PREDICTING THE ENERGY COST OF WALKING IN OLDER ADULTS 985

Abstract

The purpose of this study was twofold: to evaluate the ACSM prediction equation for energy cost of walking in older adults, and to identify predictors of the energy cost of walking in older adults. Twenty one attendants of the NY State Senior Games (8 males, 13 females, aged 55 to 75 yr) walked for a minimum of seven minutes at 80.4 m·min-1 (3 mph) on a motorized treadmill. Oxygen consumption (VO2 in ml·kg-1·min-1) was measured using an on-line gas analysis system (Ametek O2 and CO2 analyzers and Vacumed dry gas meter interfaced with a computer). Heart rate (beats·min-1) was monitored by a Polar Vantage XL heart rate monitor. Respiratory exchange ratio and caloric equivalent were used to convert VO2 in liters·min-1 to kilocalories·min-1. Average values for the last three minutes of exercise were used for data analysis. A paired t-test was used to determine that the actual VO2 (14.8 ml·kg-1·min-1±2.0) was significantly higher than the ACSM predicted VO2 (11.5 ml·kg-1·min-1) (t= 7.6, p<.0001). Stepwise regression (F-to-enter = 4.0, F-to-remove = 3.996) was used to examine body mass (kg), heart rate (HR), and sex (males = 0, females = 1) as predictors of the caloric cost of walking at 80.4 m·min-1. Each variable significantly contributed to the final equation: caloric cost(kcal·min-1) = -1.008 +.057 (mass) +.024 (HR) -.917 (sex). Mass was the strongest predictor of caloric cost (R=.886; F = 69.1, p<.0001). Heart rate entered the equation second (R =.916; F=47.0, p<.0001) and sex third with a final R of.945 (F = 47.7, p<.0001) accounting for 89% of the variance in the caloric cost of walking at 80.4 m·min-1. In conclusion, the ACSM equation did not provide an accurate estimation of the energy cost of walking on a horizontal treadmill for these older adults. Body mass, heart rate response to walking, and sex appear to provide a reasonable estimate of the energy cost of walking at a moderate pace in older adults.