This study assessed the validity of a photoplethysmographic heart rate (HR) monitor, the Polar OH1 in various sports performed in ecological conditions: running, cycling, soccer, kayaking, walking, tennis and fitness. Seventy trained athletes (56 males, 14 females) wore the Polar OH1 armband and the H7 chest belt during training. A total of 390 h and 38 min of recording were compared using a 20-bpm window to assess data quality, and Bland-Altman agreements and ICC analyses were used to test accuracy. Linear regression analyses evaluated the HR accuracy and correlation with skin tone. Training loads (TRIMPs) were compared for each session. Reliability was high for endurance sports (>99%) and lower for sports involving arm movements (92~95%). Biases were slightly negative for all sports, whereas widths of limits of agreement varied from 7–20bpm. Bland-Altman agreements were all under 5% except tennis, kayak and fitness. HR accuracy was positively correlated to skin tone (p<0.05). Finally, TRIMPs from the OH1 device were inferior to criterion’s (except walking and soccer), within a 3% range from reference. Hence, OH1 represents a valid tool to monitor instantaneous HR and training load, especially for endurance sports.

Stroke patients often exhibit difficulties performing a cognitive task while walking, defined as a dual task (DT). Their prefrontal cortex (PFC) activity is higher in DT than in single task (ST). The effects of an increasing load on PFC activity during DT in subacute stroke patients remains unexplored. Our objective was to assess the effects of N-back tasks (low/high load) on cerebral activity, gait parameters, and cognitive performances. Eleven subacute stroke patients (days post-stroke 45.8 ± 31.6) participated in this pilot study (71.4 ± 10 years, BMI 26.7 ± 4.8 kg.m⁻², Barthel index 81.8 ± 11.0). Patients completed a ST_walk, and 4 conditions with 1-back (low load) and 2-back (high load): ST_low, ST_high, DT_low, and DT_high. Overground walking was performed at a comfortable pace and -N-back conditions were carried out verbally. Both gait (speed, stride variability) and cognitive (rate of correct answers) performances were recorded. Changes in PFC oxyhemoglobin (ΔO₂Hb) and deoxyhemoglobin (ΔHHb) were measured by functional near infrared spectroscopy (fNIRS). Results showed an increase of ΔO₂Hb while walking, which was not augmented by cognitive loads in DT. Walking speed was reduced by low and high cognitive loads in DT compared to ST_walk (P < 0.05), but was not different between DT_low and DT_high. Cognitive performances were negatively impacted by both walking (P < 0.05) and cognitive load (between “low” and “high,” P < 0.001). These data highlight a “ceiling” effect in ΔO₂Hb levels while walking, leaving no available resources for simultaneous cognitive tasks, during the early recovery period following stroke. In these patients, cognitive, but not motor, performances declined with a higher cognitive load.

Background: Exercise represents a viable non-pharmacological intervention to help treating insomnia but the interaction mechanisms between sleep and physical activity still remain poorly understood. The aim of this study was to investigate the effect of a aerobic exercise training intervention on sleep and core temperature. Methods: Twenty-four adult women suffering from insomnia participated in this study. They were randomized into an exercise group and a control group. Aerobic exercise training consisted in moderate to vigorous aerobic exercise training for 12 weeks. Outcome measures included both subjective (Insomnia Severity Index, ISI) and objective (actigraphy recordings) sleep quality assessments, and core body temperature continuously recorded for a minimum 24 h. Results: The exercise group showed a decrease in ISI (p < 0.001) and in various objective sleep parameters. The core temperature batyphase value was lowered (p = 0.037) whereas its amplitude was larger (p = 0.002). We also found a tight correlation between the evolution of insomnia and the evolution of mean night-time core temperature and batyphase values. Conclusions: A moderate to vigorous aerobic exercise program appears to be an effective non-drug therapy for improving sleep in women with insomnia. In addition, exercise programs should aim to increase core body temperature during practice to induce sleep-promoting adaptations and rebound.

This study aims to evaluate the accuracy of the Garmin Forerunner 245 heart rate (HR) and pulse O₂ saturation (SpO₂) sensors compared with electrocardiogram and medical oximeter, from sea level to high altitude. Ten healthy subjects underwent five tests in normoxia and hypoxia (simulated altitudes from 3000 to 5500 m), consisting in a 5-min rest phase, followed by 5-min of mild exercise. Absolute error (±10 bpm for HR and ±3% for SpO₂, around criterion) and intraclass correlations (ICC) were calculated. Error rates for HR remained under 10%, except at 3000 m, and ICCs evidenced a good reliability between Garmin and criterion. Overall SpO₂ was higher than criterion (P50% error rate (>80% above 4800 m), and a poor reliability with criterion. The Garmin device displayed acceptable HR data at rest and exercise for all altitudes, but failed to provide trustworthy SpO₂ values, especially at high altitude, where a pronounced arterial O₂ desaturation could lead to acute mountain sickness in hypoxia-sensitive subjects, and its life-threatening complications; moreover, readings of overestimated SpO₂ values might induce trekkers into further hazardous behavior by pursuing an ascent while being already at risk. Therefore, its use to assess SpO₂ should be proscribed in altitude for acclimatization evaluation. Received: 04 August 2020 Accepted: 07 December 2020 Article published online: 17 May 2021 © 2021. Thieme. All rights reserved. Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany