Different methods for monitoring intensity during water-based aerobic exercises

The aim of this study was to compare different measurement techniques (indirect calorimetry, IC; heart rate monitoring, HR; an activity monitoring system, AH; rates of perceived exertion, RPE) to estimate physical activity intensity (light, moderate, vigorous) during water-based aerobic exercises (WE). Twelve healthy young women performed five common WE of 10-min duration at three frequencies in an indoor swimming pool. Data recorded from the 5th to 9th minute of exercise were averaged to obtain mean (V) over dotO(2) (IC), HR and AH values; RPE was recorded at the end of each WE. Oxygen uptake was also estimated from HR data using three different (V) over dotO(2) versus HR regression equation models. Significant correlations (p < 0.001) were found for the indirect methods that used HR, RPE and AH data regressed as a function of (V) over dotO(2) (IC); the highest correlations were found between the measured values of (V) over dotO(2) (IC) and those estimated from the three (V) over dotO(2) versus HR equations (R > 0.7 in all cases). An ANOVA test showed no significant differences between all predicted and measured (V) over dotO(2) values; however, when the Bland & Altman analysis was considered, AH data showed the larger explained variances (95% CI) and the larger standard errors. These data indicate that the most accurate way to estimate physical activity intensity during WE is based on HR measurements.