Objectively measured absolute and relative physical activity intensity levels in postmenopausal women

Abstract

Objectives: To investigate how objectively measured physical activity (PA) levels differ according to absolute moderate intensity recommendation (3–6 METs) and relative to individual lactate thresholds (LT1 and LT2), and to verify if high-fit women record higher PA levels compared to women with lower aerobic fitness.Methods: Seventy-five postmenopausal women performed an incremental exercise test and several constant-velocity tests wearing an accelerometer to identify the activity counts (ct min−1) corresponding to LT1 and LT2. Individual linear regression determined activity counts cut-points for each intensity: (1) sedentary (<200 ct min−1), (2) light (from 200 ct min−1 to ct min−1 at LT1), (3) moderate (ct min−1 between LT1 and LT2) and (4) vigorous (ct min−1 > LT2). Participants then wore an accelerometer during a week to measure the time spent at each PA intensity level.Results: According to absolute intensity categorisation, high-fit postmenopausal women recorded twice as much time at moderate-to-vigorous PA (MVPA) (P < 0.01) than low-fit women. However, when PA intensity was calculated relative to individual lactate thresholds, MVPA was significantly reduced by half (P < 0.01) and the data revealed no differences (P = 0.62) between groups (∼20 min day−1 at MVPA).Conclusions: Accelerometer cut-points derived from absolute moderate-intensity recommendations overestimated MVPA. Similar time at MVPA was recorded by high- and low-fit postmenopausal women when the cut-points were tailored to individual lactate thresholds. A more accurate estimation of PA behaviour could be provided with the use of individually tailored accelerometer cut-points.