Journal of the International Society of Sports Nutrition最新文献

Background: Carbohydrate mouth rinsing (CHO-MR) during periods of fasting or low muscle glycogen availability could provide a more pronounced ergogenic effect compared to fed and high muscle glycogen conditions. However, there is little evidence investigating the efficacy of CHO-MR during periods of low muscle glycogen induced by ketogenic diets. Therefore, this study aimed to investigate the impact of CHO-MR vs. a placebo (PLA-MR) on cycling time trial performance in trained endurance cyclists following their habitual diet (HD) or a 5-day ketogenic diet (KD).

Methods: Eight participants completed baseline testing and four trial conditions. For each trial, participants adhered to either their HD or a KD for 5 consecutive days. During the first 4 days of each dietary phase, they tracked daily nutrition; additionally, they recorded morning fasting blood glucose and β-hydroxybutyrate (βHB) levels for the 4 days preceding and the morning of each trial. Each trial comprised a 33.6 km simulated time trial in which rinsing was performed for ten seconds at 7 km intervals.

Results: The 5-day KD significantly increased the time to completion (TTC) compared to HD (p < .001). Although no significant differences in TTC were detected between HD + CHO-MR and KD + CHO-MR (p = .670), CHO-MR did not restore KD performance to within 2% of HD conditions (±158 s; 4.8%). While a significant main effect for diet on morning fasted blood [βHB] (p = .001) was observed on day 5, it was not significantly associated with exercise time (r ₍₁₄₎ = -.442, p = .086). Post-exercise blood [glucose] was significantly higher in the HD + CHO-MR and HD + PLA-MR conditions compared to the KD + CHO-MR (p = .038 & p = .021), and KD + PLA-MR (p = .011 and p = .003) conditions, respectively.

Conclusion: The data indicate that repeated 6.4% CHO-MR during endurance cycling is insufficient to overcome performance impairments induced via a 5-day ketogenic diet. This suggests that peripheral substrate availability may constrain the hepatic glucose output in response to central nervous system cues. Further research is required to elucidate how peripheral glycogen stores, central neural drive, and ergogenic interventions interact under low-carbohydrate conditions.

Background: Sarcopenia may disrupt the hypothalamic‒pituitary‒adrenal axis, affecting neurotransmitter and hormone levels. However, the impact of sarcopenia on these markers, particularly in comparison to non-sarcopenic controls, is understudied. Additionally, the effects of resistance exercise and nutritional support on neurotransmitter levels in sarcopenic patients are largely unknown. This study explores these neurochemical changes and their response to therapeutic interventions.

Methods: This post hoc analysis of a randomized controlled trial included 57 sarcopenic and 57 non-sarcopenic participants from the same cohort. Grip strength and body composition were measured. Sarcopenic patients received a 12-week intervention involving resistance exercise and supplementation with branched-chain amino acids, calcium, and vitamin D3. Plasma adrenaline, noradrenaline, dopamine, serotonin, and cortisol were assessed using enzyme-linked immunosorbent assay (ELISA).

Results: Sarcopenic individuals had significantly lower levels of serotonin (13.28 vs 19.21  ng/mL, p = 0.002), adrenaline (97.6 vs 110.9  pg/mL, p < 0.001), and noradrenaline (169.2 vs 302.5  pg/mL, p < 0.001), with a trend toward reduced dopamine (246.9 vs 270.6  pg/mL, p = 0.053). Cortisol levels were similar between the groups (48.2 vs 49.5  ng/mL, p = 0.436). Generalized estimating equations adjusted for age and gender, showed sarcopenia was linked to reduced serotonin (β = -5.92, p = 0.002), adrenaline (β = -13.32, p < 0.001), and noradrenaline (β = -132.9, p < 0.001), while the intervention raised noradrenaline levels (β = 27.75, p = 0.001).

Conclusion: Sarcopenic patients exhibit lower serotonin, adrenaline, and noradrenaline compared to non-sarcopenic controls, with no significant difference in cortisol levels. Resistance exercise and nutritional interventions increased noradrenaline in sarcopenic individuals. Further studies are needed to evaluate the long-term effects on neurotransmitter and hormone levels.

Background: Caffeine is a popular ergogenic aid in high-intensity sports, but it can cause side effects like cardiovascular stress and tolerance buildup. Theacrine, a structurally similar purine alkaloid, may offer comparable performance benefits with fewer adverse effects. This study aimed to assess the acute effects of theacrine, caffeine, and their combination on performance and physiological responses in elite canoe sprint athletes.

Methods: Twenty highly trained male canoe sprint athletes participated in a randomized, double-blind, placebo-controlled, crossover trial with four conditions: placebo (P), caffeine (K), theacrine (T), and a combination of caffeine and theacrine (KT). Each participant completed a 500-meter time trial and a 30-second Wingate Anaerobic Test (WAnT) on a kayak ergometer under each condition. Primary outcomes included race time, power output, muscle oxygen saturation (SmO₂), total hemoglobin (THb), and maximal accumulated oxygen deficit (MAOD), which were measured using near-infrared spectroscopy (NIRS) and VO₂ analysis.

Results: Caffeine significantly improved the 500-meter time trial (-1.872 s vs. P, p < 0.001) and WAnT distance (+2.31 m, p = 0.005), while KT produced smaller but still significant effects. Theacrine alone (T) did not lead to statistically significant performance improvements. Caffeine increased MAOD (p < 0.005), whereas KT and T showed non-significant changes. SmO₂ and THb slopes were not significantly affected in any condition, suggesting that performance gains were mediated by mechanisms other than local oxygen delivery. No significant differences were observed in heart rate, blood pressure, or perceived exertion across conditions. Strong negative correlations between race time and power output-especially under caffeine-indicated that mechanical output is the primary factor influencing performance.

Conclusion: Caffeine remains a powerful ergogenic aid in sprint paddling, enhancing both mechanical output and muscle oxygen utilization. Although theacrine alone showed limited ergogenic effects, its combination with caffeine produced additional improvements compared to placebo, indicating a possible complementary role. These findings support targeted supplementation strategies in elite sports.

Background: Although environmental chambers have traditionally been used to study passive dehydration and recovery in the context of sports nutrition, portable infrared saunas may provide a more accessible and cost-effective alternative. This study aimed to assess the efficacy and test-retest reliability of achieving target body mass (BM) losses using a portable infrared sauna.

Methods: Fifteen healthy adults (11 males: 22.46 ± 2.70 years, 175.48 ± 6.54 cm, 76.35 ± 9.78 kg; 4 females: 21.00 ± 2.58 years, 163.10 ± 2.79 cm, 54.78 ± 4.25 kg) completed two identical dehydration trials separated by at least 72 hours. After a standardized warm-up, participants alternated for up to 20 minutes of sauna exposure (~66 °C) with 5 minutes of rest (~23 °C) until reaching 2.8% ± 0.3% (males) or 2.4% ± 0.3% (females) BM loss. The dependent variables were total sauna time, maximum core temperature (MCT), average sauna temperature when entering, average sauna temperature when exiting, absolute BM loss, relative BM loss, absolute BM loss per 60 minutes, and relative BM loss per 60 minutes. Reliability was evaluated using a two-way fixed intraclass correlation coefficient (ICC) and coefficients of variation (CVs; acceptable <15%).

Results: The point estimate ICCs ranged from 0.710 to 0.969, with CVs < 5%. There were significant intertrial differences for MCT (Trial 1 > Trial 2, p < 0.05), whereas all other variables demonstrated no significant differences.

Conclusions: These findings indicate that a portable infrared sauna protocol yields reliable dehydration outcomes (CV < 5%; ICC > 0.75) and achieves > 2% BM loss in under 180 minutes, supporting its use when environmental chambers are unavailable.

Background: Amino acids activate neutrophil phagocytosis and free radical release in vitro.

Aim: We examined the effects of amino acid supplementation on post-exercise accumulation of myeloperoxidase-positive (MPO⁺) cells in human skeletal muscle using a randomized, double-blind, placebo-controlled crossover design.

Methods: Ten young men (22 ± 2.8 years) consumed either amino acids (15 g) or an isocaloric placebo before resistance exercise. Biopsies of the vastus lateralis muscle were collected at baseline, immediately after exercise (0 h), and 24 h post-exercise.

Results: Resistance exercise increased MPO⁺ cell infiltration (+161%, p = 0.02) and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels (+66%, p = 0.02) at 24 h. Amino acid supplementation accelerated MPO⁺ cell infiltration to 0 h (+100%, p = 0.03), which diminished by 24 h post-exercise (+53%, p = 0.06). Immunofluorescence co-staining revealed that MPO⁺ cells exhibited markedly higher mitochondrial density (TOM20-labeled) and integrated with the injured regions of adjacent myofibers showing lower mitochondria. Other infiltrating MPO-negative cells also contributed mitochondria to exercised muscle tissue, resulting in an overall ~2-fold increase in mitochondrial content during 24-h recovery (p < 0.001), similar under both supplementation conditions. Cellular senescence marker p16Ink4a mRNA decreased by 58% at 24 h post-exercise, with an earlier reduction observed under amino acid treatment (0 h: -49%, p = 0.05).

Conclusion: These findings indicate that amino acid supplementation accelerates the resolution of inflammation in exercised human skeletal muscle. Immunofluorescence evidence further suggests that infiltrating bone marrow-derived cells contribute to fast mitochondrial gains as part of the muscle damage-response following exercise.

Background: The female athlete triad (Triad) refers to the interrelationship between energy availability, menstrual function, and bone health, which may have clinical and subclinical manifestations including eating disorders, functional hypothalamic amenorrhea, and osteoporosis. The aim of this study was to analyze the prevalence of physically active 15- to 45-year-old Spanish women at risk for the Triad.

Methods: A descriptive cross-sectional study was carried out using the validated questionnaires 'Low Energy Availability in Females Questionnaire' (LEAF-Q) and the 'Female Athlete Screening Tool' (FAST). Exercising women were invited to participate anonymously and voluntarily by email via Spanish sports clubs and federations, as well as through social networks. The questionnaires were also distributed to elite athletes attending the High Performance Center of Sant Cugat del Vallès (Barcelona).

Results: The study participants comprised 1154 physically active women (age = 28.5 ± 7.7 years; height = 165.2 ± 6.2 cm; body weight = 60.5 ± 9.7), representing 78 recreational and competitive level sports. The results showed that 40.0% (n = 462) were considered at risk for the Triad, while 24.3% (n = 280) were at risk for subclinical eating disorder, and 7.3% (n = 84) at risk for clinical eating disorder. Other results were: menstrual dysfunction displayed a positive correlation with the LEAF-Q score (r = 0.499, p = < 0.001); FAST presented an association with the LEAF-Q score (r = 0.252, p < 0.001); and body weight (r = 0.207, p = < 0.001) and body mass index (r = 0.225, p = < 0.001) displayed a positive correlation with the FAST score.

Conclusion: Based on this research, the implementation of strategies for the prevention, diagnosis and treatment of the Triad disorders should be made a priority among physically active Spanish women.

Background: This study investigates the combined effects of time-restricted eating (TRE) and Tai Chi exercise (EX) on glycolipid metabolism and endothelial function in postmenopausal women, a population at heightened risk of metabolic and vascular disorders.

Materials and methods: A total of 142 postmenopausal women aged 50-60 years were randomly assigned to one of three groups: TRE combined with Tai Chi (TRE + EX, n = 47), TRE alone (n = 47), or a control group with conventional lifestyle (CON, n = 48). The TRE protocol required participants to consume all meals within an 8-hour window for 8 weeks, while the EX protocol involved three weekly 60-minute sessions of Yang-style 24-form Tai Chi. Outcomes included glycolipid markers, such as fasting plasma glucose, total cholesterol (Tot-Chol), and low-density lipoprotein cholesterol (LDL-C), as well as endothelial function assessed by flow-mediated dilation (FMD), nitric oxide (NO), and endothelin-1 (ET-1).

Results: Significant group-by-time interactions were observed for Tot-Chol (p = 0.001) and LDL-C (p = 0.003), with the TRE + EX group showing the largest reductions compared to the TRE group (p = 0.030; p = 0.003) and the CON group (p = 0.000; p = 0.050). For FMD, a significant interaction was also observed (p = 0.003). Both the TRE + EX group and the TRE group showed significant improvements in FMD compared to baseline (p = 0.005; p = 0.044). However, only the TRE + EX group demonstrated significantly higher FMD than the CON group (p = 0.003).

Conclusion: The combination of TRE and Tai Chi was more effective in improving lipid profiles and endothelial function than TRE alone. These findings highlight the potential of integrating dietary timing with structured exercise as a strategy for enhancing metabolic and vascular health in postmenopausal women.

Background: Electronic sports (esports) are a growing global phenomenon engaging millions of competitive players worldwide. Caffeine is a widely used compound for individuals seeking cognitive enhancement. However, evidence on consumption patterns, motivations, and safety in esports remains limited. We aimed to describe daily caffeine intake among Brazilian esports players and examine associations with competitive level, gaming habits, and adverse effects.

Methods: Cross-sectional study of 181 Brazilian esports players. A 64-item questionnaire captured demographics, gaming habits, and caffeine intake from all dietary sources. We compared amateurs vs semi-professional/professional players and performance-motivated vs other motivations, and examined dose-response using intake categories (≤100, 101-300, 301-600, >600 mg/day) and correlations for continuous variables.

Results: Median 168 mg/day (IQR 52-402; mean 280 ± 316); coffee was the main source (72.2% of total), and 55.8% consumed energy drinks, contributing 14.0% of intake. Overall, 25.7% exceeded 400 mg/day (46/179); intake did not differ between competitive levels (Amateur 172 vs Semi-Pro/Pro 121 mg/day; p = 0.387). No correlation with gaming hours (ρ = 0.068; p = 0.369). Under the primary positivity rule (≥"occasional"), adverse effects were common among respondents with symptom frequency data: any adverse effect 76.5%, insomnia 45.2%, tachycardia 29.1%, stomach pain 45.5%, tremors 23.7%. Linear trend tests across dose categories were not significant (any 0.822; insomnia 0.530; tachycardia 0.905; stomach pain 0.409; tremors 0.877), and per-category effect sizes were small (r-trend ≈ 0.01-0.08; OR per +1 category ≈ 0.89-1.16). Comparing >300 vs ≤300 mg/day for any adverse effect yielded OR 1.38 (95% CI 0.56-3.45). Performance-motivated players (12.6%) consumed more (+89 mg/day; p < 0.001). Using caffeine to combat fatigue (56.0%) was associated with higher insomnia (OR 2.50; 95% CI 1.37-4.55; q = 0.004). Notably, insomnia was common (45.2%), underscoring applied relevance.

Conclusions: Brazilian esports players show moderate caffeine intake, mainly from coffee. Adverse effects were common, although linear dose-response across intake categories was not observed; the observed fatigue-caffeine cycle highlights the need for practical guidance on timing and source awareness, alongside sleep-hygiene strategies, to support sustainable performance.

Objective: This study examined whether caffeine (4 mg/kg) enhances upper- and lower-body maximal strength and muscular power by increasing muscle recruitment and reducing in ratings of perceived exertion (RPE) and pain perception.

Methods: Fourteen resistance-trained males completed two randomized trials involving either caffeine ingestion (4 mg/kg) or a placebo. Sixty minutes after ingesting capsule, participants performed maximal strength tests (one-maximum repetition [1RM]) followed by muscular power assessments (bar velocity and power output) at 25%, 50%, 75%, and 90% of 1RM, performing 3, 2, 1, and 1 repetitions, respectively during bench press and back squat. Outcome measured included 1RM, mean and peak velocity, mean and peak power output, surface electromyographic activity of the prime movers, RPE, and pain perception.

Results: Compared to placebo, caffeine significantly increased 1RM in both bench press and back squat, while reducing RPE and pain perception and enhancing root mean square (RMS) activity in the gluteus maximus (all p < 0.05), though it did not affect the median frequency (MDF) or mean frequency (MF) in any studied muscle (all p > 0.05). The percent improvement in 1RM was larger (+7.0 ± 2.9% vs. + 4.1 ± 2.9%; p < 0.05) for the back squat than for the bench press. Furthermore, caffeine significantly increased muscular power during both exercises (all p < 0.05), without affecting surface electromyographic activity of the prime movers, RPE, and pain perception (all p > 0.05).

Conclusion: Ingesting a caffeine capsule at a dose of 4 mg/kg enhances maximal strength by increasing muscle recruitment and reducing RPE and pain perception, with greater improvement observed in the bench press than in the back squat. Caffeine also improves muscular power in both exercises without altering muscle recruitment or subjective perception.