The effect of age on the power/duration relationship and the intensity-domain limits in sedentary men

The time to fatigue (t) in response to high-intensity constant-load exercise decreases hyperbolically with increasing power (W˙), at least in active and younger individuals [i.e. (W˙−θ_F)t=W′, where θ_F is the critical power asymptote and W′ is the curvature constant]. Little is known, however, about the combined effects of age and sedetarity on these parameters. We therefore evaluated 17 non-trained males (9 aged 60–75 years and 8 aged below 30 years) who underwent ramp-incremental cycle ergometry and, on different days, 4 high-intensity constant-load tests to t. Compared to their younger counterparts, the older subjects presented significantly lower maximum oxygen uptake (i.e. the maximum value of oxygen uptake attained at the end of a progressive exercise with the subject exerting a presumably maximal effort, μV˙O₂), estimated lactate threshold (V˙O₂θ_L), V˙O₂θ_F, and W′ (P < 0.05). Interestingly, however, both V˙O₂θ_L and V˙O₂θ_F, when expressed as a percentage of μV˙O₂, were higher in older than in younger men [61.8 (6.2)% versus 45.4 (4.6)% and 87.8 (7.3)% versus 79.0 (8.2)%, P < 0.05, respectively]. Therefore, age was associated with an increase in the relative magnitude of the “moderate”, sub-θ_L exercise-intensity domain (+30.4%), mainly at the expense of the “very-heavy”, supra-θ_F domain (−56%). Our results demonstrate that age and sedentarity are associated with: (1) marked reductions in both the aerobic (θ_F) and anaerobic (W′) determinants of the W˙/t relationship, and (2) changes in either the absolute or relative magnitudes of the exercise-intensity domains. These findings are consistent with the notion that endurance-related parameters are less diminished with ageing than the maximal capacity, thereby mitigating the deleterious effects of senescence in the functional capacity. Accepted: 5 April 2000