Aerobic Exercise Produces Divergent Effects In Load And Structural Dependent Stiffness Between Sexes

Large artery stiffness increases during acute aerobic exercise and may reflect changes in a) pressure (load-dependent stiffening) and/or b) material properties of the arterial wall (structural stiffening). Sex differences in blood pressure responses during exercise may alter mechanisms of artery stiffening; however this remains to be examined. PURPOSE: Examine changes in load-dependent versus structural carotid stiffness between males and females during moderate intensity aerobic exercise. METHODS: 7 Female (28 ± 6 yrs, BMI 23 ± 3 kg/m2) and 8 male participants (30 ± 6 yrs, BMI 25 ± 2 kg/m2) underwent 21 min of aerobic exercise on a semi recumbent cycle ergometer (5 min 40 W, 8 min 70 W, 8 min 60% VO2peak). Carotid ultrasound and arterial tonometry were performed at rest and in duplicate from minutes 2-7 during the 60% VO2peak stage of exercise. Structural and load-dependent stiffness were calculated relative to a pressure of 120/80 mmHg and as the difference between total and structural stiffness, respectively, from participant-specific exponential curves via applanation tonometry and ultrasonography. RESULTS: Relative VO2 during the 60% VO2peak stage was not different between males (62 ± 3%) and females (60 ± 3%, p = 0.37). Males exhibited a larger increase in load-dependent stiffness compared to females (males ∆ + 0.62 ± 0.24 m/s; females ∆ + 0.20 ± 0.19 m/s; interaction p < 0.001). On average females had lower structural stiffness (sex effect p = 0.04), and both males and females increased structural stiffness from rest to exercise (5.82 ± 1.09 vs 4.90 ± 0.80 m/s, time effect p < 0.001). CONCLUSION: Although both males and females increased load and structural stiffness during an acute bout of aerobic exercise, males exhibited greater increases in load-dependent stiffness than females. These data suggest that sex differences in load-dependent stiffness during exercise may contribute to differing adaptations to the carotid artery with repeated exposure to aerobic exercise (i.e. training).