Skeletal muscle microvascular perfusion responses to cuff occlusion and submaximal exercise assessed by contrast‐enhanced ultrasound: the effect of age

Impairments in skeletal muscle microvascular function are frequently reported in patients with various cardiometabolic conditions for which older age is a risk factor. Whether aging per se predisposes the skeletal muscle to microvascular dysfunction is unclear. We used contrast‐enhanced ultrasound (CEU) to compare skeletal muscle microvascular perfusion responses to cuff occlusion and leg exercise between healthy young (n\ua0=\ua012, 26\ua0±\ua03\ua0years) and older (n\ua0=\ua012, 68\ua0±\ua07\ua0years) adults. Test–retest reliability of CEU perfusion parameters was also assessed. Microvascular perfusion (microvascular volume\ua0×\ua0flow velocity) of the medial gastrocnemius muscle was measured before and immediately after: (a) 5‐min of thigh‐cuff occlusion, and (b) 5‐min of submaximal intermittent isometric plantar‐flexion exercise (400\ua0N) using CEU. Whole‐leg blood flow was measured using strain‐gauge plethysmography. Repeated measures were obtained with a 15‐min interval, and averaged responses were used for comparisons between age groups. There were no differences in post‐occlusion whole‐leg blood flow and muscle microvascular perfusion between young and older participants (p\ua0>\ua0.05). Similarly, total whole‐leg blood flow during exercise and post‐exercise peak muscle microvascular perfusion did not differ between groups (p\ua0>\ua0.05). The overall level of agreement between the test–retest measures of calf muscle perfusion was excellent for measurements taken at rest (intraclass correlation coefficient [ICC] 0.85), and in response to cuff occlusion (ICC 0.89) and exercise (ICC 0.95). Our findings suggest that healthy aging does not affect muscle perfusion responses to cuff‐occlusion and submaximal leg exercise. CEU muscle perfusion parameters measured in response to these provocation tests are highly reproducible in both young and older adults