Vascular dysfunction and the age‐related decline in critical power

Abstract

AbstractAgeing results in lower exercise tolerance, manifested as decreased critical power (CP). We examined whether the age‐related decrease in CP occurs independently of changes in muscle mass and whether it is related to impaired vascular function. Ten older (63.1 ± 2.5 years) and 10 younger (24.4 ± 4.0 years) physically active volunteers participated. Physical activity was measured with accelerometry. Leg muscle mass was quantified with dual X‐ray absorptiometry. The CP and maximum power during a graded exercise test (PGXT) of single‐leg knee‐extension exercise were determined over the course of four visits. During a fifth visit, vascular function of the leg was assessed with passive leg movement (PLM) hyperaemia and leg blood flow and vascular conductance during knee‐extension exercise at 10 W, 20 W, slightly below CP (90% CP) and PGXT. Despite not differing in leg lean mass (P = 0.901) and physical activity (e.g., steps per day, P = 0.735), older subjects had ∼30% lower mass‐specific CP (old = 3.20 ± 0.94 W kg−1 vs. young = 4.60 ± 0.87 W kg−1; P < 0.001). The PLM‐induced hyperaemia and leg blood flow and/or conductance were blunted in the old at 20 W, 90% CP and PGXT (P < 0.05). When normalized for leg muscle mass, CP was strongly correlated with PLM‐induced hyperaemia (R2 = 0.52; P < 0.001) and vascular conductance during knee‐extension exercise at 20 W (R2 = 0.34; P = 0.014) and 90% CP (R2 = 0.39; P = 0.004). In conclusion, the age‐related decline in CP is not only an issue of muscle quantity, but also of impaired muscle quality that corresponds to impaired vascular function.