Low‐flow mediated constriction (L‐FMC) is a measure of vascular function complementary to flow‐mediated dilation (FMD). L‐FMC is commonly observed in the radial artery, however its presence in the brachial artery is equivocal. Furthermore, the effects of age and an acute cardiovascular stress on L‐FMC are unknown. We measured brachial L‐FMC and FMD (% change) during and following 5‐min of distal forearm occlusion in healthy young (n=7; 29±6 years [mean ± SD]) and old (n=5; 64±5 years) women before and after acute isometric handgrip exercise (IHG; 4, 2‐min unilateral contractions, each separated by 4‐min of rest, at 30% maximal voluntary contraction). Baseline L‐FMC and FMD were similar between groups (Both P>0.05). Acute IHG increased FMD in young (6.7±2.2% to 10.4±3.9%, P<0.05), but not old (7.3±5.4% to 9.7±9.6%, P>0.05) women, while L‐FMC was unchanged (P>0.05) in both groups (young: ‐3.5±6.3% to ‐3.7±4.5%; old: ‐5.5±9.5% to ‐4.0±9.0%). In young women, brachial L‐FMC and FMD were correlated before (r = 0.90; P<0.05) and after IHG (r = 0.97; P<0.05). In older women, L‐FMC and FMD were unrelated before (r = ‐0.20; P=0.74) but trended towards a correlation after IHG (r = 0.82; P=0.09). In conclusion, L‐FMC is observed in the brachial artery of healthy young and old women. Acute IHG appears to restore the relationship between constriction and dilation in old women.
Grant Funding Source: Supported by the University of Windsor
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