AMBULATORY FOOT CONTACT MONITOR TO ESTIMATE METABOLIC COST OF HUMAN LOCOMOTION

The rate of metabolic energy expenditure during locomotion (M(loco)) is propertional to body weight (W-b) divided by the time during each stride that a single foot contacts the ground (t(c)) (Nature Lond. 346: 265-267, 1990). Using this knowledge, we developed an electronic foot contact monitor. Our objective was to derive and cross-validate an equation for estimating M(loco) from W-b/t(c). Twelve males were tested [age = 19.4 +/- 1.4 (SD) yr, W-b = 78.4 +/- 8.0 kg] during horizontal treadmill walking (0.89, 1.34, and 1.79 m/s) and running (2.46, 2.91, and 3.35 m/s). Measured M(loco) was defined as the total rate of energy expenditure, measured by indirect calorimetry, minus the estimated rate of resting energy expenditure. The equation to estimate M(loco) was derived in six randomly selected subjects: M(loco) = 3.702.(W-b/t(c)) -149.6 (r(2) = 0.93). Cross-validation in the remaining six subjects showed that estimated and measured M(loco) were highly correlated (r(2) = 0.97). The average individual error between estimated and measured M(loco) was 0% (range -22 to 29%). In conclusion, M(loco) can be accurately estimated from W-b and measurements of t(c) made by an ambulatory foot contact monitor.