Cardiac autonomic nervous activity during different sleep stages in individuals with spinal cord injury: The influence of physical training

OBJECTIVE

The present study assessed the influence of physical training on cardiac autonomic activity in individuals with spinal cord injury (SCI) during different sleep stages.

METHODS

Twenty-six volunteers were allocated into three groups: 9 sedentary individuals without SCI (control, CON); 8 sedentary tetraplegic individuals with chronic SCI (SED-SCI); 9 physically trained tetraplegic individuals with chronic SCI (TR-SCI). All participants underwent nocturnal polysomnography to monitor sleep stages: wakefulness, non-rapid eye movement (NREM) sleep (N1, N2, and N3 stages), and REM sleep. The electrocardiography data obtained during this exam were extracted to analyze the heart rate variability (HRV).

RESULTS

Sleep stages influenced HRV in the time [RR interval and root mean square of successive RR interval differences (RMSSD)] and frequency [low-frequency (LF) and high-frequency (HF) powers and LF-to-HF ratio] domains (P < 0.05). SED-SCI individuals showed unchanged HRV compared to CON (P > 0.05). When comparing the TR-SCI and SED-SCI groups, no significant differences in HRV were reported in the time domain (P > 0.05). However, in the frequency domain, more accentuated HF power was observed in TR-SCI than in SED-SCI individuals during the N2 and N3 stages and REM sleep (P < 0.05). Moreover, TR-SCI had higher HF power than CON during the N3 stage (P < 0.05).

CONCLUSIONS

TR-SCI individuals have greater HF power, indicative of parasympathetic modulation, than sedentary (injured or not injured) individuals during different sleep stages. Therefore, enhanced parasympathetic activity induced by physical training may improve cardiac autonomic modulation during sleep in individuals with chronic SCI.

The Sleep Parameters of Olympic Athletes: Characteristics and Assessment Instruments

This systematic review aims to identify the sleep parameters of Olympic athletes and the instruments used to assess and monitor the sleep of these athletes. The search was conducted until February 2023 and was performed in PubMed, Web of Science, and Scopus databases. This systematic review has included studies that investigated at least one of the following sleep parameters: total sleep time (TST), sleep onset latency (SOL), sleep efficiency (SE), awakenings after sleep onset (WASO), quality of sleep, daytime sleepiness, and chronotype; the participants were Olympic athletes. The search returned a total of 280 studies. After screening based on exclusion and inclusion criteria, 11 studies were included. The main results demonstrate that Olympic athletes have TST of 06:10 h, SE of 84%, SOL of 28 min, and WASO of 49 min. The most predominant chronotype is indifferent; over half of the athletes have poor sleep quality and complaints. Furthermore, actigraphy was the most used method to assess sleep. It is concluded that Olympic athletes have TST, SE, and WASO poor than the recommended values. In addition, sleep complaints and poor sleep quality were also observed. Among the objective sleep assessment methods, actigraphy was the method most frequently used in this population.

Current Technologies and Practices to Assess External Training Load in Paralympic Sport: A Systematic Review

CONTEXT

Knowing the methods to assess the external load in Paralympic sports can help multidisciplinary teams rely on scientific evidence to better prescribe and monitor the athlete's development, improving sports performance and reducing the risk of injury/illness of Paralympic athletes.

OBJECTIVES

This review aimed to systematically explore the current practices of quantifying the external load in Paralympic sports and provide an overview of the methods and techniques used.

EVIDENCE ACQUISITION

A search in PubMed, Web of Science, Scopus, and EBSCO was carried out until November 2022. The measures of interest were objective methods for quantifying the external load of training or competition. The inclusion criteria for the studies were as follows: (1) peer-reviewed article; (2) the population were Paralympic athletes; (3) evaluated during training or competition; (4) reported at least one external load measure; and (5) published in English, Portuguese, or Spanish.

EVIDENCE SYNTHESIS

Of the 1961 articles found, 22 were included because they met the criteria, and 8 methods were identified to quantify the external load in training or competition in 8 Paralympic sports. The methods varied according to the characteristics of the Paralympic sports. To date, the devices used included an internal radiofrequency-based tracking system (wheelchair rugby) a miniaturized data logger (wheelchair tennis, basketball, and rugby); a linear position transducer (powerlifting and wheelchair basketball); a camera (swimming, goalball, and wheelchair rugby); a global positioning system (wheelchair tennis); heart rate monitors that assess external load variables in set (paracycling and swimming) and an electronic timer (swimming).

CONCLUSIONS

Different objective methods were identified to assess the external load in Paralympic sports. However, few studies showed the validity and reliability of these methods. Further studies are needed to compare different methods of external load quantification in other Paralympic sports.

Association Between Hormonal Status, Stress, Recovery, and Motivation of Paralympic Swimmers

Purpose: The present study aimed to investigate associations between hormonal profile (cortisol and testosterone) and the psychobiological aspects of Paralympic athletes during a competitive season. Method: Male Brazilian Paralympic swimmers (n = 11) were evaluated in three Training Camps (TC) during the cycle of training for the Paralympic Games RIO 2016. Questionnaires were used for data collection of stress and recovery, motivation in sport and hormonal status was assessed by salivary samples of cortisol ([Csal]) and testosterone ([Tsal]) concentrations. The Friedman test was used to identify overall significant differences at the three TC for each variable. When the overall p value indicated statistical significance (p < .05), a post hoc Wilcoxon signed-rank test for paired data was used to compare pairs of TC. The Spearman correlation was used to identify associations between the hormonal profile and the psychobiological aspects. Results: There was an association between the [Csal] and the "Conflicts/Pressure" sub-scale (r = 0.60; p = .04) in TC1 and the "Lack of Energy" subscale (r = 0.63; p = .03) in TC2. In the TC3, there were correlations between [Tsal] and "To Know" intrinsic motivation (r = 0.83, p < .01), "Objectives"(r = 0.66, p < .02), "Experiences" (r = 0.65, p < .02) and "Amotivation" (r = -0.70, p = .01). There were also associations between the [Tsal] and the "Social Recovery" (r = 0.77, p < .01), "General Wellness" (r = 0.73, p < .01), "Sleep Quality" (r = 0.63, p = .03) and "Self-efficacy" (r = 0.60, p = .05) subscales. In TC3, there was an association between [Tsal] and the "Success" (r = 0.61, p = .04), "Sleep Quality" (r = 0.62, p = .03), "Personal Accomplish" (r = 0.82, p < .01), "Self-efficacy" (r = 0.82, p < .05), "Self-regulation" (r = 0.85, p < .01) and "Physical Recovery" (r = 0.80, p < .01) subscales. The data demonstrate associations between biomarkers (salivary testosterone and cortisol) and psychobiological domains of Paralympic swimmers.

Does the compromised sleep and circadian disruption of night and shiftworkers make them highly vulnerable to 2019 coronavirus disease (COVID-19)?

Rotating and permanent night shiftwork schedules typically result in acute and sometimes chronic sleep deprivation plus acute and sometimes chronic disruption of the circadian time structure. Immune system processes and functionalities are organized as circadian rhythms, and they are also strongly influenced by sleep status. Sleep is a vital behavioral state of living beings and a modulator of immune function and responsiveness. Shiftworkers show increased risk for developing viral infections due to possible compromise of both innate and acquired immunity responses. Short sleep and sleep loss, common consequences of shiftwork, are associated with altered integrity of the immune system. We discuss the possible excess risk for COVID-19 infection in the context of the common conditions among shiftworkers, including nurses, doctors, and first responders, among others of high exposure to the contagion, of sleep imbalance and circadian disruption.

ABBREVIATIONS

ACE2: Angiotensin-converting enzyme 2; APC: Antigen.-presenting .cells; CCL: Chemokine (C-C motif) ligand; CD⁺: .Adhesion molecule expression; COVID-19: 2019 coronavirus disease; DCs: Dendritic cells; GH: Growth hormone; HPA: Hypothalamic-pituitary-adrenal; HSF: Heat shock factor; HSP70: Heat shock protein 70; HSP90: Heat shock protein 90; IL: Interleukin; INFγ: Interferon-gamma; LT/LB: T/B lymphocytes; MHC: Major histocompatibility complex; NK: Natural .killer; RAAS: renin-angiotensin-aldosterone system; SARS: .Severe acute respiratory syndrome; SCN: Suprachiasmatic nucleus;SD: Sleep deprivation; SNS: Sympathetic nervous system; Th1/Th2: T helper lymphocytes 1/2; TLR2/TLR4: Toll-like receptor 2/4; TNF-α: Tumor .necrosis .factor alpha; VEGF: Vascular endothelial growth factor.