International journal of sport nutrition and exercise metabolism最新文献

Athletes often experience poor sleep quality and quantity which may hinder physical performance and cognitive function. Presleep nutritional strategies may be an alternative to pharmacological interventions to improve sleep. The aim of this study was to examine the effect of two different doses of a nutritional intervention (both containing high Glycemic Index carbohydrate, whey, tryptophan, theanine, and 5'AMP) versus placebo on objective and subjective sleep, next-morning physical performance, cognitive function, and postural sway. Seventeen healthy, trained adult males completed three double-blind trials in a randomized, counterbalanced, crossover design. Participants were allocated to conditions using a Latin Square design. A (a) low-dose, (b) high-dose, or (c) placebo drink was provided 90 min before sleep each night. Polysomnography was used to measure objective sleep parameters. Cognitive function, postural sway, and subjective sleep quality were assessed 30 min after waking. Physical performance was assessed using a 10-min maximal effort cycling time trial each morning. All data were analyzed using linear mixed effects models and effect sizes were calculated using Cohen's d. This study was registered prospectively as a clinical trial with Australian New Zealand Clinical Trials Registry (registration number: NCT05032729). No significant main effects or improvements were observed in objective or subjective sleep parameters, physical performance, cognitive function, or postural sway. The low-dose intervention appeared to reduce N3 sleep duration compared with placebo (-13.6 min). The high-dose intervention appeared to increase N1 sleep duration compared with placebo (+7.4 min). However, the magnitude of changes observed were not likely to cause meaningful reductions in sleep quality and quantity.

This study aimed to assess the effects of caffeine ingestion incorporated into an ice slushy on cycling time-trial (CTT) performance in hot, humid conditions. Nine moderately trained recreational male cyclists or triathletes ingested 6.8 g/kg crushed ice with either 6% carbohydrate concentration only (CON) or 6% carbohydrate concentration and 3 mg/kg caffeine (CAF) consumed over a 30 min period prior to exercise in a single-blind, counterbalanced design. Postingestion, participants completed a CTT equating 1,200 kJ of work (∼40 km) in a climate-controlled chamber (33 °C and 60% relative humidity). Experimental sessions were separated by 7 days. During each CTT, rectal temperature, cycling time, heart rate, blood lactate, and ratings of perceived exertion and thermal sensation were measured at set intervals of work. The 1,200 kJ CTT was completed faster in CAF (4,716 ± 785 s) compared with CON (4,911 ±755 s) (p < .05); and split times were completed faster in CAF compared with CON from the 800 to 1,200 kJ timepoints of the CTT. Precooling lowered rectal temperature similarly in both CAF (-0.6 ± 0.2 °C) and CON (-0.6 ± 0.1 °C) (p > .05). No differences were observed between CAF and CON for heart rate, rating of perceived exertion, rating of perceived thermal sensation, or blood lactate across the measured time points (p > .05). Precooling with the combination of a carbohydrate-based ice slushy and caffeine resulted in improved CTT performance in hot conditions compared with a carbohydrate-based ice slushy alone. Therefore, the addition of caffeine to ice slushies might be considered by endurance athletes competing in the heat for enhanced performance gains.

Gut-training has been shown to improve gastrointestinal tolerance, circulatory glucose availability, and exercise performance. The study aimed to investigate the effects of a repetitive feeding-challenge using fat versus carbohydrate (CHO) on markers of gastrointestinal function, glucose availability, and subsequent performance when challenged with a high-CHO load (87 g/hr) during exercise. Forty-four endurance athletes (mean ± SD [9 females and 35 males]: body mass: 71.2 ± 9.2 kg, height: 173.6 ± 7.0 cm, V˙O2max: 55.0 ± 6.1 ml·kg-1·min-1) completed a preintervention gut-challenge trial (T1), involving a 2 hr run (60% V˙O2max) while taking a CHO gel every 20 min (87 g/hr, 10% w/v), followed by a 1 hr self-paced distance test with ad libitum water. Participants were then randomized to a fat (fat feeding-challenge [FFC]; 20 g nut butter, 124 kcal, 11 g fat, 3 g protein, and 3 g CHO) or CHO supplement (CHO feeding-challenge [CFC]; 47 g CHO gel: 123 kcal, 29 g CHO) group to complete a 7-day repetitive feeding-challenge (1 hr exercise and supplement intake every 20 min with 290 ml water), followed by a gut-challenge retrial (T2). FFC did not differ from CFC in terms of resting orocecal transit time, feeding tolerance, or substrate oxidation during T1 and T2. Peak breath hydrogen was lower in FFC than CFC (p = .028) at T2. Total (FFC: 27%, p = .005 vs. CFC: 38%, p = .001) and upper gastrointestinal symptoms severity (FFC: 26%, p = .013 vs. CFC: 40%, p < .001) during exercise was reduced similarly between groups from T1 to T2. FFC covered more distance in T2 (11.51 ± 2.02 vs. 11.08 ± 2.02 km, p = .013), but not significantly different to CFC (p = .341). A repetitive feeding-challenge with fat does not enhance nor worsen gastrointestinal and fueling outcomes compared with a CHO repetitive feeding-challenge.

This study investigated the effect of sodium hyperhydration on thermal and cardiovascular strain and exercise performance in unacclimatized endurance-trained females exercising in the heat and whether effects differ between menstrual cycle (MC) Phase 1 (low estrogen and progesterone) and MC Phase 4 (moderate estrogen and high progesterone). Twelve female cyclists/triathletes completed four trials in a randomized, double-blinded, crossover design. Participants consumed 30 ml·kg-1 fat-free mass fluid with either sodium chloride (7.5 g·L-1) or placebo (sucrose) 2 hr prior to 75 min of steady-state cycling (60% V˙O2peak) followed by a 200-kJ time trial (TT) in 34 °C and 60% relative humidity, with both interventions completed during MC Phase 1 and Phase 4. Rectal temperature and heart rate were measured at baseline, every 5 min during steady state, every 50 kJ of TT, and TT completion. Body mass was measured every 30 min preexercise and pre and post steady state and TT to assess hydration status. Linear mixed models were fitted to estimate intervention and MC phase effect. There were no significant sodium hyperhydration or MC phase effects on rectal temperature or heart rate (p > .05). Body mass increased with sodium versus placebo (0.38 [0.02, 0.74] kg; p = .04), with a greater increase in MC Phase 4 (0.69 [0.17, 1.2] kg; p < .001). TT performance improved with sodium versus placebo (-1.55 [-2.46, -0.64] min; p = .001), with a greater improvement in MC Phase 4 (-1.85 [-3.16, -0.55] min; p = .005). Sodium hyperhydration is a promising heat mitigation strategy for females undertaking prolonged exercise in the heat, especially during MC Phase 4 and when fluid access is limited.

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.

Dietary supplements have improved performance and muscle hypertrophy in athletes and nonathletes in the past few decades. Theracurmin, a nutraceutical supplement based on curcumin, has been highlighted by its anti-inflammatory and antioxidant properties in physiological and pathological conditions. This study aimed to investigate the effects of theracurmin intake (300 mg/kg), containing 30 mg/kg of curcumin, in male Swiss mice (n = 66) under distinct protocols of climbing stairs (strength exercise) and their respective detraining period. Animals, aged 7-9 weeks, were trained for 8 weeks (5 days/week), with a minimum interval of 24 hr between each session, followed by a 4-week detraining period. After euthanasia, skeletal muscle hypertrophy was evaluated through histological analysis. Tissue inflammatory release of tumor necrosis factor, interleukin (IL)-6, IL-10, and chemokine C-C motif ligand 2, as well as the activity of oxidative stress enzymes (catalase, superoxide dismutase, and lipid peroxidation), were also assessed. In trained animals, inflammatory mediators and skeletal muscle mass increased after training (p = .0004). Theracurmin did not revert the muscle hypertrophy, but it decreased tissue chemokine C-C motif ligand 2 (p = .0001) and lipid peroxidation (p < .0001) after strength training and after detraining (p = .0008 and p = .001, respectively). Tissue tumor necrosis factor was only reduced during the detraining period (p = .037), whereas IL-6 (p = .0001) and IL-10 (p < .0001) increased after the training protocol. No differences were observed in catalase and superoxide dismutase. Our data suggest that theracurmin intake contributes to the reduction of tissue inflammatory mediators during strength training and/or detraining without essential activity on skeletal muscle hypertrophy.

New Zealand black currant extract (NZBC) has been shown to increase fat oxidation during exercise and decrease the postexercise blood pressure in men and women. The change in fat oxidation by NZBC has also been shown to be correlated to body composition in men and women. There has never been a comparison of sex responses within the same study. Twenty-two participants (11 men and 11 women, age: 29 ± 8 years, maximal oxygen uptake: 44 ± 9 ml·kg-1·min-1, body fat: 18% ± 6%) had resting blood pressure measured for 2 hr (no exercise). In a double-blind, placebo-controlled (PLA), randomized crossover design, participants completed 1 hr of treadmill exercise at 50% maximal oxygen uptake with expired gas measurement, followed by 2-hr resting blood pressure measurement with 7 days of NZBC or PLA. Average fat oxidation was different between the conditions (NZBC: 0.27 ± 0.11 g/min, PLA: 0.21 ± 0.12 g/min, p < .001), but the response between men and women was not different. When combined, there was no relationship (p > .05) between body fat percentage and change in fat oxidation (r = -.079), with men also demonstrating no relationship (r = -.069), although women did demonstrate a relationship (r = .691, p < .05). In the 2-hr rest, systolic pressure delta change was larger with NZBC than PLA (no exercise vs. NZBC: -5.5 ± 5.4 mmHg vs. no exercise vs. PLA: -2.9 ± 5.1 mmHg, p < .001) but was not different between men and women. A 7-day intake of NZBC extract increases fat oxidation during moderate-intensity exercise and decreases postexercise blood pressure in men and women. The magnitude of change in fat oxidation in women is correlated to body fat percentage.

This study aimed to determine the impact of caffeine (200 mg), beta-alanine (3 g), and their combination on intraocular pressure (IOP), ocular perfusion pressure (OPP), and mean arterial pressure (MAP) at rest and after resistance training. Twenty young men (age = 23.4 ± 4.5 years) took part in this placebo-controlled, triple-blind, balanced crossover study. Participants visited the lab on four different days, with the only difference of the supplement used (caffeine, beta-alanine, caffeine + beta-alanine, and placebo). IOP and blood pressure were measured at baseline after 30 min from supplement intake, and after completing the resistance training session consisting of four alternating sets of bench press and bench pull exercises using a 20 repetition maximum load without reaching failure. In resting conditions, caffeine and the combination of caffeine + beta-alanine caused an acute IOP rise (p = .009 and .004, respectively), whereas beta-alanine and placebo intake did not affect IOP levels (p = .802 in both cases). OPP levels were not influenced by the ingestion of any supplement (p = .801), whereas MAP exhibited a significant increase after 30 min of ingesting 200 mg of caffeine (p = .012). After resistance training, there was an acute reduction of IOP, OPP, and MAP levels (p < .002 in all cases), but these effects were independent of the supplement consumed (p > .272). These findings show that beta-alanine (3 g) did not alter IOP, OPP, and MAP levels in resting conditions and after resistance training. Therefore, beta-alanine supplementation is a safe alternative when avoiding fluctuations of the ocular and cardiovascular hemodynamics is desirable (i.e., glaucoma patients or hypertensive individuals).

L-citrulline (CIT) supplementation seems to improve resistance training performance; yet, whether malate has additive ergogenic effects when combined with CIT is unknown. This randomized, double-blind, placebo-controlled crossover trial aimed to compare the acute effects of CIT versus citrulline malate (CMA) supplementation on neuromuscular performance and exertion and emotional perceptions in young, trained men and women. 43 (21 women; 24.2 ± 3.7 years) participants ingested a placebo, CIT (5.3 g of CIT), or CMA (5.3 g of CIT, 2.7 g of malate) 45 min before three experimental sessions in a counterbalanced manner. We evaluated the upper and lower limb maximal neuromuscular and ballistic performance through the two-point method and countermovement jump. Strength-endurance was assessed across three sets of 10 repetitions in the squat and bench press exercises. Exertion and emotional perceptions were evaluated before and after the assessment and during the strength-endurance assessment. CIT and CMA supplementation did not enhance maximal neuromuscular performance (all p ≥ .061, ηp2≤.066), or ballistic strength (all p ≥ .348, ηp2≤.025). Neither CIT nor CMA supplementation improved strength-endurance as observed in the total number of repetitions (all p ≥ .590, ηp2≤.013), repetitions before reaching velocity loss threshold (all p ≥ .623, ηp2≤.010), mean velocity (all p ≥ .792, ηp2≤.004), mean velocity decline (all p ≥ .293, ηp2≤.029), and mean velocity maintenance (all p ≥ .393 ηp2≤.022), or exertion and emotional perceptions (both p ≥ .306, ηp2≤.028). In conclusion, CIT and CMA supplementation may not increase the neuromuscular performance during low- to moderate-volume resistance training sessions in young, trained adults. This trial was registered at ClinicalTrials.gov (No. NCT05183893).