Oxygen consumption, heat production, and muscular efficiency during uphill and downhill walking

Oxygen consumption, heat production, and muscular efficiency for walking are parameters important to know for ergonomics models and equipment design. Most of these assume that the oxygen consumption and heat production of downhill walking are the same as for uphill walking. Eight subjects wearing insulating clothing walked on a treadmill at three uphill and three downhill grades, and at level grade at a rate of 1.1 m/s. Oxygen consumption VO2 was calculated from steady state measurements of respiratory minute volume and oxygen percentage. Heat production (q) was calculated from the rate of heat storage in the body and clothing. Least-squares best fit equations for oxygen consumption and heat production found were to be VO2 = 0.813 + 0.0361G + 0.000810G2 - 0.0000302G3 and q = 6.55 + 0.185G + 0.0114G2 - 0.000190G3 where G is percent grade. Approximations show that VO2 (downhill) = 0.5 VO2 (uphill), q (downhill) = 0.67 q (uphill), and muscular efficiency eta (downhill) = -2eta (uphill).