Altered biceps femoris muscle lengths in athletes who have returned to full participation in sport following sprint related hamstring injury

Sprint related hamstring injury accounts for 10-24% of all injuries across a range of field-based sports (1, 2) with prior injury associated with an elevated risk of subsequent re-injury (3, 4). There is a need understand factors which may contribute to increased risk of re-injury. Previously we have shown altered electromyography alongside pelvis, hip and knee kinematics during late swing in previously injured athletes (5). The aim of this study is to examine muscle-tendon (MT) hamstring lengths during sprinting using musculoskeletal modelling. Do athletes who have returned to sport following sprint related hamstring injury display altered MT length characteristics during high speed running? A 3D motion capture (3DMC) dataset comprising of n=9 Gaelic Games athletes who had returned to full participation in sport following hamstring injury, underwent extended analysis to estimate MT lengths during running. The dataset was collected with the CODAmotion system, while subjects ran at 20kph on a treadmill. All available strides over a 10 second capture were averaged for previously injured and uninjured limbs. Length of the biceps femoris long head (BFLH), semitendinosus (ST) and semimembranosus (SM) were estimated by inputting kinematic data to the OpenSIM modif-OSM-CGM-angles model (6) using OpenSIM (v 4.0) and Matlab (v 2021a). A control dataset of n=8 closely matched, uninjured teammates was also extracted with a mean of left and right sides used for comparison. Estimated MT lengths were normalised to average control peak length (n=8, 16 limbs). Subject descriptors are available in the primary paper (5). A statistical parametric mapping one-way analysis of variance (SPM ANOVA) was used to examine the difference between previously injured, contralateral and control limbs (α = 0.05). Where significant differences were detected, post-hoc analysis was conducted to understand the group interactions. There were no group differences for the ST or SM MT lengths across the running stride. The BFLH length was significantly shorter in stance phase in the previously injured limb. Post-hoc analysis indicates significant effects for previously injured BFLH length compared to contralateral and control limbs. Although not significant, the average peak BFLH length exceeded the average peak length of the control group in late swing (see Fig. 1).Download : Download high-res image (163KB)Download : Download full-size image In previously injured athletes, the BFLH demonstrates increased functional range in running. In stance phase, the BFLH is shortened compared to the contralateral side and control group. In addition, qualitative appraisal of BFLH peak length in swing indicates that the previously injured muscle, on average, exceeds to maximum length of the contralateral side and the controls. The aetiology of this phenomenon may be within the muscle (i.e. persistent impaired function) or due to altered motor control at the pelvis, hip and/or knee. The data is retrospective and the relationship to future injury risk is not determined.