LEG SPRING CHARACTERISTICS AND THE AEROBIC DEMAND OF RUNNING

Purpose: By applying a simple, linear mass-spring model to running, th e normalized leg spring stiffness (K-leg), the normalized effective ve rtical stiffness (K-vert), and the mass-specific mechanical power outp ut of the spring (P-sp) were determined and correlated with aerobic de mand. The purpose of the study was to determine whether leg spring cha racteristics explain any of the interindividual variability observed i n aerobic demand at a given submaximal running speed. Methods: Recreat ional runners (N = 16) ran on a treadmill at 3.35 m.s(-1) for physiolo gical measures and overground for biomechanical measures. The latter i ncluded a sagittal plane video record of the running motion and ground reaction data. Results: We found no relationship between the aerobic demand of running and K-leg (r = -0.18), an inverse relationship betwe en aerobic demand and K-vert (t = -0.48), and a positive correlation b etween aerobic demand and P-sp (r = 0.45). Conclusions: The inverse re lationship between K-vert and aerobic demand indicates that less econo mical runners possess a more compliant running style during ground con tact. This running style may place greater force demands on extensor m usculature.