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Background: Autonomic nervous system balance is altered in cystic fibrosis (CF), although its influence on physical fitness has been poorly explored., Objective: This study aimed to evaluate the association of heart rate variability (HRV) with exercise capacity and levels of daily physical activity in children and adolescents with mild-to-moderate CF., Methods: A cross-sectional study including individuals with CF aged 6-18 years, not under CFTR modulator therapy, was performed. Sociodemographic (age, sex) and clinical information (airway colonization, pancreatic insufficiency, and genotyping) were collected. In addition, exercise capacity (modified shuttle test - MST), lung function (spirometry), body composition (bioimpedance), levels of daily physical activity (5-day accelerometer), and HRV (both at rest and during the MST) were evaluated., Results: 30 individuals (20 females) aged 11 . 2 ± 3 . 7 years, mean FEV 1 62 . 8 ± 27 . 6 %, were included. A sympathovagal balance (LF/HF) increase ( p < 0 . 001 ) during the MST was shown, indicating a predominance of sympathetic modulation. The standard deviation of all RR intervals (SDNN) and the high frequency (HF) index during exercise correlated significantly with FEV 1 ( r = 0 . 45 , p = 0 . 01 and r = 0 . 46 , p = 0 . 01 ; respectively). MST distance also correlated positively and significantly with SDNN ( r = 0 . 43 , p = 0 . 01 ), square root of the mean of the sums of squares of frequencies between RR intervals greater than 50 ms - RMSSD ( r = 0 . 53 , p < 0 . 01 ), low frequency - LF ( r = 0 . 48 , p < 0 . 01 ), HF ( r = 0 . 64 , p < 0 . 01 ), dispersion of points perpendicular to the short-term identity line - SD1 ( r = 0 . 40 , p = 0 . 02 ) and negatively with LF/HF ( r =- 0 . 57 , p < 0 . 01 ). Regarding daily physical activity, SDNN at rest ( r = 0 . 37 , p = 0 . 04 ) and exercise ( r = 0 . 41 , p = 0 . 02 ) showed positive correlations with time in moderate-to-vigorous activities. When normalizing the SDNN and classifying individuals as normal or altered, those presenting altered SDNN showed poorest FEV 1 ( p = 0 . 001 ) and lower exercise capacity ( p = 0 . 027 )., Conclusion: HRV correlates with lung function, exercise capacity and levels of daily physical activity in children and adolescents with CF. The study highlights the influence of CF on autonomic function and suggests HRV measurement as an easy tool to be used in clinical settings as an alternative marker to monitor CF individuals., Competing Interests: The authors have no conflict of interests to declare., (© 2021, Hong Kong Physiotherapy Association.)

Study Design: Cross-sectional study., Objectives: To compare cardiac autonomic modulation of individuals with spinal cord injury (SCI) that practice different amounts of moderate to vigorous physical activity (PA) and able-bodied controls at rest and during a non-immersive Virtual Reality task., Setting: Athletes with SCI of wheelchair basketball, wheelchair tennis, wheelchair handball, WCMX (wheelchair motocross), and para-swimming were assessed at the Faca na Cadeira Institute, ICEL and Clube Espéria in São Paulo, Brazil; non-athletes with SCI and able-bodied controls were assessed at the Acreditando Centro de Recuperação Neuromotora, São Paulo, Brazil., Methods: One-hundred forty-five individuals were assessed: 36 athletes with traumatic SCI (41.1 ± 16.8 years old), 52 non-athletes with traumatic SCI (40.2 ± 14.1 years old), and 57 able-bodied individuals (39.4 ± 12.5 years old). Cardiac autonomic modulation was assessed through heart rate variability (HRV) measured in the sitting position at rest and during a VR game activity., Results: We found significantly more favourable HRV for athletes with SCI when compared to non-athletes with SCI, but no differences between athletes with SCI and able-bodied controls. In addition, athletes and able-bodied controls showed adequate autonomic nervous system (ANS) adaptation (rest versus physical activity in VR), i.e., they experienced parasympathetic withdrawal during VR physical activity, which was not found in non-athletes with SCI., Conclusion: The practice of moderate to vigorous physical activity is associated with healthier cardiac autonomic modulation in adults with SCI, which may lead to more favourable health outcomes., Trial Registration: ClinicalTrials.gov Identifier: NCT04618003, retrospectively registered., (© 2021. The Author(s), under exclusive licence to International Spinal Cord Society.)

Objective: To assess the association of sleep disorders with the findings of heart rate variability (HRV) in children and adolescents with cystic fibrosis (CF)., Methods: Cross-sectional study including children and adolescents aged six to 18 years with a clinical diagnosis of CF. Sociodemographic and clinical data were collected. Sleep disorders were evaluated using baseline nocturnal polysomnography. The autonomic nervous system (ANS) was evaluated through resting HRV., Results: A total of 30 individuals (11.2 years) with a mean forced expiratory volume in the first second (FEV1) of 62.7% were included. The respiratory disturbance index presented a median of 2.6 and obstructive sleep apnea syndrome (OSAS) was identified in 30%. In the HRV analysis, a mean standard deviation of all inter-beat (RR) intervals (SDNN) of 60.8±45.9ms was found. There was a significant correlation between the HRV low-frequency/high-frequency (LF/HF) global modulation index and the minimum SpO2 during sleep in patients with FEV1<60% (r=0.71; p=0.02). The prevalence of sleep disorders and HRV abnormalities was higher in individuals with lesser pulmonary function (FEV1<60%)., Conclusions: The results indicate a weak correlation of sleep disorders (minimum SpO2) with HRV parameters (LH/HF) in children and adolescents with CF. When pulmonary function was reduced, a stronger correlation was found, highlighting the influence of disease severity. A high prevalence of ANS disorders, nocturnal hypoxemia, and presence of OSAS was also found.