How Joint Torques Affect Hamstring Injury Risk in Sprinting Swing–Stance Transition

Abstract

PurposeThe potential mechanisms of hamstring strain injuries in athletes are not well understood. The study, therefore, was aimed at understanding hamstring mechanics by studying loading conditions during maximum-effort overground sprinting.MethodsThree-dimensional kinematics and ground reaction force data were collected from eight elite male sprinters sprinting at their maximum effort. Maximal isometric torques of the hip and knee were also collected. Data from the sprinting gait cycle were analyzed via an intersegmental dynamics approach, and the different joint torque components were calculated.ResultsDuring the initial stance phase, the ground reaction force passed anteriorly to the knee and hip, producing an extension torque at the knee and a flexion torque at the hip joint. Thus, the active muscle torque functioned to produce flexion torque at the knee and extension torque at the hip. The maximal muscle torque at the knee joint was 1.4 times the maximal isometric knee flexion torque. During the late swing phase, the muscle torque counterbalanced the motion-dependent torque and acted to flex the knee joint and extend the hip joint. The loading conditions on the hamstring muscles were similar to those of the initial stance phase.ConclusionsDuring both the initial stance and late swing phases, the large passive torques at both the knee and hip joints acted to lengthen the hamstring muscles. The active muscle torques generated mainly by the hamstrings functioned to counteract those passive effects. As a result, during sprinting or high-speed locomotion, the hamstring muscles may be more susceptible to high risk of strain injury during these two phases.

Late swing or early stance? A narrative review of hamstring injury mechanisms during high‐speed running

“…In the second half of swing, the hip produces a large extension moment (4.2 N·m·kg) while the knee displays a smaller flexion moment (1.8 N·m·kg) . During swing, net joint torques are primarily a result of muscle torques (generated from muscle contractions) and motion‐dependent torque (arising from the mechanical interaction of segments, eg, the angular acceleration of the shank) …”

“…This typically decreases prior to foot contact before a second smaller peak is observed in early stance (3‐ 11.6 N·kg −1 ) . However, it has also been proposed that the BFlh musculotendon force during early stance may have been underestimated due to over‐filtering, causing erroneously low hip and knee torques . It is argued that in early stance, ground reaction forces cause a large extension torque at the knee and a flexion torque at the hip.…”

“…It is argued that in early stance, ground reaction forces cause a large extension torque at the knee and a flexion torque at the hip. Consequently, the hamstrings would be under very high load, in order to produce large flexion torque at the knee, and extension torque at the hip, to counter the large passive forces …”

“…17,28 During swing, net joint torques are primarily a result of muscle torques (generated from muscle contractions) and motiondependent torque (arising from the mechanical interaction of segments, eg, the angular acceleration of the shank). 29,30 In contrast, during stance, the net joint torques primarily result from muscle torques and external forces (resulting from ground reaction forces). 29,30 During the beginning of the stance phase, the hip exhibits extensor dominance, reaching peak extension torque at approximately 4.1 N·m·kg, before changing to a flexion moment toward the latter half of stance.…”

“…29,30 In contrast, during stance, the net joint torques primarily result from muscle torques and external forces (resulting from ground reaction forces). 29,30 During the beginning of the stance phase, the hip exhibits extensor dominance, reaching peak extension torque at approximately 4.1 N·m·kg, before changing to a flexion moment toward the latter half of stance. 17,31,32 The reported knee moments during stance vary much more between studies, which may be attributed to different filtering techniques utilized.…”