Improved empirical estimates of work production in human walking motivate updated theory of step-to-step transition

Measuring biomechanical work performed by the body is critical for understanding muscle-tendon function, jointspecific contributions and energy-saving mechanisms during gait. Yet, we found that when we sum empirical jointand segment-level measures of work that they fail to capture substantial positive work performed by the body. For example, 25% of the total positive work that we know is performed by the human body during walking is missed by the most commonly-used estimates of work (at the hip, knee, ankle and foot). However, we discovered that this unmeasured work could be explained by extending conventional 3 degree-of-freedom (3DOF) inverse dynamics to full 6DOF joint work analysis. This 6DOF analysis, in turn, revealed that hip work may contribute more to walking than previously thought, including more positive work during mid and late stance phases of gait.