Abstract
Regular long-term physical exercise has favourable effects on endothelial function in patients with coronary artery disease (CAD). However, the effects of an acute exercise bout in the cold on endothelial function are not known. At first, the effects of moderate-intensity aerobic lower-body exercise were assessed in CAD patients (n=16) in a neutral [+22°C] and cold [-15°C] environment. Secondly, responses to static and dynamic upper-body exercise in a neutral [+22°C] and cold [-15°C] environment were investigated in CAD patients (n=15). All experiments were performed in a random order. Endothelial function was measured by flow-mediated dilation (FMD) of the brachial artery in response to reactive hyperaemia, before and after the exposures in a neutral environment. No significant temperature*exercise*condition (pre-post) interaction was observed in FMD% when comparing rest versus aerobic exercise or static versus dynamic upper-body exercise. Relative reactive hyperaemia during FMD protocol, measured by changes in shear rate, was elevated after rest compared to aerobic exercise (p=.001) and after static compared to dynamic upper-body exercise (p<.001). However, no significant temperature*exercise*condition interaction was observed when FMD% was normalizedfor shear rate. Endothelial function to an acute bout of exercise among CAD patients was not modified by the environmental temperature where the exercise was performed. The present findings argue against the hypothesis that exercise in cold environmental conditions impairs endothelial function in patients with CAD.
Highlights
Short-term exposure to cold measured as daily mean temperature has been shown to increase both morbidity and mortality (Fares, 2013; Gasparrini et al, 2015), from cardiovascular causes (Fares, 2013; Liu, Yavar, & Sun, 2015)
We tested two unique hypotheses: (1) cold exposure blunts the beneficial effects of aerobic lower-body exercise on endothelial function and (2) cold exposure together with static upper-body exercise worsens endothelial function to a greater extent than dynamic upper-body exercise
The study consisted of two groups of male patients with coronary artery disease (CAD) treated at the Oulu University Hospital and participating in two study protocols: the first evaluated the effects of lower-body aerobic and the second dynamic and static upper-body exercise in cold (Table 1)
Summary
Short-term exposure to cold measured as daily mean temperature has been shown to increase both morbidity and mortality (Fares, 2013; Gasparrini et al, 2015), from cardiovascular causes (Fares, 2013; Liu, Yavar, & Sun, 2015). Short-term episode of aerobic exercise augments shear stress and has often (Currie, McKelvie, & Macdonald, 2012; Dawson, Green, Cable, & Thijssen, 2013), but not always (Currie, McKelvie, & Macdonald, 2014), resulted in transiently increased FMD Such divergent findings are likely related to varying exercise regimes (intensity, type and duration of exercise), as well as study protocols (e.g. subjects and timing of the measurements). We tested two unique hypotheses: (1) cold exposure blunts the beneficial effects of aerobic lower-body exercise on endothelial function and (2) cold exposure together with static upper-body exercise worsens endothelial function to a greater extent than dynamic upper-body exercise This response could be due to cold-induced vasoconstriction coupled with the effect caused by the static exercise itself (i.e. reduced blood flow as a result of mechanical compression of blood vessels) and reducing postexercise FMD responses further. These questions are important from the perspective of enabling safe year-round exercise among patients with CAD in regions with cold climate
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