3D model reveals hamstring biomechanics
MedWire News: Hamstring injury-prevention and rehabilitation programs should focus on strengthening exercises involving eccentric muscle contractions, advise Australian experts.
Their recommendations are based on a new 3D model of the mechanics of the human hamstring during sprinting, insights from which are reported in Medicine & Science in Sports & Exercise.
Anthony Schade (University of Melbourne, Victoria) and team hypothesized that hamstring mechanics might explain why these muscles are so vulnerable to acute strain-type injury. To investigate, they recorded full-body kinematics and ground-reaction force data from five male and two female volunteers while sprinting on an indoor running track.
These experimental data were used to develop a 3D musculoskeletal computer model featuring 12 body segments and 92 musculotendon structures. The model was used in conjunction with an algorithm to estimate various hamstring parameters, including musculotendon strain, velocity, force, power, and work.
Schade et al note that the average sprinting speed was 8.95 m/s and that their computer model showed generally good agreement with observed experimental data.
Importantly, the model revealed that all three hamstring muscles - ie, semimembranosus, semitendinosus, and biceps femoris long head - all reached peak strain, produced peak force, and performed negative work (energy absorption) during terminal swing.
The biomechanical load differed for each hamstring muscle, however. Specifically, the biceps femoris long head exhibited the largest peak strain while the semitendinosus displayed the greatest lengthening velocity.
Meanwhile, the semimembranosus produced the highest peak force, absorbed and generated the most power, and performed the largest amount of positive and negative work.
Taken together, these findings indicate that the hamstrings are at greatest risk for injury during terminal swing, because this is when biomechanical load is greatest, Schade and co-authors surmise.
"These outcomes have implications for improving existing understanding of the pathomechanics of sprinting-related hamstring muscle strain-type injuries," they conclude.
"On this basis, hamstring injury prevention or rehabilitation programs should preferentially target strengthening exercises that involve eccentric contractions performed with high loads at longer musculotendon lengths."
By Joanna Lyford