The acute effect of resistance exercise on limb blood flow.

Current evidence indicates that to achieve maximum health benefits, regular resistance exercise should be a key component of structured physical activity. Several studies have revealed that regular resistance exercise may be associated with impaired vascular function, although this finding is inconsistent. Proposed explanations for impairment include substantial increases in blood pressure and increased retrograde blood flow in active limbs promoted by resistance exercise. However, few studies have examined the acute haemodynamics of resistance exercise in active - and even fewer in inactive - limbs. The purpose of this study was to characterise the haemodynamic responses in peripheral arteries in active and inactive limbs in response to resistance exercise using upper and lower limbs. Ten participants (five male, five female) familiar with resistance training performed three sets of 10 isotonic repetitions of right-sided bicep curls or knee extensions on separate days. Blood flow, shear rate and muscle oxygenation in the active and inactive limb, and blood pressure were measured before and for 3 min after each set. Blood flow increased in response to resistance exercise in the active limb (∼8-fold and ∼6-fold for the upper and lower limb respectively), with concurrent significant increases in mean and antegrade shear rate. In the inactive limb, blood flow more than doubled for both upper and lower limb exercise, transiently, with no significant change in retrograde shear rate. These acute blood flow profiles following resistance exercise are not indicative of long-term vessel impairment based on current understanding of blood flow and shear stress patterns.