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 V̇O2/watt ratio. Thus, to investigate the effects of aging in the arms, we measured metabolic and vascular responses to 6-minute bouts of dynamic handgrip exercise at 40% and 80% of maximal work rate (WRmax) in eleven young (26±2yr) and twelve old (80±6yr) males, applying Doppler-ultrasound combined with blood samples from a deep forearm vein. At baseline, old had a larger arterial diameter compared to young (p<0.001). During exercise, the two groups reached the same WRmax. V̇O2, blood flow, and oxygen supply were higher (40%WRmax; 80%WRmax, all p<0.01), and arterio-venous oxygen-difference lower (80%WRmax, p<0.02), in old compared to young. Old also had a higher oxygen-excess at 80%WRmax (p<0.01) than young, while 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%WRmax (p<0.001). V̇O2/watt (40%WRmax; 80%WRmax) was reduced in old compared to young (both p<0.05). In conclusion, in old and young males with a similar handgrip WRmax, old had a higher V̇O2 during 80%WRmax 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.