Exercise Physiology
Ameer F ahem Hassan Al-Shaeef; Reza Farzizadeh; Farnaz Seifi-askishahr
Abstract
Purpose: Mechanistic evidence from animal models is essential for understanding exercise-induced vascular adaptations, yet the translatability of these findings to clinical settings remains uncertain. This systematic review and meta-analysis quantified the effects of exercise training on endothelial ...
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Purpose: Mechanistic evidence from animal models is essential for understanding exercise-induced vascular adaptations, yet the translatability of these findings to clinical settings remains uncertain. This systematic review and meta-analysis quantified the effects of exercise training on endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) levels in animal models. Method: A systematic search of PubMed, Scopus, Web of Science, and Cochrane Library (January 2000–September 2025) was done. The review protocol was registered with PROSPERO (CRD420251144669). A random-effects model (REML) was used for meta-analysis, and SYRCLE's Risk of Bias tool assessed study quality.Results: Exercise training significantly increased eNOS levels (SMD = 0.99, 95% CI: 0.55–1.44, p < 0.001). In contrast, no significant effects were observed for NO (SMD = −1.26, 95% CI: −2.89–0.37, p = 0.13). Subgroup analyses showed that longer exercise duration (≥5 weeks; SMD = 2.25, p < 0.001) and specific modalities such as treadmill running (SMD = 1.92) and swimming (SMD = 4.59) were associated with substantially greater eNOS upregulation. Considerable heterogeneity was observed across most outcomes (I² > 85%). Conclusion: Exercise training effectively upregulates eNOS expression in animal models, particularly with interventions lasting five weeks or longer and with structured modalities like treadmill and swimming. However, the absence of significant effects on NO level, despite increased eNOS, reveals a translational gap that warrants further mechanistic investigation.
Exercise Physiology
Mohamadreza Rabiee; Sajjad Mohamadyari; Hamid Omidi; MohamadAli Izadi
Abstract
Background: Sleep quality is a key determinant of physical recovery, cognitive performance, and overall health. High-intensity interval training (HIIT) has emerged as a time-efficient exercise strategy with potential benefits for sleep regulation; however, the physiological mechanisms underlying these ...
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Background: Sleep quality is a key determinant of physical recovery, cognitive performance, and overall health. High-intensity interval training (HIIT) has emerged as a time-efficient exercise strategy with potential benefits for sleep regulation; however, the physiological mechanisms underlying these effects remain incompletely understood.Objective: This narrative review aimed to critically evaluate the current evidence regarding the role of HIIT in sleep quality regulation, with particular emphasis on inflammation, circadian rhythms, and the gut-brain axis.Methods: Literature published between 2000 and 2026 was identified through searches of PubMed, Scopus, Web of Science, and Google Scholar. Peer-reviewed original studies, randomized controlled trials, observational studies, systematic reviews, meta-analyses, and mechanistic reviews relevant to HIIT, sleep quality, inflammation, circadian biology, autonomic regulation, and the gut-brain axis were synthesized narratively.Results: The available evidence was interpreted according to direct evidence, indirect physiological associations, and emerging mechanistic hypotheses. Overall, current evidence suggests that HIIT may support sleep quality primarily through improvements in cardiometabolic health, autonomic recovery, inflammatory regulation, and circadian entrainment. Gut-brain axis mechanisms remain biologically plausible but are supported mainly by emerging evidence, and direct causal evidence linking HIIT-induced microbiome adaptations to improvements in sleep quality remains limited.Conclusion: HIIT appears to be a promising non-pharmacological strategy for improving sleep quality. However, the strength of evidence differs across the proposed mechanisms, and further well-designed longitudinal mechanistic studies integrating objective sleep assessment, inflammatory biomarkers, autonomic monitoring, and microbiome profiling are needed to clarify causal pathways and optimize exercise prescriptions for sleep health.
