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

Purpose To investigate the effects of age and sex in performance fatigability profile after a ramp incremental (RI) test. Methods 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 (VO(2)max) and peak power output (POpeak) were measured. Results Young females and males showed greater VO(2)max 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 x sex interaction for any performance fatigability outcome (all p >= 0.06). Conclusion 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.