A new device to measure energy expenditure during walking on uphill and downhill roads using accelerometer and barometric sensor for middle-aged and older people

Abstract

We developed a new device to measure energy expenditure during walking on uphill and downhill roads. First, we measured oxygen consumption rate (VO₂, respiratory gas analysis) and 3 dimensional acceleration (JD Mate, Kissei Comtec) in 42 middle-aged and older people(63±7(SD) yr) walking on treadmill with graded speed (2–7km/h) while the slope was varied from -15% to +15%. They walked for 3 min at subjectively slow, medial, fast, and fastest speeds for flat and uphill settings and walked at speeds of 3, 4, 5km/h for downhill settings. When the data for last 1min of each speed of walking were pooled, VO₂ (L/min) was highly correlated with the sum of a total impulse (I_total, N·min) and theoretical potential energy gain or loss (ΔPE_g or ΔPE_l, kg·m/min) with a regression equation of VO₂=0.046I_total+0.0014ΔPE_g-0.0006ΔPE_l+0.23 (R²=0.91, P<0.0001). The I_total was determined from a square root of summed accelerations of each direction, and the ΔPE_g or ΔPE_l was from a product of body weight and theoretical height change. Second, to validate the equation, we measured VO₂, I_total, and barometric pressure in 11 of 42 subjects walking on uphill and downhill roads in the field. The height changes were determined from the change in barometric pressure. The VO₂ estimated from the equation (EVO₂) was almost identical to VO₂ by respiratory gas analysis (R²=0.90, P<0.0001) with VO₂=0.91EVO₂+0.1. Thus, energy expenditure during walking on non-flat ground was precisely estimated with this device. [J Physiol Sci. 2007;57 Suppl:S187]