Measurement accuracy of heart rate and respiratory rate during graded exercise and sustained exercise in the heat using the zephyr BioHarness ^TM

The Zephyr BioHarness^TM was tested to determine the accuracy of heart rate (HR) and respiratory rate (RR) measurements during 2 exercise protocols in conjunction with either a laboratory metabolic cart (Vmax) or a previously validated portable metabolic system (K4b²). In one protocol, HR and RR were measured using the BioHarness and Vmax during a graded exercise up to V̇O_2max (n=12). In another protocol, HR and RR were measured using the BH and K4b² during sustained exercise (30% and 50% V̇O_2max for 20 min each) in a hot environment (30 °C, 50% relative humidity) (n=6). During the graded exercise, HR but not RR, obtained from the BioHarness was higher compared to the Vmax at baseline and 30% V̇O_2max (p<0.05), but showed no significant difference at other stages with high correlation coefficients for both HR (r=0.87-0.96) and RR (r=0.90-0.99 above 30% V̇O_2max). During the exercise in the heat, there were no significant differences between the BioHarness and K4b ² system. Correlation coefficients between the methods were low for HR but moderately to highly correlated (0.49-0.99) for RR. In conclusion, the BioHarness is comparable to Vmax and K4b² over a wide range of V̇O₂ during graded exercise and sustained exercise in the heat.