The Acute Effect of Fast and Slow Stepping Cadence on Regional Vascular Function.

The aim of this study was to determine if stepping cadence when controlling for total steps has a differential impact on regional vascular function. 16 young adults (21±2 years) performed fast (125 steps per min) and slow (80 steps per min) walking for a total of 3 000 steps on separate days. Doppler ultrasound was used to measure compliance, blood flow and shear rate of the common carotid artery and superficial femoral artery before walking and at 30 and 60 min after walking. Carotid compliance was significantly (p<0.05) elevated 60 min after fast (17.1±25.9%) and slow (24.1±27.3%) walking with no difference between cadences. Both fast and slow walking failed to increase femoral compliance, despite significant (p<0.05) dilation in the femoral artery that was observed at 30 (4.2±3.9%) and 60 min (3.9±5.4%) after fast walking. Consistent with this latter finding, femoral blood flow and shear rate were significantly (p<0.05) increased at 30 min after fast walking. These results indicate that a single bout of walking at a fast or slow stepping cadence increases compliance of large elastic arteries but has no acute effect on compliance of peripheral (leg) arteries.

Leg strength is associated with ventilatory efficiency in older women.

The aim of the present study was to determine if leg function is associated with ventilatory efficiency during exercise in healthy older adults. 24 women and 18 men aged 60-80 years performed treadmill exercise to fatigue for calculation of ventilatory efficiency using the ratio of ventilation to carbon dioxide at the anaerobic threshold (VE/VCO2@AT). On a separate day, participants performed leg strength testing and graded single-leg knee extension exercise. The VE/VCO2@AT was higher in women than men (33±3 vs. 30±3; p=0.03). After adjustment for age and VO(2max), leg strength (knee extensor isometric force) was inversely associated with VE/VCO2@AT in women (r= - 0.44, p=0.03) while no relationships were found for men. Strength-matched women and men had similar VE/VCO2@AT indicating that the correlation between leg strength and VE/VCO2@AT was strength- but not sex-specific. During knee extensor exercise, women with lower leg strength had increased VE/VCO2 slope across 0-15 W as compared to higher strength women (38±8 vs. 31±3; p<0.05), while no differences were found for men. These results find leg strength to be associated with ventilatory responses to exercise in healthy older women, a finding that might be related to lower leg strength in women than men.

Effects of acute exercise on inspiratory muscle strength and endurance in untrained women and men.

AIM: The purpose of this study was to determine if sex differences are present in exercise-induced inspiratory muscle function in untrained humans. METHODS: Eight young untrained women (23.8 ± 1.5 y, VO2max = 33.7 ± 4.0 mL/kg/min) and men (26.1 ± 2.0 y, VO2max = 36.7 ± 1.2 mL/kg/min) performed high-intensity cycling exercise (80% WRmax) to exhaustion. Inspiratory muscle strength and endurance were assessed pre- and post-exercise by measuring maximal inspiratory pressure (PImax) and time to task failure during a constant-load breathing test (CLBT), respectively. RESULTS: Relative intensity and time to exhaustion during high-intensity exercise was similar between women and men. Prior to exercise, PImax was similar between sexes. After exercise, women and men showed similar reductions in PImax (W: 140.4 ± 9.9 to 124.6 ± 6.7 cm H2O, P<0.05; M: 147.7 ± 10.2 to 128.1 ± 11.1 cm H2O, P<0.05). No sex difference was found in the magnitude change in PImax following exercise (W: 15.8 ± 7.9 vs. M: 19.6 ± 4.7 cm H2O). Time to task failure on the CLBT was reduced following exercise in women (360 ± 54 to 135 ± 29 s, P<0.05) and men (270 ± 36 to 150 ± 17 s, P<0.05). Women exhibited a greater reduction in time to task failure following exercise than men (W: 225 ± 55 vs. M: 120 ± 38 s, P=0.05). CONCLUSION: These data demonstrate that women exhibit a greater reduction in inspiratory muscle endurance following an acute bout of high-intensity exercise than men.

Muscle strength and pressor response.

The purpose of this study was to determine if muscle strength influences the hyperemic response to dynamic exercise. Men with low (n=8) and high (n=9) maximal forearm strength performed dynamic handgrip exercise as the same absolute workload increased in a ramp function (0.5 kg x min (-1)). Forearm blood flow (FBF) was measured instantaneously by ultrasound Doppler and blood pressure was measured by auscultation. The pressor response to exercise was greater (P<0.05) for low strength men at workloads >1.5 kg allowing volumetric FBF (ml x min (-1)) and vascular conductance to increase in proportion to absolute workload similar to high strength men. When FBF was expressed relative to forearm volume (ml x min (-1).100 ml (-1)) the hyperemic response to exercise (slope of relative FBF vs. workload) was greater in low strength men (3.2+/-1.5 vs. 1.7+/-0.4 ml x min (-1).100 ml (-1) x kg (-1), P<0.05) as was relative FBF at workloads >1.5 kg. However, when relative FBF was compared across relative work intensity, no difference was found between low and high strength groups. Together, these findings suggest men with low strength require a greater pressor response to match blood flow to exercise intensity as compared to high strength men.