Key result
In male youths, the phase II time constant of pulmonary oxygen uptake was significantly slower during moderate to very heavy-intensity cycling (42 ± 16 s) compared to unloaded to moderate cycling (23 ± 6 s, P < 0.001).
Why the study?
It was unclear whether phase II pulmonary oxygen uptake kinetics display linear, first-order behaviour in association with skeletal muscle oxygenation changes during step cycling of different intensities or initiated from an elevated work rate in youths.
Do different intensities of step cycling alter pulmonary oxygen uptake and muscle deoxygenation kinetics in male youths?
Population
19 male youths aged 11.7–15.7 years
Comparison
Step cycling transitions U → M vs U → VH vs M → VH
Authors
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Work-to-work transitions may slow O2 uptake kinetics in male youths; hypothesis-generating and leaves open effects on exercise capacity or training.
Observational (n=19)
Do different intensities of step cycling alter pulmonary oxygen uptake and muscle deoxygenation kinetics in male youths?
Absolute Event Rate: 42% vs 23%
p-value: p=<0.001
In youths, 'work-to-work' transitions slow microvascular O2 delivery-to-O2 utilization, with alterations in phase II dynamics accentuated between ages 11 and 15.
Breese et al. (2019) conducted an observational in Healthy (n=19). Moderate to very heavy-intensity step cycling (M → VH) vs. Unloaded to moderate-intensity step cycling (U → M) was evaluated on Phase II time constant of pulmonary oxygen uptake (seconds) (p=<0.001). In male youths, the phase II time constant of pulmonary oxygen uptake was significantly slower during moderate to very heavy-intensity cycling (42 ± 16 s) compared to unloaded to moderate cycling (23 ± 6 s, P < 0.001).
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