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

Abstract

Purpose: We tested the hypothesis that the described increase in oxygen uptake (V˙ O 2)-plateau incidence following a heavy-severe prior exercise is caused by a steeper increase in V˙ O 2 and muscle fiber activation in the submaximal intensity domain. Methods: Twenty-one male participants performed a standard ramp test, a 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 V˙ O 2-(Δ V˙ O 2/ Δ P) and EMG-(∆RMS/∆P) ramp test kinetics. Results: Twenty out of the 21 participants confirmed their V˙ O 2max in the verification bout. The 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 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 V˙ O 2-plateau incidence as well as steeper increases in V˙ O 2 and muscle fiber activation in the submaximal intensity domain following a heavy-severe prior exercise.