Game-play affects hamstring but not adductor muscle fiber mechanics in elite-level basketball athletes

Introduction: Game-play towards the latter part of a half or game is thought to induce ‘muscle fatigue’ which has been associated with increased risk of hamstring and hip adductor muscle tendon unit (MTU) injury. Effects of game-play are typically investigated using fixed-intensity laboratory protocols, which may be erroneous as game-play is self-paced and effects of fatigue are task dependent. There is a need to understand how actual game-play might affect muscle function, and thus performance and MTU injury risk in sport. This study aimed to quantify hamstring and adductor MTU mechanics during a cut task, a frequent movement in basketball involving hamstring and adductor activation potentially related to strain injury, before and after basketball game-play.
Methods: The cut task was performed by ten healthy elite male U20 basketball players (age=17.2±1.1years, mass=90.5±12.3kg, height=198.4±9.4cm) both before and immediately after they played in one of four competitive basketball games during a five-day national scouting camp. Three-dimensional ground reaction forces (Kistler; 2000Hz), electromyograms of hamstring and adductor muscles (Trigno EMG System; 2000Hz), and three-dimensional kinematic (Qualisys; 250Hz) data were synchronously recorded. The Calibrated EMG-informed Neuromusculoskeletal Modelling toolbox was used to calculate hamstring and adductor muscle fiber mechanics (muscle forces, fiber lengths, and fiber velocities). A region of interest one-dimensional statistical parametric mapping paired t-test (α=.05) was used to compare pre- and post-game MTU mechanics.
Results: Biceps femoris long head produced significantly lower (pre:448±364N; post:401±349N; p=.032) submaximal force postgame in the latter part of swing (30.7% to 35.0% of stride), though its peak force occurred later (~37% of stride) and remained unchanged in relation to pre-game. Semimembranosus produced significantly lower (pre:2465±1166N; post:2016±1078N; p=.006) force post-game (32.9% to 44.9% of stride), which encompassed the instance of peak force (~39% of stride). No significant post-game changes were found for any adductor muscles. Neither fiber velocity nor fiber length in any investigated muscle were significantly affected by game-play.
Discussion: This is the first study to provide insights into changes in muscle fiber mechanics resulting directly from game-play. Lower muscle forces and no significant changes in fiber length or fiber velocity post-game indicate that if basketball game-play is a factor in hamstring and adductor muscle strain injuries, it is not necessarily through changed fiber mechanics. Based on the fiber mechanics examined, the phases of increased risk for strain injury during the cut task are hypothesized as the swing-stance transition for the hamstrings and mid-late stance for the adductors. These hypotheses may be specific to the cut task but suggest that future research consider these phases.

Impact and application to the field
• Changes in hamstring and adductor MTU mechanics resulting from basketball game-play are not indicative of strain injury
• Phases of increased risk for strain injury during the cut task are swing-stance transition for hamstrings and mid-late stance for adductors

Conflict of interest statement: No competing interests declared. This study was financially supported by General Electric and National Basketball Association Orthopedics and Sports Medicine Collaboration.