Ageing exacerbates the adverse effects of respiratory muscle fatigue on vascular function, locomotor muscle fatigue and exercise performance in males.

Abstract

This study investigated the effect of respiratory muscle fatigue on cardiovascular function, locomotor muscle fatigue and exercise performance in young and master athletes, a model of successful ageing. Ten young male (YA, 27.4 ± 4.4 years) and 11 male master endurance athletes (MA, 65.0 ± 5.1 years) performed, on separate days, two constant workload cycling tests at 90% of peak power to exhaustion (CWT) following a fatiguing inspiratory loading task at 60% (ILT_60%) and a sham task at 2% (ILT_2%) of their maximal inspiratory pressure. On a third day, the sham task was replicated but CWT was interrupted at the time equal to that performed during CWT_ILT60% (CWT_ILT2%-ISO). Quadriceps fatigue was assessed by changes in maximal voluntary isometric contraction (MVC), potentiated twitch force (QT_SINGLE) and voluntary activation (VA) from 15 s to 15 min post-exercise. Mean arterial pressure (MAP) was measured using finger pulse photoplethysmography. Blood flow (Q̇_L) and limb vascular conductance (LVC) were measured using Doppler ultrasound. During ILT_60%, MA demonstrated reduced Q̇_L (P = 0.036), a greater increase in MAP (P < 0.001) and a larger decrease in LVC (P = 0.044) compared to YA. During CWT_ILT60%, MA experienced a larger decrease in time to exhaustion (-39.7 ± 14.0%) than YA (-15.5 ± 13.9%, P = 0.010). Exercise-induced reductions in MVC and QT_SINGLE (both P < 0.039) were also more pronounced during CWT_ILT60% compared to CWT_ILT2%-ISO in MA. Ageing exacerbates the adverse effects of respiratory muscle fatigue on limb vascular function and locomotor muscle fatigue during subsequent exercise, resulting in greater impairments in exercise performance.