Daily Physical Activity Is Not Related To Nitric Oxide-mediated Microvascular Function In Young Healthy Adults.

Abstract

The Physical Activity Guidelines for Americans recommend a minimum of 150 min of moderate-to-very vigorous exercise per week for adults. Meeting these requirements is associated with long-term increases in functional capacity and brain health, as well as decreases in cardiovascular disease risk and all-cause mortality. However, whether or not daily physical activity levels acutely impact vascular function are unknown. PURPOSE: To determine the relation between daily physical activity and nitric oxide-mediated microvascular function in young healthy adults. Using the skin as a model circulation, we hypothesized greater physical activity would be positively related to nitric oxide (NO)-mediated microvascular function. METHODS: 20 young (25 ± 5 years) healthy (BMI: 24 ± 3 kg/m2; SBP: 112 ± 10 mmHg; DBP: 71 ± 6 mmHg; HDL: 56 ± 8 mg/dL; LDL: 88 ± 23mh/dL; HbA1c: 4.7 ± 0.3%) adults (11 W/9 M) wore an accelerometer around their waist while awake for 7 days. A minimum of 4 wear days for ≥10 hours/day were required for inclusion in these analyses. On day 8, microvascular physiology was assessed with a standardized 39 °C local heating protocol to quantify NO-dependent vasodilation through the perfusion of 15 mM NG-nitro-l-arginine methyl ester during the plateau of the heating response. Red blood cell flux was measured (laser-Doppler flowmetry) and cutaneous vascular conductance (CVC = flux/mmHg) was calculated and expressed as a percentage of maximum (%CVCmax; 28 mM sodium nitroprusside +43 °C). RESULTS: The local heating plateau (64 ± 21 %CVCmax) and NO-dependent vasodilation (68 ± 8%) were not related to percent time spent in sedentary (68 ± 7%; R2 = 0.01, p = 0.63; R2 = 0.06, p = 0.30), light (57 ± 7%; R2 = 0.03, p = 0.49; R2 = 0.06, p = 0.30), or moderate-to-very vigorous (6 ± 4%; R2 = 0.06, p = 0.35; R2 < 0.01, p = 0.80) physical activity. The local heating plateau and NO-dependent vasodilation were also not correlated with average steps per day (8111 ± 3374 steps; R2 < 0.01, p = 0.72; R2 < 0.01, p = 0.97). CONCLUSION: Daily physical activity was not related to cutaneous NO-mediated microvascular physiology in young healthy adults. These results indicate that the microvascular physiology in healthy young adults is unrelated to physical activity or sedentary behavior, likely due to robust redundant mechanisms underlying their vascular function.