The ratio of heart rate to heart rate variability reflects sympathetic activity during incremental cycling exercise

The relationship between resting heart rate variability and sportive performance, sleep and body awareness in soccer players

BACKGROUND

Heart rate variability (HRV) is a key marker of autonomic nervous system function and has been proposed as a tool for monitoring training adaptations. However, its relationship with performance beyond aerobic capacity remains unclear in football players. This study aimed to examine the associations between resting HRV and aerobic capacity, agility, neuromuscular coordination, sleep quality, and body awareness.

METHODS

Twenty-five male football players (mean age 20 ± 3 years) underwent HRV assessment via the Polar H10 system. Performance tests included the 20 m Shuttle Test (VO2max), Illinois Agility Test, Hexagon Test (neuromuscular coordination), and Vertical Jump Tests (muscular strength). Sleep quality and body awareness were assessed using the Pittsburgh Sleep Quality Index and Body Awareness Questionnaire.

RESULTS

HRV Score was positively correlated with VO2max (r = 0.4, p = 0.04), while LF/HF ratio showed a negative correlation with shuttle test distance (rs=-0.52, p = 0.007). Mean RR correlated with neuromuscular coordination (r = 0.56, p = 0.004), sleep quality (r = 0.45, p = 0.024), and body awareness (rs = 0.46, p = 0.019). No significant correlations were found with muscular strength.

CONCLUSIONS

Resting HRV is associated with key performance indicators in football players, supporting its potential use in monitoring physiological readiness and training adaptations. Future research should establish reference values and evaluate HRV-based interventions for performance enhancement.

The relationship between acute aerobic exercise and inhibitory control in college students: The impact of physical and cognitive engagement

OBJECTIVE

Evidence suggests that acute exercise is an effective way for improving inhibition control, however, the effect of different types of Acute Aerobic Exercise and Inhibitory Control (IC) remains unclear.

METHOD

Using a crossover design, 25 participants (M = 20.20year, SD=0.91) completed 20 min of interventions at 1) moderate intensity exercise, 2) moderate intensity exercise with high cognitive demand (high cognitive-demand exercise), 3) moderate intensity exercise with high physical demand (high physical-demand exercise), and 4) rest condition (low physical and cognitive demand) in a counterbalanced way. Flanker task was completed before and after each intervention to evaluate their inhibitory control ability.

RESULTS

The four interventions significantly reduce reaction times for both congruent and incongruent trials with Flanker task (all P < 0.05). Compared to acute moderate intensity exercise, high physical-demand exercise induced a greater reduction in reaction times for both trial types, whereas high cognitive-demand exercise led to faster reaction times in incongruent trials.

CONCLUSION

Although each intervention effectively enhanced inhibitory control, the exercise demanding high cognitive and physical effort contributed to a more pronounced improvement in inhibitory control performance. This indicates that both increased physical and cognitive engagement can significantly improve the level of inhibitory control in young adults.

24-h continuous non-invasive multiparameter home monitoring of vitals in patients with Rett syndrome by an innovative wearable technology: evidence of an overlooked chronic fatigue status

Background

Sleep is disturbed in Rett syndrome (RTT), a rare and progressive neurodevelopmental disorder primarily affecting female patients (prevalence 7.1/100,000 female patients) linked to pathogenic variations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene. Autonomic nervous system dysfunction with a predominance of the sympathetic nervous system (SNS) over the parasympathetic nervous system (PSNS) is reported in RTT, along with exercise fatigue and increased sudden death risk. The aim of the present study was to test the feasibility of a continuous 24 h non-invasive home monitoring of the biological vitals (biovitals) by an innovative wearable sensor device in pediatric and adolescent/adult RTT patients.

Methods

A total of 10 female patients (mean age 18.3 ± 9.4 years, range 4.7-35.5 years) with typical RTT and MECP2 pathogenic variations were enrolled. Clinical severity was assessed by validated scales. Heart rate (HR), respiratory rate (RR), and skin temperature (SkT) were monitored by the YouCare Wearable Medical Device (Accyourate Group SpA, L'Aquila, Italy). The average percentage of maximum HR (HRmax%) was calculated. Heart rate variability (HRV) was expressed by consolidated time-domain and frequency-domain parameters. The HR/LF (low frequency) ratio, indicating SNS activation under dynamic exercise, was calculated. Simultaneous continuous measurement of indoor air quality variables was performed and the patients' contributions to the surrounding water vapor partial pressure [PH2O (pt)] and carbon dioxide [PCO2 (pt)] were indirectly estimated.

Results

Of the 6,559.79 h of biovital recordings, 5051.03 h (77%) were valid for data interpretation. Sleep and wake hours were 9.0 ± 1.1 h and 14.9 ± 1.1 h, respectively. HRmax % [median: 71.86% (interquartile range 61.03-82%)] and HR/LF [median: 3.75 (interquartile range 3.19-5.05)] were elevated, independent from the wake-sleep cycle. The majority of HRV time- and frequency-domain parameters were significantly higher in the pediatric patients (p ≤ 0.031). The HRV HR/LF ratio was associated with phenotype severity, disease progression, clinical sleep disorder, subclinical hypoxia, and electroencephalographic observations of multifocal epileptic activity and general background slowing.

Conclusion

Our findings indicate the feasibility of a continuous 24-h non-invasive home monitoring of biovital parameters in RTT. Moreover, for the first time, HRmax% and the HR/LF ratio were identified as potential objective markers of fatigue, illness severity, and disease progression.

Anaerobic threshold using sweat lactate sensor under hypoxia

We aimed to investigate the reliability and validity of sweat lactate threshold (sLT) measurement based on the real-time monitoring of the transition in sweat lactate levels (sLA) under hypoxic exercise. In this cross-sectional study, 20 healthy participants who underwent exercise tests using respiratory gas analysis under hypoxia (fraction of inspired oxygen [FiO2], 15.4 ± 0.8%) in addition to normoxia (FiO2, 20.9%) were included; we simultaneously monitored sLA transition using a wearable lactate sensor. The initial significant elevation in sLA over the baseline was defined as sLT. Under hypoxia, real-time dynamic changes in sLA were successfully visualized, including a rapid, continual rise until volitionary exhaustion and a progressive reduction in the recovery phase. High intra- and inter-evaluator reliability was demonstrated for sLT's repeat determinations (0.782 [0.607-0.898] and 0.933 [0.841-0.973]) as intraclass correlation coefficients [95% confidence interval]. sLT correlated with ventilatory threshold (VT) (r = 0.70, p < 0.01). A strong agreement was found in the Bland-Altman plot (mean difference/mean average time: - 15.5/550.8 s) under hypoxia. Our wearable device enabled continuous and real-time lactate assessment in sweat under hypoxic conditions in healthy participants with high reliability and validity, providing additional information to detect anaerobic thresholds in hypoxic conditions.

Heart rate variability in patients with psychiatric disorders from adolescence to adulthood

OBJECTIVE

Age is associated with changes in autonomic nervous system activity. These changes are assessed using heart rate variability(HRV) indicators; however, the effect of age on HRV in patients with psychiatric disorders remains unclear. Our study aimed to explore this effect and determine its variance across different lifespans.

METHOD

Consecutive patients(N = 3315), comprising 1833 patients with psychotic disorders, 1040 with mood disorders, and 442 with anxiety disorders, were recruited. The patients were divided into four age groups: adolescence(10-24 years), early adulthood(25-39 years), middle adulthood(40-59 years), and late adulthood(60+ years). HRV indicators were measured during a 5-min rest period.

RESULTS

The heart rate and HRV indices were higher in the adolescent and early adulthood groups than they were in the middle and late adulthood groups(increased HRV is beneficial for health, while reduced HRV is detrimental). Age and all the HRV indices were negatively correlated(r-values 0.153-0.350, p < 0.001), with these correlation patterns being more evident in the adolescent and early adulthood groups than in the middle and late adulthood groups. Stratified by sex, the low-frequency/high-frequency ratio was higher in men than in women across most age groups(p < 0.05), except the late adulthood group(p = 0.085). Stratified by diagnosis, most HRV variables(except very low-frequency) were lower in the psychotic disorder group than they were in the mood and anxiety disorder groups, especially in middle and late adulthood patients. After adjusting for confounders, the HRV variables were significantly associated with age, while older age was associated with lower HRV.

CONCLUSIONS

These results indicate that the substantial reduction in HRV with age in patients with psychiatric disorders. The association remains significant after correction for sex, heart rate, and diagnoses; this may prove useful to clinical practice and further research.

The Validity of Ultra-Short-Term Heart Rate Variability during Cycling Exercise

Ultra-short-term heart rate variability (HRV) has been validated in the resting state, but its validity during exercise is unclear. This study aimed to examine the validity in ultra-short-term HRV during exercise considering the different exercise intensities. HRVs of twenty-nine healthy adults were measured during incremental cycle exercise tests. HRV parameters (Time-, frequency-domain and non-linear) corresponding to each of the 20% (low), 50% (moderate), and 80% (high) peak oxygen uptakes were compared between the different time segments of HRV analysis (180 s (sec) segment vs. 30, 60, 90, and 120-sec segments). Overall, the differences (bias) between ultra-short-term HRVs increased as the time segment became shorter. In moderate- and high-intensity exercises, the differences in ultra-short-term HRV were more significant than in low intensity exercise. Thus, we discovered that the validity of ultra-short-term HRV differed with the duration of the time segment and exercise intensities. However, the ultra-short-term HRV is feasible in the cycling exercise, and we determined some optimal time duration for HRV analysis for across exercise intensities during the incremental cycling exercise.