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 exercis e decreases hyperbolically with increasing power ((W) over dot) at least in active and younger individuals [i.e. ((W) over dot - theta(F))t = W', wher e theta(F) is the critical power asymptote and W' is the curvature constant ]. Little is known. however, about the combined effects of age and sedetari ty 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 cycl e ergometry and, on different days, 4 high-intensity constant-load tests to t. Compared to their younger counterparts, the older subjects presented si gnificantly lower maximum oxygen uptake (i.e. the maximum value of oxygen u ptake attained at the end of a progressive exercise with the subject exerti ng a presumably maximal effort, mu(V) over dot O-2), estimated lactate thre shold ((V) over dot O(2)theta(L)), (V) over dot O(2)theta(F), and W' (P < 0 .05). Interestingly, however, both (V) over dot O(2)theta(L) and (V) over d ot O(2)theta(F), when expressed as a percentage of mu(V) over dot O-2, 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 a ssociated with an increase in the relative magnitude of the "moderate", sub -theta(L) exercise-intensity domain (+30.4%), mainly at the expense of the "very-heavy, supra-theta(F) domain (-56%). Our results demonstrate that age and sedentarity are associated with: (1) marked reductions in both the aer obic (theta(F)) and anaerobic (W') determinants of the (W) over dot /t rela tionship, and (2) changes in either the absolute or relative magnitudes of the exercise-intensity domains. These findings are consistent with the noti on that endurance-related parameters are less diminished with ageing than t he maximal capacity, thereby mitigating the deleterious effects or senescen ce in the functional capacity.