| Summary |
Despite equal changes in energy, the amount of muscle work from joint powers is greater while walking up vs. down an incline or stairway. We previously hypothesized a generalized biomechanical principle that muscles generate more mechanical energy during gait tasks that raise the body center of mass compared to the energy they dissipate during gait tasks that lower the center of mass. The purpose of this study was to compare the work produced by the lower extremity muscles during ascending and descending running. Twenty-six people were tested during level, and ascent and descent running on a 10° ramp. Lower extremity joint powers and work were calculated through inverse dynamics. We assumed this work quantified muscle contributions to changes in energy. Total work per stride was calculated from the change in total energy per stride in each task. Joint work for both limbs during descent, level, and ascent were -142 (±36), 27 (±17), and 203 (±34) J. The magnitude of joint work was 1.43 fold greater during ascent than descent. All sample means were significantly different from each other, p<0.05. Total work per stride during descent and ascent had magnitudes of-198 (±77), and 237 (±86) J respectively and were not significantly different. Joint work accounted for 72% of the total energy change during descent running and 86% during ascent running. Lower extremity muscles produced more work as calculated through joint powers and are responsible for more of the total work during ascent vs. descent running. The hypothesis was supported and appears to describe a robust biomechanical phenomenon. |
