Different ramp-incremental slopes elicit similar V̇o2max and fatigability profiles in females and males despite differences in peak power output

Abstract

The aim of this article is to investigate the effects of different ramp-incremental (RI) slopes on fatigability and its recovery in females and males. Ten females and 11 males performed RI tests with distinct slopes, in separated and randomized sessions, 15 (RI₁₅), 30 (RI₃₀), and 45 (RI₄₅) W·min^-1. Performance fatigability was assessed by femoral nerve electrical stimuli evoked during and after isometric maximal voluntary contraction (IMVC) of knee extensors at baseline and after task failure at min 0.5, 1.5, 2.5, 5, and 10. Maximal oxygen uptake (V̇o_2max) and peak power output (POpeak) were also measured. There were significant and similar declines from pre- to post-RI test in RI₁₅, RI₃₀, and RI₄₅ for IMVC (-23%; -25%; -25%, respectively; P < 0.05) and potentiated single twitch (-46%; -47%; -49%; P < 0.05), whereas voluntary activation did not change (-1%; -1%; 0%; P > 0.05). There were no RI condition effects, nor time × condition interaction for IMVC, potentiated single twitch and voluntary activation (all P > 0.05). V̇o_2max was not different among RI₁₅, RI₃₀, and RI₄₅ conditions (3.30, 3.29, and 3.26 L·min^-1, respectively; P = 0.717), but POpeak was (272, 304, and 337 W, respectively; P < 0.001). Overall, performance fatigability profiles were similar between sexes after the RI tests and during recovery. In addition, during recovery, high-frequency doublets and single twitch recovered faster after RI₃₀ and RI₄₅ compared with RI₁₅, regardless of sex (all P > 0.05 for sex differences). In conclusion, RI tests of different slopes that elicited similar V̇o_2max but different POpeak did not affect the profile of performance fatigability at task failure in females and males.NEW & NOTEWORTHY It was unknown whether performance fatigability and its recovery are affected by different slopes in a ramp incremental (RI) test. It was also uncertain if females and males would respond differently. Performance fatigability was the same regardless of the RI slope adopted and the sex of the population, which was accompanied by similar maximal oxygen uptake but different power output achieved. The recovery of contractile function was similar between sexes but delayed after slower RI slopes.

Keywords: Central fatigue; cycling; neuromuscular function; peripheral fatigue; sex differences.