Energy expenditure estimates of the Caltrac accelerometer for running, race walking, and stepping.

OBJECTIVE To examine the accuracy of the Caltrac accelerometer for estimating energy expenditure (EE) during three exercise modes. METHODS A subset of 31 women (mean (SEM) age 22.6 (5) years) as selected from a training study comparing various physiological parameters during race walking, running, and stepping. Subjects each performed mode specific graded exercise tests to peak VO2. Regression equations for VO2 v heart rate (HR) were generated from each individual's test data. EE (kcal and kJ) was estimated for each VO2 value based on the respiratory exchange ratio, and kcal v HR regression equations were generated to predict EE from each subject's HR data (EE-HR). HR in the field was monitored by telemetry, and two Caltrac monitors, one set for EE and one to give counts, were attached to a belt over opposite hips. RESULTS EE-HR was not significantly different across exercise modes. Caltrac overestimated EE (P < 0.01) in runners (14%) and walkers (19%) but underestimated EE in steppers by about 10% (P = 0.12). CONCLUSIONS The Caltrac is a reliable instrument but it did not accurately distinguish EE in running, race walking, or stepping in a group of young women.