Monitoring intensity during head-out water based activities (water fitness): a comparison among different measurement techniques

The aim of this study was to compare different measurement techniques (indirect calorimetry, IC; heart rate monitoring, HR; Actiheart, AH, an activity monitoring system; rates of perceived exertion, RPE) to estimate physical activity intensity (PAI) during water based exercises (WE). Twelve young active women performed five different WE at three different movement frequencies (15 trials) in an indoor swimming pool (Raffaelli et al., 2010). During the trials the subjects were monitored with: a portable metabolic system (K4b2, Cosmed, I), a heart rate monitor (T31, Polar, Fi), the Actiheart (Cambridge Neurotechnology, UK) and the Borg Scale. Each trial lasted 10 min, with a 5 min rest in between; the data recorded at steady state (5 – 9th min) were averaged to obtain mean VO2, HR and AH values. Finally, VO2 was also estimated from HR data using three different HR/VO2 regression equation models (ACSM, 1998; Brown al., 1998; Raffaelli et al., 2010). The values obtained by means of AH, HR and RPE were all significantly related with data of IC (p<0.001); the highest correlations were found between the measured values of VO2 (IC) and the values of VO2 estimated from the three HR/VO2 equations (r>0.8 in all cases). The ANOVA test showed a non significant difference between all predicted and measured VO2 values. When the Bland&Altman analysis was considered, the Actiheart values showed the larger explained variances (95% CI) and the larger standard errors. In conclusion, even if all the analyzed methods are able to detect changes of intensity during WE and are significantly correlated with IC data, the more accurate way to estimate PAI during WE is still based on HR measurements