Journal of the International Society of Sports Nutrition最新文献

Creatine monohydrate supplementation (CrM) is a safe and effective intervention for improving certain aspects of sport, exercise performance, and health across the lifespan. Despite its evidence-based pedigree, several questions and misconceptions about CrM remain. To initially address some of these concerns, our group published a narrative review in 2021 discussing the scientific evidence as to whether CrM leads to water retention and fat accumulation, is a steroid, causes hair loss, dehydration or muscle cramping, adversely affects renal and liver function, and if CrM is safe and/or effective for children, adolescents, biological females, and older adults. As a follow-up, the purpose of this paper is to evaluate additional questions and misconceptions about CrM. These include but are not limited to: 1. Can CrM provide muscle benefits without exercise? 2. Does the timing of CrM really matter? 3. Does the addition of other compounds with CrM enhance its effectiveness? 4. Does CrM and caffeine oppose each other? 5. Does CrM increase the rates of muscle protein synthesis or breakdown? 6. Is CrM an anti-inflammatory intervention? 7. Can CrM increase recovery following injury, surgery, and/or immobilization? 8. Does CrM cause cancer? 9. Will CrM increase urine production? 10. Does CrM influence blood pressure? 11. Is CrM safe to consume during pregnancy? 12. Does CrM enhance performance in adolescents? 13. Does CrM adversely affect male fertility? 14. Does the brain require a higher dose of CrM than skeletal muscle? 15. Can CrM attenuate symptoms of sleep deprivation? 16. Will CrM reduce the severity of and/or improve recovery from traumatic brain injury? Similar to our 2021 paper, an international team of creatine research experts was formed to perform a narrative review of the literature regarding CrM to formulate evidence-based responses to the aforementioned misconceptions involving CrM.

Background: Appropriate and adequate nutrition is essential for the health and performance of tactical athletes, including army recruits and trainees. However, previous research shows they commonly experience suboptimal intakes of energy and carbohydrate. To date, little research has been conducted to understand the causes of their poor dietary intakes. The objectives of this study were to (1) assess infantry trainees' dietary intakes and (2) explore their beliefs, barriers, and self-efficacy toward performance nutrition using the Health Belief Model (HBM).

Methods: Participants undergoing their 17-week Australian Army Infantry Initial Employment Training (Infantry IET) were recruited. During weeks 1 and 17, self-reported dietary intakes were assessed, and four focus groups were conducted.

Results: Mean daily energy, carbohydrate, and protein intakes were 7864 ± 1135 kJ, 1.8 ± 0.6 g/kg, and 1.5 ± 0.3 g/kg, respectively, in week 1, and 9084 ± 2535 kJ/day, 2.2 ± 1.1 g/kg and 1.5 ± 0.2 g/kg, respectively, in week 17. Three themes and seven subthemes were developed from the focus group data, falling under the following HBM domains: Cues to Action, Perceived Barriers, and Self-Efficacy.

Conclusions: Infantry trainees' ability to eat well for their health and performance was hindered by their limited time during their intensive training schedule, their limited access to a sufficient variety of healthy foods, and their limited self-efficacy regarding performance nutrition. They require further performance nutrition knowledge, especially in regard to adopting practical fueling and refueling strategies surrounding physical training, as well as access to a greater quantity and variety of healthy foods outside of their main mealtimes.

Background: Caffeine's ergogenic potential in vertical jumping remains contested, particularly at dosages compliant with collegiate athletic regulations. The NCAA enforces a caffeine urinary threshold equivalent to ~5 mg/kg body mass, yet evidence supporting its efficacy in enhancing explosive performance among trained athletes is inconsistent. This study examined whether acute caffeine ingestion at this threshold improves squat jump (SJ) and countermovement jump (CMJ) performance in NCAA Division II student-athletes, while exploring sex-specific responses and trial-to-trial variability.

Methods: Forty NCAA Division II athletes (18 females, 22 males; 21.3 ± 2.4 years) participated in a single-blind, randomized, crossover trial. Participants ingested 5 mg/kg caffeine or placebo, followed by SJ and CMJ testing on a force platform 60 minutes post-consumption. Three trials per jump type were retained to preserve intra-individual variance. Linear mixed-effects models (LMMs) assessed fixed effects of condition, sex, and trials, with random intercepts and slopes accounting for individual variability. A priori power analyses guided sample size determination, targeting sensitivity to detect small-to-medium effects (Cohen's f ≥ 0.2).

Results: Caffeine elicited trivial, non-significant differences in SJ (β =  -0.24 cm, p = 0.646) and CMJ (β =  -0.71 cm, p = 0.183) heights compared to placebo. Males outperformed females in both SJ (Δ = 9.50 cm, p < 0.001) and CMJ (Δ = 11.30 cm, p < 0.001), though no condition-by-sex interactions emerged. Trial effects were observed, with SJ improving 2.31 cm (p < 0.001) and CMJ 1.05 cm (p = 0.014) from first to second attempts, suggesting warm-up or neuromuscular potentiation. High intraclass correlation coefficients (ICC = 0.76-0.85) underscored substantial interindividual variability. Models demonstrated robust fit (conditional R² = 0.86-0.92), with sufficient power to detect medium-to-large effects (f ≥ 0.25).

Conclusions: A 5 mg/kg caffeine dose, compliant with NCAA thresholds, did not enhance vertical jump performance in habituated collegiate athletes, challenging prior assertions of its universal ergogenicity for ballistic tasks. While sex differences in baseline performance persisted, caffeine did not modulate these disparities, implicating neuromuscular and anthropometric factors as primary determinants. The absence of ergogenic effects aligns with NCAA safety-focused policies but highlights the need for personalized dosing strategies and research into higher doses, genetic variability, and hormonal influences. Future studies should integrate biomechanical metrics and controlled hormonal assessments to elucidate caffeine's nuanced role in anaerobic power sports.

Introduction: Most youth do not meet national nutrition recommendations and overconsume high-calorie, low nutrient-dense foods. Adequate nutritional intake is crucial for growth and development. Nutrition practices play a key role in sports performance and recovery. Nutritional knowledge can affect eating patterns. However, there is limited research on general and sport-specific nutrition knowledge and behaviors of adolescent athletes.

Purpose: To examine general and sport-specific nutrition knowledge and behaviors of adolescent athletes.

Methods: Adolescent athletes were assessed on nutrition knowledge and general and sport-specific nutrition behaviors, including food group consumption, hydration practices, and sport supplement use. Gender differences in general and sport-specific nutrition behaviors were compared using a Mann-Whitney U test. Odds ratios and logistic regression, controlling for age, ethnicity, and years in sport participation were used to determine differences in correct responses between genders. Significance was set at the p < 0.05 level.

Results: One hundred and ninety-four athletes (n = 63 male, n = 132 female, mean age = 14.9 ± 1.63 years) were assessed. Differences in nutrition behaviors were found in fruit, dairy, and sugary beverage consumption between genders. Male athletes were more likely to monitor hydration and use sports supplements. Both males and females scored less than 50% on both general and sport-specific knowledge questions.

Conclusion: Adolescent athletes report lower than recommended food group consumption and lack knowledge of general and sport-specific nutrition information. Improvements in these areas can play a significant role in the health and performance of adolescent athletes.

Background: Caffeine is a well-known ergogenic aid that can enhance physical and cognitive performance. However, it often induces side effects, such as anxiety and overstimulation, which can be problematic in high-pressure sports like wrestling. L-theanine, a non-stimulant amino acid found in tea, may help mitigate these effects by promoting a calm yet focused mental state. This study aimed to investigate the acute effects of caffeine, L-theanine, and their combination on physical performance, cognitive function, and anxiety in elite male wrestlers.

Methods: In a double-blind, placebo-controlled, crossover design, 12 elite male wrestlers (21.8 ± 2.1 years) completed four test sessions under randomized conditions: placebo (PLA), caffeine (CAF; 3 mg/kg), L-theanine (THE; 3 mg/kg), and caffeine + L-theanine (CAF+THE; 3 mg/kg each). After 60 minutes, athletes performed the wall-squat test, vertical jump height (VJH), medicine ball throw (MBT), handgrip strength, and the Specific Wrestling Fitness Test (SWFT). Cognitive function was assessed pre- and post-SWFT using a computerized Stroop test. Anxiety was assessed using the State-Trait Anxiety Inventory (STAI), and side effects were recorded.

Results: CAF+THE outperformed PLA in wall-squat time (p = 0.001), MBT (p = 0.005), VJH (p = 0.011), and grip strength (p = 0.004). SWFT throw count was highest in CAF+THE versus all other conditions (p < 0.001). Post-SWFT Stroop reaction time was faster in CAF+THE than PLA (p = 0.004) and THE (p = 0.036), and accuracy was also higher (p = 0.009 vs PLA). CAF alone increased state anxiety compared to PLA (p = 0.021), while CAF+THE reduced anxiety to below placebo levels (8% incidence vs 33%). Trait anxiety was lower in CAF+THE compared to CAF (p = 0.018). The prevalence of caffeine-induced tachycardia (92%) was notably reduced under CAF+THE (17%).

Conclusion: CAF+THE (3 mg/kg each) enhances elite wrestlers' strength, endurance, cognitive speed, and accuracy while reducing anxiety and physiological side effects commonly associated with caffeine alone. This combination represents a safe, practical supplement strategy for combat sports athletes who must maintain explosive performance and mental control under stress. Coaches are encouraged to trial CAF+THE protocols during training to personalize timing and dosage.

Background: Recent evidence suggests that both animal and plant proteins support strength and hypertrophy gains when paired with resistance training and adequate protein intake. The purpose of this study was to investigate the effects of supplementary protein source (blend of plant-based [PLNT] vs. animal based [ANML]) to habitual diet on changes in muscle mass and strength in healthy young men undertaking resistance training.

Methods: Forty-four young untrained males were recruited for this study. Subjects were randomly allocated into two groups, and consumed three 15-g daily doses (45 g. d-¹ total) of either a mixed plant- (i.e.; soy and pea) or animal-based (i.e.; whey) protein in drink form as a supplementary source of protein in their main meals of the day (i.e.; breakfast, lunch, and dinner) for 12 weeks combined with a 3 times/week linear periodized and supervised resistance training program. Prior to the start of the trial, three (2 nonconsecutive weekdays and 1 weekend day) 24-h dietary recalls were collected to determine baseline habitual protein intake and were repeated during the protocol at weeks 4, 8, and 12. Muscle cross-sectional area (CSA, via ultrasonography imaging) determination, body composition (via dual emission x-ray absorptiometry, DXA), and lower-body maximum dynamic strength (1RM, via leg press) were assessed at baseline (PRE) and after 12 weeks of intervention (POST).

Results: Both groups showed significant (all p < 0.0001) PRE-to-POST increases in whole-body lean mass (PLNT: 2.4 kg ±1.6, ANML: 2.5 kg ±3.9), appendicular lean mass (PLNT: 1.2 kg ±0.2; ANML: 1.8 kg ±0.2) and leg lean mass (PLNT: 0.9 kg ±0.2; ANML: 1.3 kg ±0.2), vastus lateralis mCSA (PLNT: 0.9 cm² ±0.2; ANML: 1.3 cm² ±0.2) and leg-press 1RM (PLNT: 64 kg ±7.8; ANML: 63 kg ±7.5), with no between-group differences for any of the variables (all p > 0.05).

Conclusion: Complementing dietary protein intake with either a blend of plant- or an animal-based protein similarly supported resistance training-induced muscle adaptations.

Trial registration: Distinct Sources of Supplementary Protein in the Resistance Exercise Training-induced Adaptations, NCT05710614, 08/01/2023.

Aim: While it is well established that reducing ectopic fat can help prevent insulin resistance in individuals with overweight or obesity, it remains unclear whether diet alone, exercise alone, or their combination is most effective in reducing specific ectopic fat depots. Therefore, the objective of this study was to investigate the effects of diet-only, and combined diet-plus-exercise interventions versus exercise only on ectopic fat reduction, and weight loss in adults with overweight or obesity.

Methods: Web of Science, PubMed, and Scopus were searched for original articles, published until 1 March 2024 (no limitation on publication dates) that included diet only/or exercise and diet versus exercise alone on body weight, and ectopic fat in adults with overweight or obesity. Weighted mean differences (WMD) for body weight, liver fat, standardized mean differences (SMD) for visceral fat area (VFA), and intramuscular triglyceride (IMTG), and 95% confidence intervals (95% CI) were determined using random-effects models. Studies using noninvasive imaging techniques such as Computerized Tomography (CT), Magnetic Resonance Imaging (MRI), and hydrogen-based Magnetic Resonance Spectroscopy (H-MRs) for ectopic fat were included in this meta-analysis.

Results: A total of 17 studies, including 732 participants aged 24.27 to 70.5 years (309 participants with metabolic diseases, and 423 without metabolic diseases) and 38 intervention groups, met the inclusion criteria. The combined intervention of exercise and diet significantly reduced body weight compared to exercise alone [WMD = -2.85 kg, p = 0.001], with significant reductions observed in both adults with and without metabolic disease, and for interventions lasting more than 12 weeks. However, the combined intervention did not significantly reduce liver fat, VFA, or IMTG compared to exercise alone. Diet-only interventions significantly reduced body weight compared to exercise alone [WMD = -2.57 kg, p = 0.010], but did not significantly affect liver fat, VFA, or IMTG. Meta-regression indicated that weight loss was a significant moderator of the effect of combined interventions on VFA (coefficient: -0.15; p = 0.030), but not for other outcomes. Also, based on subgroup analysis by intervention duration, both exercise and calorie restriction interventions in long-term (more than 12 weeks) have been successful in decreasing VFA in adults with overweight/or obesity.

Conclusion: Combined exercise and dietary interventions are more effective than exercise alone in reducing body weight. While VFA was reduced following long-term interventions of exercise in combination with caloric restriction, our analyses showed no change in liver fat, or IMTG. Additional investigation is required to delve into the processes behind these findings and to pinpoint treatments that efficiently focus on reducing ectopic fat

Background: Childhood and adolescence are critical developmental periods during which dietary protein plays a crucial role in musculoskeletal health. While the significance of protein in muscle development is well acknowledged, the complex associations between dietary protein intake and musculoskeletal parameters during these stages remain incompletely elucidated.

Methods: This cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014 cycles, including 3,455 children and adolescents aged 8-19 years. Dietary protein intake was assessed through two 24-hour dietary recalls. Appendicular lean mass index (ALMI) and combined grip strength were measured as indicators of musculoskeletal health. Multivariate linear regression models and smooth curve fitting techniques were employed to analyze associations.

Results: Higher protein intake was positively associated with both ALMI (β = 0.003, 95% CI: 0.002, 0.004, p < 0.001) and combined grip strength (β = 0.043, 95% CI: 0.027, 0.058, p < 0.001) in fully adjusted models. Notably, sex-specific effects were observed, with stronger associations in boys, particularly in the 8-11 years age group.

Conclusions: This study reveals significant positive associations between dietary protein intake and musculoskeletal health indicators in children and adolescents, with pronounced sex-specific effects. These findings underscore the importance of adequate protein intake during critical developmental periods and may inform targeted nutritional strategies for optimizing long-term musculoskeletal health.