Meeting Abstract

17.2  Jan. 4  Complex Effect of Limb Length on Cost of Transport in Running Humans MYERS, M.J.*; WALL-SCHEFFLER, C.M.; WEAVER, T.D.; STEUDEL-NUMBERS, K.L.; College of St. Catherine, St. Paul; University of Wisconsin-Madison; University of California-Davis; University of Wisconsin-Madison mjmyers@stkate.edu

It is unclear whether longer limbs relative to body mass (BM) should increase the cost of transport during running (greater mechanical work due to larger limb inertia) or decrease it (longer stride lengths, fewer strides), or whether these effects might offset one another. We recruited 13 subjects (6F,7M; 18-30 y) whose legs were relatively long or short for their BM (BM 50.0-96.4 kg, limb length 73.5-99.0 cm). Subjects ran on a treadmill at 2.68 m/s while expired gases were collected to calculate net metabolic cost of transport (NCOT, met power/distance). Kinematic variables were determined from high-speed video. Leg moment-of-inertia (LI) was calculated from anthropometric and kinematic measures: (avg distance from hip to limb center-of-mass during swing)squared*(estimated limb mass). BM explained 82% of variation in NCOT; limb length (LL) explained an additional 12% and the effect was negative (relatively longer limbs correlated with lower NCOT). This effect was mainly due to relatively shorter-legged people who chose a longer stride length (SL) for their BM. Although relatively longer limbs (residuals from regression against body mass as a control for body size) have relatively higher LI, which should increase NCOT, relatively longer-legged individuals use kinematic patterns that counteract the expected increase in cost. The effect of LL/LI on NCOT (not accounted for by BM), depends upon the SL chosen (when speed is fixed). Subjects with the lowest NCOT have relatively long legs/high LI/long SL and swing their legs with lower angular velocity for their BM. Subjects with the highest NCOT have relatively short legs/low LI/long SL and swing their legs with higher angular velocity for their BM.