1Human Evolutionary Biology, Harvard University, 2Organismic and Evolutionary Biology, Harvard University
Friday 49, Plaza Level
The human iliotibial band (ITB) is a complex structure in the lower limb derived from the fascia lata (FL) of the thigh that is unique to humans among apes but whose function is not well understood. The anatomy of the ITB makes it a candidate for elastic energy storage and recovery of the limb’s fluctuating energy in swing. Because in vivo measures of human muscle and tendon function are limited and the FL of cursorial quadrupeds may be convergent with the human ITB, we used a goat model to examine energy storage. Sonomicrometry crystals were implanted in the FL to measure strain during locomotion. Using sonomicrometry and electromyography, we also examined how the tensor fascia lata and gluteobiceps (GB) muscles contract to transmit force via the FL.
If the goat FL stores energy at the end of stance and recovers the energy in initial swing, we would expect the FL to stretch through stance and then shorten after initial swing. During trotting and galloping, the FL stretches through the stance-swing transition and then shortens after initial swing. While the FL stretches GB actively shortens, indicating that the FL is stretched by GB contraction. These data indicate that the goat FL stores and recovers elastic energy during swing. These results suggest that swing phase energy storage in the human ITB should be explored further. The role of the human ITB in energy storage is likely to improve the economy of human gait and may provide insight into the evolution of bipedalism.