Purpose: The accuracy of heart rate measured with a wrist photoplethysmography monitor can be influenced by the tightening of the wristband, movement of arms, or kinetics of the signal (eg, steady-state exercise vs on- and off-transients). To test these hypotheses, photoplethysmographic and electrocardiographic (ECG) signals were compared. Methods: Thirty participants (50% female) randomly performed two 13′ sequences (3′ rest, 5′ submaximal-intensity exercise, and 5′ passive recovery) on a motorized treadmill and a bicycle ergometer. Heart rate was measured concomitantly with a 10-lead ECG, a chest-strap monitor, and 2 wrist photoplethysmography monitors (Polar Unite) with different tightening (free vs imposed at the maximum tolerable). Results: The level of association (r) and coefficient of variation (CV; ie, the error of measurement) of the Polar Unite versus the 10-lead ECG is affected by the tightness of the wristband (normal vs high; r = .83 and .96, CV = 16.1 and 8.1% for the treadmill, respectively; r = .71 and .97, CV = 20.3% and 6.2% for the bicycle, respectively) by the phase of the signal (transition vs steady state; r = .90 and .97, CV = 9.0% and 7.6% for the treadmill, respectively; r = .93 and .99, CV = 7.5% and 3.1% for the bicycle, respectively) and movement of arms (treadmill vs bicycle; r = .90 and .93, CV = 9.0% and 7.5% during the transition phase, respectively; r = .97 and .99, CV = 7.6% and 3.1% during the steady-state phase, respectively). Conclusion: The accuracy of heart rate measured with a wrist photoplethysmography monitor is affected by the tightness of the wristband and the phase of the signal. A high tightening is required when high accuracy is expected.

Purpose: The accuracy of heart rate (HR) measured with a wrist-worn photoplethysmography (PPG) monitor is altered during rest–exercise and exercise–rest transitions, which questions the validity of postexercise HR-recovery (HRR) parameters estimated from this device. Methods: Thirty participants (50% female) randomly performed two 13-minute sequences (3′ rest, 5′ submaximal-intensity exercise, and 5′ passive recovery) on treadmill and bicycle ergometers. HR was measured concomitantly with a 10-lead electrocardiogram (ECG) and a wrist-worn PPG monitor (Polar Unite). HRR was assessed by calculating Δ60 (the difference between HR during exercise and HR 60 s after exercise cessation) and by fitting HRR data into a monoexponential model. Results: By focusing on Δ60 and τ (the time constant of the monoexponential curve), levels of association (r) of the Unite versus the 10-lead ECG were high to very high (.73 < r < .93), and coefficients of variation were >20% (in absolute value), except for Δ60 in the bicycle ergometer condition (11.7%). In 97% of cases, the decrease in HR after exercise appeared later with the Unite. By adjusting the time window used for the analysis according to this time lag, coefficients of variation of Δ60 decreased below 10% in the bicycle ergometer condition. Conclusions: If a wrist-worn PPG monitor is used to assess HRR, we recommend performing the submaximal-intensity exercise on a bicycle ergometer and focusing on Δ60. Furthermore, to obtain a more accurate Δ60, the time lag between the end of the exercise and the effective decrease in HR should also be considered before the calculation.

Background: In patients with obstructive lung disease, maintaining adequate ventilation during exercise may require greater contraction of the respiratory muscles, which may lead to a compression of muscle capillaries. Furthermore, dynamic hyperinflation (DH) is frequent during exercise in these patients, as it allows to reach higher expiratory flows and to satisfy respiratory demand. However, in such situation, intercostal muscles are likely to be stretched, which could affect the diameter of their capillaries. Thus, in a context of high level of expiratory resistance, intercostal muscle oxygenation may be disturbed during exercise, especially if DH occurs.Methods: Twelve participants (22±2 years) performed two sessions of moderate exercise (20 min) by breathing freely with and without a 20-cmH2O expiratory threshold load (ETL). Tissue saturation index (TSI) and concentration changes from rest (∆) in oxygenated ([O2Hb]) and total haemoglobin ([tHb]) were measured in the seventh intercostal space using near-infrared spectroscopy. Respiratory, metabolic and cardiac variables were likewise recorded.Results: Throughout exercise, dyspnea was higher and TSI was lower in ETL condition than in control (p<0.01). After a few minutes of exercise, ∆ [O2Hb] was also lower in ETL condition, as well as ∆ [tHb], when inspiratory capacity started to be reduced (p<0.05). Changes in [O2Hb] and dyspnea were correlated with changes in expiratory flow rate (Vt/Te) (r = -0.66 and 0.66. respectively; p<0.05).Conclusion: During exercise with ETL, impaired muscle oxygenation could be due to a limited increase in blood volume resulting from strong muscle contraction and/or occurrence of DH.

Sleep is a critical determinant of health, performance, and recovery in athletes, particularly elite populations who are exposed to high training loads and competitive demands [1,2]. Adequate sleep...

This study examined whether performance changes following a taper incorporating sleep-enhancing strategies differed according to the pre-taper fatigue level in elite swimmers. Physiological, psychological, and biomechanical parameters were assessed in twenty-seven elite swimmers at two time points to estimate pre-taper fatigue: T0 and T1 (10 and 3 weeks before the main competition, respectively). Race performance was officially recorded at T1 and during the main competition. Sleep-enhancing strategies included two sleep education sessions, five consecutive evenings of cryostimulation, and the use of a mattress topper with high thermal conductivity. Statistical significance was set at p ≤ 0.05. Thirteen swimmers (17 ± 2 y) were classified as acutely fatigued (AF) and fourteen (17 ± 1 y) as functionally overreached (F-OR). From T1 to competition, performance changes were not different between groups (AF: +1.2 ± 1.6% vs. F-OR: +0.4 ± 2.3%). A total of 82% of swimmers in the AF group and 67% in the F-OR group achieved a performance improvement greater than 0.5% (p > 0.05). Following a tapering period incorporating sleep-enhancing interventions, no significant differences were observed between AF and F-OR swimmers in the magnitude of performance change or in the proportion of swimmers exhibiting a performance improvement greater than 0.5%.