Evening consumption of a whey protein rich in the amino acid tryptophan, alpha-lactalbumin (ALAC), has previously shown to benefit sleep—particularly among poor sleepers. Given trained populations often experience sleep difficulty, this study investigated whether evening supplementation of ALAC would influence sleep outcomes, mood, and next-day cognitive performance within a trained population with sleep difficulties. Nineteen trained participants (females, n = 11) with sleep difficulties (Athlete Sleep Screening Questionnaire: 8.1 ± 3.1; Pittsburgh Sleep Quality Index: 10.5 ± 4.1) completed this double-blinded, counterbalanced, randomized, crossover trial. Forty grams of ALAC or control were supplemented 2 hr presleep for three consecutive nights in a controlled environment, with sleep measured using dry electroencephalography. Blood samples were taken on the first evening of each experimental trial, with mood, sleepiness, and recovery assessed across the evening and morning. A cognitive testing battery was also completed each morning. During the ALAC condition, the primary findings were that participants had raised plasma tryptophan levels ( p < .01), increased nonrapid eye movement Stage 2 sleep duration (CON: 205.9 ± 33.3; ALAC: 216.5 ± 33.1 min), reduced rapid eye movement duration (CON: 110.8 ± 27.9; ALAC: 99.7 ± 23.1 min), and improved reaction time in cognitive tests involving sensory motor speed, spatial orientation, and vigilant attention ( p < .05). Data suggest evening supplementation of 40 g ALAC alters sleep architecture and improves next-morning reaction time in trained populations with sleep difficulties. Therefore, trained individuals experiencing sleep difficulty may benefit from acute ALAC supplementation to assist next-day performance. Future research should investigate this effect within habitual environments, outside of a tightly controlled setting.
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 (
Fluid loss during prolonged exercise in hot conditions poses thermoregulatory and cardiovascular challenges for athletes that can lead to impaired performance. Pre-exercise hyperhydration using nutritional aids is a strategy that may prevent or delay the adverse effects of dehydration and attenuate the impact of heat stress on exercise performance.The aim of this systematic review was to examine the current literature to determine the effect of pre-exercise hyperhydration on performance, key physiological responses and gastrointestinal symptoms.English language, full-text articles that compared the intervention with a baseline or placebo condition were included. An electronic search of Medline Complete, SPORTDiscus and Embase were used to identify articles with the final search conducted on 11 October 2022. Studies were assessed using the American Dietetic Association Quality Criteria Checklist.Thirty-eight studies involving 403 participants (n = 361 males) were included in this review (n = 22 assessed exercise performance or capacity). Two studies reported an improvement in time-trial performance (range 5.7-11.4%), three studies reported an improvement in total work completed (kJ) (range 4-5%) and five studies reported an increase in exercise capacity (range 14.3-26.2%). During constant work rate exercise, nine studies observed a reduced mean heart rate (range 3-11 beats min-1), and eight studies reported a reduced mean core temperature (range 0.1-0.8 °C). Ten studies reported an increase in plasma volume (range 3.5-12.6%) compared with a control. Gastrointestinal symptoms were reported in 26 studies, with differences in severity potentially associated with factors within the ingestion protocol of each study (e.g. treatment, dose, ingestion rate).Pre-exercise hyperhydration may improve exercise capacity during constant work rate exercise due to a reduced heart rate and core temperature, stemming from an acute increase in plasma volume. The combination of different osmotic aids (e.g. glycerol and sodium) may enhance fluid retention and this area should continue to be explored. Future research should utilise valid and reliable methods of assessing gastrointestinal symptoms. Furthermore, studies should investigate the effect of hyperhydration on different exercise modalities whilst implementing a strong level of blinding. Finally, females are vastly underrepresented, and this remains a key area of interest in this area.
This research examined the effect restricted sleep has on wildland firefighters’ cytokine levels during 3 days and 2 nights of simulated physical wildfire suppression work. Firefighters completed multiple days of physical firefighting work separated by either an 8-h (Control condition; n=18) or 4-h (Awake condition; n=17) sleep opportunity each night. Blood samples were collected 4 times a day from which plasma cytokine levels (IL-6, IL-8, IL-1β, TNF-α, IL-4, IL-10) were measured.
The current study combined, for the first time, video footage of individual firefighters wearing heart rate monitors and personal GPS units to quantify the frequency, duration and intensity of tasks performed by Australian rural fire crews when. suppressing bushfires. Across the four fireground 'shifts', the firefighters performed 34 distinct fireground tasks. Per shift, the task frequency ranged from once (raking fireline in teams, carrying a quick fill pump) to 103 times {lateral repositioning of a 38-mm charged firehose) .. The tasks lasted between 4 ± 2 s (bowling out 3-8-mm firehose) and 461 ± 387 s (raking fireline in teams). The task intensity~ as measured by average heart rate ranged between 97 ± 16 beats·min-1 (55.7 ± 8.7. %HRmax) and 157 ± 15 beats·min-1 (86.2 ± 10.8 %HRmax)· The tasks were performed a speeds that ranged from 0.12 ± 0.08 m·s-1 (manual hose retraction of 38-mm charged firehose) to 0.79 ± 0.40 m·s-1 (carrying a 38-mm coiled hose). Tasks found to be simultaneously frequent, long and intense (or two of these three) are likely to form the basis for job-specific testing of Australian rural firefighters suppressing bushfires.
(1) Background: About one in four workers undertake shift rosters that fall outside the traditional 7 a.m.–6 p.m. scheduling. Shiftwork alters workers’ exposure to natural and artificial light, sleep patterns, and feeding patterns. When compared to the rest of the working population, shiftworkers are at a greater risk of developing metabolic impairments over time. One fundamental component of metabolic health is skeletal muscle, the largest organ in the body. However, cause-and-effect relationships between shiftwork and skeletal muscle health have not been established; (2) Methods: A critical review of the literature was completed using online databases and reference lists; (3) Results: We propose a conceptual model drawing relationships between typical shiftwork consequences; altered light exposure, sleep patterns, and food and beverage consumption, and drivers of skeletal muscle health—protein intake, resistance training, and hormone release. At present, there is no study investigating the direct effect of shiftwork on skeletal muscle health. Instead, research findings showing that acute consequences of shiftwork negatively influence skeletal muscle homeostasis support the validity of our model; (4) Conclusion: Further research is required to test the potential relationships identified in our review, particularly in shiftwork populations. Part of this testing could include skeletal muscle specific interventions such as targeted protein intake and/or resistance-training.
Labour productivity is a key factor affecting the performance of construction projects. This research adopts a systems perspective to investigate and analyse various factors affecting labour productivity in Australian multi-storey building construction projects. The factors affecting labour productivity are identified based on the opinions of experts. The complicated interrelated links between influencing factors are drawn using cause and effect feedback loops. These factors are then modelled and analysed taking into account their interactions using the Decision-Making Trial and Evaluation Laboratory (DEMATEL) method, and the most significant factors affecting labour productivity are determined. These factors include level of skill and experience, fatigue, inadequate supervision, award rates and communication problem with foreign workers. The influencing factors are then divided into cause and effect groups and project size, level of skill and expereince and communication problem with foreign workers are identified as the most impressive factors that affect labour productivity. The proposed method offers a more precise and accurate analysis of various factors affecting labour productivity since the complex inter-related structure of influencing factors is taken into account. The output of this research will give project managers a roadmap for improving labour productivity through the selection and adaptation of most efficient strategies.
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