Femoral shear rate response to knee extensor exercise: an age and sex comparison

Shear stress is considered an important stimulus for vascular adaptations with exercise training, yet the shear rate response to exercise has not been carefully examined in women or in healthy older adults. Therefore, the purpose of this study was to determine if age or sex differences are present in common femoral artery (CFA) shear rates during leg exercise. Diameter and mean blood velocity were measured in the CFA using Doppler ultrasound in young (20-30 yr) and older (60-79 yr) men and women at rest and during single-leg knee extensor exercise. Shear rate was calculated. Resting shear rate was lower in older compared to young adults (33.9+/-3.7 vs. 58.3+/-3.6 s(-1), respectively; p<0.05) and lower in men than women (36.8+/-3.8 vs. 55.4+/-3.5 s(-1), respectively; p<0.05). During exercise, older adults had overall lower shear rates compared to young adults (within-sex comparison, p<0.05). The rise in shear rate with work rate showed no age difference but was lower in men than women (4.6+/-0.4 vs. 8.6+/-0.4 s(-1) per W, p<0.05). These results suggest that age and sex differences are present in CFA shear rates during exercise which could have implications for vascular adaptability with exercise training.