Key result
Endurance training status dissociates the slow components of phosphocreatine and pulmonary oxygen uptake during heavy exercise, minimizing the PCr slow component in trained athletes.
Observational (n=13)
The study challenges the mechanistic link between phosphocreatine and pulmonary O2 uptake slow components, demonstrating they can be dissociated depending on training status.
May not yet inform exercise testing or training; challenges assumed PCr-VO2 slow-component coupling in observational data.
To better understand the mechanisms underlying the pulmonary O(2) uptake (V(O(2P))) slow component during high-intensity exercise, we used (31)P magnetic resonance spectroscopy, gas exchange, surface electromyography and near-infrared spectroscopy measurements to examine the potential relationship between the slow components of V(O(2P)) and phosphocreatine (PCr), muscle recruitment and tissue oxygenation in endurance-trained athletes and sedentary subjects. Specifically, six endurance-trained and seven sedentary subjects performed a dynamic high-intensity exercise protocol during 6 min at an exercise intensity corresponding to 35-40% of knee-extensor maximal voluntary contraction. The slow component of V(O(2P))(117 ± 60 ml min(-1), i.e. 20 ± 10% of the total response) was associated with a paradoxical PCr resynthesis in endurance-trained athletes (-0.90 ± 1.27 mm, i.e. -12 ± 16% of the total response). Meanwhile, oxygenated haemoglobin increased throughout the second part of exercise and was significantly higher at the end of exercise compared with the value at 120 s (P < 0.05), whereas the integrated EMG was not significantly changed throughout exercise. In sedentary subjects, a slow component was simultaneously observed for V(O(2P)) and [PCr] time-dependent changes (208 ± 14 ml min(-1), i.e. 38 ± 18% of the total V(O(2P))response, and 1.82 ± 1.39 mm, i.e. 16 ± 13% of the total [PCr] response), but the corresponding absolute or relative amplitudes were not correlated. The integrated EMG was significantly increased throughout exercise in sedentary subjects. Taken together, our results challenge the hypothesis of a mechanistic link between [PCr] and V(O(2P)) slow components and demonstrate that, as a result of a tighter metabolic control and increased O(2) availability, the [PCr] slow component can be minimized in endurance-trained athletes while the V(O(2P)) slow component occurs.
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Layec et al. (2012) conducted an observational in Healthy subjects (endurance-trained and sedentary) (n=13). Endurance training status vs. Sedentary status was evaluated on Relationship between the slow components of pulmonary O2 uptake (VO2P) and phosphocreatine (PCr). Endurance training status dissociates the slow components of phosphocreatine and pulmonary oxygen uptake during heavy exercise, minimizing the PCr slow component in trained athletes.
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