Background: Sleep deprivation is prevalent in high-pressure environments and among shift workers, and may contribute to autonomic nervous system (ANS) dysregulation, contributing to cardiovascular diseases, mood disorders, and cognitive impairment. Heart rate variability (HRV), an important indicator of ANS function, reflects fluctuations in sympathetic and parasympathetic activity and is commonly used to assess the autonomic effects of sleep deprivation. However, existing studies exhibit considerable heterogeneity due to inconsistencies in HRV measurement methods, variations in deprivation duration, and inadequate control of confounding factors.Objective: This study aimed to comprehensively evaluate the impact of sleep deprivation on HRV through a systematic review and meta-analysis of randomized controlled trials (RCTs), to elucidate the potential mechanisms underlying sleep deprivation-induced cardiac autonomic dysfunction, and to provide insights for optimizing sleep-related interventions and preventing cardiovascular disease.Methods: A systematic search was conducted in PubMed, Embase, CNKI, Wanfang, and VIP databases for RCTs investigating the effects of sleep deprivation on HRV, covering the period from January 2010 to May 2024. The Cochrane Risk of Bias tool was used for methodological quality assessment. Meta-analyses were performed using Review Manager 5.4 and Stata 17.0 software.Results: A total of 11 eligible studies involving 549 participants were included. The meta-analysis revealed that: (1) In the time domain, sleep deprivation was associated with a non-significant reduction in SDNN (p > 0.05), while RMSSD showed a significant decrease (p < 0.05). (2) In the frequency domain, both LF and LF/HF significantly increased after sleep deprivation (p < 0.05), whereas HF showed a decreasing trend that did not reach statistical significance (p > 0.05).Conclusion: This meta-analysis indicates that sleep deprivation may impair cardiac autonomic function, as evidenced by decreased RMSSD and increased LF and LF/HF, suggesting sympathetic predominance and vagal suppression. However, changes in other HRV indices such as SDNN and HF were not statistically significant. These findings imply a potential disruption of the dynamic balance between sympathetic and parasympathetic activity following sleep deprivation. Future research should adopt standardized HRV measurement protocols to validate these findings and further explore the underlying physiological mechanisms. This study provides important evidence for understanding the dynamic changes in autonomic function associated with sleep deprivation.Systematic review registration: https://inplasy.com/projects/, identifier INPLASY202560023.

Introduction: Exhaustive exercise is a common training method in sports, but its impact on the autonomic nervous system of the human body remains unclear. Understanding the effects of exhaustive exercise on the body and its connection with the autonomic nervous system and central nervous system is crucial for guiding healthy training methods.Methods: Twenty-three participants were selected, and exhaustive exercise intervention was performed using the Bruce Protocol. By measuring heart rate variability (HRV), the effects of exhaustive exercise on the autonomic nervous system function were analyzed.Results: After exhaustive exercise, time-domain indices SDNN, RMSSD, and PNN50 all significantly decreased, with changes reaching significant levels (p < 0.01). Among them, the decrease in pNN50 was particularly pronounced, with a change rate of −94.55%. Frequency-domain indices VLF, LF, and HF also showed significant decreases (p < 0.01), but the ratio of LF to HF showed an upward trend (p < 0.01), with LF showing a greater decrease. Nonlinear indices SD1 and SD2 showed extremely significant decreases (p < 0.01), and the SD2/SD1 ratio showed a significant increase (p < 0.01), indicating significant changes in HRV nonlinear characteristics after exercise.Discussion: Exhaustive exercise leads to a decrease in autonomic nervous system activity and an increase in sympathetic nervous system activity. These findings underscore the profound impact of exhaustive exercise on the autonomic nervous system, with implications for understanding the physiological responses to intense physical exertion. Further research is warranted to explore the long-term effects of exhaustive exercise on autonomic regulation and its potential implications for training methodologies and athlete health.

Background: Caffeine, a widely used central nervous system stimulant, has been extensively studied for its potential to enhance exercise performance. However, systematic evaluations of its effects on badminton-specific performance remain limited, particularly in the domains of cognitive function and technical skills.Purpose: This study aimed to evaluate the acute effects of caffeine ingestion on cognitive, physical, and technical performance in elite badminton players.Methods: A randomized, double-blind, placebo-controlled crossover design was employed. Fifteen elite male badminton players holding a national first-class athlete certificate participated. Each ingested either caffeine (5 mg/kg body mass) or a placebo, followed by a 45-min absorption period and a 50-min standardized fatigue protocol. Participants then completed badminton-specific performance tests, including the Anticipation Skills Test (AST), Smash Accuracy Test (SAT), Shuttle Run Agility Test (SRAT), and Repeated Sprint Test (RST). A 7-day washout period was applied between conditions.Results: Significant treatment × time interaction effects were observed for anticipation accuracy (F = 4.992, p = 0.029), reaction time (F = 4.084, p = 0.048), and visual search frequency (F = 8.514, p = 0.005), indicating improved post-fatigue performance in the caffeine condition, whereas the placebo condition declined or remained unchanged. In terms of physical performance, the caffeine group demonstrated superior overall agility in the SRAT (F = 4.097, p = 0.048) and showed an anti-fatigue effect in the RST (F = 5.283, p = 0.025). However, caffeine ingestion did not significantly affect smash accuracy (p = 0.942) or ratings of perceived exertion (RPE; p = 0.917).Conclusion: Acute ingestion of 5 mg/kg caffeine significantly enhanced cognitive and physical performance under fatigue in elite badminton players, while exerting no apparent effect on fine technical skills.

Objective: This study aimed to systematically review and meta-analyze the effects of acute high-altitude exposure on heart rate variability (HRV), in order to elucidate the adaptive changes of the autonomic nervous system under high-altitude environments. Methods: Following the PRISMA 2020 guidelines, PubMed, Web of Science, Cochrane Library, Embase, China National Knowledge Infrastructure (CNKI), and Wanfang databases were searched from inception to June 2025. Eligible studies included healthy adults who acutely ascended to high altitude (≥2,500 m, exposure duration ≤7 days) and reported HRV-related indices, including Standard Deviation of Normal-to-Normal intervals (SDNN), Root Mean Square of Successive Differences (RMSSD), Percentage of successive NN intervals differing by more than 50 ms (pNN50), High-Frequency power (HF), and Low-Frequency power (LF). Statistical analyses were performed using Stata 17.0 and RevMan 5.4. Effect sizes were expressed as standardized mean differences (SMDs) with 95% confidence intervals (CIs). Subgroup analyses, sensitivity analyses, and publication bias assessments were also conducted. Results: A total of 15 studies involving 698 participants were included. Meta-analysis revealed that after acute high-altitude exposure, SDNN, RMSSD, pNN50, HF, and LF were all significantly (all p < 0.001) reduced compared with sea-level values, whereas the LF/HF ratio increased significantly (p < 0.001). Altitude subgroup analysis indicated that at ≥3500 m, SDNN decreased more and LF/HF increased more than at <3,500 m (p < 0.05), while no significant between-group differences were found for RMSSD, pNN50, HF, or LF (all p > 0.05). In the fitness subgroups, SDNN, RMSSD, pNN50, and HF did not differ significantly between trained individuals and healthy adults (all p > 0.05), although trained individuals exhibited a smaller reduction in LF and a more pronounced increase in LF/HF (p < 0.05). Sensitivity analyses confirmed the robustness of the results, and no obvious publication bias was detected. Conclusion: Acute high-altitude exposure markedly reduces both time- and frequency-domain HRV indices, accompanied by an increase in the LF/HF ratio, indicating an autonomic response characterized by “reduced variability, vagal withdrawal, and relative sympathetic predominance.” This response becomes more pronounced at higher elevations (≥3,500 m). Both trained and healthy adults experience vagal inhibition; however, trained show better preservation of low-frequency oscillations and stronger sympathetic regulatory capacity. Accordingly, strategies such as gradual ascent, maintaining stable breathing rhythms, and incorporating recovery-focused training before and after entering high altitude may help mitigate autonomic disturbances and facilitate early acclimatization. Systematic Review Registration: https://inplasy.com/projects/ , identifier INPLASY202590004.

Insufficient sleep causes muscle fatigue, impacting performance. The mechanism of brain–muscle signaling remains uncertain. In this study, we examined the impact of sleep deprivation on muscle endurance during isometric contractions and explored the changes in brain–muscle connectivity. Methods: The research involved 35 right-handed male participants who took part in an exercise test that included isometric contractions of the left and right biceps in both sleep-deprived and well-rested states. Muscle contraction duration and electroencephalogram (EEG) and electromyography (EMG) signals were recorded. Functional connectivity between brain regions was assessed using the phase locking value (PLV), while partial directed coherence (PDC) was used to analyze signal directionality between motor centers and muscles. Results: The connectivity strength between Brodmann areas (BAs) 1-5 and the right BA6, 8 regions was significantly decreased in the isometric contractions after sleep deprivation. Insufficient sleep enhanced the PDC signals from the motor center of the right brain to the left biceps, and it decreased the PDC signals from both biceps to their opposite motor centers. Conclusions: Sleep deprivation shortened muscle isometric contraction duration by affecting the interaction between the somatosensory motor cortex and the right premotor cortex, reducing biceps feedback signal connectivity to the contralateral motor center in the brain.

Traditional assessment methods in physical education often emphasize final grades, lacking real-time monitoring and feedback during the learning process. To address this limitation and enhance the formative evaluation of student performance, this study proposes a real-time assessment system for Baduanjin instruction in physical education, utilizing a commercially available inertial measurement unit-based motion capture device. The system was developed in four stages. First, a dataset was created by recruiting 20 university students and one expert physical education instructor. Participants were asked to perform standardized Baduanjin routines while wearing wireless inertial measurement unit sensors on key body joints. The collected kinematic data, sampled at 100 Hz, included joint angles and movement trajectories. Second, preprocessing and feature extraction techniques were applied to the raw data to construct a labeled dataset for training. Third, supervised machine learning algorithms were used to build models for motion type recognition and motion accuracy evaluation. Model performance was assessed using cross-validation and compared with expert evaluations. Finally, a user-facing formative assessment system was developed and tested in a controlled classroom environment. The system demonstrated a high motion recognition accuracy of 99.77%, and the correlation coefficient between system-assessed motion accuracy and expert ratings exceeded 0.80, indicating strong validity. The results demonstrate that the formative assessment system built on inertial measurement unit is appropriate for the Baduanjin physical education.