Individualized Accelerometer Activity Cut-Points for the Measurement of Relative Physical Activity Intensity Levels

Purpose: The aim of this study was to compare the widely used accelerometer activity cut-points derived from the absolute moderate intensity recommendation (3-6 METs), with relative intensity cut-points according to maximal cardiorespiratory fitness (46%-63% ) and to individual lactate thresholds (LT1 and LT2) in postmenopausal women. Method: Thirty postmenopausal women performed several exercise tests with measures of heart rate, blood lactate, accelerometer activity counts and oxygen consumption. Individual regressions were developed to derive the accelerometer activity counts at absolute and relative moderate intensity recommendations and at individual LTs. Results: The activity counts calculated at the lower moderate intensity boundary were lower for the absolute 3 METs threshold (2026 +/- 808 ct center dot min(-1)) compared to relative 46 % intensity threshold (p < .01, ES: 1.95) and LT1 (p < .01, ES: 2.27), which corresponded to 4.6 +/- 0.7 METs. The activity counts at the upper moderate intensity boundary were higher for LT2 (7249 +/- 2499 ct center dot min(-1)) compared to the absolute 6 METs threshold (p < .01, ES: 0.72) and relative 63% intensity threshold (p < .01, ES: 0.55). The interindividual variability in activity counts at relative intensity thresholds was high (CV = 30-34%), and was largely explained by cardiorespiratory fitness level (R-2 = similar to 50%). Conclusion: Individually tailored (relative to or submaximal LTs) rather than fixed accelerometer intensity cut-points derived from the classic absolute moderate physical activity intensity (3-6 METs) would result in a more accurate measurement of an individual ' s activity levels and reduce the risk of overestimating or underestimating physical activity.