- Email: [email protected]
Symmetry, not asymmetry, of abdominal muscle morphology is associated with low back pain in cricket fast bowlers
Accepted Manuscript Title: Symmetry, not asymmetry, of abdominal muscle morphology is associated with low back pain in cricket fast bowlers Author: Janine Gray Kerith D. Aginsky Wayne Derman Christopher L. Vaughan Paul W. Hodges PII: DOI: Reference:
S1440-2440(15)00091-2 http://dx.doi.org/doi:10.1016/j.jsams.2015.04.009 JSAMS 1173
To appear in:
Journal of Science and Medicine in Sport
Received date: Revised date: Accepted date:
9-6-2014 4-3-2015 18-4-2015
Please cite this article as: Gray J, Aginsky KD, Derman W, Vaughan CL, Hodges PW, Symmetry, not asymmetry, of abdominal muscle morphology is associated with low back pain in cricket fast bowlers, Journal of Science and Medicine in Sport (2015), http://dx.doi.org/10.1016/j.jsams.2015.04.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.
*Manuscript (excluding all author details and affiliations)
1
Symmetry, not asymmetry, of abdominal muscle morphology is associated with low
2
back pain in cricket fast bowlers
3 Abstract
5
Objectives: Although abdominal muscle morphology is symmetrical in the general population,
6
asymmetry has been identified in rotation sports. This asymmetry includes greater thickness of
7
obliquus internus abdominis (OI) on the non-dominant side in cricketers. Cricket fast bowlers
8
commonly experience low back pain (LBP) related to bowling action, and this depends on trunk
9
muscle control. This study aimed to compare abdominal muscle thickness between fast bowlers with
an
us
cr
ip t
4
and without LBP.
11
Design: Cross sectional descriptive study
12
Methods: Twenty-five adolescent provincial league specialist fast bowlers (16 with and nine without
13
LBP) participated. Static ultrasound images (US) of OI, and obliquus externus (OE) and transversus
14
abdominis (TrA) were captured on the dominant and non-dominant side in supine.
15
Results: Total combined thickness of OE, OI and TrA muscles was greater on the non-dominant than
16
dominant side (p=0.02) for fast bowlers without LBP, but symmetrical for those with pain. Total
17
thickness was less on the non-dominant side for bowlers with pain than those without (p=0.03).
18
When individual muscles were compared, only the thickness of OI was less in bowlers with LBP than
19
those without (p=0.02). All abdominal muscles were thicker on the non-dominant side in controls
20
(p<0.001) but symmetrical in LBP.
21
Conclusions: Asymmetry of abdominal muscle thickness in fast bowlers is explained by the
22
asymmetrical biomechanics of fast bowling. Lesser OI muscle thickness in fast bowlers with LBP
23
suggests modified trunk control in the transverse/frontal plane and may underpin the incidence of
Ac
ce pt
ed
M
10
Page 1 of 19
24
lumbar pathology. The implications for rehabilitation following LBP in fast bowlers requires further
25
investigation.
26
ce pt
ed
M
an
us
cr
ip t
Key words: Ultrasound imaging, abdominal muscles, obliquus internus abdominis, sports injury
Ac
27
Page 2 of 19
28
Introduction Although asymmetry of the trunk muscles has been linked to low back pain (LBP) in the
30
general population 2;21, in individuals who participate in specific sports this may be adaptive in order
31
to meet the asymmetrical demands of sport-specific skills 23;25. This is particularly relevant for sports
32
such as cricket, in which fast bowlers use asymmetrical motion of the body to accelerate the ball.
33
Fast bowling in cricket is associated with a high risk of lower back injury5;13 and the biomechanics of
34
the bowling action has been highlighted as a major contributor 3;13. Increased counter-rotation of the
35
shoulders during the delivery stride has been highlighted as a variable associated with LBP 11;13 and is
36
dependent on control of trunk rotator muscles. The relationship between symmetry/asymmetry of
37
the trunk muscles, and fast bowling and low back pain remains contentious.
an
us
cr
ip t
29
The asymmetrical action of cricket fast bowling combines the movements of lumbar flexion,
39
extension, rotation and side flexion; factors which have been identified generally in the aetiology of
40
LBP
41
asymmetry10. Consequently asymmetry of lumbar muscles is commonly observed in cricket fast
42
bowlers
43
sectional area of the quadratus lumborum (QL) and multifidus/erector spinae muscles on the
44
dominant side, and psoas major and obliquus internus abdominis (OI) muscles on the non-dominant
45
side is greater than the contralateral muscle15. Some aspects of trunk muscle asymmetry have been
46
linked to pain and/or injury12. QL asymmetry has been associated with the development of a pars
47
interarticularis lesions in cricketers in a single study
48
later research23;24 . In the general population, asymmetry of the multifidus
49
muscles is present in individuals with acute and chronic LBP. Taken together these data imply that
50
asymmetry of trunk muscle morphology has negative impact on the health of the spine.
M
38
14
ed
. High volume of cricket bowling is also a risk factor for LBP and would encourage muscle
12;15;27
Ac
ce pt
. In a group of cricket players including spinners, pace bowlers and batsmen, cross-
12
but this finding has not been supported by 9;21
and psoas major
2
51
Although implementation of an exercise program can train symmetry of multifidus in the
52
general population17 and cricketers19, the relevance of asymmetry/symmetry is contentious.
Page 3 of 19
Asymmetry might imply abnormal load on the spine and warrant intervention to correct, but
54
alternatively, it may be a necessary adaptation for the demands of the sport. Recent work reports
55
that decreased asymmetry of QL was linked to pars defects in fast bowlers 24. Yet considering their
56
critical contribution to the control of rotational forces the lateral abdominal muscles have received
57
surprisingly limited attention in the cricket literature. A previous investigation in cricketers which
58
included a small group fast bowlers (n=9) showed thicker OI on the non-dominant side
59
relevance of these muscles to the control of asymmetrical rotation in the bowling action means
60
investigation of symmetry/asymmetry of this muscle group is likely to provide important insight into
61
its relevance for pain.
ip t
53
16
us
cr
. The
This study aimed to compare the thickness of the abdominal muscles (measured with
63
ultrasound (US) imaging) between the dominant and non-dominant sides of representative
64
adolescent cricket fast bowlers, and to compare this between fast bowlers with and without LBP.
M
an
62
66
ed
65 Methodology
Twenty-five adolescent cricket fast bowlers were recruited for this study. The group
68
consisted of 16 fast bowlers with chronic LBP and nine fast bowlers with no history of previous or
69
current injury to the lower back (non-low back pain [NLBP]). Participants were between 14-18 years
70
old and were currently playing representative cricket at a provincial level.
Ac
71
ce pt
67
The inclusion criteria for the LBP group included, players currently experiencing LBP (for a
72
minimum of 6 weeks) associated with the activity of fast bowling, players were currently playing
73
cricket but the pain was of sufficient severity that it had caused them to miss a game or practice in
74
the previous 6 weeks. Exclusion criteria for both groups included previous lower back surgery or
75
facet blocks with local anaesthetic or back pain in the last 2 years. Participants were included in the
76
NLBP group if they had no history of LBP in the past two years (self-reported). This 2 year period was
Page 4 of 19
chosen as the long term changes in the function, and hence possibly morphology, has been
78
previously described18. The Research Ethics Committee of the University of Cape Town approved the
79
study. The participants and a guardian provided written informed consent prior to the study.
80
Independent t-tests showed no statistical differences between groups for age, height, weight and
81
years bowling (LBP – 17(1) years, 179(7) cm, 75(7) kg, 7(2) years bowling; NLBP – 16(1) years, 175(7)
82
cm, 67(13) kg, 7(3) years bowling, respectively).
ip t
77
cr
83
Real-time US imaging (Sonoline G50, Siemens Medical Solutions USA, Inc.) with a 12 MHz
85
linear transducer was used to assess the thickness of the lateral abdominal muscles. Thickness was
86
used rather than cross sectional area as it was not possible to visualise the entire muscles in the US
87
image 26.
M
an
us
84
The US transducer was placed transversely, approximately 2.5 cm anterior to the mid-point
89
between the ribs and the inferior border of the iliac crest. The medial edge of the transducer head
90
was positioned approximately 10 cm from the midline. This position allowed simultaneous imaging
91
of the TrA, OI, and OE muscles 8;22.
ce pt
ed
88
Participants were positioned supine with the hips flexed to ~45° and knees flexed to ~90 to
93
ensure a neutral position of the lumbar spine and relaxation of the abdominal muscles. Once
94
accurate visualization of the three abdominal muscles (OE, OI, TrA) was obtained the image was
95
frozen at the end of a normal quiet expiration and saved for analysis. Thickness of the three
96
abdominal muscles was measured on both sides of the trunk and designated as non-dominant and
97
dominant based on the arm used when bowling.
Ac
92
98
Thickness of the three lateral abdominal muscles was measured using image-J software
99
(NIH, USA). The caliper function was used to measure thickness at three sites, at 1-cm intervals on
100
either side of, and including, the middle of the image (Figure 1). The calipers were placed on the
Page 5 of 19
101
inner border of the hyperechoic region regions related to the fascia separating the muscle layers.
102
The three thickness values obtained for each muscle were averaged and converted to millimeters
103
using the calibration scale on each image. The total combined thickness of all abdominal muscles
104
was also calculated by summing the values for each muscle. Statistical analysis was performed using the Statistica software package, version 7
106
(StatsoftInc, Tulsa, Ok, USA). Statistical significance was set at p<0.05. Thickness of the abdominal
107
muscle layers was compared between Muscles (OE, OI, TrA), Group (LBP vs. NLBP) and Sides
108
(dominant vs. non-dominant) with an analysis of variance (ANOVA). A separate ANOVA was used to
109
compare total combined thickness. The Bonferroni test was used for post-hoc analysis where
110
appropriate.
111
Results
M
an
us
cr
ip t
105
The total combined thickness of the muscles (OE, OI and TrA) on the non-dominant side was
113
greater than that on the dominant side in the fast bowlers without pain (Interaction: Group x Side –
114
p=0.02; post hoc p=0.01), but did not differ between sides (i.e. symmetrical) for the bowlers with
115
LBP (post hoc p=1.0). Between groups, the total thickness was greater in bowlers without pain (3.0 ±
116
0.4cm) than with LBP (2.4 ± 0.4cm) on the non-dominant side (post hoc – p=0.03), and similar for
117
both groups on the dominant side (NLBP: 2.5 ± 0.4cm; LBP: 2.5 ±0.4cm) (post hoc – p=1.0) (Figure
118
2A).
ce pt
Ac
119
ed
112
Comparison of the individual muscles indicated that OI was thicker than OE, which was
120
thicker than TrA for both groups (Interaction: Muscle x Group – p=0.05; post hoc – all p<0.001).
121
Thickness of OI was less in the LBP than control group (post hoc – all p=0.02), and although the
122
interaction between Group x Muscle x Side was not significant (p=0.44) it is apparent from the data
123
presented in Figure 2B that this was accounted for by reduced thickness of OI on the non-dominant
124
side. There was no difference in thickness of OE or TrA between groups (post hoc – both p=1.0).
125
Thickness of each abdominal muscle was greater on the non-dominant side (i.e. asymmetrical) for
Page 6 of 19
126
participants in NLBP group (Interaction: Side x Group – p<0.001; post hoc – p<0.001), but did not
127
differ between sides (i.e. symmetrical) in bowlers with LBP (post hoc – p=0.01).
128 Discussion
ip t
129
The results of this study show that adolescent cricket fast bowlers with LBP have
131
symmetrical morphology of the abdominal muscles in contrast to the asymmetry identified in
132
adolescent fast bowlers without pain. This observation implies that the hypertrophy of OI associated
133
with high repetition bowling action is absent in the group experiencing pain. In contrast to a non-
134
sporting population, asymmetry would appear to be protective rather than provocative for LBP.
an
us
cr
130
Greater thickness of OI on the non-dominant side in fast bowlers is consistent with the
136
research findings previously reported in a group of cricketers (bowlers and batsmen), including a
137
small group of fast bowlers (n=9, including five with LBP) 15. Unlike that study, the present study
138
identified asymmetry of trunk muscles in painfree fast bowlers, whilst the differences in findings
139
may be explained by a mix of cricketing disciplines in the previous study. Asymmetry of the trunk
140
muscles has been identified in other sports. Rectus abdominis is hypertrophied in professional tennis
141
players, with greater size on the non-dominant side 29. In healthy but non-sporting individuals, the
142
abdominal muscles are usually symmetrical
143
individuals
144
abdominal muscle thickness is specific to fast bowlers and when compared to measures of OI
145
thickness for a non-sporting population the data imply the asymmetry of OI is related to hypertrophy
146
of the muscle on the non-dominant side (see Table 1 for comparative data). This finding lends
147
support to a link between the biomechanics of bowling and the adaptive development of asymmetry
148
in the trunk muscles.
26
ce pt
ed
M
135
8
or have minor asymmetry that varies between
Ac
. Taken together these data imply that the characteristics of asymmetry of the
149
Page 7 of 19
The injury risk associated with the fast bowling technique has largely focused around the
151
mixed action technique with a greater degree of shoulder counter-rotation being associated with a
152
greater risk of injury4;13. More recently, researchers have proposed that contralateral lumbar flexion
153
occurring around the time of FFI and ball release may be a more relevant biomechanical variable
154
associated with risk28. Further, bowlers with greater lumbopelvic lateral flexion loads during bowling
155
appear to have greater QL asymmetry7. While, the relationship between injury risk, asymmetry and
156
bowling biomechanics requires further investigation, the impact of bowling biomechanics in the
157
development of an asymmetry must be acknowledged.
cr
ip t
150
The OI muscle generates ipsilateral rotation and side flexion when contracting unilaterally 6..
159
OI on the non-dominant side would contribute to the strong forward rotation of the thorax and
160
shoulders prior to and during ball release. In addition, the high lateral flexion loads identified during
161
movement of the thorax towards the non-dominant side would also be performed by the non-
162
dominant OI. High exposure to these actions in cricket fast bowlers is likely to explain the
163
hypertrophy of the rotator muscles. Although some have argued that asymmetry of lumbar muscles
164
may be aetiologic for back injury 12;15, it may indeed also be necessary for adequate performance of
165
the task. Further insight into this issue comes from consideration of the observed symmetry of OI in
166
the fast bowlers with LBP.
ce pt
ed
M
an
us
158
Asymmetry of trunk muscle size has been commonly observed for a range of trunk muscles
168
in individuals with LBP. This includes QL, multifidus, psoas major and the erector spinae muscles
169
2;9;21
170
QL and MF and LBP
171
lateral abdominal muscles in the aetiology of LBP in fast bowlers is not clear. Although the potential
172
negative effect of asymmetry has been extensively argued on the basis of its potential role in
173
suboptimal loading of tissues 12, the relevance of symmetry has only recently been acknowledged. In
174
contrast to earlier data 12, one recent study showed less asymmetry of QL in adult fast bowlers with
175
pain 24. One interpretation of the greater symmetry of QL in that study, and the lateral abdominal
Ac
167
. In cricket fast bowlers, some studies have found an association between greater asymmetry of 12;15;27
. However, the implication of symmetry of the resting thickness of the
Page 8 of 19
muscles in the present study, is that the particular style of bowling associated with injury may
177
promote a more symmetrical development of muscle than other bowling techniques. For instance,
178
less asymmetry may imply less transverse and frontal plane motion in the bowling action. The
179
controversial “mixed action” bowling technique, has been associated with lesions of the pars
180
interarticularis and disc, and LBP 5;13. Fast bowlers using this technique have demonstrated increased
181
extension and lateral flexion to the non-dominant side during fast bowling 4. A further consideration
182
would include whether the lateral flexion to the non-dominant side was the result of an active
183
contraction of the non-dominant OI or an uncontrolled ‘falling away’ of the thorax towards the non-
184
dominant side. Bowling biomechanics was not assessed in the present study and a direct correlation
185
between bowling biomechanics, muscle symmetry of the OI and lumbar injury should be considered
186
in future work.
an
us
cr
ip t
176
Current contemporary arguments advocate strengthening strategies aimed at enhancing
188
symmetry for management of fast bowlers with LBP. A recent rehabilitation trial in a mixed discipline
189
group of cricketers with LBP trained and enhanced symmetry in the deep abdominal muscles and
190
this program was associated with reduced pain 20, but it was unclear whether this decrease in pain
191
was achieved in the subgroup of fast bowlers. Others have argued that asymmetrical function should
192
be trained in sport specific settings 1. Until clinical trials are conducted to compare these approaches
193
it is unclear which would provide most optimal results. However, training of bowling technique is
194
most likely necessary in addition to muscle re-education.
ed
ce pt
Ac
195
M
187
The present results should be interpreted with consideration of several methodological
196
issues. First, abdominal muscle thickness does not measure cross sectional area as the area of
197
muscle visualized is limited by the US width. Although thickness of the muscle was averaged over
198
measures at 3 points to be more representative of the muscle, the measures may not be easily
199
extrapolated to differences in muscle strength as the muscle shape may also change. Second, the
200
anatomy of the abdominal muscles is complex with regional variation in muscle thickness and
Page 9 of 19
30
fascicle orientation
. This has further implications for interpretation of strength of the muscles
202
from the present data. Thirdly, similar to other studies24;27 investigating muscle asymmetry, the fast
203
bowling kinematics were not collected as part of the study and the impact of these on asymmetry
204
and LBP could not be assessed. Lastly, although the sample size was small, the group was targeted to
205
be homogeneous on the basis of participant age and level of exposure to cricket and skill level. This
206
is likely to reduce the variability between participants, but may also limit extrapolation to other
207
groups.
cr
ip t
201
208 Conclusion
210
Asymmetry of the resting thickness of OI was characteristic of cricket players without back pain who
211
were fast bowlers at a provincial level and this was apparent as hypertrophy on the non-dominant
212
side. This asymmetry is consistent with a sport-specific adaptation associated with the rotary
213
demands of fast bowling. In direct contrast to observations in other populations, individuals with LBP
214
tended to have more symmetrical abdominal muscle size. The clinical implication of these findings
215
with regards to rehabilitation of injured fast bowlers is not clear.
ed
M
an
us
209
218
Practical implications
219 220
asymmetry, of the abdominal muscles was characteristic of cricket fast bowlers with LBP.
221 222
Contrary to the conventional view, this study identified that symmetry, rather than
Ac
217
ce pt
216
These data imply that asymmetry of the trunk muscles is necessary for performance of a safe fast bowling action in cricketers.
The role of rehabilitation in addressing muscle asymmetry in fast bowlers is not clear.
223 224
Acknowledgements
Page 10 of 19
PH is supported by a Research Fellowship from the National Health and Medical Research Council
226
(NHMRC) of Australia (APP1002190). AK was supported by the Ernest Oppenheimer Memorial Trust
227
Scholarship at the time of the study. No other funding was received to support the study.
Ac
ce pt
ed
M
an
us
cr
ip t
225
Page 11 of 19
228
Reference List
229 230
1. Allison GT, Morris SL, Lay B. Feedforward responses of transversus abdominis are directionally specific and act asymmetrically: implications for core stability theories. J Orthop
232
Sports Phys Ther 2008;38:228-237.
ip t
231
2. Barker KL, Shamley DR, Jackson D. Changes in the cross-sectional area of multifidus and
234
psoas in patients with unilateral back pain: the relationship to pain and disability. Spine
235
(Phila Pa 1976.) 2004;29:E515-E519.
238
us
review. J Sports Sci 1996;14:403-424.
an
237
3. Bartlett RM, Stockill NP, Elliott BC et al. The biomechanics of fast bowling in men's cricket: a
4. Burnett AF, Barrett CJ, Marshall RN et al. Three-dimensional measurement of lumbar spine
M
236
cr
233
kinematics for fast bowlers in cricket. Clin Biomech (Bristol., Avon.) 1998;13:574-583.
240
5. Burnett AF, Khangure MS, Elliott BC et al. Thoracolumbar disc degeneration in young fast
241
bowlers in cricket: a follow-up study. Clin Biomech (Bristol., Avon.) 1996;11:305-310.
244 245 246 247 248 249
ce pt
243
6. Cresswell AG, Grundstrom H, Thorstensson A. Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man. Acta Physiol Scand 1992;144:409-418.
7. Crewe H, Campbell A, Elliott B et al. Lumbo-pelvic biomechanics and quadratuslumborum
Ac
242
ed
239
asymmetry in cricket fast bowlers. Med Sci Sports Exerc 2013;45:778-783.
8. Critchley D, Coutts F. Abdominal muscle function in chronic low back pain patients. Physiotherapy 2002;88(6): 322-332. 9. Danneels LA, Vanderstraeten GG, Cambier DC et al. CT imaging of trunk muscles in chronic low back pain patients and healthy control subjects. Eur Spine J 2000;9:266-272.
Page 12 of 19
250 251
252
10. Dennis RJ, Finch CF, Farhart PJ. Is bowling workload a risk factor for injury to Australian junior cricket fast bowlers? Br J Sports Med 2005;39:843-846.
11. Elliott BC, Hardcastle P, Burnett A et al. The influence of fast bowling and physical factors on the radiologic features in high performance young fast bowlers. Sports Med Train Rehab
254
1992;3, 113-130
255
ip t
253
12. Engstrom CM, Walker DG, Kippers V et al. Quadratus lumborum asymmetry and L4 pars injury in fast bowlers: a prospective MR study. Med Sci Sports Exerc 2007;39:910-917.
257
13. Foster D, John D, Elliott B et al. Back injuries to fast bowlers in cricket: a prospective study.
261
us
an
260
14. Hensinger RN. Spondylolysis and spondylolisthesis in children and adolescents. J Bone Joint Surg Am 1989;71:1098-1107.
M
259
Br J Sports Med 1989;23:150-154.
15. Hides J, Stanton W, Freke M et al. MRI study of the size, symmetry and function of the trunk
ed
258
cr
256
muscles among elite cricketers with and without low back pain. Br J Sports Med
263
2008;42:509-513.
264
ce pt
262
16. Hides J, Wilson S, Stanton W et al. An MRI investigation into the function of the transversus abdominis muscle during "drawing-in" of the abdominal wall. Spine (Phila Pa 1976.)
266
2006;31:E175-E178.
267 268
269 270
Ac
265
17. Hides JA, Jull GA, Richardson CA. Long-term effects of specific stabilizing exercises for firstepisode low back pain. Spine (Phila Pa 1976.) 2001;26:E243-E248.
18. Hides JA, Richardson CA, Jull GA. Multifidus muscle recovery is not automatic after resolution of acute, first-episode low back pain. Spine (Phila Pa 1976.) 1996;21:2763-2769.
Page 13 of 19
271
19. Hides JA, Stanton WR, McMahon S et al. Effect of stabilization training on multifidus muscle
272
cross-sectional area among young elite cricketers with low back pain. J Orthop Sports Phys
273
Ther 2008;38:101-108.
276
elite cricketers with low back pain. Scand J Med Sci Sports 2010;20:834-842.
ip t
275
20. Hides JA, Stanton WR, Wilson SJ et al. Retraining motor control of abdominal muscles among
21. Hides JA, Stokes MJ, Saide M et al. Evidence of lumbar multifidus muscle wasting ipsilateral
cr
274
to symptoms in patients with acute/subacute low back pain. Spine (Phila Pa 1976.)
278
1994;19:165-172.
283 284
285 286
287 288
289 290
an
M
282
23. Kountouris A, Portus M, Cook J. Quadratus lumborum asymmetry and lumbar spine injury in junior cricket fast bowlers. J Sci Med Sport 2012;15:393-397.
ed
281
ultrasound imaging. Muscle Nerve 2003;27:682-692.
24. Kountouris A, Portus M, Cook J. Cricket Fast Bowlers Without Low-Back Pain Have Larger Quadratus Lumborum Asymmetry Than Injured Bowlers. Clin J Sport Med 2013;23:300-304.
ce pt
280
22. Hodges PW, Pengel LH, Herbert RD et al. Measurement of muscle contraction with
25. McGregor AH, Anderton L, Gedroyc WM. The trunk muscles of elite oarsmen. Br J Sports Med 2002;36:214-217.
Ac
279
us
277
26. Rankin G, Stokes M, Newham DJ. Abdominal muscle size and symmetry in normal subjects. Muscle Nerve 2006;34:320-326.
27. Ranson CA, Burnett A, O'Sullivan PB et al. The lumbar paraspinal muscle morphometry of fast bowlers in cricket. Clin J Sports Med 2008; 18(1):31-37.
Page 14 of 19
291
28. Ranson CA, Burnett AF, King M et al. The relationship between bowling action classification
292
and three-dimensional lower trunk motion in fast bowlers in cricket. J Sports Sci 2008; 26(3):
293
267-276.
295
296
29. Sanchis-Moysi J, Idoate F, Dorado C et al. Large asymmetric hypertrophy of rectus abdominis muscle in professional tennis players. PLoS One 2010;5:e15858.
ip t
294
30. Urquhart DM, Barker PJ, Hodges PW et al. Regional morphology of the transversus
abdominis and obliquus internus and externus abdominis muscles. Clin Biomech (Bristol.,
298
Avon.) 2005;20:233-241.
us
cr
297
Ac
ce pt
ed
M
an
299
Page 15 of 19
300
Figure legends
301
Fig. 1
302
of transversus abdominis (TrA), obliquus internus abdominis (OI), obliquus externus abdominis (OE)
303
were made in the middle of the image and at 1-cm intervals on either side.
Measurement of muscle thickness from ultrasound imaging. Measurements of the thickness
ip t
304 Fig. 2
A. Total combined thickness of the abdominal muscles. Mean and standard deviation are
306
shown for muscles on the dominant and non-dominant side for fast bowlers with and without low
307
back pain. B. Thickness of the individual abdominal muscles. Mean and standard deviation are
308
shown for thickness of the muscles on the dominant and non-dominant side for fast bowlers with
309
and without low back pain.
an
us
cr
305
Ac
ce pt
ed
M
310
Page 16 of 19
Table 1
Table 1 Resting thickness measures of in participants with no low back pain OE (mm)
OI (mm)
TrA (mm)
De Troyer et al., (1990)
25-39
7.2±0.9
11.5±2.7
4.6±1.0
Critchley & Coutts (2002)
18-60
5.9±1.6
9.3±4.0
5.1±1.2
Hodges et al., (2003)
27-45
4.3±0.8
7.7±1.8
3.2±0.8
McKeekan et al., (2004)
29-52
Current study
14-18
Dominant
ip t
Age (years)
7.0±0.3
Non-dominant
9.0±1.9
16.3±2.7
7.4±1.9
12.3±2.2
4.9±1.4
cr
Author
4.1±0.9
Ac
ce pt
ed
M
an
us
TrA – transversus abdominis, OI – obliquus internus abdominis, OE – obliquus externus abdominis
Page 17 of 19
Ac
ce
pt
ed
M
an
us
cr
i
Figure 1
Page 18 of 19
Ac
ce
pt
ed
M
an
us
cr
i
Figure 2
Page 19 of 19
S1440-2440(15)00091-2 http://dx.doi.org/doi:10.1016/j.jsams.2015.04.009 JSAMS 1173
To appear in:
Journal of Science and Medicine in Sport
Received date: Revised date: Accepted date:
9-6-2014 4-3-2015 18-4-2015
Please cite this article as: Gray J, Aginsky KD, Derman W, Vaughan CL, Hodges PW, Symmetry, not asymmetry, of abdominal muscle morphology is associated with low back pain in cricket fast bowlers, Journal of Science and Medicine in Sport (2015), http://dx.doi.org/10.1016/j.jsams.2015.04.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.
*Manuscript (excluding all author details and affiliations)
1
Symmetry, not asymmetry, of abdominal muscle morphology is associated with low
2
back pain in cricket fast bowlers
3 Abstract
5
Objectives: Although abdominal muscle morphology is symmetrical in the general population,
6
asymmetry has been identified in rotation sports. This asymmetry includes greater thickness of
7
obliquus internus abdominis (OI) on the non-dominant side in cricketers. Cricket fast bowlers
8
commonly experience low back pain (LBP) related to bowling action, and this depends on trunk
9
muscle control. This study aimed to compare abdominal muscle thickness between fast bowlers with
an
us
cr
ip t
4
and without LBP.
11
Design: Cross sectional descriptive study
12
Methods: Twenty-five adolescent provincial league specialist fast bowlers (16 with and nine without
13
LBP) participated. Static ultrasound images (US) of OI, and obliquus externus (OE) and transversus
14
abdominis (TrA) were captured on the dominant and non-dominant side in supine.
15
Results: Total combined thickness of OE, OI and TrA muscles was greater on the non-dominant than
16
dominant side (p=0.02) for fast bowlers without LBP, but symmetrical for those with pain. Total
17
thickness was less on the non-dominant side for bowlers with pain than those without (p=0.03).
18
When individual muscles were compared, only the thickness of OI was less in bowlers with LBP than
19
those without (p=0.02). All abdominal muscles were thicker on the non-dominant side in controls
20
(p<0.001) but symmetrical in LBP.
21
Conclusions: Asymmetry of abdominal muscle thickness in fast bowlers is explained by the
22
asymmetrical biomechanics of fast bowling. Lesser OI muscle thickness in fast bowlers with LBP
23
suggests modified trunk control in the transverse/frontal plane and may underpin the incidence of
Ac
ce pt
ed
M
10
Page 1 of 19
24
lumbar pathology. The implications for rehabilitation following LBP in fast bowlers requires further
25
investigation.
26
ce pt
ed
M
an
us
cr
ip t
Key words: Ultrasound imaging, abdominal muscles, obliquus internus abdominis, sports injury
Ac
27
Page 2 of 19
28
Introduction Although asymmetry of the trunk muscles has been linked to low back pain (LBP) in the
30
general population 2;21, in individuals who participate in specific sports this may be adaptive in order
31
to meet the asymmetrical demands of sport-specific skills 23;25. This is particularly relevant for sports
32
such as cricket, in which fast bowlers use asymmetrical motion of the body to accelerate the ball.
33
Fast bowling in cricket is associated with a high risk of lower back injury5;13 and the biomechanics of
34
the bowling action has been highlighted as a major contributor 3;13. Increased counter-rotation of the
35
shoulders during the delivery stride has been highlighted as a variable associated with LBP 11;13 and is
36
dependent on control of trunk rotator muscles. The relationship between symmetry/asymmetry of
37
the trunk muscles, and fast bowling and low back pain remains contentious.
an
us
cr
ip t
29
The asymmetrical action of cricket fast bowling combines the movements of lumbar flexion,
39
extension, rotation and side flexion; factors which have been identified generally in the aetiology of
40
LBP
41
asymmetry10. Consequently asymmetry of lumbar muscles is commonly observed in cricket fast
42
bowlers
43
sectional area of the quadratus lumborum (QL) and multifidus/erector spinae muscles on the
44
dominant side, and psoas major and obliquus internus abdominis (OI) muscles on the non-dominant
45
side is greater than the contralateral muscle15. Some aspects of trunk muscle asymmetry have been
46
linked to pain and/or injury12. QL asymmetry has been associated with the development of a pars
47
interarticularis lesions in cricketers in a single study
48
later research23;24 . In the general population, asymmetry of the multifidus
49
muscles is present in individuals with acute and chronic LBP. Taken together these data imply that
50
asymmetry of trunk muscle morphology has negative impact on the health of the spine.
M
38
14
ed
. High volume of cricket bowling is also a risk factor for LBP and would encourage muscle
12;15;27
Ac
ce pt
. In a group of cricket players including spinners, pace bowlers and batsmen, cross-
12
but this finding has not been supported by 9;21
and psoas major
2
51
Although implementation of an exercise program can train symmetry of multifidus in the
52
general population17 and cricketers19, the relevance of asymmetry/symmetry is contentious.
Page 3 of 19
Asymmetry might imply abnormal load on the spine and warrant intervention to correct, but
54
alternatively, it may be a necessary adaptation for the demands of the sport. Recent work reports
55
that decreased asymmetry of QL was linked to pars defects in fast bowlers 24. Yet considering their
56
critical contribution to the control of rotational forces the lateral abdominal muscles have received
57
surprisingly limited attention in the cricket literature. A previous investigation in cricketers which
58
included a small group fast bowlers (n=9) showed thicker OI on the non-dominant side
59
relevance of these muscles to the control of asymmetrical rotation in the bowling action means
60
investigation of symmetry/asymmetry of this muscle group is likely to provide important insight into
61
its relevance for pain.
ip t
53
16
us
cr
. The
This study aimed to compare the thickness of the abdominal muscles (measured with
63
ultrasound (US) imaging) between the dominant and non-dominant sides of representative
64
adolescent cricket fast bowlers, and to compare this between fast bowlers with and without LBP.
M
an
62
66
ed
65 Methodology
Twenty-five adolescent cricket fast bowlers were recruited for this study. The group
68
consisted of 16 fast bowlers with chronic LBP and nine fast bowlers with no history of previous or
69
current injury to the lower back (non-low back pain [NLBP]). Participants were between 14-18 years
70
old and were currently playing representative cricket at a provincial level.
Ac
71
ce pt
67
The inclusion criteria for the LBP group included, players currently experiencing LBP (for a
72
minimum of 6 weeks) associated with the activity of fast bowling, players were currently playing
73
cricket but the pain was of sufficient severity that it had caused them to miss a game or practice in
74
the previous 6 weeks. Exclusion criteria for both groups included previous lower back surgery or
75
facet blocks with local anaesthetic or back pain in the last 2 years. Participants were included in the
76
NLBP group if they had no history of LBP in the past two years (self-reported). This 2 year period was
Page 4 of 19
chosen as the long term changes in the function, and hence possibly morphology, has been
78
previously described18. The Research Ethics Committee of the University of Cape Town approved the
79
study. The participants and a guardian provided written informed consent prior to the study.
80
Independent t-tests showed no statistical differences between groups for age, height, weight and
81
years bowling (LBP – 17(1) years, 179(7) cm, 75(7) kg, 7(2) years bowling; NLBP – 16(1) years, 175(7)
82
cm, 67(13) kg, 7(3) years bowling, respectively).
ip t
77
cr
83
Real-time US imaging (Sonoline G50, Siemens Medical Solutions USA, Inc.) with a 12 MHz
85
linear transducer was used to assess the thickness of the lateral abdominal muscles. Thickness was
86
used rather than cross sectional area as it was not possible to visualise the entire muscles in the US
87
image 26.
M
an
us
84
The US transducer was placed transversely, approximately 2.5 cm anterior to the mid-point
89
between the ribs and the inferior border of the iliac crest. The medial edge of the transducer head
90
was positioned approximately 10 cm from the midline. This position allowed simultaneous imaging
91
of the TrA, OI, and OE muscles 8;22.
ce pt
ed
88
Participants were positioned supine with the hips flexed to ~45° and knees flexed to ~90 to
93
ensure a neutral position of the lumbar spine and relaxation of the abdominal muscles. Once
94
accurate visualization of the three abdominal muscles (OE, OI, TrA) was obtained the image was
95
frozen at the end of a normal quiet expiration and saved for analysis. Thickness of the three
96
abdominal muscles was measured on both sides of the trunk and designated as non-dominant and
97
dominant based on the arm used when bowling.
Ac
92
98
Thickness of the three lateral abdominal muscles was measured using image-J software
99
(NIH, USA). The caliper function was used to measure thickness at three sites, at 1-cm intervals on
100
either side of, and including, the middle of the image (Figure 1). The calipers were placed on the
Page 5 of 19
101
inner border of the hyperechoic region regions related to the fascia separating the muscle layers.
102
The three thickness values obtained for each muscle were averaged and converted to millimeters
103
using the calibration scale on each image. The total combined thickness of all abdominal muscles
104
was also calculated by summing the values for each muscle. Statistical analysis was performed using the Statistica software package, version 7
106
(StatsoftInc, Tulsa, Ok, USA). Statistical significance was set at p<0.05. Thickness of the abdominal
107
muscle layers was compared between Muscles (OE, OI, TrA), Group (LBP vs. NLBP) and Sides
108
(dominant vs. non-dominant) with an analysis of variance (ANOVA). A separate ANOVA was used to
109
compare total combined thickness. The Bonferroni test was used for post-hoc analysis where
110
appropriate.
111
Results
M
an
us
cr
ip t
105
The total combined thickness of the muscles (OE, OI and TrA) on the non-dominant side was
113
greater than that on the dominant side in the fast bowlers without pain (Interaction: Group x Side –
114
p=0.02; post hoc p=0.01), but did not differ between sides (i.e. symmetrical) for the bowlers with
115
LBP (post hoc p=1.0). Between groups, the total thickness was greater in bowlers without pain (3.0 ±
116
0.4cm) than with LBP (2.4 ± 0.4cm) on the non-dominant side (post hoc – p=0.03), and similar for
117
both groups on the dominant side (NLBP: 2.5 ± 0.4cm; LBP: 2.5 ±0.4cm) (post hoc – p=1.0) (Figure
118
2A).
ce pt
Ac
119
ed
112
Comparison of the individual muscles indicated that OI was thicker than OE, which was
120
thicker than TrA for both groups (Interaction: Muscle x Group – p=0.05; post hoc – all p<0.001).
121
Thickness of OI was less in the LBP than control group (post hoc – all p=0.02), and although the
122
interaction between Group x Muscle x Side was not significant (p=0.44) it is apparent from the data
123
presented in Figure 2B that this was accounted for by reduced thickness of OI on the non-dominant
124
side. There was no difference in thickness of OE or TrA between groups (post hoc – both p=1.0).
125
Thickness of each abdominal muscle was greater on the non-dominant side (i.e. asymmetrical) for
Page 6 of 19
126
participants in NLBP group (Interaction: Side x Group – p<0.001; post hoc – p<0.001), but did not
127
differ between sides (i.e. symmetrical) in bowlers with LBP (post hoc – p=0.01).
128 Discussion
ip t
129
The results of this study show that adolescent cricket fast bowlers with LBP have
131
symmetrical morphology of the abdominal muscles in contrast to the asymmetry identified in
132
adolescent fast bowlers without pain. This observation implies that the hypertrophy of OI associated
133
with high repetition bowling action is absent in the group experiencing pain. In contrast to a non-
134
sporting population, asymmetry would appear to be protective rather than provocative for LBP.
an
us
cr
130
Greater thickness of OI on the non-dominant side in fast bowlers is consistent with the
136
research findings previously reported in a group of cricketers (bowlers and batsmen), including a
137
small group of fast bowlers (n=9, including five with LBP) 15. Unlike that study, the present study
138
identified asymmetry of trunk muscles in painfree fast bowlers, whilst the differences in findings
139
may be explained by a mix of cricketing disciplines in the previous study. Asymmetry of the trunk
140
muscles has been identified in other sports. Rectus abdominis is hypertrophied in professional tennis
141
players, with greater size on the non-dominant side 29. In healthy but non-sporting individuals, the
142
abdominal muscles are usually symmetrical
143
individuals
144
abdominal muscle thickness is specific to fast bowlers and when compared to measures of OI
145
thickness for a non-sporting population the data imply the asymmetry of OI is related to hypertrophy
146
of the muscle on the non-dominant side (see Table 1 for comparative data). This finding lends
147
support to a link between the biomechanics of bowling and the adaptive development of asymmetry
148
in the trunk muscles.
26
ce pt
ed
M
135
8
or have minor asymmetry that varies between
Ac
. Taken together these data imply that the characteristics of asymmetry of the
149
Page 7 of 19
The injury risk associated with the fast bowling technique has largely focused around the
151
mixed action technique with a greater degree of shoulder counter-rotation being associated with a
152
greater risk of injury4;13. More recently, researchers have proposed that contralateral lumbar flexion
153
occurring around the time of FFI and ball release may be a more relevant biomechanical variable
154
associated with risk28. Further, bowlers with greater lumbopelvic lateral flexion loads during bowling
155
appear to have greater QL asymmetry7. While, the relationship between injury risk, asymmetry and
156
bowling biomechanics requires further investigation, the impact of bowling biomechanics in the
157
development of an asymmetry must be acknowledged.
cr
ip t
150
The OI muscle generates ipsilateral rotation and side flexion when contracting unilaterally 6..
159
OI on the non-dominant side would contribute to the strong forward rotation of the thorax and
160
shoulders prior to and during ball release. In addition, the high lateral flexion loads identified during
161
movement of the thorax towards the non-dominant side would also be performed by the non-
162
dominant OI. High exposure to these actions in cricket fast bowlers is likely to explain the
163
hypertrophy of the rotator muscles. Although some have argued that asymmetry of lumbar muscles
164
may be aetiologic for back injury 12;15, it may indeed also be necessary for adequate performance of
165
the task. Further insight into this issue comes from consideration of the observed symmetry of OI in
166
the fast bowlers with LBP.
ce pt
ed
M
an
us
158
Asymmetry of trunk muscle size has been commonly observed for a range of trunk muscles
168
in individuals with LBP. This includes QL, multifidus, psoas major and the erector spinae muscles
169
2;9;21
170
QL and MF and LBP
171
lateral abdominal muscles in the aetiology of LBP in fast bowlers is not clear. Although the potential
172
negative effect of asymmetry has been extensively argued on the basis of its potential role in
173
suboptimal loading of tissues 12, the relevance of symmetry has only recently been acknowledged. In
174
contrast to earlier data 12, one recent study showed less asymmetry of QL in adult fast bowlers with
175
pain 24. One interpretation of the greater symmetry of QL in that study, and the lateral abdominal
Ac
167
. In cricket fast bowlers, some studies have found an association between greater asymmetry of 12;15;27
. However, the implication of symmetry of the resting thickness of the
Page 8 of 19
muscles in the present study, is that the particular style of bowling associated with injury may
177
promote a more symmetrical development of muscle than other bowling techniques. For instance,
178
less asymmetry may imply less transverse and frontal plane motion in the bowling action. The
179
controversial “mixed action” bowling technique, has been associated with lesions of the pars
180
interarticularis and disc, and LBP 5;13. Fast bowlers using this technique have demonstrated increased
181
extension and lateral flexion to the non-dominant side during fast bowling 4. A further consideration
182
would include whether the lateral flexion to the non-dominant side was the result of an active
183
contraction of the non-dominant OI or an uncontrolled ‘falling away’ of the thorax towards the non-
184
dominant side. Bowling biomechanics was not assessed in the present study and a direct correlation
185
between bowling biomechanics, muscle symmetry of the OI and lumbar injury should be considered
186
in future work.
an
us
cr
ip t
176
Current contemporary arguments advocate strengthening strategies aimed at enhancing
188
symmetry for management of fast bowlers with LBP. A recent rehabilitation trial in a mixed discipline
189
group of cricketers with LBP trained and enhanced symmetry in the deep abdominal muscles and
190
this program was associated with reduced pain 20, but it was unclear whether this decrease in pain
191
was achieved in the subgroup of fast bowlers. Others have argued that asymmetrical function should
192
be trained in sport specific settings 1. Until clinical trials are conducted to compare these approaches
193
it is unclear which would provide most optimal results. However, training of bowling technique is
194
most likely necessary in addition to muscle re-education.
ed
ce pt
Ac
195
M
187
The present results should be interpreted with consideration of several methodological
196
issues. First, abdominal muscle thickness does not measure cross sectional area as the area of
197
muscle visualized is limited by the US width. Although thickness of the muscle was averaged over
198
measures at 3 points to be more representative of the muscle, the measures may not be easily
199
extrapolated to differences in muscle strength as the muscle shape may also change. Second, the
200
anatomy of the abdominal muscles is complex with regional variation in muscle thickness and
Page 9 of 19
30
fascicle orientation
. This has further implications for interpretation of strength of the muscles
202
from the present data. Thirdly, similar to other studies24;27 investigating muscle asymmetry, the fast
203
bowling kinematics were not collected as part of the study and the impact of these on asymmetry
204
and LBP could not be assessed. Lastly, although the sample size was small, the group was targeted to
205
be homogeneous on the basis of participant age and level of exposure to cricket and skill level. This
206
is likely to reduce the variability between participants, but may also limit extrapolation to other
207
groups.
cr
ip t
201
208 Conclusion
210
Asymmetry of the resting thickness of OI was characteristic of cricket players without back pain who
211
were fast bowlers at a provincial level and this was apparent as hypertrophy on the non-dominant
212
side. This asymmetry is consistent with a sport-specific adaptation associated with the rotary
213
demands of fast bowling. In direct contrast to observations in other populations, individuals with LBP
214
tended to have more symmetrical abdominal muscle size. The clinical implication of these findings
215
with regards to rehabilitation of injured fast bowlers is not clear.
ed
M
an
us
209
218
Practical implications
219 220
asymmetry, of the abdominal muscles was characteristic of cricket fast bowlers with LBP.
221 222
Contrary to the conventional view, this study identified that symmetry, rather than
Ac
217
ce pt
216
These data imply that asymmetry of the trunk muscles is necessary for performance of a safe fast bowling action in cricketers.
The role of rehabilitation in addressing muscle asymmetry in fast bowlers is not clear.
223 224
Acknowledgements
Page 10 of 19
PH is supported by a Research Fellowship from the National Health and Medical Research Council
226
(NHMRC) of Australia (APP1002190). AK was supported by the Ernest Oppenheimer Memorial Trust
227
Scholarship at the time of the study. No other funding was received to support the study.
Ac
ce pt
ed
M
an
us
cr
ip t
225
Page 11 of 19
228
Reference List
229 230
1. Allison GT, Morris SL, Lay B. Feedforward responses of transversus abdominis are directionally specific and act asymmetrically: implications for core stability theories. J Orthop
232
Sports Phys Ther 2008;38:228-237.
ip t
231
2. Barker KL, Shamley DR, Jackson D. Changes in the cross-sectional area of multifidus and
234
psoas in patients with unilateral back pain: the relationship to pain and disability. Spine
235
(Phila Pa 1976.) 2004;29:E515-E519.
238
us
review. J Sports Sci 1996;14:403-424.
an
237
3. Bartlett RM, Stockill NP, Elliott BC et al. The biomechanics of fast bowling in men's cricket: a
4. Burnett AF, Barrett CJ, Marshall RN et al. Three-dimensional measurement of lumbar spine
M
236
cr
233
kinematics for fast bowlers in cricket. Clin Biomech (Bristol., Avon.) 1998;13:574-583.
240
5. Burnett AF, Khangure MS, Elliott BC et al. Thoracolumbar disc degeneration in young fast
241
bowlers in cricket: a follow-up study. Clin Biomech (Bristol., Avon.) 1996;11:305-310.
244 245 246 247 248 249
ce pt
243
6. Cresswell AG, Grundstrom H, Thorstensson A. Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man. Acta Physiol Scand 1992;144:409-418.
7. Crewe H, Campbell A, Elliott B et al. Lumbo-pelvic biomechanics and quadratuslumborum
Ac
242
ed
239
asymmetry in cricket fast bowlers. Med Sci Sports Exerc 2013;45:778-783.
8. Critchley D, Coutts F. Abdominal muscle function in chronic low back pain patients. Physiotherapy 2002;88(6): 322-332. 9. Danneels LA, Vanderstraeten GG, Cambier DC et al. CT imaging of trunk muscles in chronic low back pain patients and healthy control subjects. Eur Spine J 2000;9:266-272.
Page 12 of 19
250 251
252
10. Dennis RJ, Finch CF, Farhart PJ. Is bowling workload a risk factor for injury to Australian junior cricket fast bowlers? Br J Sports Med 2005;39:843-846.
11. Elliott BC, Hardcastle P, Burnett A et al. The influence of fast bowling and physical factors on the radiologic features in high performance young fast bowlers. Sports Med Train Rehab
254
1992;3, 113-130
255
ip t
253
12. Engstrom CM, Walker DG, Kippers V et al. Quadratus lumborum asymmetry and L4 pars injury in fast bowlers: a prospective MR study. Med Sci Sports Exerc 2007;39:910-917.
257
13. Foster D, John D, Elliott B et al. Back injuries to fast bowlers in cricket: a prospective study.
261
us
an
260
14. Hensinger RN. Spondylolysis and spondylolisthesis in children and adolescents. J Bone Joint Surg Am 1989;71:1098-1107.
M
259
Br J Sports Med 1989;23:150-154.
15. Hides J, Stanton W, Freke M et al. MRI study of the size, symmetry and function of the trunk
ed
258
cr
256
muscles among elite cricketers with and without low back pain. Br J Sports Med
263
2008;42:509-513.
264
ce pt
262
16. Hides J, Wilson S, Stanton W et al. An MRI investigation into the function of the transversus abdominis muscle during "drawing-in" of the abdominal wall. Spine (Phila Pa 1976.)
266
2006;31:E175-E178.
267 268
269 270
Ac
265
17. Hides JA, Jull GA, Richardson CA. Long-term effects of specific stabilizing exercises for firstepisode low back pain. Spine (Phila Pa 1976.) 2001;26:E243-E248.
18. Hides JA, Richardson CA, Jull GA. Multifidus muscle recovery is not automatic after resolution of acute, first-episode low back pain. Spine (Phila Pa 1976.) 1996;21:2763-2769.
Page 13 of 19
271
19. Hides JA, Stanton WR, McMahon S et al. Effect of stabilization training on multifidus muscle
272
cross-sectional area among young elite cricketers with low back pain. J Orthop Sports Phys
273
Ther 2008;38:101-108.
276
elite cricketers with low back pain. Scand J Med Sci Sports 2010;20:834-842.
ip t
275
20. Hides JA, Stanton WR, Wilson SJ et al. Retraining motor control of abdominal muscles among
21. Hides JA, Stokes MJ, Saide M et al. Evidence of lumbar multifidus muscle wasting ipsilateral
cr
274
to symptoms in patients with acute/subacute low back pain. Spine (Phila Pa 1976.)
278
1994;19:165-172.
283 284
285 286
287 288
289 290
an
M
282
23. Kountouris A, Portus M, Cook J. Quadratus lumborum asymmetry and lumbar spine injury in junior cricket fast bowlers. J Sci Med Sport 2012;15:393-397.
ed
281
ultrasound imaging. Muscle Nerve 2003;27:682-692.
24. Kountouris A, Portus M, Cook J. Cricket Fast Bowlers Without Low-Back Pain Have Larger Quadratus Lumborum Asymmetry Than Injured Bowlers. Clin J Sport Med 2013;23:300-304.
ce pt
280
22. Hodges PW, Pengel LH, Herbert RD et al. Measurement of muscle contraction with
25. McGregor AH, Anderton L, Gedroyc WM. The trunk muscles of elite oarsmen. Br J Sports Med 2002;36:214-217.
Ac
279
us
277
26. Rankin G, Stokes M, Newham DJ. Abdominal muscle size and symmetry in normal subjects. Muscle Nerve 2006;34:320-326.
27. Ranson CA, Burnett A, O'Sullivan PB et al. The lumbar paraspinal muscle morphometry of fast bowlers in cricket. Clin J Sports Med 2008; 18(1):31-37.
Page 14 of 19
291
28. Ranson CA, Burnett AF, King M et al. The relationship between bowling action classification
292
and three-dimensional lower trunk motion in fast bowlers in cricket. J Sports Sci 2008; 26(3):
293
267-276.
295
296
29. Sanchis-Moysi J, Idoate F, Dorado C et al. Large asymmetric hypertrophy of rectus abdominis muscle in professional tennis players. PLoS One 2010;5:e15858.
ip t
294
30. Urquhart DM, Barker PJ, Hodges PW et al. Regional morphology of the transversus
abdominis and obliquus internus and externus abdominis muscles. Clin Biomech (Bristol.,
298
Avon.) 2005;20:233-241.
us
cr
297
Ac
ce pt
ed
M
an
299
Page 15 of 19
300
Figure legends
301
Fig. 1
302
of transversus abdominis (TrA), obliquus internus abdominis (OI), obliquus externus abdominis (OE)
303
were made in the middle of the image and at 1-cm intervals on either side.
Measurement of muscle thickness from ultrasound imaging. Measurements of the thickness
ip t
304 Fig. 2
A. Total combined thickness of the abdominal muscles. Mean and standard deviation are
306
shown for muscles on the dominant and non-dominant side for fast bowlers with and without low
307
back pain. B. Thickness of the individual abdominal muscles. Mean and standard deviation are
308
shown for thickness of the muscles on the dominant and non-dominant side for fast bowlers with
309
and without low back pain.
an
us
cr
305
Ac
ce pt
ed
M
310
Page 16 of 19
Table 1
Table 1 Resting thickness measures of in participants with no low back pain OE (mm)
OI (mm)
TrA (mm)
De Troyer et al., (1990)
25-39
7.2±0.9
11.5±2.7
4.6±1.0
Critchley & Coutts (2002)
18-60
5.9±1.6
9.3±4.0
5.1±1.2
Hodges et al., (2003)
27-45
4.3±0.8
7.7±1.8
3.2±0.8
McKeekan et al., (2004)
29-52
Current study
14-18
Dominant
ip t
Age (years)
7.0±0.3
Non-dominant
9.0±1.9
16.3±2.7
7.4±1.9
12.3±2.2
4.9±1.4
cr
Author
4.1±0.9
Ac
ce pt
ed
M
an
us
TrA – transversus abdominis, OI – obliquus internus abdominis, OE – obliquus externus abdominis
Page 17 of 19
Ac
ce
pt
ed
M
an
us
cr
i
Figure 1
Page 18 of 19
Ac
ce
pt
ed
M
an
us
cr
i
Figure 2
Page 19 of 19