# The independent effects of age and sex in performance fatigability profile after a ramp incremental cycling test

## TL;DR

This study examines how age and sex affect muscle fatigue after a cycling test, finding that younger people and males experience greater declines in performance.

## Contribution

The study reveals distinct effects of age and sex on muscle fatigability without a combined interaction, offering new insights into physiological responses.

## Key findings

- Young participants showed greater declines in maximal voluntary contraction and single twitch compared to older participants.
- Males experienced greater voluntary activation decline than females, but no age-by-sex interaction was observed.
- Contractile function impairment was more pronounced in younger individuals, with no combined effect of age and sex.

## Abstract

To investigate the effects of age and sex in performance fatigability profile after a ramp incremental (RI) test.

Older females (n = 13; 66 ± 5 yrs) and males (n = 13; 68 ± 4 yrs), and young females (n = 11; 25 ± 5 yrs) and males (n = 12; 25 ± 4 yrs) performed a RI test immediately preceded and followed by performance fatigability assessments that included: knee-extension isometric maximal voluntary contraction (IMVC) and femoral nerve electrical stimuli during and after the IMVC to calculate voluntary activation (VA) and contractile function (e.g., potentiated doublets at 10 and 100 Hz, and single twitches). Maximal oxygen uptake (V̇O2max) and peak power output (POpeak) were measured.

Young females and males showed greater V̇O2max and POpeak compared to older counterparts (all p < 0.05). The IMVC declined more in young (females:  −27 ± 14%; males:  −44 ± 7%) than older (females:  −23 ± 9%; males:  −26 ± 9%) (p < 0.01), and in males compared to females (p < 0.01). Single twitch declined more in young (females:  −43 ± 15%; males:  −54 ± 15%) than older participants (females:  −33 ± 10%; males:  −27 ± 18%) (p = 0.01), without sex differences (p = 0.59). Similar responses were observed for 100 Hz and 10 Hz stimulus for age and sex (all p > 0.05). Voluntary activation was not different (p = 0.11) between young (females:  −5 ± 5%; males:  −8 ± 6%) and older (females:  −7 ± 6%; males:  −12 ± 6%), but declined less in females than males (p = 0.03). There was no age × sex interaction for any performance fatigability outcome (all p ≥ 0.06).

Contractile function was more impaired in young than older participants, whereas males showed greater decline in VA than females. There was no combined effect of age and sex in performance fatigability responses.