Sex-specific Effect Of Age On Submaximal Leg Exercise Hemodynamics In Middle-aged Adults

Abstract

PURPOSE: To examine predictors of the leg hemodynamic response to exercise in middle-aged men and women. METHODS: We measured femoral artery blood flow (FBF; from Doppler-ultrasound derived measurements of diameter and blood velocity), mean arterial pressure (MAP), and femoral vascular conductance (FVC; calculated as the quotient of FBF and MAP) at rest and during five minutes of steady-state single knee-extensor exercise at an ∼ 10 watt (W) workload in healthy men (n=23) and women (n=30) (ages 40-72). Exercising FBF and FVC were normalized to power output achieved during exercise (FBF/W and FVC/W, respectively). Age, maximal quadriceps isometric and isokinetic strength (isokinetic dynamometer), maximal oxygen uptake (VO2max; graded treadmill test to maximal exertion), estimated physical activity (scores from the Paffenbarger Physical Activity Questionnaire), blood pressure, and anthropometric variables (estimated quadriceps muscle mass and body mass index (BMI)) were investigated with stepwise multiple linear regression as predictors of FBF/W and FVC/W in men and women separately. RESULTS: The effect of age on FBF/W and FVC/W was negative and marginally significant in men (p = 0.06 and 0.09, respectively) but highly insignificant in women (p = 0.91 and 0.89, respectively). Exercising FBF/W was predicted by age, BMI, and resting femoral blood flow (p < 0.01) and exercising FVC/W was predicted by age, BMI and resting femoral vascular conductance (p < 0.01) in men. Conversely, both exercising FBF/W and FVC/W were predicted by resting systolic blood pressure and weekly physical activity (Paffenbarger question 6 score) (p < 0.01 and p = 0.01, respectively) in women. CONCLUSIONS: There is sex-specificity in factors mediating exercising leg blood flow and vascular conductance in middle-aged adults. Notably, there is no relation between age and submaximal leg exercise hemodynamics in women across this age range, suggesting that the significant deficits in exercising leg vasodilator responses previously observed in older women may either occur prior to middle-age or be mediated by factors other than chronological age. Research Supported by NIH award 5R01HL081893-03.