Biceps femoris long head muscle architecture in professional male soccer players with a recent history of T-junction hamstring injury: a preliminary case-control study in an English Premier League Club

To describe and compare biceps femoris long head (BFlh) muscle architecture between limbs with and without a recent history of T-junction hamstring injury. Case-control study. English Premier League club. Participants were 30 professional male soccer players, including 5 cases with recent history of unilateral T-junction hamstring injury and 25 controls with no recent hamstring injury. Participants had their BFlh fascicle length (FL), pennation angle (PA) and muscle thickness (MT) assessed bilaterally using wide-field-of-view ultrasound. Paired t-tests compared FL, PA and MT between previously injured (left) BFlh and contralateral uninjured (right) BFlh within cases. Un-paired t-tests compared left BFlh – right BFlh (asymmetry) in these measures between the case and control groups. Within cases, MT was significantly less in previously injured compared to contralateral uninjured BFlh (p<0.01; mean paired difference [95%CI] =-0.48cm [-0.59cm to -0.36cm]; p<0.01). Asymmetry in BFlh muscle thickness was significantly larger in the case group compared to control group (p<0.01; between-group mean difference [95%CI] = -0.51cm [-0.64cm to -0.37cm]). . BFlh FL and PA did not differ significantly within cases, or between the case and control groups. Between-limb deficits in BFlh MT exist following T-junction hamstring injury. • T-junction hamstring injury is associated with high re-injury risk in sport • Biceps femoris long head (BFlh) muscle architecture alters hamstring injury risk • This is the first investigation of BFlh muscle architecture after T-junction injury • Recent history of T-junction hamstring injury impairs BFlh muscle thickness