Counterbalanced Crossover Study Research Articles

Resetting of the Human Circadian Melatonin Rhythm by Ambient Hypoxia.

Circadian clocks in the body drive daily cycles in physiology and behavior. A master clock in the brain maintains synchrony with the environmental day-night cycle and uses internal signals to keep clocks in other tissues aligned. Work in cell cultures uncovered cyclic changes in tissue oxygenation that may serve to reset and synchronize circadian clocks. Here we show in healthy humans, following a randomized controlled single-blind counterbalanced crossover study design, that one-time exposure to moderate ambient hypoxia (FiO2 ~15%, normobaric) for ~6.5 h during the early night advances the dim-light onset of melatonin secretion by 9 min (95% CI: 1-16 min). Exposure to moderate hypoxia may thus be strong enough to entrain circadian clocks to a 24-h cycle in the absence of other entraining cues. Together, the results provide direct evidence for an interaction between the body's hypoxia-sensing pathway and circadian clocks. The finding offers a mechanism through which behaviors that change tissue oxygenation (e.g., exercise and fasting/eating) can affect circadian timing and through which hypoxia-related diseases (e.g., obstructive sleep apnea and chronic obstructive pulmonary disease) can result in circadian misalignment and associated pathologies. Trial Registration: Registration number: DRKS00023387; German Clinical Trials Register: http://www.drks.de.

Combined Effects of Listening to Preferred Music and Video Feedback, during Warm-Up, on Physical Performance in Young Kickboxers.

Although studies have indicated that the prior use of video feedback and music listening separately improves physical performance and positive feelings in various sports, to our knowledge, no studies have investigated their combined effect in combat-sports-specific tasks. The aim of this study was to determine the combined effect of listening to preferred music and video feedback on aerobic and anaerobic performance in male kickboxers. In a counterbalanced crossover study design, twenty kickboxers underwent three kicking exercises under one of three conditions: (1) control condition, (2) combined listening to preferred music and video feedback, and (3) video feedback during 10-min of rope warm-up. Kickboxers performed a ten-second kicking test, multiple ten-second kick test, and progressive taekwondo test. The total number of kicks, fatigue index, heart rate, rate of perceived exertion, and feeling scale were measured. The combined music and video feedback condition improved the number of kicks with a better positive feeling scale (F ≥ 7.4, p ≤ 0.002, ηp2 ≥ 0.28) than the video feedback and control conditions in all three kicking exercises, while the video feedback alone led to better kick performances and a better feeling scale than the control condition in the ten-second and multiple ten-second kicking tests (p ≤ 0.016). The combined listening to preferred music and video feedback condition was more effective at enhancing the positive feeling scale and repeated roundhouse kick performance. Future investigations should examine the application of video feedback and listening to music in various kickboxing tasks including punches and kicks.

THE EFFECT OF DRY AND HUMID HEAT ACCLIMATION ON PERFORMANCE IN EACH ENVIRONMENT

BACKGROUND Athletes adopt heat acclimation (HA) to partly restore heat-mediated decrements in performance. However, the influence of environmental characteristics during HA on performance in dry and humid conditions is unclear. Therefore, this study aimed to compare dry and humid HA on performance in each environment. METHODS In a counterbalanced crossover study, ten trained male cyclists (age 43 ± 9 y; body mass 80.8 ± 7.3 kg; maximal oxygen uptake; 59 ± 7 mL.kg-1.min-1) completed a 30-min time-trial in hot-dry (TT-DRY; 42°C, 25% RH) and warm-humid (TT-HUM; 33°C, 80% RH) conditions before and after 8 days of controlled heart rate (HR) HA in either dry (DRY-HA) or humid conditions (HUM-HA). A Bayesian multi-level model was used to determine posterior means, 90% credible intervals, and probability of direction (%). RESULTS The improvement in power output during TT-HUM was similar following DRY-HA (13 W [3, 22]; 99%) and HUMID-HA (11 W [3, 19]; 98%). In TT-DRY, the improvement in power output was 12 W ([1, 22]; 97%) higher following DRY-HA (19 W [10, 28]; >99%) compared to HUM-HA (7 W [-2, 17]; 91%). During TT-HUM, mean rectal temperature changed following HUM-HA (0.03°C [-0.11, 0.17]; 63%) and DRY-HA (-0.14°C [-0.29, 0.02]; 92%), with a difference of 0.16°C ([-0.36, 0.03]; 92%). During TT-DRY, the difference was -0.20°C ([-0.40, 0.01]; 94%) between HUM-HA (-0.22°C [-0.38, -0.06]; 98%) and DRY-HA (-0.03°C [-0.19, 0.13]; 63%). Mean HR during TT-DRY (3 beats·min-1 [-2, 8]; 85%) and TT-HUM (-4 beats·min-1 [-10, 2]; 85%) was similar following DRY-HA and HUM-HA. CONCLUSIONS DRY-HA further improved mean power output during TT-DRY compared to HUM-HA. However, HUM-HA tended to lower rectal temperature more than DRY-HA during TT-DRY. HA condition did not influence HR during either TT. Our data indicate that performance is further improved in hot-dry conditions when acclimating to the same environment.

Moral decision-making at night and the impact of night work with blue-enriched white light or warm white light: a counterbalanced crossover study

Background Cognitive function, including moral decision-making abilities, can be impaired by sleep loss. Blue-enriched light interventions have been shown to ameliorate cognitive impairment during night work. This study investigated whether the quality of moral decision-making during simulated night work differed for night work in blue-enriched white light, compared to warm white light. Methods Using a counterbalanced crossover design, three consecutive night shifts were performed in blue-enriched white light (7000 K) and warm white light (2500 K) provided by ceiling-mounted LED luminaires (photopic illuminance: ∼200 lx). At 03:30 h on the second shift (i.e. twice) and at daytime (rested), the Defining Issues Test-2, assessing the activation of cognitive schemas depicting different levels of cognitive moral development, was administered. Data from 30 (10 males, average age 23.3 ± 2.9 years) participants were analysed using linear mixed-effects models. Results Activation of the post-conventional schema (P-score), that is, the most mature moral level, was significantly lower for night work in warm white light (EMM; estimated marginal mean = 44.3, 95% CI = 38.9–49.6; p holm=.007), but not blue-enriched white light (EMM = 47.5, 95% CI = 42.2–52.8), compared to daytime (EMM = 51.2, 95% CI = 45.9–56.5). Also, the P-score was reduced for night work overall (EMM = 45.9, 95% CI = 41.1–50.8; p=.008), that is, irrespective of light condition, compared to daytime. Neither activation of the maintaining norms schema (MN-score), that is, moderately developed moral level, nor activation of the personal interest schema (i.e. the lowest moral level) differed significantly between light conditions. The MN-score was however increased for night work overall (EMM = 26.8, 95% CI = 23.1–30.5; p=.033) compared to daytime (EMM = 23.1, 95% CI = 18.9–27.2). Conclusion The results indicate that moral decisions during simulated night work in warm white light, but not blue-enriched white light, become less mature and principle-oriented, and more rule-based compared to daytime, hence blue-enriched white light may function as a moderator. Further studies are needed, and the findings should be tentatively considered. Trial registration: ClinicalTrials.gov (ID: NCT03203538) Registered: 26/06/2017; https://clinicaltrials.gov/study/NCT03203538

Peer Verbal Encouragement Is More Effective than Coach Encouragement in Enhancing CrossFit-Specific 1-RM Strength, Functional Endurance, and Psychophysiological Assessment Performance.

This study compares the effects of coach verbal encouragement (CVE) and peer verbal encouragement (PVE) on CrossFit-specific one-repetition maximum (1-RM) strength, functional endurance, and psychophysiological assessments. A total of 36 sports science students (18 males, 18 females; mean age: 21.3 ± 0.5 years) participated in a randomized, counterbalanced crossover study in which 1-RM strength and endurance assessment sessions were undertaken under PVE, CVE, and no verbal encouragement (NVE) on separate days. Here, 1-RM strength was assessed through squat, deadlift, and bench press exercises, while endurance was evaluated using 8 min time trials (8MTT). Following the physical assessments, psychophysiological evaluations were conducted using the Borg Rating of Perceived Exertion (RPE) and the Feeling Scale (FS). The findings revealed that, after PVE, all the 1-RM strength test, 8MTT, RPE, and FS values exhibited significant increases compared to those of CVE (p [<0.001-<0.01], r = -0.84 [large]) and NVE (p [<0.001-<0.05], r [-0.43-0.52] [small]). Exceptions were noted in 1-RM-deadlift (p > 0.05, r = -0.43 [small]) and 1-RM-bench-press (p > 0.05, r = -0.43 [small]), where CVE demonstrated higher scores (1-RM-squat, 8MTT, RPE, and FS) (p [<0.001-<0.05], r = -0.64 [large]) in comparison to NVE. In conclusion, the study established that PVE is more impactful than CVE in enhancing CrossFit-specific 1-RM strength, functional endurance, and psychophysiological assessment performance. These findings suggest that coaches/teachers should consider involving their athletes in the reinforcement process for evaluated peers. This collaborative approach may not only optimize performance outcomes but also foster a supportive and motivational training environment.

Pedaling to Performance: Exploring the Effects of Pre-Tournament Cycling on Rocket League Esports Performance

ABSTRACT Purpose Exercise has been well documented to elicit cognitive benefits; therefore, we aimed to examine the effect on performance of a single bout of cycling exercise before an esports tournament. Methods Twenty healthy males (age, 24 ± 6 yr; height, 177.3 ± 7.3 cm; body mass, 80.7 ± 20.9 kg; ranked between Gold 1 and Champion 3) participated in a randomized, counterbalanced crossover study involving 1) a 20-min cycling exercise bout at 60%–70% heart rate reserve or 2) 20 min of rest before competing in an esports tournament. Tournaments consisted of 10 paired, rank-matched Rocket League 1 vs. 1 matches played in three series. Participants were assessed before and after the tournament for hemodynamics, cognition, and gameplay mechanics. Heart rate was monitored throughout the tournament, with gameplay performance and post-match surveys completed after each match. Results Exercising before the tournament led to higher initial fatigue (P = 0.002), higher average heart rates throughout the tournament (P &lt; 0.001), lower perceived individual performance in series 1 (P = 0.03), lower overall perceived opponent performance (P = 0.03), and improved goal percentage in series 3 (P = 0.04) compared with rest. Participant save percentage decreased over time in both conditions (P = 0.04). No differences were observed in cognition measures, gameplay mechanics, or hemodynamics. Conclusions A single bout of cycling exercise completed before a Rocket League 1 vs. 1 tournament had no negative effects on performance or wins. It did, however, lower perceived match performance and fatigue at the beginning of the tournament while improving goal percentage during the last series.

Influence of cuff stiffness on hemodynamics and perceived cuff pressure in the upper extremities in males and females: implications for practical blood flow restriction training

BackgroundPractical blood flow restriction (pBFR) during exercise is a cost-saving alternative to traditional blood flow restriction using pneumatic cuffs, particularly when exercising in a group setting. Depending on the pBFR technique, several factors (e.g., cuff width, limb circumference) have already been shown to be of importance when applying the pBFR pressure. Given that elastic cuffs are often used for pBFR, the cuff stiffness might be an additional influencing factor. Therefore, the present study compared the acute effects of three elastic cuffs with identical width but different stiffness (high stiffness (HS), medium stiffness (MS), and low stiffness (LS)) on hemodynamic measures and perceived cuff pressure at rest.MethodsIn a randomized, counter-balanced cross-over study, 36 young and normotensive participants completed three experimental trials. After a 10-min rest period in supine position, the cuff was loosely and proximally applied to the right upper arm. Following baseline data recording, the cuff was successively tightened in 10%-increments with respect to the limb circumference (%overlap) until arterial blood flow was occluded. At baseline and during each %overlap, systolic peak blood flow velocity of the brachial artery, rating of perceived cuff pressure, as well as muscle oxygen saturation and total hemoglobin concentration of the biceps brachii muscle were recorded.ResultsThe %overlap required to occlude arterial blood flow was different between the three cuffs (HS: 30.9 ± 3.8%, MS: 43.9 ± 6.1%, LS: 54.5 ± 8.3%). Furthermore, at 30% overlap, systolic peak blood flow velocity was lower when applying the HS (9.0 ± 10.9 cm∙s− 1) compared to MS (48.9 ± 21.9 cm∙s− 1) and LS cuff (62.9 ± 19.1 cm∙s− 1). Rating of perceived cuff pressure at 30% overlap was higher when using the HS (6.5 ± 1.5 arbitrary unit (a.u.)) compared to MS (5.1 ± 1.4 a.u.) and LS cuff (4.9 ± 1.5 a.u.) with no difference between the MS and LS cuff. However, muscle oxygen saturation and total hemoglobin concentration were not different between the three cuffs.ConclusionsThe present study revealed that the cuff stiffness influenced blood flow velocity and arterial occlusion pressure. Therefore, cuff stiffness seems an important factor for the application of pBFR.

0005 A circadian-informed lighting intervention markedly improves vigilance in a simulated night shift setting

Abstract Introduction Due to misalignment between circadian timing and the work/rest schedule, cognitive performance during night shift-work is often poor. This study tested a circadian-informed lighting strategy designed to improve on-shift cognitive performance through alerting effects, faster circadian adjustment to the shift-work schedule and promoting more sleep off-shift, compared to standard lighting. Methods A randomised controlled, within-subjects, counter-balanced cross-over study was performed to examine circadian-informed versus standard lighting on cognitive performance during a simulated 8-day night shift-work schedule. Nineteen healthy sleepers (12 males/7 females, mean±SD aged 28.7±10.4 years) underwent two separate 8-day experimental conditions in the sleep laboratory. The standard lighting condition mimicked current lighting on submarines (largely dim, blue-depleted light), while the circadian-informed lighting administered bright, blue-enriched and dim, blue-depleted lighting at times estimated to facilitate rapid circadian delay. After an adaptation sleep opportunity from 22:00 – 07:00 (day 1), participants remained awake for 27 hours to transition to sleeping during the day (10:00 - 19:00) and undertaking simulated night shift-work (00:00 - 08:00) at night on days 3-7. The primary performance outcome was the number of lapses (&amp;gt;500ms responses) on the psychomotor vigilance task (PVT), administered six times across each simulated work shift. Median reaction time and other PVT outcomes were also compared between lighting conditions. Results There were significant day-by-condition interactions on PVT lapses, p&amp;lt; 0.05. The circadian-informed lighting intervention resulted in ~50% fewer lapses by the final day compared to standard lighting (mean±SD 7.4±5.0 vs. 15.6±6.1 lapses). Similar effects were observed across other PVT outcomes. Conclusion Circadian-informed lighting resulted in markedly better vigilance than standard lighting under simulated night shift-work conditions. These findings indicate the considerable potential for automated lighting interventions to improve performance and safety in shift-workers. Support (if any) This research is supported by the Commonwealth of Australia as represented by the Defence Science and Technology Group of the Department of Defence through the Research Network for Undersea Decision Superiority (research agreement number: 9334), with additional financial support from Flinders University and lighting provision support from REDARC.

Concurrent Contribution of Co-contraction to Error Reduction during Dynamic Adaptation of the Wrist.

MRI-compatible robots provide a means of studying brain function involved in complex sensorimotor learning processes, such as adaptation. To properly interpret the neural correlates of behavior measured using MRI-compatible robots, it is critical to validate the measurements of motor performance obtained via such devices. Previously, we characterized adaptation of the wrist in response to a force field applied via an MRI-compatible robot, the MR-SoftWrist. Compared to arm reaching tasks, we observed lower end magnitude of adaptation, and reductions in trajectory errors beyond those explained by adaptation. Thus, we formed two hypotheses: that the observed differences were due to measurement errors of the MR-SoftWrist; or that impedance control plays a significant role in control of wrist movements during dynamic perturbations. To test both hypotheses, we performed a two-session counterbalanced crossover study. In both sessions, participants performed wrist pointing in three force field conditions (zero force, constant, random). Participants used either the MR-SoftWrist or the UDiffWrist, a non-MRI-compatible wrist robot, for task execution in session one, and the other device in session two. To measure anticipatory co-contraction associated with impedance control, we collected surface EMG of four forearm muscles. We found no significant effect of device on behavior, validating the measurements of adaptation obtained with the MR-SoftWrist. EMG measures of co-contraction explained a significant portion of the variance in excess error reduction not attributable to adaptation. These results support the hypothesis that for the wrist, impedance control significantly contributes to reductions in trajectory errors in excess of those explained by adaptation.

Mixed Tree Nuts, Cognition, and Gut Microbiota: A 4-Week, Placebo-Controlled, Randomized Crossover Trial in Healthy Nonelderly Adults

Beneficial effects of nut supplementation on cognitive function have previously been demonstrated in young and older adults. Alterations to gut microbiota have also been shown following tree nut consumption. However, no data exists on the effects of nuts on cognition and intestinal microbial communities assessed within the same study. The study aimed to examine the effects of daily consumption of tree nuts for 4 wk on cognitive function (primary outcome), mood, metabolomics, and gut microbial species (secondary outcomes) in healthy, nonelderly adults. This randomized, placebo-controlled, double-blind, counterbalanced crossover study assessed the effects of 4 wk of supplementation with 30 g/d mixed tree nuts versus placebo on cognition and mood in 79 healthy adults aged 18-49 y. Metabolic responses, gut bacterial community structure, and the potential for these to impact cognition were explored using a multi-omic approach. Bacterial community analysis was conducted in Quantitative Insights Into Microbial Ecology 2 (QIIME2). Mixed model analysis indicated that nut consumption led to significant improvements to accuracy (placebo M = 92.2% compared with NUTS M = 94.5%; P = 0.019) and speed of response (placebo M = 788 ms compared with NUTS M = 757 ms; P = 0.004) on a picture recognition task. No significant changes to bacterial community α or β diversity were observed when comparing nut consumption to the placebo arm. However, an unclassified Lachnospiraceae amplicon sequence variant (ASV) was significantly enriched in participants when supplemented with nuts (P = 0.015). No correlations were observed between the changes to picture recognition and the changes to the unclassified Lachnospiraceae ASV. There were no significant changes to the urinary metabolome. These findings indicate a positive effect of nut on cognition following only 4 wk of consumption in a healthy nonelderly sample, as well as upregulation of a microbial taxa associated with gut health. The effects appear to be independent of one another, but further exploration is required in those experiencing cognitive decline and/or gut dysbiosis.

Effects of Hypoxia-Hyperoxia Preconditioning on Indicators of Muscle Damage After Acute Resistance Exercise in Male Athletes.

PurposeThe purpose of this study was to investigate the effects of acute repeated hypoxia–hyperoxia preconditioning on resistance exercise (RE)-induced muscle damage in male athletes.MethodsEleven young male athletes participated in this randomized double-blind counter-balanced crossover study, and were divided into Normoxia (N) and Hypoxia–Hyperoxia (HH) trials. Subjects of the respective trials were supplied with normoxic (FiO2 = 0.21), or alternating hypoxic/hyperoxic air (FiO2 = 0.10/0.99, 5 min each) for 60 min. Thirty minutes after preconditioning, subjects performed acute bouts of RE consisting of bench press, deadlift, and squats. Each exercise included 6 sets of 10 repetitions at 75% one-repetition maximum (1RM) with 2 min rest between sets. After a 2-week washout period, subjects changed trials and completed the same study procedure after the alternate preconditioning. Muscle soreness, maximal voluntary contraction (MVC), and circulating biochemical markers were tested before preconditioning (baseline) and during recovery at 0, 24, and 48 h after exercise.ResultsAcute RE significantly increased levels of muscle soreness, creatine kinase (CK) and myoglobin (Mb), and decreased levels of peak knee extension torque in the N trial. Muscle soreness, CK, and Mb levels of the HH trial were significantly lower than that of the N trial after exercise. Interestingly, interleukin-6 (IL-6) levels of the HH trial increased significantly 0 h after exercise compared to baseline and were significantly higher than that of the N trial 0 and 24 h after exercise. However, no significant differences of thiobarbituric acid reactive substances (TBARS), cortisol, testosterone, peak torque, and average power levels were found between N and HH trials during recovery.ConclusionOur data suggest that pre-exercise treatment of alternating hypoxic/hyperoxic air could attenuate muscle damage and pain after acute RE, but has no effect on muscle strength recovery in young male athletes.

Bright light exposure during simulated night work improves cognitive flexibility

ABSTRACT Night work leads to sleepiness and reduced vigilant attention during work hours, and bright light interventions may reduce such effects. It is also known that total sleep deprivation impairs cognitive flexibility as measured by reversal learning tasks. Whether night work impairs reversal learning task performance or if bright light can mitigate reversal learning deficits during night work is unclear. In this counterbalanced crossover study (ClinicaTrials.gov Identifier NCT03203538), young healthy individuals completed a reversal learning task twice during each of three consecutive simulated night shifts (23:00–07:00 h). The night shifts were performed in a laboratory under a full-spectrum (4000 K) bright light (~900 lx) and a standard light (~90 lx) condition. Reversal learning task performance was reduced towards the end of the night shifts (04:50 h), compared to the first part of the night shifts (00:20 h) in both light conditions. However, with bright light, the reversal learning task performance improved towards the end of the night shifts, compared to standard light. The study shows that bright light may mitigate performance deficits on a reversal learning task during night work and implies that bright light interventions during night work may be beneficial not only for vigilant attention but also for cognitive flexibility.

Systemic Lactate Elevation Induced by Tobacco Smoking during Rest and Exercise Is Not Associated with Nicotine.

Lactate is a metabolite produced during anaerobic glycolysis for ATP resynthesis, which accumulates during hypoxia and muscle contraction. Tobacco smoking significantly increases blood lactate. Here we conducted a counter-balanced crossover study to examine whether this effect is associated with inhaling nicotine or burned carbon particles. Fifteen male smokers (aged 23 to 26 years) were randomized into 3 inhalation conditions: tobacco smoking, nicotine vaping, and nicotine-free vaping, conducted two days apart. An electronic thermal evaporator (e-cigarette) was used for vaping. We have observed an increased blood lactate (+62%, main effect: p < 0.01) and a decreased blood glucose (−12%, main effect: p < 0.05) during thermal air inhalations regardless of the content delivered. Exercise-induced lactate accumulation and shuttle run performance were similar for the 3 inhalation conditions. Tobacco smoking slightly increased the resting heart rate above the two vaping conditions (p < 0.05), implicating the role of burned carbon particles on sympathetic stimulation, independent of nicotine and thermal air. The exercise response in the heart rate was similar for the 3 conditions. The results of the study suggest that acute hypoxia was induced by breathing thermal air. This may explain the reciprocal increases in lactate and decreases in glucose. The impaired lung function in oxygen delivery of tobacco smoking is unrelated to nicotine.

Effects of Time-Restricted Feeding on Supramaximal Exercise Performance and Body Composition: A Randomized and Counterbalanced Crossover Study in Healthy Men.

Using a crossover design, we explored the effects of both short- and long-term time-restricted feeding (TRF) vs. regular diet on Wingate (WnT) performance and body composition in well-trained young men. Twelve healthy male physical education students were included (age: 22.4 ± 2.8 years, height: 174.0 ± 7.1 cm, body mass: 73.6 ± 9.5 kg, body mass index: 24.2 ± 2.0 kg/m2). The order of dieting was randomized and counterbalanced, and all participants served as their own controls. TRF was limited to an 8-h eating window and non-TRF involved a customary meal pattern. Participants performed WnT tests and body composition scans at baseline, post-one and post-four weeks of the assigned diet. Before testing, participants were asked to fill out a dietary record over four consecutive days and were instructed to continue their habitual training throughout the study. Energy intake and macronutrient distribution were similar at baseline in both conditions. WnT mean power and total work output increased post-four weeks of TRF. Both conditions were similarly effective in increasing fat-free mass after four weeks of intervention. However, there was no correlation between change in fat-free mass and WnT mean power after TRF. TRF did not elicit any changes in WnT performance or body composition one week post-intervention. Thus, long-term TRF can be used in combination with regular training to improve supramaximal exercise performance in well-trained men.

The deleterious effects of acute hypoxia on microvascular and large vessel endothelial function.

What is the central question of this study? The aim was primarily to determine the effect of hypoxia on microvascular function and secondarily whether superior cardiorespiratory fitness is protective against hypoxia-induced impairment in vascular function. What is the main finding and its importance? Hypoxia reduced endothelium-dependent but not endothelium-independent microvascular function. The extent of impairment was twofold higher in the microcirculation compared with the large blood vessels. This study suggests that individuals with superior cardiorespiratory fitness might preserve microvascular function in hypoxia. These findings highlight the sensitivity of the microvascular circulation to hypoxia. Hypoxia is associated with diminished bioavailability of the endothelium-derived vasodilator, nitric oxide (NO). Diminished NO bioavailability can have deleterious effects on endothelial function. The endothelium is a heterogeneous tissue; therefore, a comprehensive assessment of endothelial function is crucial to understand the significance of hypoxia-induced endothelial dysfunction. We hypothesized that acute hypoxia would have a deleterious effect on microvascular and large vessel endothelial function. Twenty-nine healthy adults [24(SD = 4 )years of age] completed normoxic and hypoxic [inspired O2 fraction=0.209] trials in this double-blinded, counterbalanced crossover study. After 30min, we assessed the laser Doppler imaging-determined perfusion response to iontophoresis of ACh as a measure of endothelium-dependent microvascular function and iontophoresis of sodium nitroprusside as a measure of endothelium-independent microvascular function. After 60min, we assessed brachial flow-mediated dilatation as a measure of large vessel endothelial function. Thirty minutes of hypoxia reduced endothelium-dependent microvascular function determined by the perfusion response to ACh (median difference (x̃∆)=-109% {interquartile range: 542.7}, P<0.05), but not endothelium-independent microvascular function determined by the perfusion response to sodium nitroprusside (x̃∆ = 69% {interquartile range: 453.7}, P=0.6). In addition, 60min of hypoxia reduced allometrically scaled flow-mediated dilatation compared with normoxia ( [95% CI = -1.80, -0.58 (Confidence Intervals)]%, P<0.001). The decrease in microvascular endothelial function was associated with cardiorespiratory fitness (r =0.45, P=0.02). In conclusion, acute exposure to normobaric hypoxia significantly reduced endothelium-dependent vasodilatory capacity in small and large vessels. Collectively, these findings highlight the sensitivity of the microvascular circulation to hypoxic insult, particularly in those with poor cardiorespiratory fitness.

Tuning environmental lighting improves objective and subjective sleep quality in older adults

This study investigated the effects of two whole-day ambient lighting interventions applied in living rooms on the objective and subjective sleep quality in older adults. Both lighting interventions were designed to apply a direct/indirect ambient illumination that delivered a high illuminance level (500lux) in the morning (8:00–12:00). The illumination was gradually dimmed throughout the day and reached 100lux in the evening (after 20:00). One lighting condition (L1) provided a constant Correlated Color Temperature (CCT) of 2700 K. In the other lighting condition (L2), the CCT changed in a range of 6500 K – 2700 K from the morning to the evening. Twenty-one older adults (mean age = 78.81, 16 female) from three residential communities participated in a counterbalanced crossover study. Participants were exposed to each lighting intervention for nine days. Using 41-day actigraphy and standard questionnaires, objective and subjective data of sleep were collected before, during, and after exposure to interventions. Both interventions significantly increased sleep duration at night compared to the baseline with significantly more increase after L2 intervention. Additionally, the L2 intervention significantly improved sleep efficiency and sleep quality and decreased sleep disturbance, sleep-related impairment, and sleep onset latency compared to Baseline and L1. These results provided promising evidence that daily exposure to a whole-day lighting scheme that follows the light/dark cycle could improve sleep quality in older adults; thereby it could be considered as an effective design solution in creating healthy living environments for the senior population.

Fermented soybean enhances post-meal response in appetite-regulating hormones among Indonesian girls with obesity

ObjectiveTo assess the post-meal response in appetite-regulating hormones acyl-ghrelin and insulin after fermented soybean (tempeh) consumption in girls with obesity. MethodsA randomized counter-balanced crossover study was conducted using a breakfast (307 kcal, protein: 28%, fat: 23%, and carbohydrate: 55%) containing fermented soybean or isocaloric non-fermented soybean among 13 females (aged 18–20 y; BMI 25–30) after an overnight fast. The outcome variables were plasma acyl-ghrelin, insulin, arginine and score of the visual analog scale (VAS) appetite questionnaire. ResultsWhile no change was observed after the non-fermented soybean meal, plasma acyl-ghrelin decreased by 35% at 30 min and remained below baseline until 120 min after the fermented soybean meal (P < 0.05). Plasma insulin increased after consumption of both meals and fermented soybean meal-induced 30% greater response in insulin at 120 min than non-fermented soybean meal (P < 0.05). Circulating arginine levels were slightly greater (24%) at 120 min after the fermented soybean meal than the non-fermented soybean meal (P < 0.05). No difference in subjective appetite was observed between the fermented soybean meal and the non-fermented soybean meal. ConclusionsFermented soybean meal induced greater response in appetite-regulating hormones compared with non-fermented soybean meal. No difference in post-meal satiety feeling between fermented and non-fermented soybean meal suggests poor sensitivity of the brain to the appetite-regulating hormones among girls with obesity.

The porous high-press? An experimental approach investigating tactical behaviours from two pressing strategies in football

ABSTRACT The aim of this study was to analyse footballers’ tactical behaviours from their position data, as an effect of two contrasting pressing strategies, high-press defending and deep-defending, using a trial-based experimental approach. Sixty-nine youth footballers participated in this 11 versus 11 study, performing 72 trials of attack versus defence, in a counterbalanced crossover study design. Players’ position data were captured using a local positioning system, and processed to calculate measures of inter-team distance, trial duration, distance to nearest opponent, dispersion, team length, team width, team shape, space control gain, inter-line distance, and individual area. This was augmented by the notational analyses of passes. The findings showed that using a high-press defending strategy leads to: closer inter-team distance; larger dispersion, due to a longer team length; and larger inter-line distances between defenders, midfielders, and forwards. The resulting effects on the attacking team include reduced ball possession time; larger individual areas for attacking midfielders and forwards; longer team length; and more penetrative passes performed. Some differences in marking behaviour were also observed. Consequently, the study recommends that high-press defending be used sparingly due to these trade-offs.

Chemically Activated Cooling Vest's Effect on Cooling Rate Following Exercise-Induced Hyperthermia: A Randomized Counter-Balanced Crossover Study.

Background and objectives: Exertional heat stroke (EHS) is a potentially lethal, hyperthermic condition that warrants immediate cooling to optimize the patient outcome. The study aimed to examine if a portable cooling vest meets the established cooling criteria (0.15 °C·min−1 or greater) for EHS treatment. It was hypothesized that a cooling vest will not meet the established cooling criteria for EHS treatment. Materials and Methods: Fourteen recreationally active participants (mean ± SD; male, n = 8; age, 25 ± 4 years; body mass, 86.7 ± 10.5 kg; body fat, 16.5 ± 5.2%; body surface area, 2.06 ± 0.15 m2. female, n = 6; 22 ± 2 years; 61.3 ± 6.7 kg; 22.8 ± 4.4%; 1.66 ± 0.11 m2) exercised on a motorized treadmill in a hot climatic chamber (ambient temperature 39.8 ± 1.9 °C, relative humidity 37.4 ± 6.9%) until they reached rectal temperature (TRE) >39 °C (mean TRE, 39.59 0.38 °C). Following exercise, participants were cooled using either a cooling vest (VEST) or passive rest (PASS) in the climatic chamber until TRE reached 38.25 °C. Trials were assigned using randomized, counter-balanced crossover design. Results: There was a main effect of cooling modality type on cooling rates (F[1, 24] = 10.46, p < 0.01, η2p = 0.30), with a greater cooling rate observed in VEST (0.06 ± 0.02 °C·min−1) than PASS (0.04 ± 0.01 °C·min−1) (MD = 0.02, 95% CI = [0.01, 0.03]). There were also main effects of sex (F[1, 24] = 5.97, p = 0.02, η2p = 0.20) and cooling modality type (F[1, 24] = 4.38, p = 0.047, η2p = 0.15) on cooling duration, with a faster cooling time in female (26.9 min) than male participants (42.2 min) (MD = 15.3 min, 95% CI = [2.4, 28.2]) and faster cooling duration in VEST than PASS (MD = 13.1 min, 95% CI = [0.2, 26.0]). An increased body mass was associated with a decreased cooling rate in PASS (r = −0.580, p = 0.03); however, this association was not significant in vest (r = −0.252, p = 0.39). Conclusions: Although VEST exhibited a greater cooling capacity than PASS, VEST was far below an acceptable cooling rate for EHS treatment. VEST should not replace immediate whole-body cold-water immersion when EHS is suspected.

Acute hyperglycaemia can impair driving skill in young type 1 diabetes mellitus patients

AimDrivers with diabetes are at increased risk of being involved in road accidents. Therefore, this study aimed to evaluate the effects of acute hyperglycaemia (AH) compared with euglycaemia on driving ability in patients with type 1 diabetes mellitus (T1DM). MethodsEighteen drivers with T1DM were asked to navigate twice through nine hazardous scenarios, using a driving simulator, during euglycaemia and then again during AH (mean blood glucose: 138 ± 34 mg/dL and 321 ± 29 mg/dL, respectively) in a counterbalanced crossover study. Driving performance was continually monitored for driving speed, steering wheel angle, acceleration, and location and velocity of other vehicles and obstacles, with drivers wearing a mobile head-mounted eye-tracking system. ResultsThe main findings were that, during AH, participants were less likely to identify a hazard [probability of identification (POI): 0.5725 ± 0.5], glanced fewer times at the hazard (3.24 ± 5.9), maintained shorter headway (between-vehicle) distance (mean: 40.87 ± 20.15 m) and had an increased number of braking events per km driven (6.69 ± 5.20) compared with driving during euglycaemia (POI: 0.733 ± 0.4; number of glances: 3.69 ± 6.99; headway distance: 50.46 ± 26.2 m; number of braking events per km driven: 4.31 ± 3.87; P < 0.05 for all parameters). ConclusionThis study provides evidence that AH impairs driving performance in young T1DM patients by demonstrating the negative effects of AH on both hazard perception and speed management.