Methods for calculating internal mechanical work: comparison using elite runners.

Two methods for calculating internal work-the absolute work method, based on changes in mechanical energy, and the absolute power method, based on the powers produced by the joint moments of force-were compared. The results from both methods were normalized to body mass and running speed to obtain the 'internal biomechanical cost' (IBC). The IBCs of normal running for eight runners were compared to their IBCs for four inefficient running styles. The absolute power method was able to detect the inefficient runs significantly more often than the absolute work method (chi2 = 3.22, P < 0.05). In addition, the absolute power method showed less variability quantifying both internal and external work. In conclusion, the absolute power method was judged the superior technique for quantifying mechanical energy costs of running.