Key result
Constant-load cycling at 85% of maximal work-load compared to 75% significantly increased VO2 slow component (+59%) but did not change deoxyhemoglobin slow component (3.44 vs 3.10 A.U.; p=0.60).
Why the study?
Does exhaustive constant-load cycling at 85% vs 75% of maximal workload alter respiratory and vastus lateralis oxygenation responses in moderately-trained males?
RCT (n=8)
Randomized
Does exhaustive constant-load cycling at 85% vs 75% of maximal workload alter respiratory and vastus lateralis oxygenation responses in moderately-trained males?
Exercise intensity affects the contribution of locomotor muscles to the VO2 slow component magnitude, but not that of ventilation.
Answers are grounded in this paper and cite their sources.
Intensity selection may modulate VO2 slow component during exhaustive cycling; leaves open muscle deoxygenation contributions in trained athletes.
Objective: We investigated the respiratory and vastus lateralis oxygenation responses to exhaustive, constant-load cycling at two exercise intensities. Methods: Eight moderately-trained male randomly cycled to exhaustion at 75% and 85% of maximal work-load (CL75 and CL85, respectively) measured during a maximal incremental test. From continuous recordings of respiratory variables and near-infrared spectroscopy signals of the vastus lateralis muscle, VO2 slow component (SC) and deoxyhemoglobin (HHb) SC were calculated. Results: At exhaustion, VO2 (+19 ± 25%), VO2 SC (+59 ± 24%) and minute ventilation (+14 ± 14%) were significantly higher during CL85 vs. CL75, whereas oxyhemoglobin (-67 ± 22%) and total hemoglobin (-36 ± 3%) responses were lower (all p<0.05). Additionally, VO2 SC during CL75 and CL85 were strongly correlated (r=0.88, p<0.001). The HHb SC did not differ between CL75 and CL85 (3.10 ± 0.75 vs. 3.44 ± 1.1 A.U, respectively; p=0.60). HHb SC and VO2 SC during CL85 (r=0.94, p<0.001), but not during CL75 (r=-0.08, p=0.90), were correlated. Finally, HHb SC during CL75 and CL85 were unrelated (r=-0.20, p=0.70). Conclusion: Our results highlight that only the contribution of locomotor muscles to the VO2 SC magnitude is affected by the exercise intensity and not that of ventilation.
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Oueslati et al. (2018) conducted an RCT in Healthy moderately-trained males (n=8). Constant-load cycling at 85% of maximal work-load (CL85) vs. Constant-load cycling at 75% of maximal work-load (CL75) was evaluated on Deoxyhemoglobin (HHb) slow component (A.U.) (p=0.60). Constant-load cycling at 85% of maximal work-load compared to 75% significantly increased VO2 slow component (+59%) but did not change deoxyhemoglobin slow component (3.44 vs 3.10 A.U.; p=0.60).
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