Aging increases metabolic capacity and reduces work efficiency during handgrip exercise in males

Maximal oxygen uptake and exercise performance typically decline with age. However, there are indications of preserved vascular function and blood flow regulation during arm exercise. Yet, it is unknown if this potential physiological preservation with age is mirrored in peripheral metabolic capacity and V̇o(2)/W ratio. Thus, to investigate the effects of aging in the arms, we measured metabolic and vascular responses to 6-min bouts of dynamic handgrip exercise at 40% and 80% of maximal work rate (WR(max)) in 11 young (26 ± 2 yr) and 12 old (80 ± 6 yr) males, applying Doppler-ultrasound combined with blood samples from a deep forearm vein. At baseline, the old had a larger arterial diameter compared with young (P < 0.001). During exercise, the two groups reached the same WR(max). V̇o(2), blood flow, and oxygen supply were higher (40%WR(max); 80%WR(max), all P < 0.01), and arteriovenous oxygen difference was lower (80%WR(max), P < 0.02), in old compared with young. Old also had a higher oxygen excess at 80%WR(max) (P < 0.01) than young, whereas no difference in muscle diffusion or oxygen extraction was detected. Only young exhibited an increase in intensity-induced arterial dilation (P < 0.05), and they had a lower mean arterial pressure than old at 80%WR(max) (P < 0.001). V̇o(2)/W (40%WR(max); 80%WR(max)) was reduced in old compared with young (both P < 0.05). In conclusion, in old and young males with a similar handgrip WR(max), old had a higher V̇o(2) during 80%WR(max) intensity, achieved by an increased blood flow. This may be a result of the available cardiac output reserve, compensating for reduced work efficiency and attenuated vascular response observed in old. NEW & NOTEWORTHY Contrasting the typically observed decline in V̇o(2max) with age, the current study reveals an age-related increase in forearm metabolic capacity during handgrip exercise in old, mediated by an increased forearm blood flow. Exercise with a small muscle mass in arms, where central components of the oxygen transport are not limiting, allows old to attain a similar maximal work rate as young despite their increased V̇o(2)/W ratio.