Time-Dependent Effects of Physical Activity on Cardiovascular Risk Factors in Adults: A Systematic Review

Abstract

Purpose: Physical activity is an important non-drug-related method to prevent and treat cardiovascular diseases, but how exercise duration affects the cardiovascular metabolic risk factors in adults remains uncertain. This review systematically examines the time-dependent effects of physical activity on cardiovascular risk factors in adults and aims to further the understanding of the temporal therapeutics of exercise. Methods: Following the PRISMA guidelines, the PubMed, Web of Science, EMBASE, and CNKI databases were systematically searched for relevant scientific studies from January 2000 to June 2022. Results: A total of 16 studies met the inclusion criteria and were included in the systematic review. The sample size ranged from 11–275 participants who were diagnosed with obesity, hypertension, diabetes mellitus type 2 (T2DM), and Coronary Heart Disease (CAD), while the subjects in four studies did not report any metabolic or cardiovascular disease. Four studies conducted trials of acute exercise interventions, while the remaining intervention periods ranged from 12 days to 12 weeks. The exercise interventions included aerobic training, resistance training, aerobic training that was combined with resistance training, compound exercise, and high-intensity interval exercise, and the training frequency varied from 2–5 times/week. Conclusions: Overall, this review found some evidence that the cardiovascular risk factors in adults may be time-dependent in response to physical activity. However, it is limited by the small sample size for each of the outcomes and several methodological issues, leading to poor comparability between studies. A randomized controlled trial with a larger sample size is supposed to be designed for the relevant population to completely test whether synchronizing the exercise time point in the day with the individual’s circadian rhythm can amplify the benefits of the exercise for improving cardiovascular health.

Time of Day Effects on Exercising in Cardiac Rehabilitation

“…The CLOCK gene encodes proteins on the positive transcription circadian feedback loop 5,7. Evidence suggests that TC or CC genotypes are associated with higher total cholesterol, hypertension, and increased risk for ACS events 4,7,10. Experts hypothesize that C carriers have less autonomic nervous system activity compared to TT carriers which may contribute to the increased risk for ACS events especially in the morning hours 10.…”

“…Despite decades of research demonstrating the effectiveness of cardiac rehabilitation (CR), participants with post-revascularizations for acute coronary syndromes (ACS) pose a significant financial burden to hospitals due to high health care utilization (ie, readmissions and emergency department [ED] visits) 1,2. Evidence supports that circadian rhythms affect cardiac pathophysiology, resulting in 24-hr patterning of ACS symptoms and cardiac arrests 3–5. Emerging evidence suggests that exercising concordantly to inherit circadian rhythm patterns improves outcomes such as blood pressure and inflammatory cytokines 3,6.…”

“…Circadian rhythms arise from the molecular level and circadian CLOCK genes. The CLOCK gene has been associated with rhythmic patterns and ACS events 4,7. Evidence supports that single nucleotide polymorphism (SNP) rs1801260, TT genotypes perform physically better in the morning than the C allele (TC/CC)8 and thus may benefit from morning CR sessions while TC/CC may benefit more from afternoon CR.…”

“…1,2 Evidence supports that circadian rhythms affect cardiac pathophysiology, resulting in 24-hr patterning of ACS symptoms and cardiac arrests. [3][4][5] Emerging evidence suggests that exercising concordantly to inherit circadian rhythm patterns improves outcomes such as blood pressure and inflammatory cytokines. 3,6 However, exercising nonconcordantly may produce adverse outcomes.…”

“…The CLOCK gene has been associated with rhythmic patterns and ACS events. 4,7 Evidence supports that single nucleotide polymorphism (SNP) rs1801260, TT genotypes perform physically better in the morning than the C allele (TC/CC) 8 and thus may benefit from morning CR sessions while TC/CC may benefit more from afternoon CR. Hence, the primary aim for this study was to explore the interactions (concordance * CLOCK genes) for ED utilization and hospital admissions at 30, 60, and 90 d, among post-revascularization participants with ACS who completed 18 CR sessions.…”