Predicting walking METs and energy expenditure from speed or accelerometry

Purpose: a) Compare the predictive potential of speed and CSA_hip (Computer Science Applications accelerometer positioned on the hip) for level terrain walking METs (1 MET = VO₂ of 3.5 mL·kg ^-1·min^-1) and energy expenditure (kcal·min^-1); b) cross-validate previously published CSA _hip- and speed-based MET and energy expenditure prediction equations; c) measure self-paced walking speed, exercise intensity (METs) and energy expenditure in the middle aged population. Methods: Seventy-two 35- to 45-yr-old volunteers walked around a level, paved quadrangle at what they perceived to be a moderate pace. Oxygen consumption was measured using the criterion Douglas bag technique. Speed, CSA_hip, heart rate, and Borg rating of perceived exertion were also monitored. Results: Speed explained 10% more variance of walking METs than CSA_hip. Speed and mass explained 8% more variance of walking energy expenditure (kcal·min^-1) than CSA_hip and mass. The best previously published regression equations predict our walking METs and energy expenditures within 95% prediction limits of ± 0.7 METs (8) and ± 1.0 kcal·min^-1 (23), respectively. Women paced themselves at a significantly higher mean speed (5.5 km·h^-1) and intensity (4.1 METs) than their male counterparts (5.2 km·h^-1 and 3.8 METs). Both genders expended ∼0.75 kcal·kg^-1 for every kilometer of level terrain walked. Conclusion: Speed-based MET and energy expenditure predictions during level terrain walking were more accurate than those utilizing CSA_hip.