion [p = .07]), at the faster velocities (tables 7 and 8).
FleXlrs
EXtMWXS
Burn
Control
Bllrn
Control
.a5
l.OSRad Peak torque 1.57Rad Work Power 3.14Rad Peak torque 1.57Rad Work Power
.86 .93 .75
.75 .72 .80 .74
.82 .77 .91 .74
.77 .81 .81 .76
.77 .77 .92 .79
.71 .69 .68 .64
.76 .79 .90 .76
.73 .75 .77 .75
Average
.83
In each burn and control described in table 3.
group,
.72
.81
n = 9. Rad values,
work,
.77 and power
as
extremity bums. All patients had received skin grafting (partial thickness skin grafting) under general anesthesia. All except two patients had a thermal injury. One subject had a chemical bum, and another had an electrical bum. Both of these subjects were among those whose bums covered less than 30% TBSA. There was no significant age difference between subjects burnt more or less than 30% of TBSA. The average length of hospitalization was 46.6 2 28.7 days. Patients burned more than 30% of TBSA stayed in the hospital significantly longer than those with less severe bums (58.6 +- 30.6 vs 32.8 ? 19.2 days, respectively). Physiotherapy was provided to both groups of patients on a daily basis. Initial treatment focused on range of motion exercises. If patients were alert and could collaborate, they were given an exercise program to do on their own. After skin grafting or wound healing, prolonged progressive stretching, strength, and endurance exercises were added to the program. Upon discharge from the acute care facility, four patients were sent to a rehabilitation center, where they received daily treatment. Three of these patients belonged to the group with bums of less than 30% of TBSA. The other patients were discharged home and were seen in an outpatient clinic up to four times per week. The length of time between injury and testing was similar in both groups of patients (35.2 + 13.8 vs 40.6 5 26.3 months, respectively [p > .OS]). Bum and control subjects did not differ significantly in age, body stature, laterality, or weekly energy expenditure (tables 1 and 2). Measures were similar in bum and control groups on the Fatigue Severity Scale (4.6 ? 1.2 and 4.7 ? 1.1, respectively) and the VAS measuring fatigue (3.3 2 2.4 and 3.4 ? 2.2, respectively).
For the burned subjects, significant correlations were observed between knee strength and current weekly energy expenditure (Y = .38, p = .02) and generalized fatigue perception, as measured by the Fatigue Severity Scale (1. = .32, p = .04) and the VAS (I = -.34, p = .03). There was no significant relationship between the knee strength measures and the length of time between trauma and testing. For control subjects, significant correlations were observed between physical activity level and knee strength (I = .30, p = .05). No other significant correlations were observed.
DISCUSSION The most important finding in this study was the persistence of muscle weakness in people burned more than 30% of TBSA. Indeed, muscle weakness (15% to 20%) was still present a mean of 35 months after injury. In contrast, the muscle strength of subjects with less severe bums was comparable to that of healthy controls. The difference in the extent of recovery between the two groups could not be attributed to age because both groups of patients were of similar age. There are, however, other differences between the two groups of patients that may have contributed to these results. There may
Strength testing was found to be reliable and painless. Excellent reliability (ICC > .80) was found for most measurements 5: Knee Extensor
Torque,
Work,
and Power
in Subjects
St-Pierre
Source of Variation in the Strength Measures
Muscle Strength
Table
BURNS,
With
Burns
of 530%
or >30%
of TBSA
and Their
TBSA of 530% (n = 141
1.05Rad Peak torque (Nm) Work (Nm) Power (watts) 3.14Rad Peak torque Work Power Values reported l p < .05. + p < ,002. *p < .OOl.
Arch
Phys Med
as mean
Rehabil
February
Controls
In = 16)
Burn
Control
Burn
Control
151.1 + 41.3 850.0 t 165.6 120.3 + 25.1
149.8 -t 33.9 792.4 z 178.8 115.9 2 26.6
136.6 i- 40.0 715.5 2 248.3 107.7 2 40.4
152.8 + 40.2 843.5 + 271.4* 119.7 + 39.7
116.0 & 36.2 661.4 k 160.6 224.8 ? 59.1
116.8 ? 30.7 618.2 +- 136.3 214.3 + 46.9
103.8 t 38.1 542.0 2 226.6 190.6 I 85.0
123.6 -c 40.7* 681.7 ? 232.6* 232.0 2 81.9’
5 SD.
Vol79,
Matching TBSA of >30%
1998
STRENGTH
Table
6: Knee
Flexor
Torque,
Work,
and Power
IN PEOPLE
WITH
in Subjects
With
HEALED
Burns
BURNS,
of 530%
159
St-Pierre
or >30%
of TBSA
and Their
TBSAofr30%
Matching TBSAof>30%
(n = 14)
(n = 16) Control
Burn
Control
86.5 2 25.5 492.4 i 105.6 70.2 2 17.2
82.9 t 22.8 443.2 + 120.9 64.2 I 17.4
77.9 t 26.0 409.4 F 148.9 60.6 f 23.6
79.8 2 31.9 456.1 t 198.6 63.6 i 27.2
64.8 2 19.9 380.2 + 103.2 224.8 + 59.1
59.5 t 16.8 324.6 t 99.8 214.3 t 46.9
59.6 2 26.1 311.0 ? 143.0 190.6 k 85.0
59.9 2 24.6 328.8 2 171.4 232.0 + 81.9
BUi-fl
1.05Rad Peaktorque (Nm) Work(Nm) Power (watts) 3.14Rad Peaktorque Work Power Values
reported
as mean
t SD.
have been a greater degree of muscle atrophy in patients with more severe burns. The severity of the injury could have influenced the initial degree of associated muscle atrophy both directly and indirectly: directly because of the detrimental effect of burn severity on muscle protein catabolism,1g*20and indirectly because subjects with severe burns may have been confined to bed for long periods of time or may have experienced more pain. Indeed, chronic nociceptive stimulation has been shown to induce muscle atrophy (reflex muscular atrophy).32,33Bed rest (deconditioning) is also associated with a loss of muscle mass and strength.34-3gThese changes are significant after only 2 weeks of bed rest3’ and affect predominantly the antigravity muscles of the lower extremity.38 The combined effect of protein catabolism and bed rest may have contributed to the observation that differences in muscle strength between burn and control subjects were more predominant in the lower extremities. Indeed, subjects who were burnt more than 30% of TBSA were hospitalized for longer periods of time than subjects with less severe burns (59 vs 33 days). The fact that strength deficits were more marked at the faster velocities suggests a preferential atrophy of fast-twitch fibers. The ability to torque at the fast velocities has been found to be correlated to the percent area occupied by fast-twitch fibers.40,41 It has been suggested that burn-induced muscle proteolysis may be mediated by glucocorticoids.42 Fast-twitch fibers are more sensitive to the catabolic effect of glucocorticosteroids on protein turnover than slow-twitch fibers.43 Myofibrillar protein breakdown was reported to be more severe in the rat extensor digitomm longus than in the soleus, in animals burned 30% of TBSA.42Furthermore, a glucocorticoid receptor antagonist (RU 38486) was able to prevent the increase in muscle proteolysis4’ Persistent muscle weakness may also have resulted from incomplete rehabilitation. Follow-up of these subjects after discharge from the acute care setting was often not optimal, yet they may still have had substantial muscle atrophy and weakness. All patients were seen daily by a physiotherapist while in Table
7: Elbow
Extensor
Torque,
Work,
and Power
in Subjects
With
the acute care facility. Only four patients were transferred to a rehabilitation facility for further intense rehabilitation. The other patients were discharged home and seen up to four times a week in outpatient clinics. The fact that only four patients were transferred to a rehabilitation unit may seem surprising at first glance; however, the length of stay in the acute care facility was long. More protracted rehabilitation may be required for further recovery of muscle function after discharge, but few studies have investigated the effects of additional exercise programs on patient outcome. Cronan and colleagues’ reported less muscle weakness in bum subjects, who, in addition to a treatment program consisting of splinting, stretching, and isometric and isotonic work loads, participated in a cardiovascular training program and a velocity-spectrum isokinetic protocol. Their study, however, had severalmethodologic limitations. They compared the outcome of a small number of nonrandomized subjects who were treated at two different centers. In addition, the length of follow-up was not standardized. Zeller and associates44have advocated the benefits of a work hardening program, but such a program has not yet been subjected to randomized clinical trials. According to the activity recall questionnaire, subjects in this study could be classified as sedentary to moderately active.45 Many, however, reported that they were unable to achieve the same level of activity in comparison to their preburn status. Significant correlations were observed between current weekly energy expenditure and knee strength, suggesting that part of the persistent muscle weakness could have resulted from deconditioning. It is not known at this time whether a longer outpatient rehabilitation program would have permitted the patients to achieve a greater fitness level and, thus, permitted them to return to their prior level of physical activity. To determine if further recovery is possible in this patient population, we are presently conducting a randomized clinical trial investigating the effects of high-resistance strength training on muscle strength and size and quality of life in individuals with major bums. Burns
of 530%
or >30%
of TBSA
and Their
TBSA of ~30% (n = 14)
1.05Rad Peaktorque (Nm) Work(Nm) Power (watts) 3.14Rad Peaktorque Work Power Values reported *p = .07.
as mean
Controls
Matching
TBSAof
Controls
>30%
(n = 16)
Burn
Control
Burn
Control
41.3 i- 14.4 334.4 ? 89.1 36.9 t 11.1
41.6 2 16.2 311.8 i 79.4 34.7 2 11.2
37.0 f 15.4 267.3 ir 131.0 30.1 k 15.1
39.5 2 14.6 320.6 F 148.2 35.1 2 17.1
29.8 t 11.7 246.7 k 76.9 68.7 i- 24.3
32.4 f 15.7 207.5 + 86.5 57.3 ?I 25.3
28.9 i 13.6 190.4 i- 118.0 53.3 t 33.8
29.7 i 12.3 233.2 '- 154.6 66.0 i 43.8"
f SD.
Arch
Phys
Med
Rehabil
Vol79,
February
1998
160
STRENGTH
Table
8: Elbow
Flexor
Torque,
Work,
and Power
IN PEOPLE
WITH
in Subjects
With
HEALED
Burns
BURNS,
of 530%
St-Pierre
or >30%
of TBSA
and Their
TBSA of ~30% (II = 14) BWll
1.05Rad Peak torque (Nm) Work (Nm) Power (watts) 3.14Rad Peak torque Work Power Values reported * p = .07.
as mean
Control
45.3 2 16.7 374.1 + 126.4 41.1 + 15.2
43.9 t 325.8 t 36.7 t
32.4 2 13.6 271.0 + 109.4 15.8 2 33.9
35.0 2 16.4 243.2 2 93.5 68.2 t- 28.4
rehabilitation after discharge from the acute care limits in the degree of muscle plasticity may underlie muscle weakness in individuals with burn injuries more than 30% of TBSA. More research will be shed additional light on the cause of persistent muscle after major bums.
Acknowledgments: The authors thank Jocelyne Fortin for contacting and screening eligible candidates, Rachel Marquis for her assistance in data collection, Mike Dispirit0 and Marc Dumont for data analysis, and Debby Knuutila for her editorial comments. Sincere thanks are extended to all the subjects who participated in the study. References 1. Deitch EA. The management of bums. N Engl J Med 1990;323: 1249-53. 2. Helm PA. Bum rehabilitation: dimentions of the problem. Clin Plast Surg 1992; 19:551-9. 3. Curreri PW, Luterman A, Braun DW, Shires GT. Bum injury: analysis of survival and hospitalization time for 937 patients. Ann Surg 1980; 192:472-7. 4. Muller MJ, Hemdon DN. The challenge of bums. Lancet 1994; 343:216-20. 5. Cronan T, Hammond J, Ward CG. The value of isokinetic exercise and testing in bum rehabilitation and determination of back-to-work status. J Bum Care Rehabil 1990; 11:224-7. 6. Helm PA, Kevorkian CG, Lushbaugh M, Pullium G, Heas MD, Cromes GF. Bum injury: rehabilitation management in 1982. Arch Phys Med Rehabil 1982;63:6-16. 7. Richard RL, Staley MJ. Bum patient evaluation and treatment planning. In: Richard RL, Staley MJ, editors. Bum care and rehabilitation: principles and practice. Philadelphia: F.A. Davis; 1994. p. 201. 20. 8. Harden NG, Luster SH. Rehabitilation consideration in the care of the acute bum patient. Crit Care Nurs Clin North Am 1991; 3:24553. 9. Apfel LM, Irwin CP, Staley MJ, Richard RL. Approaches to positioning the bum patient. In: Richard RL, Staley MJ, editors. Bum care and rehabilitation: principles and practice. Philadelphia: F.A. Davis; 1994. p. 221-41. 10. Humphrey CN, Richard RL, Staley MJ. Soft tissue management and exercise. In: Richard RL, Staley MJ, editors. Bum care and rehabilitation: principles and practice. Philadelphia: F.A. Davis; 1994. p. 324-60. 11. Daugherty MB, Carr-Collins JA. Splinting techniques for the bum patient. In: Richard RL, Staley MJ, editors. Bum care and rehabilitation: principles and practice. Philadelphia: F.A. Davis; 1994. p. 242323. 12. Blalock SJ, Bunker BJ, Moore JD, Foreman N, Walsh JF. The impact of bum injury: a preliminary investigation. J Bum Care Rehabil 1992; 13:487-92. 13. Cheng S, Rogers JC. Changes in occupational role performance after a severe bum: a retrospective study. Am J Occup Ther 1989; 43: 17.24.
Arch
Phys Med
Rehabil
Controls
17.3 101.6 14.6
Burn
Control
40.4 t 17.0 300.4 it 148.5 34.2 t 17.4
41.2 +- 17.1 339.4 t 175.5 37.3 -c 20.2
30.3 t 14.8 213.6 t 136.2 60.3 t 38.8
32.4 t 15.4 259.2 t 173.4 74.2 2 49.6*
-t SD.
CONCLUSION Insufficient setting or persistent involving needed to weakness
Matching
TBSA of 130% (n = 16)
Vol79,
February
1998
14. Malenfant D, Forget R, Papillon J, Amsel R, Frigon J-Y, Choiniere M. Prevalence and characteristics of chronic sensory problems in bum patients. Pain 1996;67:493-500. 15. Helm PA, Walker SC. Return to work after bum injury. J Bum Care Rehabil 1992; 13:53-7. 16. Cunningham JJ. Factors contributing to increased energy expenditure in thermal injury: a review of studies exploring indirect calorimetry. J Parenteral Enteral Nutr 1990; 14:649-56. 17. Garrel DG, de Jonge L. Thermogenic response to feeding in severely burned patients: relation to resting metabolic rate. Bums 1993; 19: 467-72. 18. Wood RR. Metabolic response to bum injury: nutritional implications. Semin Nephrol 1993; 13:359-70. 19. Tomera JF, Martyn J, Hoaglin DC. Neuromuscular dysfunction in bums and its relationship to bum size, hypermetabolism, and immunosuppression. J Trauma 1988;28:1499-504. 20. Odessey R, Parr B. Effect of insulin and leucine on protein turnover in rat soleus muscle after bum injury. Metabolism 1982;31:82-7. 21. Schantz P, Randall-Fox E, Hutchison W, Tyden A, Astrand P-A. Muscle fibre type distribution, muscle cross-sectional area and maximal voluntary strength in humans. Acta Physiol Stand 1983; 117:219-26. 22. Sallis JF, William HL, Wood PD, Fortmann SP, Rogers T, Blair SN, et al. Physical activity assessment methodology in the five-city project. Am J Epidemiol 1985;121:91-106. 23. Ainsworth BE, Haskell WL, Leon AS, Jacobs DR, Montoye HJ, Sallis JF, et al. Compendium of physical activities-classification of energy costs of human physical activities. Med Sci Sports Exert 1993;25:71-80. 24. Dishman RK, Steinhardt M. Reliability and concurrent validity for a 7-d re-call of physical activity in college students. Med Sci Sports Exert 1988;20:14-25. R, Casey K, Haskell WL. 25. Taylor CB, Coffey T, Berra K, Iaffaldano Seven-day activity and self-report compared to a direct measure of physical activity. Am J Epidemiol 1984; 120:818-24. 26. Blair SN, Haskell WL, Ho P, Paffenbarger RS, Vranizan KM, Farquhar JW, et al. Assessment of habitual physical activity by a sevenday recall in a community survey and controlled experiments. Am J Epidemiol 1985; 122:794-804. 27. Krupp LB, LaRocca NG, Muir-Nash J, Steinberg AD. The fatigue severity scale: Application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol 1989;46: 1121-3. 28. Packer TL, Sauriol A, Brouwer B. Fatigue secondary to chronic illness-postpolio syndrome, chronic fatigue syndrome, and multiple sclerosis. Arch Phys Med Rehabil 1994;75:1122-6. 29. Arvidsson I, Eriksson E, Knutsson E, Amer S. Reduction of pain inhibition on voluntary muscle activation by epidural analgesia. Orthopedics 1986;9:1415-9. 30. Stokes M, Young A. The contribution of reflex inhibition to arthrogenous muscle weakness. Clin Sci 1984;67:7-14. 31. Scott J, Huskisson EC. Graphic representation of pain. Pain 1976; 2: 175-84. 32. Hnik P, Holas M, Payne R. Reflex muscle atrophy induced by chronic peripheral nociceptive stimualtion. J Physiol 1977;73:24150. 33. Urbancova H, Hnik P, Vejsada R. Bone fracture induces reflex
STRENGTH
34.
35.
36. 37.
38. 39.
IN PEOPLE
WITH
muscle atrophy which Is sex-dependent. Physiol Res 1993;42:3540. Duvoisin MR, Convertino VA, Buchanan P, Gollnick PD, Dudley GA. Characteristics and preliminary observations of the influence of electromyostimulation on the size and function of human skeletal muscle during 30 days of simulated microgravity. Aviat Space Environ Med 1989;60:671-8. Ellis S, Kirby LC, Greenleaf JE. Lower extremity muscle thickness during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training. Aviat Space Environ Med 1993;64: 1011-5. Greenleaf JE, Bernauer EM, Ertl AC, Trowbridge TS, Wade CE. Work capacity during 30 days of bed rest with isotonic and isokinetic exercise training. J Appl Physiol 1989; 67: 1820-6. Greenleaf JE, Bernauer EM, Ertl AC, Bulbulian R, Bond M. Isokinetic strength and endurance during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training. Aviat Space Environ Med 1994;65:45-50. Leblanc AD, Schneider VS, Evans HJ, Pientok C, Rowe R, Spector E. Regional changes in muscle mass following 17 weeks of bed rest. J Appl Physiol 1992;73:2172-8. Suzuki Y, Murakami T, Haruna Y, Kawakubo K, Goto S, Makita Y, et al. Effects of 10 and 20 days bed rest on leg muscle mass and strength in young subjects. Acta Physiol Stand 1994; 150 Suppl 616:5-18.
HEALED
BURNS,
161
St-Pierre
40. Gregor RJ, Edgerton VR, Perrine JJ, Campion DS, DeBus C. Torque-velocity relationships and muscle fiber composition in elite female athletes. J Appl Physiol 1979;47:388-92. 4 1. Thorstensson A, Grimby G, Karlsson J. Force-velocity relations and fiber composition in human knee extensor muscles. J Appl Physiol 1976;40:12-6. 42. Fang CH, James HJ, Ogle C, Fischer JE, Hasselgren PO. Influence of bum injury on protein metabolism in different types of skeletal muscle and the role of glucocorticoids. J Am Co11 Surg 1995; 180: 33-42. 43. Falduto MT, Czerwinski SM, Hickson RC. Glucocorticoid-induced muscle atrophy prevention by exercise in fast-twitch fibers. J Appl Physiol 1990;69:1058-62. 44. Zeller J, Sturm G, Cruse CW. Patients with burns are successful in work hardening programs. J Burn Care Rehabil 1993; 14:189-96. 45. Dishman RK, Darracott CR, Lambert LT. Failure to generalize determinants of self-reported physical activity to a motion sensor. Med Sci Sports Exert 1992;24:904-10. Suppliers a. Cybex, 10 Trotter Drive, Medway, MA 02053. b. Gold Tech, 135 Dufresne, St.-Basil Le Grand, Quebec J3W lB6, Canada. c. Flex-0-Calc; Electrosport, Inc., Box 413; Stn “A” Weston, Ontario M9N 3N1, Canada.
Arch
Phys
Med Rehabil
Vol79,
February
1998