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Erschienen in:
01.08.2015 | Original Article
Oxygen uptake and heart rate kinetics during dynamic upper and lower body exercise: an investigation by time-series analysis
Erschienen in: European Journal of Applied Physiology | Ausgabe 8/2015
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Purpose
The study compared the kinetic responses of heart rate (HR), pulmonary (\(\dot V\)O2pulm) and muscular oxygen uptake (\(\dot V\)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). \(\dot V\)O2pulm was measured breath-by-breath and HR beat-to-beat. \(\dot V\)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), \(\dot V\)O2pulm (τ
\(\dot V\)O2pulm) and \(\dot V\)O2musc (τ
\(\dot V\)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
\(\dot V\)O2musc (UpBody: 41.1 ± 11.3 s vs LoBody: 29.5 ± 5.2 s; p < 0.05), but not for τ
\(\dot V\)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 \(\dot V\)O2pulm and \(\dot V\)O2musc kinetics exist for both UpBody and LoBody exercise during rapid work rate changes. Therefore, isolated \(\dot V\)O2pulm kinetic estimations without the consideration of the circulatory distortions may not allow a reliable assessment of \(\dot V\)O2musc kinetics.