Hip Abductors and Lumbar Lateral Flexors act as Energy Generators in Running Single-leg Jumps

In humans, hip abductor and lumbar lateral flexor muscles are well-developed as side-to-side lumbopelvic stabilizers. We hypothesized that the hip abductors and lumbar lateral flexors act as energy generators during a running single-leg jump, although they are generally recognized as stabilizers. We collected kinematics and ground reaction force data in running single-leg jumps by 13 male high jumpers and calculated three-dimensional kinetic variables. Hip abduction and lumbosacral lateral flexion towards free leg side torques were exerted during almost the entire take-off phase, exerting positive power during the terminal 2/3 of the phase. The positive work of the hip abductors (1.08±0.30 J/kg) was as large as that of the ankle plantar-flexors, suggesting that the energy-generating potential of the hip abductors compares with that of the extensors of the stance-leg joints. The lumbosacral lateral flexors also performed positive work (0.36±0.18 J/kg), which was 47±25% of the knee extensors, albeit less than the extensors of the stance leg joints. The results implied that the hip abductors and lumbar lateral flexors have substantial potentials not only as stabilizers but also as energy generators and that they act as substantial energy generators during running single-leg jumps.