Investigating Taste Perception of Maltodextrins Using Lactisole and Acarbose.

Previous research has demonstrated that complex carbohydrates (maltodextrins) can be perceived in the oral cavity. However, little research has been conducted to thoroughly investigate complex carbohydrate taste perception and contributing factors. This study explored the effects of the degree of polymerization and the concentration of complex carbohydrates on taste perception. Additionally, the impact of lactisole and acarbose on carbohydrate taste perception was investigated. Using a blinded, Latin Square design, participants (n = 40) received samples (control) or samples with acarbose (5 mM) or lactisole (1.4 mM). Per visit, participants received solutions: (1) short chain maltodextrin (average DP 6) (SCM), (2) long chain maltodextrin (average DP 24) (LCM), (3) maltose, and (4) glucose. Samples were evaluated in duplicate, both at low concentration and high concentration. Participants tasted the samples and rated sweetness, starchiness, and viscosity (mouthfeel) perceived on a 10 cm continuous line scale and perceived intensity on a Labelled Magnitude Scale. There was a significant effect of degree of polymerisation on sweetness (p = 0.001) and intensity (p = 0.001). For low concentration samples, no significant differences were found between LCM and acarbose LCM or SCM and acarbose SCM for sweetness, starchiness, or mouthfeel (all p > 0.05). Significant differences were observed between LCM and lactisole LCM for sweetness (1.1 ± 0.1 vs. 2.5 ± 0.3, p = 0.001), starchiness (1.4 ± 0.2 vs. 2.3 ± 0.3, p = 0.005), and mouthfeel (1.4 ± 0.2 vs. 2.3 ± 0.3, p = 0.013). In conclusion, the taste perception of maltodextrins is influenced by the degree of polymerisation. Furthermore, for this study, the sweet taste receptor was not involved in maltodextrin taste perception. While salivary α-amylase did not appear to influence taste perception with low concentration maltodextrins, further investigation is necessary.

The interactive effect of sustained sleep restriction and resistance exercise on skeletal muscle transcriptomics in young females.

Both sleep loss and exercise regulate gene expression in skeletal muscle, yet little is known about how the interaction of these stressors affects the transcriptome. The aim of this study was to investigate the effect of nine nights of sleep restriction (SR), with repeated resistance exercise (REx) sessions, on the skeletal muscle transcriptome of young, trained females. Ten healthy females aged 18-35 yr old undertook a randomized cross-over study of nine nights of SR (5 h time in bed) and normal sleep (NS; ≥7 h time in bed) with a minimum 6-wk washout. Participants completed four REx sessions per condition (days 3, 5, 7, and 9). Muscle biopsies were collected both pre- and post-REx on days 3 and 9. Gene and protein expression were assessed by RNA sequencing and Western blot, respectively. Three or nine nights of SR had no effect on the muscle transcriptome independently of exercise. However, close to 3,000 transcripts were differentially regulated (false discovery rate < 0.05) 48 h after the completion of three resistance exercise sessions in both NS and SR conditions. Only 39% of downregulated genes and 18% of upregulated genes were common between both conditions, indicating a moderating effect of SR on the response to exercise. SR and REx interacted to alter the enrichment of skeletal muscle transcriptomic pathways in young, resistance-trained females. Performing exercise when sleep restricted may not provide the same adaptive response for individuals as if they were fully rested.NEW & NOTEWORTHY This study investigated the effect of nine nights of sleep restriction, with repeated resistance exercise sessions, on the skeletal muscle transcriptome of young, trained females. Sleep restriction and resistance exercise interacted to alter the enrichment of skeletal muscle transcriptomic pathways in young, resistance-trained females. Performing exercise when sleep restricted may not provide the same adaptive response for individuals as if they were fully rested.

Total fermentable oligo-, di-, monosaccharides and polyols intake, carbohydrate malabsorption and gastrointestinal symptoms during a 56 km trail ultramarathon event.

AIMS: To explore the relationship between nutritional intake, fermentable oligo-, di, monosaccharides and polyols, and carbohydrate malabsorption, with gastrointestinal symptoms during a 56 km trail ultramarathon event and identify differences in nutritional intake between runners with severe and non-severe gastrointestinal symptoms. METHODS: Forty-four ultramarathoners recorded and self-reported dietary intake 3 days before, morning of, and during the ultramarathon with gastrointestinal symptoms obtained retrospectively and nutrient analysis via FoodWorks. Carbohydrate malabsorption was determined via breath hydrogen content pre- and post-race. Spearman's rank-order and Mann-Whitney U-tests were used to identify relationships and differences between groups. RESULTS: Total fermentable oligo-, di, monosaccharides and polyols intake were not associated with gastrointestinal symptoms, but weak associations were observed for lower energy (rs = -0.302, p = 0.044) and fat intake (rs = -0.340, p = 0.024) 3 days before with upper gastrointestinal symptoms and higher caffeine intake 3 days before with overall gastrointestinal symptoms (rs = 0.314, p = 0.038). Total fermentable oligo-, di-, monosaccharides and polyols intake and breath hydrogen were not different between those with severe versus non-severe symptoms (p > 0.05). Although those with severe symptoms had higher caffeine (p = 0.032), and total polyols intake (p = 0.031) 3 days before, and higher % energy from fat (p = 0.043) and sorbitol intake (p = 0.026) during the race, and slower ultramarathon finish times (p = 0.042). CONCLUSION: Total fermentable oligo-, di-, and monosaccharides intake and carbohydrate malabsorption were not associated with gastrointestinal symptoms. Additional research on the effect of fat, caffeine, and polyol intake on exercise-associated gastrointestinal symptoms is warranted and presents new nutritional areas for consideration when planning nutritional intake for ultramarathoners.

Carbohydrate Oral Rinsing, Cycling Performance and Individual Complex Carbohydrate Taste Sensitivity.

The aim of this pilot study was to determine the effect of individual complex carbohydrate taste sensitivity on cycling performance with complex carbohydrate oral rinsing. Ten male participants completed five cycling time trials in a fasted state with a seven-day washout period between each trial. Participants completed a fixed amount of work (738.45 ± 150.74 kJ) as fast as possible on a cycle ergometer while rinsing with an oral rinse for 10 s every 12.5% of the trial. An oral rinse (maltodextrin, oligofructose, glucose, sucralose or water control) was given per visit in a randomised, crossover, blinded design. Afterwards, participants had their taste assessed with three stimuli, complex carbohydrate (maltodextrin), sweet (glucose) and sour (citric acid), using taste assessment protocol to determine individual taste sensitivity status. Participants were subsequently grouped according to their complex carbohydrate taste sensitivity and complex carbohydrate taste intensity. There were no significant effects of the oral rinses on cycling performance time (p = 0.173). Participants who did not have improvements in exercise performance with the maltodextrin rinse experienced a stronger taste intensity with complex carbohydrate stimuli at baseline (p = 0.047) and overall (p = 0.047) than those who did have improvements in performance. Overall, a carbohydrate oral rinse was ineffective in significantly improving cycling performance in comparison with a water control. However, when participants were grouped according to complex carbohydrate taste intensity, differences in exercise performance suggest that individual sensitivity status to complex carbohydrates could impact the efficacy of a carbohydrate-based oral rinse.

Alpha-lactalbumin and sleep: A systematic review.

Insufficient sleep is a growing global problem, with poor sleep associated with many negative health and performance outcomes. Previous reviews investigating the effect of diet on sleep have highlighted the amino acid tryptophan as a promising sleep-promoting nutrient, with the richest food source of tryptophan, ⍺-lactalbumin, requiring further investigation. Therefore, this systematic review aimed to review the existing evidence of association between ⍺-lactalbumin and sleep. Four electronic databases (CINAHL Complete, Embase, MEDLINE Complete, and SPORTDiscus with Full Text) were searched from database inception to March 2023, with primary research articles included if they contained α-lactalbumin as an independent variable, an outcome measure of sleep or sleepiness, and participants were ≥ 18 years old. Eight studies were reviewed, with four studies recruiting athletic populations (50%) and four recruiting healthy participants (50%). Sleep or sleepiness was measured objectively in six studies (75%), with two studies employing polysomnography and four utilizing actigraphy to assess sleep. Across the studies, 20-60 g of ⍺-lactalbumin was supplemented, with five studies (63%) observing a positive association between α-lactalbumin and sleep. Sleep-onset latency was the primary sleep metric improved following evening supplementation of α-lactalbumin (≤ 3.5 hr pre-sleep), with no studies observing any negative associations with sleep. Data from this review suggest that individuals that have difficulty initiating sleep may benefit most from pre-sleep α-lactalbumin supplementation. Further research is required to establish the effect that α-lactalbumin has on sleep architecture, through the use of more comprehensive sleep analysis tools such as portable electroencephalography or polysomnography, in combination with stringent dietary controls.

Overnight heart rate variability responses to military combat engineer training.

The study aimed to determine if overnight heart rate variability (HRV) is reflective of workload and stress during military training. Measures of cognitive load, perceived exertion, physical activity, nocturnal HRV, cognitive performance and sleep were recorded for a 15-day assessment period in 32 combat engineers. The assessment period consisted of 4 phases, PRE, FIELD, BASE and RECOVERY that exposed trainees to periods of sleep deprivation and restriction. The FIELD phase was characterised by an increase in mood disturbance, perceived exertion, physical activity, HRV and a reduction in sleep quantity (p < 0.05). Measures of HRV returned to PRE-values quicker than subjective wellbeing responses. The combination of sleep duration (ß = -0.002, F = 13.42, p < 0.001) and physical activity (metabolic equivalents, ß = -0.483, F = 5.95, p = 0.017), the main stressors of the exercise, provided a significant effect in the best predictive model of HRV. The different recovery rates of HRV and subjective wellbeing suggest a different physiological and psychological response.

Characterising Psycho-Physiological Responses and Relationships during a Military Field Training Exercise.

Over a 15-day period, that included an eight-day field trial, the aims of this study were to (1) quantify the physical workload, sleep and subjective well-being of soldiers in training; (2a) Explore relationships between workload and well-being, and (2b) sleep and well-being; (3) Explore relationships between workload, sleep, and well-being. METHODS: Sixty-two Combat Engineer trainees (59 male, 3 female; age: 25.2 ± 7.2 years) wore an ActiGraph GT9X to monitor daily energy expenditure, physical activity, and sleep. Rating of perceived exertion (RPE), sleep quality, and fatigue were measured daily, subjective well-being was reported days 1, 5, 9, 13 and 15. Multi-level models were used for the analysis. RESULTS: Well-being was affected by a combination of variables including workload, subjective sleep quality, sleep duration, and sleep efficiency. RPE and subjective sleep quality were consistently significant parameters within the models of best fit. CONCLUSIONS: Perceptions of well-being were lower during the field training when physical workload increased, and sleep decreased. Energy expenditure was comparatively low, while daily sleep duration was consistent with field training literature. Subjective assessments of workload and sleep quality were consistently effective in explaining variations in well-being and represent an efficient approach to monitor training status of personnel.

Sleep, Workload, and Stress in Aerial Firefighting Crews.

BACKGROUND:The challenges of climate change and increasing frequency of severe weather conditions has demanded innovative approaches to wildfire suppression. Australia's wildfire management includes an expanding aviation program, providing both fixed and rotary wing aerial platforms for reconnaissance, incident management, and quick response aerial fire suppression. These operations have typically been limited to day visual flight rules operations, but recently trials have been undertaken extending the window of operations into the night, with the assistance of night vision systems. Already a demanding job, night aerial firefighting operations have the potential to place even greater physical and mental demands on crewmembers. This study was designed to investigate sleep, fatigue, and performance outcomes in Australian aerial firefighting crews.METHODS:A total of nine subjects undertook a 21-d protocol, completing a sleep and duty diary including ratings of fatigue and workload. Salivary cortisol was collected daily, with additional samples provided before and after each flight, and heart rate variability was monitored during flight. Actigraphy was also used to objectively measure sleep during the data collection period.RESULTS:Descriptive findings suggest that subjects generally obtained >7 h sleep prior to flights, but cortisol levels and self-reported fatigue increased postflight. Furthermore, the greatest reported workload was associated with the domains of 'performance' and 'mental demand' during flights.DISCUSSION:Future research is necessary to understand the impact of active wildfire response on sleep, stress, and workload on aerial firefighting crews.Sprajcer M, Roberts S, Aisbett B, Ferguson S, Demasi D, Shriane A, Thomas MJW. Sleep, workload, and stress in aerial firefighting crews. Aerosp Med Hum Perform. 2022; 93(10):749-754.

Sustained Sleep Restriction Reduces Resistance Exercise Quality and Quantity in Females.

INTRODUCTION: Female athletes sleep less and report more sleep problems than their male counterparts. Inadequate sleep reduces maximal strength in male athletes; however, little is known about the impact of sleep restriction (SR) on the quantity and quality of resistance exercise performed by female athletes. This study investigated the effect of nine nights of moderate SR on repeated resistance exercise performance, hormonal responses, and perceived fatigue in females. METHODS: Ten healthy, resistance-trained, eumenorrheic females age 18-35 yr underwent nine nights of SR (5-h time in bed) and normal sleep (NS; ≥7-h time in bed) in a randomized, crossover fashion with a minimum 6-wk washout. Participants completed four resistance exercise sessions per trial, with blood samples collected before and after exercise. Exercise performance was assessed using volume load, reactive strength index, and mean concentric velocity with rating of perceived exertion recorded after exercise. Participants completed awakening saliva sampling and the Multi-component Training Distress Scale daily. RESULTS: Volume load decreased trivially (<1%, P < 0.05) with SR. Mean concentric velocity per set was slower during SR for the lower-body (up to 15%, P < 0.05), but not the upper-body, compound lifts. Intraset velocity loss was up to 7% greater during SR for back squats ( P < 0.05). SR increased salivary cortisol area under the curve (by 42%), total training distress (by 84%), and session perceived exertion (by 11%). CONCLUSIONS: Sustained SR reduces markers of resistance exercise quality (bar velocity) more than quantity (volume load) and increases perceived effort at the same relative intensity in resistance-trained females. Markers of exercise quality and internal load may be more sensitive than volume load, to advise coaches to the decline in lifting performance for female athletes experiencing SR.

The Impact of Dietary Factors on the Sleep of Athletically Trained Populations: A Systematic Review.

Many athletic populations report poor sleep, especially during intensive training and competition periods. Recently, diet has been shown to significantly affect sleep in general populations; however, little is known about the effect diet has on the sleep of athletically trained populations. With sleep critical for optimal recovery and sports performance, this systematic review aimed to evaluate the evidence demonstrating that dietary factors influence the sleep of athletically trained populations. Four electronic databases were searched from inception to May 2022, with primary research articles included if they contained a dietary factor(s), an outcome measure of sleep or sleepiness, and participants could be identified as 'athletically trained'. Thirty-five studies were included, with 21 studies assessed as positive quality, 13 as neutral, and one as negative. Sleep or sleepiness was measured objectively in 46% of studies (n = 16). The review showed that evening (≥5 p.m.) caffeine intakes >2 mg·kg−1 body mass decreased sleep duration and sleep efficiency, and increased sleep latency and wake after sleep onset. Evening consumption of high glycaemic index carbohydrates and protein high in tryptophan may reduce sleep latency. Although promising, more research is required before the impact of probiotics, cherry juice, and beetroot juice on the sleep of athletes can be resolved. Athletic populations experiencing sleep difficulties should be screened for caffeine use and trial dietary strategies (e.g., evening consumption of high GI carbohydrates) to improve sleep.

Sex differences among endurance athletes in the pre-race relationships between sleep, and perceived stress and recovery.

This study examined sex differences among endurance athletes in pre-race relationships between sleep, and perceived stress and recovery. Thirty-six athletes completed the Short Recovery and Stress Scale, and had sleep monitored via actigraphy, over four consecutive days prior to an ultra-marathon. Overall, compared with males, females had shorter wake after sleep onset (mean ± SD, 50 ± 23 vs 65 ± 23 min, p = .04) and lower emotional balance (3.9 ± 1.1 vs 4.8 ± 1.1 arbitrary units, p = .001). The day before the race, females scored higher for all stress-related items (p < 0.05). Among females, higher scores for emotional balance (ß = -31 min, p = .01) and negative emotional state (ß = -21 min, p < .001) were associated with reduced sleep duration. Among males, higher scores for overall stress were associated with increased sleep duration (ß = 22 min, p = .01). Across all athletes, longer sleep duration was associated with improved overall recovery (ß = 0.003 arbitrary units, p = .02). Females experienced greater pre-race stress than males, and their sleep duration was associated with emotional factors. The SRSS may help identify female athletes at risk of sleep difficulties prior to competition.

Does game-day circadian misalignment or environmental temperature influence team performance in the Australian Football League? An examination of historical data.

OBJECTIVES: Examine Australian Football League results for evidence that game-day circadian misalignment or environmental temperature influence games with competing teams from each of Western Australia and Victoria. DESIGN: Retrospective observational study. METHODS: Data were obtained for games (n = 791) contested by Western Australian and Victorian teams; including game location, start time, and outcome. Start times were categorised as afternoon, twilight, or night. Game-day maximum temperature (°C) for afternoon games was obtained from the Australian Bureau of Meteorology. Mixed effects generalised linear models examined evidence for a circadian advantage to Victorian teams in afternoon games, and to Western Australian teams in night games. Models examined evidence for an advantage to Western Australian teams as game-day temperature increases. RESULTS: Odds of winning and point margin for home games played in the afternoon, twilight, and night, were not different between Victorian and Western Australian teams (p > 0.05). For afternoon games, each 1 °C increase in temperature improved odds of Western Australian teams winning by 11% (p < 0.001) and their point margin by 2.1 points (p < 0.001). For games played in Victoria, each 1 °C increase in temperature improved odds of Western Australian teams winning by 6% (p = 0.028) and their point margin by 1.7 points (p = 0.005). CONCLUSIONS: There is no evidence here that circadian misalignment between teams influences game outcomes in the AFL. Western Australian teams are more likely to win afternoon games played in warm conditions. This may reflect superior heat acclimatisation among AFL players based in Western Australia.

Monitoring Responses to Basic Military Training with Heart Rate Variability.

INTRODUCTION: Heart rate variability (HRV) has shown sensitivity to the acute stressors experienced by defense personnel. This study examines the suitability of overnight HRV as a repeated measure of allostatic load in defense personnel. METHODS: Daily measures of sleep, cognitive load, and perceived exertion were reported for the 12-wk duration of basic military training (BMT) in 48 recruits. Physical activity, subjective well-being, and HRV were measured weekly. The natural log of the root mean square of successive differences of interbeat intervals (Ln RMSSD) and the Ln RMSSD to interbeat interval ratio (Ln RMSSD:RRi ratio) during predicted slow wave sleep were used for HRV. Physical performance was assessed via the 20-m shuttle run and maximal push-up test in weeks 2 and 8 of BMT with predicted V̇O 2 peak values calculated. RESULTS: Predicted V̇O 2 peak increased from 42.6 ± 4.5 to 48.0 ± 2.7 mL·kg -1 ·min -1 ( P < 0.001). Ln RMSSD was elevated in weeks 7 and 10, and the Ln RMSSD:RRi ratio was elevated in week 10 above all other weeks ( P < 0.05). An increase in perceived exertion ( F = 9.10, P = 0.003) and subjective fatigue ( F = 6.97, P = 0.009), as well as a reduction in V̇O 2 peak ( F = 7.95, P = 0.009), individually predicted an increase in Ln RMSSD. The best predictive model of Ln RMSSD included perceived exertion ( F = 8.16, P = 0.005), subjective fatigue ( F = 8.49, P = 0.004), the number of awakenings during sleep ( F = 7.79, P = 0.006), and the change in V̇O 2 peak ( F = 19.110, P < 0.001). CONCLUSIONS: HRV was predicted by subjective recruit responses to BMT workloads rather than objective measures of physical activity. Improvements in cardiorespiratory fitness depicted recruits who experienced enough stress to facilitate physiological adaptation, which was reflected by a reduction in HRV during BMT. Monitoring HRV and HRV in relation to interbeat interval length may provide a better tool for determining allostatic load than HRV alone.

Sleep of recruits throughout basic military training and its relationships with stress, recovery, and fatigue.

OBJECTIVE: Studies in basic military training (BMT) examining sleep are largely cross-sectional, and do not investigate relationships between sleep, stress, recovery and fatigue. The aims of this study were to (1a) quantify changes in recruits' sleep quantity and quality over 12 weeks of BMT; (1b) quantify changes in recruits' perceptions of stress, fatigue and recovery over BMT; and (2) explore relationships between sleep, and perceptions of stress, fatigue and recovery. METHODS: 45 recruits (37 male; 8 female, age: 25.2 ± 7.2 years, height: 176.2 ± 10.0 cm, mass: 76.8 ± 15.0 kg) wore ActiGraph GT9X's for 12 weeks of BMT, collecting sleep duration, efficiency and awakenings. Subjective sleep quality, fatigue were measured daily, with stress and recovery measured weekly. Multi-level models assessed relationships between sleep, and stress, recovery, and fatigue. RESULTS: Objective daily means for sleep duration were 6.3 h (± 1.2 h) and 85.6% (± 5.5%) for sleep efficiency. Main effects were detected for all mean weekly values (p < 0.05). Sleep quality showed the strongest relationships with stress, recovery and fatigue. The best model to explain relationships between, stress, recovery and fatigue, included sleep quality, sleep duration, sleep efficiency and awakenings. CONCLUSIONS: The reported mean sleep duration of 6.3 h per night may negatively impact training outcomes across BMT. Combining both subjective and objective measures of sleep best explained relationships between sleep metrics stress, fatigue and recovery. Perceived sleep quality was most strongly related to change in stress, recovery, or post-sleep fatigue.

Evening Whey Protein Intake, Rich in Tryptophan, and Sleep in Elite Male Australian Rules Football Players on Training and Nontraining Days.

OBJECTIVES: To investigate the effect of evening whey protein supplementation, rich in tryptophan, on sleep in elite male Australian Rules Football players. DESIGN: Double-blinded, counterbalanced, randomized, cross-over study. METHODS: Sleep was assessed using wrist activity monitors and sleep diaries in 15 elite male Australian Football League players on two training and nontraining days following evening consumption of an isocaloric whey protein supplement or placebo in preseason. A 5-day preintervention period was implemented to determine habitual dietary intake and baseline sleep measures. These habitual data were used to inform the daily dietary intake and timing of ingestion of the evening whey protein supplement or placebo on the intervention days. The whey protein supplement or placebo was consumed 3 hr prior to habitual bedtime. RESULTS: Separate one-way repeated-measures analyses of covariance revealed no differences between the whey protein supplement and the placebo on sleep duration, sleep onset latency, sleep efficiency, or wake after sleep onset on either training or nontraining days. CONCLUSIONS: Evening whey protein supplementation, rich in tryptophan, does not improve acute sleep duration or quality in elite male Australian Football League players. However, elite athletes may be able to ingest a high protein/energy intake close to bedtime without impairing sleep, which is important for athlete recovery. Future research should investigate the effect of evening protein intake, high in tryptophan, on sleep duration and quality, including sleep staging during periods of restricted sleep and in poor-sleeping athletes.

Sleep duration and quality are associated with nutrient intake in elite female athletes.

OBJECTIVES: Sleep is important for athlete health and performance; however, the relationship between diet and sleep in elite female athletes is not well understood. This study examined associations between energy, macronutrient and micronutrient intakes, and sleep in elite female Australian footballers. DESIGN: Prospective cohort study. METHODS: Thirty-two players had their diet and sleep monitored for 10 consecutive days during pre-season. Sleep was monitored using activity monitors and sleep diaries. Sleep outcomes included sleep duration, sleep onset latency (SOL), wake time after sleep onset (WASO), and sleep efficiency (SE). Dietary intake was monitored using the smartphone applications Easy Diet Diary and FoodWorks. Relationships between nutrient intake and sleep were assessed using Generalised Estimating Equations. RESULTS: For each 1-g·kg-1 increase in carbohydrate intake, WASO increased by 3.6 min (p = 0.007) and SE decreased by 0.6% (p = 0.007). For each 1-g increase in daily saturated fat intake, SOL decreased by 0.27 min (p = 0.030). For each 1-mg increase in iron intake, sleep duration increased by 0.55 min (p < 0.001). For each 1-mg increase in zinc intake, SE increased by 0.23% (p = 0.006). For each 1-µg increase in vitamin B12 intake, WASO decreased by 1.72 min (p < 0.02) and SE increased by 0.40% (p = 0.033). CONCLUSIONS: Nutrient intake in elite female athletes is associated with sleep and may contribute to sleep problems. Research should explore causal relationships between nutrient intake and sleep, and the efficacy of dietary interventions for improving sleep in female athletes with nutrient deficiencies.

Monitoring Effects of Sleep Extension and Restriction on Endurance Performance Using Heart Rate Indices.

ABSTRACT: Roberts, SSH, Aisbett, B, Teo, W-P, and Warmington, S. Monitoring effects of sleep extension and restriction on endurance performance using heart rate indices. J Strength Cond Res 36(12): 3381-3389, 2022-Heart rate (HR) indices are useful for monitoring athlete fatigue or "readiness to perform." This study examined whether HR indices are sensitive to changes in readiness following sleep restriction (SR) and sleep extension (SE). Nine athletes completed a crossover study with 3 conditions: SR, normal sleep (NS), and SE. Each condition required completion of an endurance time trial (TT) on 4 consecutive days (D1-D4). Athletes slept habitually before D1; however, time in bed was reduced by 30% (SR), remained normal (NS), or extended by 30% (SE), on subsequent nights (D1-D3). Daily resting HR and HR variability were recorded. The maximal rate of HR increase and HR recovery was determined from a constant-load test before TTs. Exercise intensity ratios incorporating mean HR, mean power (W), and perceived exertion (RPE) were recorded at steady state during constant-load tests (W:HR SS ) and during TTs (W:HR TT , RPE:HR TT ). Compared with D4 of NS, RPE:HR TT was lower on D4 of SE ( p = 0.008)-when TT performances were faster. Compared with D1 of SR, RPE:HR TT was higher on D3 and D4 of SR ( p < 0.02). Moderate correlations were found between percentage changes in W:HR TT and changes in TT finishing time in SR ( r = -0.67, p = 0.049) and SE ( r = -0.69, p = 0.038) conditions. Intensity ratios incorporating mean HR seem sensitive to effects of sleep duration on athlete readiness to perform. When interpreting intensity ratios, practitioners should consider potential effects of prior sleep duration to determine whether sleep-promoting interventions are required (e.g., SE).

The Relationship Between Psychological Stress and Anxiety with Gastrointestinal Symptoms Before and During a 56 km Ultramarathon Running Race.

BACKGROUND: This study assessed relationships and sex differences between psychological state (recovery, stress, anxiety, and self-confidence) and gastrointestinal symptoms (GIS) prior to and during a 56 km ultramarathon running race and identified predictive factors of race GIS. Forty-four (26 males, 18 females) ultramarathon competitors completed anxiety, recovery, stress and GIS questionnaires for three days prior to the race and immediately pre-race. Race GIS were assessed immediately post-race. Spearman's rank order, Mann-Whitney U tests and regression analyses were used to determine correlations and identify sex differences between psychological state and GIS and determine predictors of race GIS. RESULTS: Race GIS were significantly correlated with recovery (rs = - 0.381, p = 0.011), stress (rs = 0.500, p = 0.001) and anxiety (rs = 0.408, p = 0.006), calculated as the mean of the three days preceding the race and on race morning. The correlation between anxiety and GIS was strongest in the 24 h immediately prior to the race (all rs > 0.400, and all p < 0.05), but unclear patterns were identified for stress and recovery. Regression analyses showed 36% and 40% of variation in the severity and number of race GIS was accounted for by body mass and measures of stress, anxiety, and GIS over the three days preceding the race and on race morning (both p < 0.001). There were no sex differences in the number and severity of GIS leading up to or during the race (all p > 0.05), however, females reported greater state anxiety (p = 0.018) and lower self-confidence than males (p = 0.006) over the three days preceding the race and on race morning. CONCLUSION: Endurance athletes that experience GIS during competition should investigate elevated stress and/or anxiety as a potential contributor and identify if management strategies can reduce the occurrence and severity of GIS.

The Impact of Chronotype on the Sleep and Training Responses of Elite Female Australian Footballers.

The primary aims of the present study were to examine the impact of chronotype on sleep/wake behaviour, perceived exertion, and training load among professional footballers. Thirty-six elite female professional football player's (mean ± SD: age, 25 ± 4 y; weight, 68 ± 7 kg) sleep and training behaviours were examined for 10 consecutive nights during a pre-season period using a self-report online player-management system and wrist activity monitors. All athletes completed the Morningness-Eveningness Questionnaire (rMEQ) on the first day of data collection. Eleven participants were morning types, seventeen participants were intermediate types, and three participants were evening types. Separate linear mixed models were conducted to assess differences in sleep, perceived exertion, and training behaviours between chronotype groups. Morning types woke up earlier (wake time: 07:19 ± 01:16 vs. 07:53 ± 01:01, p = 0.04) and reported higher ratings of perceived exertion compared to intermediate types (6.7 ± 1.1 vs. 5.9 ± 1.2, p = 0.01). No differences were observed between chronotype groups for bedtime, time in bed, total sleep time, sleep efficiency, training duration, or training load. In circumstances where professional female football players are required to train at a time opposing their natural circadian preference (e.g., morning type training in the evening), their perceived exertion during training may be higher than that of players that are training at a time that aligns with their natural circadian preference (e.g., evening type training in the evening). It is important for practitioners to monitor individual trends in training variables (e.g., rating of perceived exertion, training load) with relation to athlete chronotype and training time. Future research should examine the relationship between chronotype, training time, and rating of perceived exertion across different training durations.

Monitoring stress and allostatic load in first responders and tactical operators using heart rate variability: a systematic review.

BACKGROUND: Awareness of the cumulative stress placed on first responders and tactical operators is required to manage acute fatigue, which can impair occupational performance, and may precipitate negative chronic health outcomes. The aim of this review was to investigate the utility of heart rate variability (HRV) to monitor stress and allostatic load among these populations. METHODS: A systematic search of Academic Search Complete, MEDLINE complete, PsycINFO, SPORTDiscus and Scopus databases was conducted. Eligibility criteria: original peer reviewed research articles, written in English, published between 1985 and 2020, using human participants employed as a first responder or tactical operator, free from any psychological disorder. RESULTS: Of the 360 articles screened, 60 met the inclusion criteria and were included for full text assessment. Articles were classified based on single or repeated stressor exposure and the time of HRV assessment (baseline, during stressor, post stressor). Singular stressful events elicited a reduction in HRV from baseline to during the event. Stressors of greater magnitude reduced HRV for extended durations post stressor. Lower resting HRV was associated with lower situational awareness and impaired decision-making performance in marksmanship and navigation tasks. There were insufficient studies to evaluate the utility of HRV to assess allostatic load in repeated stressor contexts. CONCLUSION: A reduction in HRV occurred in response to acute physical and cognitive occupational stressors. A slower rate of recovery of HRV after the completion of acute occupational stressors appears to occur in response to stressors of greater magnitude. The association between lower HRV and lower decision-making performance poses as a useful tool but further investigations on within subject changes between these factors and their relationship is required. More research is required to investigate the suitability of HRV as a measure of allostatic load in repeated stress exposures for fatigue management in first responder and tactical operators.