Cardiorespiratory fitness modulates the acute flow-mediated dilation response following high-intensity but not moderate-intensity exercise in elderly men

Tom G. Bailey, Maria Perissiou, Mark Windsor, Fraser Russell, Jonathan Golledge, Daniel J. Green, Christopher D. Askew
2017 Journal of applied physiology  
39 Impaired endothelial function is observed with ageing and in those with low cardiorespiratory 40 fitness (VO 2peak ). Improvements in endothelial function with exercise training are somewhat 41 dependent on the intensity of exercise. While the acute stimulus for this improvement is not 42 completely understood, it may, in part, be due to the flow-mediated dilation (FMD) response to 43 acute exercise. We examined the hypothesis that exercise-intensity alters the brachial (systemic) 44 FMD
more » ... ystemic) 44 FMD response in elderly men, and is modulated by VO 2peak . Forty-seven elderly men were 45 stratified into lower-(VO 2peak = 24.3±2.9 ml.kg -1 .min -1 , n=27) and higher-fit groups (VO 2peak = 46 35.4±5.5 ml.kg -1 .min -1 , n=20) after a test of cycling peak power output (PPO). In randomised 47 order, participants undertook moderate-intensity continuous (MICE; 40% PPO) or high-intensity 48 interval cycling exercise (HIIE; 70% PPO), or no-exercise control. Brachial FMD was assessed 49 at rest, 10 and 60 min after exercise. FMD increased after MICE in both groups [increase of 0.86 50 % (95% CI, 0.17 to 1.56), P=0.01], and normalised after 60 min. In the lower-fit group, FMD 51 reduced after HIIE [reduction of 0.85 % (95% CI, 0.12 to 1.58), P=0.02), and remained 52 decreased at 60 min. In the higher-fit group, FMD was unchanged immediately after HIIE and 53 increased after 60 min [increase of 1.52 % (95% CI, 0.41 to 2.62), P<0.01, which was correlated 54 with VO 2peak , r =0.41; P<0.01]. In the no-exercise control, FMD reduced in both groups after 60 55 min (P=0.05). Exercise-intensity alters the acute FMD response in elderly men and VO 2peak 56 modulates the FMD response following HIIE, but not MICE. The sustained decrease in FMD in 57 the lower-fit group following HIIE may represent a signal for vascular adaptation or endothelial 58 fatigue. 59 60 Downloaded from 75 (58, 59). Endothelial dysfunction is considered an important prognostic factor and precursor to 76 the development of atherosclerosis (23, 49), and is strongly associated with the risk of 77 cardiovascular events (23, 61). In addition, endothelial dysfunction is suggested to contribute to 78 other age-associated disorders including cognitive impairment and insulin resistance (64, 66, 76). 79 As such, interventions that prevent or slow the detrimental changes in endothelial function are 80 important in reducing cardiovascular risk and mortality associated with increasing age (60, 61). 81 82 Importantly, age-associated endothelial dysfunction, measured using flow-mediated dilation 83 (FMD) of the brachial artery (63), can be attenuated with both regular physical activity (75) and 84 exercise training (16, 24). Results of cross-sectional studies indicate that exercise-trained older 85 adults have preserved endothelial function (17, 42, 48, 53), and reduced cardiovascular disease 86 risk (63), compared with those who are not habitually active. This adaptive response is 87 commonly attributed to the repeated episodes of elevated blood flow, and consequently shear 88 stress, observed during acute exercise that induces vascular adaptation (22). 89 90 While the positive impact of chronic aerobic exercise on endothelial function is well described, 91 the significance of the transient changes observed in endothelial function with acute exercise is 92 less clear (15). To elucidate which forms of exercise are most likely to benefit cardiovascular 93 health and function, recent studies have focussed on the acute FMD response and how it is 94 modulated by factors such as exercise intensity. Some evidence suggests that the FMD response 95 by 10.220.33.2 on March 7, 2017 http://jap.physiology.org/ Downloaded from 7 also hypothesised that this overall response would be attenuated in those with a higher 119 cardiorespiratory fitness. 120 121 METHODS 122 Research Design 123 Participants underwent four laboratory visits, each following an overnight fast, refraining from 124 alcohol and exercise for 24h, and caffeine for 12h, before each visit. Participants consumed a 125 standardised snack (4 oat breakfast biscuits, 20g carbohydrate, 8g fat) 3h prior to attending the 126 laboratory, and the macronutrient content of this snack was unlikely to influence endothelial 127 function (25, 74). Visit 1 consisted of baseline measurements of height, body mass and estimated 128 body composition using bio-impendence scales (BC 545N, Tanita, Australia). After 10 min of 129 supine rest, blood pressure was measured using a manual sphygmomanometer, which was 130 followed by a maximal cycling test to determine cardiorespiratory fitness (VO 2peak ) and peak 131 power output (PPO). Experimental visits (2-4) were randomised, counter-balanced and consisted 132 of two separate acute cycling exercise conditions (moderate-intensity continuous vs. high-133 intensity interval) or a no-exercise control condition. Blood pressure and brachial FMD were 134 assessed at baseline following 20 min of supine rest, and then repeated at 10-and 60-min 135 following exercise/control. Laboratory conditions were standardised for each visit (room 136 temperature: 23 ± 1°C) (67). 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doi:10.1152/japplphysiol.00935.2016 pmid:28209742 fatcat:ye2orch3arghlkbrftmkz3v4hq