Evidence for a greater elevation in vascular shear stress after morning exercise

Effects of exercise timing on metabolic health

The increasing prevalence of metabolic syndrome is associated with major health and socioeconomic consequences. Currently, physical exercise, together with dietary interventions, is the mainstay of the treatment of obesity and related metabolic complications. Although exercise training includes different modalities, with variable intensity, duration, volume, or frequency, which may have a distinct impact on several characteristics related to metabolic syndrome, the potential effects of exercise timing on metabolic health are yet to be fully elucidated. Remarkably, promising results with regard to this topic have been reported in the last few years. Similar to other time-based interventions, including nutritional therapy or drug administration, time-of-day-based exercise may become a useful approach for the management of metabolic disorders. In this article, we review the role of exercise timing in metabolic health and discuss the potential mechanisms that could drive the metabolic-related benefits of physical exercise performed in a time-dependent manner.

Difference of cardiac rehabilitation in the morning or evening on indexes of left ventricular and N-terminal pro-brain natriuretic peptide: a randomized controlled trial

The present study aimed to evaluate the effects a cardiac rehabilitation program (CRP) performed in the morning or evening on left ventricular (LV) filling indices and the level of N-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) in patients undergoing percutaneous coronary angioplasty during the COVID-19 pandemic.

Methods

This was a randomized controlled single-blinded clinical trial. Ninety-six patients (mean age: 50.2 ± 8.1 years, 36 women and 44 men) with percutaneous coronary angioplasty were divided into two groups of intervention and control. In each group, the CRP was performed in either morning or evening. The CRP included walking and performing push-ups and sit-ups for 8 weeks. The participants of the control groups received routine care. The functional indices of LV, including LV ejection fraction, systolic function, and diastolic function (i.e. the transmitral flow), the E/e' to left atrium peak strain ratio (as an estimation for LA stiffness), and NT-proBNP level were measured in all participants before starting and at the end of the CRP.

Results

In the intervention group, the individuals performing the CRP in the evening had significantly higher E-wave (0.76±0.02 vs. 0.75±0.03; P=0.008), ejection fraction (52.5±5.64 vs. 55.5±3.59; P=0.011), and diastolic function velocity (E/A ratio, 1.03±0.06 vs. 1.05±0.03; P=0.014) and significantly lower A-wave (0.72±0.02 vs. 0.71±0.01; P=0.041), E/e' ratio (6.74±0.29 vs. 6.51±0.38; P=0.038), and NT-proBNP level (2007.9±214.24 vs. 1933.9±253.13; P=0.045) compared with those performing the program in the morning.

Conclusions

A supervised CRP performed in the evening compared with morning was more effective in improving LV functional indices. Therefore, such home-based interventions are recommended to be performed in the evening during the COVID-19 pandemic.

Association of Time-of-Day Physical Activity With Incident Cardiovascular Disease: The UK Biobank Study

INTRODUCTION

Early morning is characterized by an increased risk of cardiovascular events, a sudden rise in blood pressure, impaired endothelial function, and exacerbated hemodynamic changes during physical activity. The study aims to examine whether the time of day of physical activity is associated with incident cardiovascular disease (CVD).

METHODS

We prospectively analyzed 83,053 participants in the UK Biobank with objectively measured physical activity and initially free of CVD. Based on the diurnal patterns of physical activity, participants were categorized into 4 groups: early morning (n = 15,908), late morning (n = 22,371), midday (n = 24,764), and evening (n = 20,010). Incident CVD was defined as the first diagnosis of coronary heart disease or stroke.

RESULTS

During 197.4 million person-years of follow-up, we identified 3454 CVD cases. After adjusting for the overall acceleration average, the hazard ratios and 95% confidence intervals were 0.95 (0.86-1.07) for late morning, 1.15 (1.03-1.27) for midday, and 1.03 (0.92-1.15) for evening, as compared with the early morning group. In the joint analyses, higher levels of physical activity were associated with a lower risk of incident CVD in a similar manner across the early morning, late morning, and evening groups. However, the beneficial association was attenuated in the midday group.

CONCLUSION

In conclusion, early morning, late morning, and evening are all favorable times of day to engage in physical activity for the primary prevention of CVD, while midday physical activity is associated with an increased risk of CVD compared with early morning physical activity after controlling for the levels of physical activity.

Association of the time of day of peak physical activity with cardiovascular mortality: Findings from the UK Biobank study

Cardiovascular physiology and pathophysiology display pronounced circadian rhythms. The study is designed to examine whether the time of day of physical activity is associated with cardiovascular mortality. We analyzed 94,489 UK Biobank adults with objectively measured physical activity, including 53,328 morning-type participants and 30,962 evening-type participants based on self-reported chronotypes. The time of day of peak physical activity was categorized using a machine learning algorithm: early morning (n = 18,477), late morning (n = 25,700), midday (reference) (n = 27,803), and night (n = 22,509). Hazard ratios of cardiovascular mortality were examined using the Cox proportional hazards model. During a median follow-up of 6.9 years (interquartile range, 6.3-7.4 years), we identified 629 cardiovascular deaths. The hazard of cardiovascular mortality was elevated in the early morning group (hazard ratio = 1.56, 95% Confidence Interval [1.23-1.98]) and night group (1.49, [1.18-1.88]) but not in the late morning group (1.21, [0.98-1.47]) compared to the referent midday group. In the chronotype-stratified analysis, the increased cardiovascular mortality in the morning group was only observed in the evening-type participants, while the increased cardiovascular mortality in the night group was only observed in the morning-type participants. In conclusion, optimizing the timing of peak physical activity according to cardiovascular circadian rhythms and individual chronotypes could be a potential therapeutic target that brings additional health benefits.

Do acute effects of exercise on vascular function predict adaptation to training?

Purpose

No previous study has explored the importance of exercise-induced changes in vascular function to prolonged adaptations. Therefore, the purpose was to explore the within-subject relationship between the acute post-exercise change in brachial artery endothelial function (flow-mediated dilation, FMD) and the change in resting FMD after a 2-week exercise training in healthy volunteers.

Methods

Twenty one healthy, young men (24 ± 5 years) underwent assessment of brachial artery FMD using high-resolution ultrasound before and after 30-min of moderate-intensity cycle exercise (80% maximal heart rate). Subsequently, subjects performed five 30-min cycle exercise bouts at 80% maximal heart rate across a 2-week period, followed by repeat assessment of resting brachial FMD post-training.

Results

Correcting for changes in diameter and shear, FMD did not change after the initial exercise bout (P = 0.26). However, a significant correlation was found between post-exercise changes in FMD and adaptation in resting FMD after training (r = 0.634, P = 0.002), where an acute decrease in post-exercise FMD resulted in a decrease in baseline FMD after 2 weeks and vice versa. We also found a positive correlation between antegrade shear rate during exercise and change in FMD% after acute exercise and after exercise training (r = 0.529 and 0.475, both P < 0.05).

Conclusion

Our findings suggest that acute post-exercise changes in vascular function are related to changes in resting FMD after a 2-week endurance exercise training period in healthy men, an effect that may be related to exercise-induced increases in antegrade shear rate. This provides further insight into the relevance of acute changes in shear and FMD for subsequent adaptation.

Association between Time of Day of Sports-Related Physical Activity and the Onset of Acute Myocardial Infarction in a Chinese Population

Objective

To investigate the association between the time of day of sports-related physical activity and the onset of acute myocardial infarction (AMI) in a coronary artery disease (CAD) population in China.

Methods

Between February 2014 and March 2015, a total of 696 patients from Nanjing, China, who had CAD were studied and divided into two groups (Non-AMI and AMI groups). The work-related activity and sports-related physical activity information were obtained from a self-reporting predesigned patient questionnaire.

Results

Sports-related physical activity was associated with a lower risk of the onset of AMI, after adjusting the established and potential confounders, with an adjusted odds ratio (OR) of 0.67 (95% CI, 0.47–0.94) compared with those who did not have any sports-related physical activity. A dose–response relationship was observed for intensity, duration, and frequency of sports-related physical activity. Further stratification analysis revealed that the protective effects of sports-related physical activity were significant in the morning and evening groups, and patients who exercised in the evening were at a lower risk of AMI than those doing sports-related physical activity in the morning. The adjusted ORs for doing sports-related physical activity in the morning and evening groups were 0.60(0.36–0.98) and 0.56(0.37–0.87), respectively, compared with inactivity (all P<0.05). On the occurrence of AMI, doing sports-related physical activity in the evening had an adjusted OR of 0.93 (95% CI, 0.54–1.64, P = 0.824) compared with in the morning group.

Conclusions

Sports-related physical activity is associated with a lower risk of onset of AMI than inactivity in Chinese people. For CAD patients, we suggest they participate in sports-related physical activity of high intensity, long duration, and high frequency. Doing sports-related physical activity in the evening and in the morning have similar benefits on the prevention of the onset of AMI.

Effects of exercise timing on sleep architecture and nocturnal blood pressure in prehypertensives

Background

During nocturnal sleep, blood pressure (BP) “dips” compared to diurnal BP, reducing stress on the cardiovascular system. Both the hypotensive response elicited by acute aerobic exercise and sleep quality can impact this dipping response.

Purpose

The purpose of this study was to investigate the effects of aerobic exercise timing on circadian BP changes and sleep architecture.

Materials and methods

Twenty prehypertensive subjects completed the study. During four test sessions, participants first completed a graded exercise test to exhaustion and then performed 30 minutes of treadmill exercise at 7 am (7A), 1 pm (1P), and 7 pm (7P) in a random, counterbalanced order at 65% of the heart rate obtained at peak oxygen uptake. An ambulatory cuff was used to monitor BP responses during 24 hours following exercise, and an ambulatory sleep-monitoring headband was worn during sleep following each session.

Results

Aerobic exercise at 7A invoked a greater dip in nocturnal systolic BP than exercise at 1P or 7P, although the greatest dip in nocturnal diastolic BP occurred following 7P. Compared to 1P, 7A also invoked greater time spent in deep sleep.

Conclusion

These data indicate that early morning may be the most beneficial time to engage in aerobic exercise to enhance nocturnal BP changes and quality of sleep.

Effect of cinnamon on gastric emptying, arterial stiffness, postprandial lipemia, glycemia, and appetite responses to high-fat breakfast

Background

Cinnamon has been shown to delay gastric emptying of a high-carbohydrate meal and reduce postprandial glycemia in healthy adults. However, it is dietary fat which is implicated in the etiology and is associated with obesity, type 2 diabetes and cardiovascular disease. We aimed to determine the effect of 3 g cinnamon (Cinnamomum zeylanicum) on GE, postprandial lipemic and glycemic responses, oxidative stress, arterial stiffness, as well as appetite sensations and subsequent food intake following a high-fat meal.

Methods

A single-blind randomized crossover study assessed nine healthy, young subjects. GE rate of a high-fat meal supplemented with 3 g cinnamon or placebo was determined using the ¹³C octanoic acid breath test. Breath, blood samples and subjective appetite ratings were collected in the fasted and during the 360 min postprandial period, followed by an ad libitum buffet meal. Gastric emptying and 1-day fatty acid intake relationships were also examined.

Results

Cinnamon did not change gastric emptying parameters, postprandial triacylglycerol or glucose concentrations, oxidative stress, arterial function or appetite (p < 0.05). Strong relationships were evident (p < 0.05) between GE T_half and 1-day palmitoleic acid (r = -0.78), eiconsenoic acid (r = -0.84) and total omega-3 intake (r = -0.72). The ingestion of 3 g cinnamon had no effect on GE, arterial stiffness and oxidative stress following a HF meal.

Conclusions

3 g cinnamon did not alter the postprandial response to a high-fat test meal. We find no evidence to support the use of 3 g cinnamon supplementation for the prevention or treatment of metabolic disease. Dietary fatty acid intake requires consideration in future gastrointestinal studies.

Trial registration

Trial registration number: at http://www.clinicaltrial.gov: NCT01350284

Acute change in vascular tone alters intima-media thickness

Atherosclerosis is a lifelong process involving artery wall thickening. Increased wall thickness has been widely adopted as a preclinical surrogate marker of atherosclerosis. A prerequisite for such a surrogate marker is that it is a structural characteristic of the vessel wall that is not subject to acute changes. The purpose of this study was to examine the acute effects of vasodilator drug administration on wall thickness of the carotid and superficial femoral arteries. High-resolution ultrasound was used to examine carotid and femoral artery diameters and wall thickness in 15 young (25±4 years of age) and 15 older (70±6 years of age) healthy men who were administered sublingual glyceryl trinitrate. Diameter and wall thickness were collected before and across a 10-minute period after glyceryl trinitrate administration. Glyceryl trinitrate induced a significant increase in carotid and femoral artery diameter and a decrease in wall thickness in both young and older men (both P<0.001). The latter was significantly larger than in young men (both P<0.01). The changes in carotid artery wall thickness in both young (35±23 μm) and older men (71±46 μm) approximate those considered prognostically relevant. Collectively, our data suggest that vasodilator drug administration induces a rapid and marked decrease in wall thickness, which mirrors conduit artery vasodilation in both young and older men. This finding confirms the presence of acute changes in wall thickness and has important implications for future studies that assess artery wall characteristics as a surrogate measure of atherosclerosis.

α1-Adrenoreceptor activity does not explain lower morning endothelial-dependent, flow-mediated dilation in humans

Early morning reduction in endothelium-dependent, flow-mediated dilation (FMD) may contribute to the high incidence of sudden cardiac death at this time of day. The mechanisms underpinning diurnal variation in FMD are unclear, but potentially relate to a circadian rhythm in sympathetic nerve activity. We hypothesized that blockade of α1-mediated sympathetic nerve activity would act to attenuate the diurnal variation in FMD. In a randomized and placebo-controlled design, we measured brachial artery FMD in 12 participants (mean age = 26 yr, SD = 3) at 0600 and 1600 after ingestion of an α1-blocker (prazosin, 1 mg/20 kg body mass) or placebo. Arterial diameter and shear rate were assessed using edge-detection software. Heart rate and blood pressure were also measured. Data were analyzed using linear mixed modeling. Following placebo, FMD was 8 ± 2% in the morning compared with 10 ± 3% in the afternoon ( P = 0.04). Blockade with prazosin led to a slight but nonsignificant increase in morning FMD ( P = 0.24) and a significant ( P = 0.04) decrease in afternoon FMD, resulting in no diurnal variation ( P = 0.20). Shear rate did not differ in the morning or afternoon under either condition ( P > 0.23). Blood pressure was lower following prazosin compared with placebo ( P < 0.02), an effect that was similar at both times of day ( P > 0.34). Heart rate and norepinephrine levels were higher in the afternoon following prazosin. These data indicate that α1-adrenoreceptor activity does not explain lower morning endothelium-dependent FMD.

Intermittent exercise abolishes the diurnal variation in endothelial-dependent flow-mediated dilation in humans

It is currently unclear to what extent diurnal variation and exercise effect endothelium-dependent nitric oxide (NO)-mediated vasodilation. Therefore, we measured brachial artery flow-mediated dilation (FMD) in 10 males (mean age = 28 yr, SD = 7), before and after a bout of intermittent cycling at 70% peak oxygen uptake on separate days beginning either at 0800 or 1600. Edge-detection and wall-tracking software was used to measure changes in arterial diameter, while shear rate (SR) was assessed using simultaneously derived blood flow velocity and B-mode diameter data. The FMD data were analyzed before and after normalization for SR with repeated-measures models. Before exercise, mean + or - SD FMD was 7 + or - 3% in the morning compared with 11 + or - 6% in the afternoon (P = 0.01). This diurnal variation persisted after data were normalized for SR, which was found to be unaffected by time of day (P = 0.33). Postexercise SR was higher than at baseline (pre-exercise) (P = 0.01) to a similar extent at both times of day. FMD was unaffected by exercise in the morning (P = 0.96) but decreased by 4 + or - 3% following exercise in the afternoon (P = 0.01) so that postexercise measurements did not differ between times of day. These data indicate that endothelium-dependent FMD is lower in the morning, and this finding was not altered by normalization of FMD for diurnal variation in SR. This infers a reduced function of the intrinsic endothelial NO-vasodilator system in the morning. We also report, for the first time, that a bout of intermittent exercise abolishes this diurnal variation in endothelium-dependent FMD.

Circadian variation in the circulatory responses to exercise: relevance to the morning peaks in strokes and cardiac events

Sudden cardiac and cerebral events are most common in the morning. A fundamental question is whether these events are triggered by the increase in physical activity after waking, and/or a result of circadian variation in the responses of circulatory function to exercise. Although signaling pathways from the master circadian clock in the suprachiasmatic nuclei to sites of circulatory control are not yet understood, it is known that cerebral blood flow, autoregulation and cerebrovascular reactivity to changes in CO(2) are impaired in the morning and, therefore, could explain the increased risk of cerebrovascular events. Blood pressure (BP) and the rate pressure product (RPP) show marked 'morning surges' when people are studied in free-living conditions, making the rupture of a fragile atherosclerotic plaque and sudden cardiac event more likely. Since cerebral autoregulation is reduced in the morning, this surge in BP may also exacerbate the risk of hemorrhagic and ischemic strokes in the presence of other acute and chronic risk factors. Increased sympathetic activity, decreased endothelial function, and increased platelet aggregability could also be important in explaining the morning peak in cardiac and cerebral events but how these factors respond to exercise at different times of day is unclear. Evidence is emerging that the exercise-related responses of BP and RPP are increased in the morning when prior sleep is controlled. We recommend that such 'semi-constant routine' protocols are employed to examine the relative influence of the body clock and exogenous factors on the 24-h variation in other circulatory factors.

24-hour variation in the reactivity of rate-pressure-product to everyday physical activity in patients attending a hypertension clinic

The exercise-related response of the rate-pressure-product (RPP) is a prognostic marker of autonomic imbalance, cardiovascular mortality, and silent myocardial ischemia in hypertension. In view of the well-known 24 h variation in out-of-hospital sudden cardiac events, our aim was to investigate whether the reactivity of RPP to everyday physical activities varies over the 24 h. Ambulatory measurements of systolic blood pressure (BP) and heart rate were recorded every 20 min for 24 h in 440 diurnally active patients attending a hypertension clinic. Wrist activity counts were summed over the 15 min that preceded a BP measurement. An RPP reactivity index was derived for each of twelve 2 h data bins by regressing the change in RPP against the change in logged activity counts. The RPP showed 24 h variation (p < 0.0005), with a peak of 11,004 (95% CI = 10,757 to 11,250) beat . min(-1) . mmHg occurring at 10:00 h (2 h after mean wake-time). The overall 24 h mean of RPP reactivity was 477 beat . min(-1) . mmHg . logged activity counts(-1) (95% CI = 426 to 529). The largest increase in RPP reactivity occurred within the first 2 h after waking (p < 0.0005). There were no subsequent significant differences in RPP reactivity up to 14 h after waking. The lowest RPP reactivity was found 18-20 h after waking, with a peak-to-trough variation of 593 beat . min(-1) . mmHg . logged activity counts(-1) (95% CI = 394 to 791, p < 0.0005). Although this variation was not moderated by BP status, age, or sex, less variability in RPP reactivity was found for the medicated individuals during the waking hours. These data suggest that under conditions of normal living, the reactivity of RPP to a given change in physical activity increases markedly during the first 2 h after waking from nocturnal sleep, the time when out-of-hospital sudden cardiac events are also most common. Therefore, these data add weight to the notion that reactivity of RPP to physical activity could be a prognostic marker of autonomic imbalance and cardiovascular mortality, although more research is needed to assess the specific prognostic value of 24 h ambulatory measurements of RPP and physical activity.