Biceps femoris fascicle length is shorter in a previously
hamstring injured athlete.
David
1 School
1#
Opar ,
Kirsten
2
Porter ,
Morgan
2,3
Willaims , Anthony
1
Shield
of Exercise and Nutrition Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Australia
2School of Exercise Science, Australian Catholic University, Australia
3Division of Sport and Science, University of Glamorgan, Wales
#Corresponding author: d.opar@qut.edu.au
INTRODUCTION
Hamstring strain injury is the primary injury
type sustained across a number of sports. Of
further importance reinjury rates have been
high for many years and a previous insult is
commonly identified as the primary risk factor
for future injury. These data suggest that
maladaptation associated with previous injury
increases the risk of reinjury, however scant
attention has been paid to the impact of
hamstring strains on the architecture of the
previously injured hamstring. Therefore, the
purpose of this study was to determine the
impact of a previous hamstring strain injury on
biceps femoris long head muscle thickness,
pennation angle and fascicle length.
Table 1 Test-retest reliability for between limb mean differences (left – right) of biceps femoris long head architecture
variables assessed from ultrasound (n=26).
Test 1 (MeanSD)
Test 2 (MeanSD)
ICC (95% CI)
TE (95% CI)
-0.030.13
-0.030.13
0.97 (0.93 to 0.99)
0.02 (0.02 to 0.03)
Pennation Angle (°)
-0.32.0
-0.31.9
0.97 (0.93 to 0.99)
0.4 (0.3 to 0.5)
Fascicle Length (cm)
0.051.43
-0.051.41
0.96 (0.92 to 0.98)
0.29 (0.23 to 0.40)
Muscle Thickness (cm)
SD, standard deviation; 95%CI, 95% confidence intervals; ICC, intra-class correlation co-efficient ; TE, typical error.
METHODS
Thirty-one
participants
consented
to
participate in the study (22.4 ± 3.2 years; 1.82 ±
0.08m; 80.5 ± 9.6kg), which consisted of elite
male Australian footballers (n=14) and
recreational male athletes (n=17). Of the 31
participants, 18 reported a history of prior
unilateral hamstring strain injury, whilst the
remaining 13 formed an uninjured control
group. Details of injury history were
ascertained from notes taken during clinical
examination.
B-mode ultrasound (General Electric Vivid-i)
was performed on both limbs at a capture
depth of 8cm and a frequency of 12Hz with a
7Mhz linear-array transducer. Scan site was
determined as 50% of the distance between
the greater trochanter of the femur and the
lateral knee joint line, with the probe
positioned directly over the biceps femoris long
head. All ultrasonography was performed with
the muscle in a rested state and was collected
and analysed by the same investigator (KNP),
between 9am and 12pm, who was blinded to
the injury history of each participant. A subset
of 26 of the 31 participants were assessed five
to ten days following their first assessment to
determine the test-retest reliability of the
between limb differences of the measures.
Analysis was performed using Image J freeware
to determine biceps femoris long head muscle
thickness, pennation angle and fascicle length
(Figure 1). To determine reliability intra-class
correlation co-efficeint (ICC) and typical error
(TE) was determined. Dependent t-tests were
used to compared dependent variables in the
injured and uninjured limbs. Mean between
limb differences with 95% confidence intervals
were reported. Significance was set at p < 0.05.
RESULTS
Superficial aponuerosis
PA
MT
FL
Deep aponuerosis
Figure 1 Example ultrasound image of the biceps femoris
long head. Muscle thickness (MT), pennation angle (PA)
and fascicle length (FL) was determined using Image J.
Data pertaining to the reliability of the measures
of architecture variables assessed can be found in
Table 1. Based on intra-class correlation coefficient all measures displayed high levels of
reliability. Pennation angles (p = 0.001) and
fascicle lengths (p = 0.013) were significantly
different in the previously injured biceps femoris
long head compared to the contralateral uninjured
muscle, however muscle thickness did not differ (p
= 0.466) (Figure 2). There were no significant
between limb differences in muscle thickness
(mean difference = 0.02 cm, 95%CI = 0.00 to 0.03
cm; p = 0.0961), pennation angle (mean difference
= -0.1°, 95%CI = -0.9 to 0.8°; p = 0.8822) or fascicle
length (mean difference = -0.01 cm, 95%CI = -0.68
to 0.67 cm; p = 0.9864) in the uninjured group.
CONCLUSION
*
*
Ultrasound displayed high levels of measurement
reliability for biceps femoris long head muscle
thickness, pennation angle and fascicle length. A
previously injured biceps femoris long head
displays differences in pennation angle and fascicle
length compared to an uninjured contralateral
biceps femoris long head. These architectural
variations may partly explain the high tendency for
hamstring strain injuries to reoccur. Further work
is needed to confirm if differences in architecture
confer an increased risk of hamstring strain injury
or re-injury.
‘REAL WORLD’ IMPLICATIONS
Figure 2 Comparisons of architectural variables of
previously injured and uninjured biceps femoris long head
muscle. *p < 0.05 compared to injured limb.
•Hamstring muscle architecture data obtained via
ultrasound may present a methodology which
allows more objective assessment of rehabilitation
success .
•Clinicians should consider the assessment of
hamstring muscle architecture as a screening tool
for hamstring strain injury and reinjury.