Chronotype predicts working memory-dependent regional cerebral oxygenation under conditions of normal sleep and following a single night of sleep extension.

The aim of this study was to test the hypothesis that the association between sleep duration and brain activation as assessed by regional cerebral oxygenation using near-infrared spectroscopy (NIRS) is dependent on chronotype. Sleep was tracked across two weeks by actigraphy in 22 adults instructed to keep their normal sleep behavior. Chronotype was assessed by the midpoint of sleep on free days corrected for sleep debt on workdays (MSFsc). Prefrontal cerebral oxygenation (ΔHbDiff) during a visuospatial working memory task was measured in the morning after a night of normal sleep and after one night of extended sleep. Sleep extension was included to experimentally test the robustness of the association between sleep duration and ΔHbDiff. Habitual sleep duration (r = 0.43, p = 0.04) and MSFsc (r = - 0.66, p < 0.001) were significantly correlated with ΔHbDiff. After adjusting for MSFsc the relationship between sleep duration and ΔHbDiff was reduced to nonsignificant levels (r = 0.34, p = 0.11), while adjusting for sleep duration did not change the significant relationship between MSFsc and ΔHbDiff (r = - 0.62, p = 0.001). One night of sleep extension increased sleep duration by 140 min, on average, but no change in ΔHbDiff was observed. Dividing participants into earlier and later chronotypes revealed greater ΔHbDiff responses in earlier chronotypes that persisted after the night of sleep extension (mean ΔHbDiff difference = 1.35 µM, t = 2.87, p = 0.006, Hedges' g = 0.89). These results find chronotype to predict regional cerebral oxygenation responses during working memory processing under conditions of normal sleep and following a single night of sleep extension.

Muscle Damage, Inflammation, and Muscular Performance following the Physical Ability Test in Professional Firefighters.

Proper monitoring of fatigue and muscular damage may be used to decrease the high levels of cardiovascular disease, overuse musculoskeletal injuries, and workers compensation claims within the profession of firefighting. The purpose of this study was to examine muscle damage, muscular fatigue, and inflammation responses following a typical firefighting shift. Twenty-four professional firefighters completed two Physical Ability Tests to standardize the tasks typically performed in a day of work, and to elicit similar physiological responses. Participants were then monitored for 48 h. Prior to, and 48 h following the Physical Ability Tests, participants were evaluated for changes in strength, power, range-of-motion, as well as blood markers including myoglobin and c-reactive protein. Following the Physical Ability Tests, significant differences in myoglobin (p < 0.05), grip strength (p < 0.05), vertical jump (p < 0.05), and sit-and-reach (p < 0.05) were observed. No difference in c-reactive protein was observed (p > 0.05). After 24 hours following a shift, firefighters exhibited decreased strength, power, and range-of-motion. This may lead to decreases in performance and an increased risk of injury.

A Menthol-Enhanced "Cooling" Energy Gel Does Not Influence Laboratory Time Trial Performance in Trained Runners.

l-menthol (menthol) is an organic compound derived from peppermint which imparts a refreshing mint flavor and aroma to oral hygiene products, chewing gum, and topical analgesics. Menthol has been identified as a non-thermal sensory cooling strategy for athletes when ingested or mouth-rinsed during exercise in hot environments. Therefore, sports nutrition products delivering a controlled concentration of menthol could be beneficial for athletes exercising in the heat. We sought to test the performance and perceptual outcomes of a novel menthol energy gel during treadmill running in the heat (33 °C, 49% RH). Fourteen trained runners (mean ± SD; age: 31 ± 6 years, VO2max: 56.5 ± 10.1 mL·kg-1·min-1, BMI: 23.2 ± 2.4 kg/m2; six female) participated in a randomized, crossover, double-blind, and placebo-controlled study. A menthol-enhanced energy gel (0.5% concentration; MEN) or flavor-matched placebo (PLA) was ingested 5 min before and again at 20 and 40 min of a 40 min treadmill exercise preload at 60% VO2max, followed by a 20 min self-paced time trial. The total distance, vertical distance, perceptual measures (thermal comfort, thermal sensation, rating of perceived exertion, and affect), and cognitive performance via computerized neurocognitive assessment were measured. No difference between 20 min self-paced time trial total distance (MEN: 4.22 ± 0.54 km, PLA: 4.22 ± 0.55 km, p = 0.867), vertical distance (MEN: 49.2 ± 24.6 m, PLA: 44.4 ± 11.4 m, p = 0.516), or any perceptual measures was observed (all p > 0.05). Cognitive performance was not different between the trials (all p > 0.05). These results suggest that a menthol energy gel is not superior to a non-menthol gel in terms of performance or perception during treadmill running in the heat. More research is needed to confirm whether these findings translate to ecologically valid settings, including outdoor exercise in ambient heat and during competition.

Acute Supplementation with Cannabidiol Does Not Attenuate Inflammation or Improve Measures of Performance following Strenuous Exercise.

Supplementation with cannabidiol (CBD) may expedite recovery when consumed after exercise. The purpose of this study was to determine if supplementation with CBD reduces inflammation and enhances performance following strenuous eccentric exercise in collegiate athletes. Twenty-four well-trained females (age = 21.2 ± 1.8 years, height = 166.4 ± 8 cm, weight = 64.9 ± 9.1 kg) completed 100 repetitions of unilateral eccentric leg extension to induce muscle damage. In this crossover design, participants were randomized to receive 5 mg/kg of CBD in pill form or a placebo 2 h prior to, immediately following, and 10 h following muscle damage. Blood was collected, and performance and fatigue were measured prior to, and 4 h, 24 h, and 48 h following the muscle damage. Approximately 28 days separated treatment administration to control for the menstrual cycle. No significant differences were observed between the treatments for inflammation, muscle damage, or subjective fatigue. Peak torque at 60°/s (p = 0.001) and peak isometric torque (p = 0.02) were significantly lower 24 h following muscle damage, but no difference in performance was observed between treatments at any timepoint. Cannabidiol supplementation was unable to reduce fatigue, limit inflammation, or restore performance in well-trained female athletes.

Six nights of sleep extension increases regional cerebral oxygenation without modifying cognitive performance at rest or following acute aerobic exercise.

Long sleep durations (≥540 min) are associated with poor cognitive performance in ageing adults, but the underlying cause is unclear. The aim of this study was to investigate the effect of extended sleep on cognitive performance and cerebral vascular function before and then after aerobic exercise. In all, 12 adults completed 6 nights of 8- (control) and 10+-h (sleep extension) time in bed in a randomised, crossover experiment. Sleep was measured using wrist actigraphy. On the last day of each time in bed protocol, participants performed three bouts of brisk walking. Sustained attention, spatial rotation ability, mental flexibility, and working memory were assessed, while prefrontal oxygen saturation index (ΔTSI) was measured using near-infrared spectroscopy. A two-way repeated-measures analysis of variance (time in bed × before/after exercise) was used for statistical analysis. Average sleep duration was longer following sleep extension as compared to control, at a mean (SD) of 551 (16) versus 428 (20) min (p < 0.001). Sleep extension did not alter cognitive performance as compared to control, but increased ΔTSI during tests of spatial rotation ability (main effect for time in bed, p = 0.03), mental flexibility (p = 0.04), and working memory (p < 0.01). Cognitive performance was improved (main effect for exercise, p < 0.05) following brisk walking for all cognitive domains except sustained attention with no interaction with time in bed. In summary, 6 nights of extended time in bed accompanied by long sleep durations does not impair cognitive performance at rest or alter the positive effect of acute aerobic exercise on cognition but may increase frontal cerebral oxygenation during cognitive functioning.

Effect of five nights of sleep extension on peripheral vascular function: a randomized crossover investigation into long sleep duration.

Long sleep duration, defined as ≥9 h, is associated with increased cardiovascular mortality. We sought to determine the effect of sleep extension on peripheral vascular health. Twelve middle-aged adults were randomly assigned to spend five nights with 8 h (control) or 10+ hours time in bed (TIB) in a crossover fashion. Sleep was assessed using wrist actigraphy. Peak reactive hyperemia in the forearm was measured using venous-occlusion plethysmography as an index of microvascular vasodilation. Nighttime and morning blood pressure was recorded along with pulse wave velocity (arterial stiffness). Average sleep duration was 7.1 ± 0.3 and 9.3 ± 0.3 h for 8 and 10+ hours TIB (P < 0.001), respectfully. On average, sleep was extended by 127 ± 29 min with nine participants reaching average sleep durations >9 h. Extended sleep did not change nighttime or morning blood pressure, or pulse wave velocity (all P > 0.05). In contrast, peak forearm vascular conductance (FVC, 0.27 ± 0.08 vs. 0.23 ± 0.07 ml/100 ml/min/mmHg, P = 0.02) and total excess blood flow (28 ± 9 vs. 24 ± 11 ml/100 ml, P < 0.01) were increased following sleep extension. The change in FVC and total excess blood flow were inversely correlated with the change in wake after sleep onset and TIB (both r = -0.62, P < 0.05), but not with sleep duration. These results demonstrate that extended time in bed accompanied by long sleep durations does not impair peripheral vascular function, but rather, may increase microvasculature vasodilatory capacity in midlife adults.