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 = 12, 26 ± 3 years) and older (n = 12, 68 ± 7 years) adults. Test-retest reliability of CEU perfusion parameters was also assessed. Microvascular perfusion (microvascular volume × flow 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 N) 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 > .05). Similarly, total whole-leg blood flow during exercise and post-exercise peak muscle microvascular perfusion did not differ between groups (p > .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.