Analysis of heart rate and oxygen uptake kinetics studied by two different pseudo-random binary sequence work rate amplitudes.

Purpose: The aim of the study was to compare the kinetics responses of heart rate (HR), pulmonary (V˙Opulm) and predicted muscular (V˙Omusc) oxygen uptake between two different pseudo-random binary sequence (PRBS) work rate (WR) amplitudes both below anaerobic threshold.

Methods: Eight healthy individuals performed two PRBS WR protocols implying changes between 30W and 80W and between 30W and 110W. HR and V˙Opulm were measured beat-to-beat and breath-by-breath, respectively. V˙Omusc was estimated applying the approach of Hoffmann et al. (Eur J Appl Physiol 113: 1745-1754, 2013) considering a circulatory model for venous return and cross-correlation functions (CCF) for the kinetics analysis.

Results: HR and V˙Omusc kinetics seem to be independent of WR intensity (p>0.05). V˙Opulm kinetics show prominent differences in the lag of the CCF maximum (39±9s; 31±4s; p<0.05).

Conclusions: A mean difference of 14W between the PRBS WR amplitudes impacts venous return significantly, while HR and V˙Omusc kinetics remain unchanged.