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Oxygen uptake and heart rate kinetics during dynamic upper and lower body exercise: an investigation by time-series
U Drescher1, J Koschate, U Hoffmann
1German Sport University, Institute of Physiology and Anatomy, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany, Drescher@dshs-koeln.de.
Purpose:
The study compared the kinetic responses of heart rate (HR), pulmonary ([Formula: see text]O2pulm) and muscular oxygen uptake ([Formula: see text]O2musc) for upper (UpBody) and lower body (LoBody) exercise.
Methods:
Eleven healthy men (24 ± 2 years, 184 ± 8 cm, 79 ± 7 kg) performed pseudo-random binary sequence (PRBS) work rate (WR) changes on a semi-recumbent cycle ergometer (30 and 80 W) and an arm cranking exercise device (20 and 50 W); followed by stepwise increases in WR (UpBody: 20 W 5 min(-1); LoBody: 50 W 5 min(-1)). [Formula: see text]O2pulm was measured breath-by-breath and HR beat-to-beat. [Formula: see text]O2musc was estimated by the approach as reported by Hoffmann et al. (Eur J Appl Physiol 113:1745-1754, 2013), accounting for circulatory distortions. Time constants (τ) for HR (τHR), [Formula: see text]O2pulm (τ [Formula: see text]O2pulm) and [Formula: see text]O2musc (τ [Formula: see text]O2musc) were estimated during the PRBS phases by time-series analysis.
Results:
Peak oxygen uptake differed significantly between UpBody (37.8 ± 5.0 ml min(-1) kg(-1)) and LoBody exercises (56.1 ± 7.4 mL min(-1) kg(-1); p < 0.001). Significant differences were observed for τ [Formula: see text]O2musc (UpBody: 41.1 ± 11.3 s vs LoBody: 29.5 ± 5.2 s; p < 0.05), but not for τ [Formula: see text]O2pulm (49.1 ± 17.1 s vs 39.6 ± 11.2 s; p > 0.05) and τHR (29.1 ± 15.6 s vs 25.6 ± 8.0 s; p > 0.05).
Conclusions:
Meaningful dissociations between [Formula: see text]O2pulm and [Formula: see text]O2musc kinetics exist for both UpBody and LoBody exercise during rapid work rate changes. Therefore, isolated [Formula: see text]O2pulm kinetic estimations without the consideration of the circulatory distortions may not allow a reliable assessment of [Formula: see text]O2musc kinetics.
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