Effect of Habitual Physical Activity on Strength Loss and Fatigability in Old and Very Old Men

Age-related neuromuscular and cardiovascular declines may increase relative effort and thus fatigability during daily activities. Habitual physical activity (PA) may mitigate these alterations. This study examined the effects of age and PA on fatiguability in ecological conditions. Thirty-nine young men (YM, 22.1 ± 3.4 years), 34 old men (OM, 71.7 ± 4.1 years), and 23 very old men (VOM, 85.8 ± 2.7 years) performed a fatigue task. Increments were scaled in percentage body mass. Maximal knee extensor force (MVC), voluntary activation (VA), and twitch amplitude (Tw) were measured at baseline, after each stage and at task failure (TF). On a separate day, maximum oxygen consumption (V̇O₂max) was quantified during a maximal ramp test. Results For a given workload (i.e., last common stage, LCS), MVC in percentage of baseline was lower in VOM (84.6% ± 9.2%) compared to YM (94.0% ± 7.0%; p < 0.001) and OM (91.7% ± 6.3%; p < 0.01). At LCS, Tw was lower in VOM (89.3% ± 12.7%) compared to OM (99.7% ± 10.5%; p < 0.05). MVC loss was greater in YM (-35.6% ± 14.5% of baseline) compared to VOM (-23.4% ± 11.3%; p < 0.01) at TF. No difference was found between YM and OM for loss in MVC and Tw. PA level was correlated with V̇O₂max but did not affect fatigability. Tw loss at LCS was correlated with V̇O₂max in VOM (r = 0.69; p < 0.05). VOM, but not OM, was more fatigued than YM for a given submaximal workload but the opposite was true at exhaustion. Fatigability in VOM was due to peripheral factors and was correlated with aerobic capacity. In VOM, unlike YM and OM, higher PA levels may be sufficient to improve aerobic capacity and reduce fatigability. Trial Registration: ClinicalTrials.gov identifier: NCT05413590.