Journal of the International Society of Sports Nutrition最新文献

Background: The aim of this study was to explore the effects of a low dose (LD) of 0.625 mg and a high dose (HD) of 2.5 mg of phenylcapsaicin (PC) on full squat (SQ) performance, active muscle (RPE-AM) and overall body (RPE-OB) ratings of perceived exertion, muscle damage, protein breakdown, metabolic response, and 24-h recovery in comparison to placebo (PLA).

Method: Twenty-five resistance-trained males (age = 21.00 ± 2.15 years, SQ 1-repetition maximum [1RM] normalized = 1.66 ± 0.22 kg) were enrolled in this randomized, triple-blinded, placebo-controlled, crossover trial. Participants completed 2 weekly sessions per condition (LD, HD, and PLA). The first session consisted of pre-blood testing of lactate, urea, and aspartate aminotransferases (AST) and 2 SQ repetitions with 60% 1RM followed by the resistance exercise protocol, which consisted of SQ sets of 3 × 8 × 70% 1RM monitoring lifting velocity. RPE-OB and RPE-AM were assessed after each set. After the first session, 2 SQ repetitions with 60% 1RM were performed, and blood lactate and urea posttests were collected. After 24 h, AST posttest and 1 × 2 × 60% 1RM were determined as biochemical and mechanical fatigue outcomes.

Results: HD reported significant differences for RPE-AM, AST, and SQ performance compared to LD and PLA. Post-hoc analyses revealed that HD attained faster velocities in SQ than LD (p = 0.008). HD induced a lower RPE-AM when compared with LD (p = 0.02) and PLA (p = 0.004). PLA resulted in higher AST concentrations at 24-h post than HD (p = 0.02). No significant differences were observed for the rest of the comparisons.

Conclusions: This study suggests that PC may favorably influence SQ performance, RPE-AM, and muscle damage compared to PLA. However, HD exhibited most of the biochemical and mechanical anti-fatigue effects instead of LD.

Background: YouTube is one of the most widespread social media channels, which is of growing importance in science communication and health education. The validity of medical and health-related information available on YouTube cannot be assured, and videos often contain potentially misleading or inaccurate information. Communication on sport nutrition may have a profound effect on the change in nutrition behavior among athletes, so evidence-based nutrition information must reach athletes. The main goal of the research is to evaluate the quality, reliability, and applicability of sports nutrition YouTube videos as educational material for athletes.

Methods: A descriptive cross-sectional design was applied, and a systematic search was performed on YouTube. The quality and reliability of the videos were evaluated by applying the most frequently used and highly reliable scoring systems in the literature (e.g., DISCERN, Global Quality Score, and JAMA criteria) and a sports nutrition-specific scoring system (SNSS). Descriptive statistical analyses, two-sample t-test, Spearman correlation, Kruskal - Wallis, and Mann - Whitney U test were used to evaluate the results. A total of 114 YouTube videos met the inclusion criteria.

Results: In 25% of the videos, the sports nutrition information was presented by a dietitian, while in two-thirds, coaches and athletes and other professionals shared sports nutrition knowledge. In terms of video content, the three most common topics were nutrition and health (33%), special diets (21%), and the training diet (17%). For the majority of the videos that received low GQS, JAMAS, DISCERN, and SNSS scores, the accuracy and quality of the analyzed YouTube videos on sports nutrition were inadequate. Videos uploaded by dietitians achieved significantly higher DISCERN, JAMAS, GQS, and SNSS scores. The GQS, SNSS, and DISCERN scores of videos from sports organizations, nonprofit organizations, and independent user sources were lower compared to videos uploaded by academic and professional organizations. Popular sport nutrition videos among users that contain personal stories or the experiences of athletes were deemed less reliable by experts or showed lower educational quality. Henceforth, we found a negative correlation between video popularity and JAMAS, GQS, and SNSS scores.

Conclusion: This study revealed that sports nutrition videos on the YouTube video platform show low accuracy and reliability. Professionals working with athletes need to consider misconceptions from sports nutrition videos in their nutrition counseling practice. Due to the popularity of the videos, professionals and professional organizations could use YouTube as an online educational tool to increase the nutrition knowledge of athletes.

Background: Iron deficiency (ID) and iron deficiency anemia (IDA) are long-standing health problems in athletes, affecting both performance and health. ID prevalence in young athletes remains high and a matter of concern. ID and IDA can lead to fatigue, reduced endurance, and decreased oxygen transport, potentially compromising athletic performance. We hypothesized that ID would still be a major health concern in university athletes across sports clubs in Japan.

Purpose: The study aimed to investigate the prevalence of ID and IDA in athletes participating in Kendo, badminton, baseball, and handball at the University of Tsukuba (Tsukuba, Ibaraki Prefecture, Japan). The study also examined the correlation between hypoferritinemia and other variables, such as previous use of iron supplements, body mass index (BMI), energy intake, and years of athletics.

Methods: Between January and December 2019, 126 university athletes, consisting of 79 males and 47 females, underwent physical measurements and blood tests. The blood test included complete blood count, levels of serum ferritin, serum iron, and total iron-binding capacity. The anemia was defined in accordance with the WHO criteria. Daily energy and iron intake were estimated with the food frequency questionnaire in Japanese (FFQg). Thirty-four female athletes responded to a survey about their menstruation and low-dose estrogen-progestin (LEP) usage.

Results: While none of the athletes had anemia, 22 (47%) female athletes exhibited serum ferritin levels of 30 ng/mL or less, defining them as hypoferritinemia. The multivariate logistic regression model revealed that a shorter duration of the athletic experience (adjusted odd ratio [95% confidence interval]: 0.62 [0.43-0.90]), lower energy intake (0.994 [0.989-0.999]), and higher dietary iron intake (4.40 [1.12-17.26]) were associated with hypoferritinemia. Seventeen (50%) female athletes reported a decline in subjective performance during menstruation, albeit two took LEP regularly.

Conclusions: This study reveals that ID is a prevalent health concern among young female athletes across sports clubs. It underscores the need for their education on the importance of assessing ID status. Limitation includes the nature of single-site and observational study, the absence of hepcidin measurement, and an unspecified amount of exercise. Comprehensive investigations are needed to elucidate the causes and optimal treatments for ID in young athletes.

Position Statement: The International Society of Sports Nutrition (ISSN) presents this position based on a critical examination of literature surrounding the effects of essential amino acid (EAA) supplementation on skeletal muscle maintenance and performance. This position stand is intended to provide a scientific foundation to athletes, dietitians, trainers, and other practitioners as to the benefits of supplemental EAA in both healthy and resistant (aging/clinical) populations. EAAs are crucial components of protein intake in humans, as the body cannot synthesize them. The daily recommended intake (DRI) for protein was established to prevent deficiencies due to inadequate EAA consumption. The following conclusions represent the official position of the Society: 1. Initial studies on EAAs' effects on skeletal muscle highlight their primary role in stimulating muscle protein synthesis (MPS) and turnover. Protein turnover is critical for replacing degraded or damaged muscle proteins, laying the metabolic foundation for enhanced functional performance. Consequently, research has shifted to examine the effects of EAA supplementation - with and without the benefits of exercise - on skeletal muscle maintenance and performance. 2. Supplementation with free-form EAAs leads to a quick rise in peripheral EAA concentrations, which in turn stimulates MPS. 3. The safe upper limit of EAA intake (amount), without inborn metabolic disease, can easily accommodate additional supplementation. 4. At rest, stimulation of MPS occurs at relatively small dosages (1.5-3.0 g) and seems to plateau at around 15-18 g. 5. The MPS stimulation by EAAs does not require non-essential amino acids. 6. Free-form EAA ingestion stimulates MPS more than an equivalent amount of intact protein. 7. Repeated EAA-induced MPS stimulation throughout the day does not diminish the anabolic effect of meal intake. 8. Although direct comparisons of various formulas have yet to be investigated, aging requires a greater proportion of leucine to overcome the reduced muscle sensitivity known as "anabolic resistance." 9. Without exercise, EAA supplementation can enhance functional outcomes in anabolic-resistant populations. 10. EAA requirements rise in the face of caloric deficits. During caloric deficit, it's essential to meet whole-body EAA requirements to preserve anabolic sensitivity in skeletal muscle.

Introduction: Chronic pain affects 19% of adults in the United States, with increasing prevalence in active and aging populations. Pain can limit physical activity and activities of daily living (ADLs), resulting in declined mental and social health. Nutritional interventions for pain currently target inflammation or joint health, but few influence both. Collagen, the most abundant protein in the human body and constituent of the extra cellular matrix, is such a nutraceutical. While there have been reports of reductions in pain with short-term collagen peptide (CP) supplementation, there are no long-term studies specifically in healthy middle-aged active adults.

Purpose: To determine the effects of daily CP consumption over 3, 6, and 9 months on survey measures of pain, function, and physical and mental health using The Knee Injury & Osteoarthritis Outcomes Score (KOOS) and Veterans Rand 12 (VR-12) in middle-aged active adults.

Methods: This study was a double-blind randomized control trial with three treatment groups (Placebo, 10 g/d CP, and 20 g/d CP).

Results: Improvements in ADLs (p = .031, η_p² = .096) and pain (p = .037, η_p² = .164) were observed with 10 g/d CP over 6 months, although pain only improved in high frequency exercisers (>180 min/week). Additionally, VR-12 mental component scores (MCS) improved with 10 g/d of CP over 3-9 months (p = .017, η_p² = .309), while physical component scores (PCS) improved with 20 g/d of CP over 3-9 months, but only in females (p = .013, η_p²= .582).

Conclusion: These findings suggest 10 to 20 g/d of CP supplementation over 6 to 9 months may improve ADLs, pain, MCS, and PCS in middle-aged active adults.

Background: Citrulline may amplify the effects of L-arginine and nitric oxide concentration, which may augment vasodilation and blood flow, thereby enhancing aerobic exercise performance. The purpose of this randomized, double-blind, placebo-controlled crossover study was to investigate effects of L-citrulline + Glutathione on aerobic exercise performance and blood flow in well-trained men.

Methods: Twenty-five males (Mean ± SD; Age: 22.2 ± 2.4 yrs; Height: 177.0 ± 4.8 cm; Weight: 75.3 ± 6.9 kg) were randomly assigned to the L-citrulline + Glutathione (Setria Performance Blend: SPB; L-citrulline [2 g] + glutathione [200 mg], 6 capsules) or placebo (PL; 3.1 g cellulose, 6 capsules) group. Participants performed a maximal oxygen consumption treadmill test to determine peak velocity (PV) and returned after eight days of ingesting either PL or SPB. Three timed treadmill runs to exhaustion (TTE) were performed at 90%, 100%, and 110% PV. Brachial artery blood flow and vessel diameter were assessed using ultrasound at 1-hr prior to exercise (1hrPrEX), after each exercise bout, immediately post-exercise (immediate PEX), and 30 minutes post exercise (30minPEX) at visits 2 and 4. Blood analytes were assessed via venous blood draws at visit 1, visit 3, and 1hrPEX, immediate PEX, and 30minPEX at visits 2 and 4. After a 14-day washout, participants repeated the same procedures, ingesting the opposite treatment. Separate repeated measures ANOVAs were performed for TTE, vessel diameter, blood flow, and blood analytes.

Results: Blood flow was significantly augmented 30minPEX (p = 0.04) with SPB in comparison with PL. L-citrulline and L-arginine plasma concentrations were significantly elevated immediately PEX (p = 0.001) and 30-minPEX (p = 0.001) following SPB in comparison to PL.

Conclusion: Acute ingestion of SPB after eight days may enhance blood flow, L-citrulline, and L-arginine plasma concentrations after high-intensity exercise, which may enhance performance.

Clinical trial registration: [https://clinicaltrials.gov/ct2/show/nct04090138], identifier [NCT04090138].

Background: Pre-exercise protein consumption does not seem to influence substrate metabolism during exercise compared to fasted exercise, however it is unclear if the protein dose impacts on this effect.

Methods: In a randomized, double-blinded within-subject design trial, healthy, active males and females (n = 15, 25 ± 5 yrs, O2peak: 47.5 ± 8.8 ml/kg/min) completed 1 h of cycling exercise at 60% peak power output 30 min after having consumed either 0, 20, or 40 g of whey protein. Indirect calorimetry was used to measure substrate oxidation during exercise and baseline and post-exercise resting energy expenditure. Blood samples were taken throughout the trials to measure metabolic responses. Free-living food intake post-trial was collected using food diaries.

Results: Fat oxidation rates during exercise did not differ between the three conditions (p = 0.19) with small effect sizes between conditions (Cohen's dz: 0 vs. 20 g = 0.22, 0 vs. 40 g = 0.47, 20 vs. 40 g = 0.27). Serum insulin was higher in the protein groups vs. 0 g (p < 0.05), whereas non-esterified fatty acids were higher in the 0 g compared to 20 and 40 g (p < 0.05). Glucose was significantly lower after 15 min of exercise in 20 and 40 g vs. 0 g (p = 0.01). Resting energy expenditure was elevated post-exercise (p < 0.001), without an interaction for protein dose (p = 0.90). Post-trial free-living energy intake was not different between conditions (p = 0.31), but 24-h energy intake was significantly higher in 40 vs. 0 g (p = 0.04).

Conclusion: Protein doses up to 40 g do not seem to impair fat oxidation rates during exercise compared to fasted exercise and could be considered as a nutritional strategy for exercising individuals who struggle to include fasted exercise in their training.

Background: Sport-related nutritional supplements (SRNS) include sport drinks, sport bars, and sport gels. This investigation examined temporal patterns in SRNS use and adverse effects (AEs) reported by a single cohort of United States active-duty service members (SMs) surveyed before and during the coronavirus disease 2019 (COVID-19) pandemic.

Methods: A stratified random sample (n = 22,858) of SMs (Air Force, Army, Navy, and Marine Corps) who completed a questionnaire on their SRNS use and AE experiences and were still on active duty were asked to complete the identical questionnaire on a second occasion. Twenty-five percent of successfully contacted SMs completed both questionnaires (n = 5,778) and were included in this investigation. The average ± standard deviation time between questionnaires was 1.3 ± 0.2 years.

Results: Prevalence of reported SRNS use ≥1 time/week in the baseline (BL) and follow-up (FU) phases were as follows: any SRNS: BL = 46%, FU = 41%; sport drinks: BL = 31%, FU = 28%; sport bars: BL = 30%, FU = 24%; sport gels: BL = 4%, FU = 4%. Reported weekly aerobic and resistance training durations were reduced in the FU period (8% and 26%, respectively). The proportion of SMs reporting SRNS use in both study phases was as follows: any SRNS = 62%, sport drinks = 54%, sport bars = 50%, sport gels = 35%. Prevalence of reported AEs in the BL and FU phases were as follows: any SRNS: BL = 1.9%, FU = 1.9%; sport drinks: BL = 1.0%, FU = 1.3%; sport bars: BL = 1.7%, FU = 1.4%; sport gels: BL = 3.3%, FU = 2.5%. The proportion of SMs reporting AEs in both phases was as follows: any SRNS = 14%, sport drinks = 11%, sport bars = 17%, sport gels = 0%.

Conclusions: Overall SRNS use prevalence decreased slightly in the FU period, possibly because of reduced physical training related to military restrictions imposed during the emergence of COVID-19 between surveys. A large proportion of SMs reported changing their use patterns in the FU with some discontinuing use and others initiating use. The AE incidence was similarly low in the BL and FU phases, and few SMs reported AEs in both phases suggesting AEs were transitory. AE reporting for SRNSs was much lower than previously found for dietary supplements, possibly because of greater government regulatory control over SRNSs.