Effect of intensive prior exercise on muscle fiber activation, oxygen uptake kinetics, and oxygen uptake plateau occurrence

Abstract

Abstract Purpose We tested the hypothesis that the described increase in oxygen uptake ($$\dot{V}{\text{O}}_{{2}}$$ V ˙ O 2 )-plateau incidence following a heavy-severe prior exercise is caused by a steeper increase in $$\dot{V}{\text{O}}_{{2}}$$ V ˙ O 2 and muscle fiber activation in the submaximal intensity domain. Methods Twenty-one male participants performed a standard ramp test, a $$\dot{V}{\text{O}}_{{{\text{2max}}}}$$ V ˙ O 2max verification bout, an unprimed ramp test with an individualized ramp slope and a primed ramp test with the same ramp slope, which was preceded by an intensive exercise at 50% of the difference between gas exchange threshold and maximum workload. Muscle fiber activation was recorded from vastus lateralis, vastus medialis, and gastrocnemius medialis using a surface electromyography (EMG) device in a subgroup of 11 participants. Linear regression analyses were used to calculate the $$\dot{V}{\text{O}}_{{2}}$$ V ˙ O 2 -($$\Delta \dot{V}{\text{O}}_{{2}} /\Delta P$$ Δ V ˙ O 2 / Δ P ) and EMG-(∆RMS/∆P) ramp test kinetics. Results Twenty out of the 21 participants confirmed their $$\dot{V}{\text{O}}_{{{\text{2max}}}}$$ V ˙ O 2max in the verification bout. The $$\dot{V}{\text{O}}_{{2}}$$ V ˙ O 2 -plateau incidence in these participants did not differ between the unprimed (n = 8) and primed (n = 7) ramp test (p = 0.500). The $$\Delta \dot{V}{\text{O}}_{{2}} /\Delta P$$ Δ V ˙ O 2 / Δ P was lower in the primed compared to the unprimed ramp test (9.40 ± 0.66 vs. 10.31 ± 0.67 ml min−1 W−1, p < 0.001), whereas the ∆RMS/∆P did not differ between the ramp tests (0.62 ± 0.15 vs. 0.66 ± 0.14% W−1; p = 0.744). Conclusion These findings do not support previous studies, which reported an increase in $$\dot{V}{\text{O}}_{{2}}$$ V ˙ O 2 -plateau incidence as well as steeper increases in $$\dot{V}{\text{O}}_{{2}}$$ V ˙ O 2 and muscle fiber activation in the submaximal intensity domain following a heavy-severe prior exercise.