Strenuous endurance exercise imposes substantial physiological stress on the cardiovascular system and has been associated with transient elevations in cardiac biomarkers. Vitamin D₃ has been suggested to influence oxidative stress and immune responses. In this study, we investigated the effects of vitamin D₃ supplementation on biomarkers of cardiac, muscle, and immune responses following a marathon race. Twenty-one amateur runners were allocated to either a vitamin D₃ supplementation group (receiving vitamin D₃ for 8 weeks) or a placebo group. All participants completed an official full marathon (42.195 km). Blood biomarkers were measured from 24 h before to 24 h after the race. Post-race increases in markers of muscle damage and cardiac stress were observed. Vitamin D₃ supplementation was associated with attenuated elevations in selected biomarkers demonstrating significant interaction effects. Compared with the placebo group, the vitamin D₃ group demonstrated attenuation of protein carbonyls (PC), the only oxidative stress marker showing a significant Group × Time interaction. No significant interaction effects were observed for thiobarbituric acid reactive substances (TBARS) or antioxidant enzymes. Both groups showed post-race increases in white blood cell counts, particularly neutrophils, whereas lymphocyte counts significantly decreased at 0.5 h and 2 h post-race. Immunoprofiling revealed time-dependent alterations in selected immune cell subsets, although no significant interaction effects were detected. Descriptive differences in recovery patterns were observed between groups, and exploratory correlation analyses suggested time-specific associations between immune cell subsets and biochemical markers during recovery. Vitamin D₃ supplementation may attenuate PC responses and was associated with lower creatine kinase (CK) and creatine kinase-MB (CK-MB) levels at 24 h post-race following marathon running. Immune alterations were time-dependent, with descriptive differences in recovery patterns between groups.

ABSTRACTBackgroundAlthough caffeine is widely used in athletes due to its ergogenic effects, the effects of its main metabolite, paraxanthine, on performance and sleep have not been adequately investigated.PurposeThis study aimed to comparatively investigate the effects of caffeine and its main metabolite paraxanthine on rowing performance and sleep quality.MethodsThe study was designed as a randomized, double-blind, crossover study and included 14 male university-level rowers (21.6 ± 1.9 age; 2.2 ± 1 years of rowing experience). The participants participated in 2000-m rowing ergometer time trials under four different supplementation conditions (caffeine + paraxanthine, caffeine + placebo, paraxanthine + placebo, and placebo with 200 mg each). Performance data (completion time, mean power, and heart rate), sleep quality, and daytime sleepiness were assessed by subjective scales. The data were analyzed by repeated-measures analysis of variance (ANOVA) and Bonferroni post-hoc tests.ResultsCompared with the placebo, the combined caffeine + paraxanthine condition was associated with faster 2000-m performance and higher mean power output (p = 0.044; Cohen's d = 0.30). Caffeine alone and paraxanthine alone did not show clear evidence of performance improvement in this sample, although estimates favored both conditions versus placebo. Conditions containing caffeine were associated with poorer subjective sleep quality, whereas paraxanthine alone showed more favorable sleep-related outcomes.ConclusionThese results indicate that the combined ingestion of caffeine and paraxanthine elicited the most pronounced performance benefits, while paraxanthine alone did not demonstrate clear standalone ergogenic efficacy at the administered dose. However, paraxanthine was associated with better subjective sleep outcomes compared to caffeine, suggesting that its potential value may be related more to tolerability rather than superior performance enhancement, particularly for athletes training in the evening. Study limitations, including the small sample size and lack of objective sleep measures, should be considered when interpreting the results.Practical applicationsParaxanthine may represent a practical option for athletes who prioritize sleep quality or experience sensitivity to caffeine-related sleep disturbances, although further dose‒response studies are required to clarify its ergogenic potential.

BackgroundCreatine is one of the most extensively studied ergogenic aids, with over three decades of research supporting its role in exercise performance, recovery, and health.MethodsThis narrative review summarizes the historical development of creatine supplementation and evaluates evidence regarding its mechanisms, efficacy across active, athletic populations (e.g. strength, endurance, team-sport), and tactical (e.g. military, law enforcement) populations, and its safety profile.ResultsThe evidence suggests that creatine enhances phosphocreatine resynthesis and cellular energy availability, resulting in consistent improvements in high-intensity exercise performance, training adaptations, lean body mass, strength, and power. Additional findings indicate that creatine may attenuate exercise-induced muscle damage and inflammation, support recovery, and improve functional outcomes following strenuous activity. Emerging research suggests benefits for endurance and team-sport athletes through enhanced glycogen resynthesis, calcium handling, oxidative stress mitigation, and repeated-sprint performance. In tactical populations, creatine may support occupational readiness by improving strength, hydration status, thermoregulation, cognition, sleep quality, and recovery, with possible neuroprotective and cardiometabolic implications. Soccer-specific evidence demonstrates improvements in repeated-sprint ability and tolerance to high training loads, with preliminary data suggesting protective effects against neurotrauma and gut barrier disruption. Importantly, pooled analyses from hundreds of clinical trials report no greater incidence of adverse events compared with placebo, reinforcing creatine's established safety profile.ConclusionOverall, the evidence suggests that creatine is a versatile supplement with strong evidence to enhance performance and recovery across diverse populations. Future research should prioritize individualized dosing strategies, long-term outcomes in underrepresented groups, and exploration of novel therapeutic applications in health and disease

BackgroundAge-associated sarcopenia and declining physical function in older women are connected to changes in hormones, inflammation, and disrupted protein metabolism. Myokines and cytokines play central roles in muscle atrophy. While both resistance exercise (RE) and essential amino acid (EAA) supplementation are promising interventions, limited randomized trials have assessed their combined effect in healthy elderly populations. Early targeted strategies may help delay sarcopenia and promote healthier aging.MethodsA 12-week randomized controlled trial was performed involving 96 healthy women aged ≥ 65 years without insulin resistance. Participants were randomized into four groups: control, RE, EAA, or RE + EAA. The intervention consisted of a circuit-based training program conducted three times per week, with each session lasting 60 minutes at moderate intensity. Participants in EAA and RE + EAA groups consumed 5.5g of EAA twice daily. Assessments before and after the intervention included body composition, muscle fitness, serum myokines, and inflammatory cytokines. Data analysis involved two-way repeated measures ANOVA, Bonferroni post-hoc comparisons, and one-way ANOVA for changes in the follistatin/myostatin ratio.ResultsThe RE + EAA group demonstrated a significant increase in muscle mass (F(3, 72) = 5.042, p < 0.001, partial η² = 0.174) and greater improvements in the senior fitness test (p ranging from < 0.05 to < 0.001). There was a reduction in myostatin levels (p < 0.05) and an elevation in follistatin in both the RE (p < 0.05) and RE + EAA (p < 0.001) groups. The follistatin/myostatin ratio increased most in the RE + EAA group (F(3, 72) = 5.556, p = 0.002, partial η² = 0.188), with significance versus control (p < 0.001), EAA (p < 0.05) groups. IL-6 and IL-1β were significantly reduced in the RE (p < 0.05) and RE + EAA (p < 0.05) groups, whereas TNF-α decreased only in the RE + EAA group (p < 0.05).ConclusionA 12-week intervention combining resistance exercise and essential amino acid supplementation was superior to either intervention alone in enhancing muscle mass, muscle fitness, myokine profiles, and reducing inflammatory markers among healthy older women. These results support the development of early combined interventions for the prevention of sarcopenia and may guide personalized exercise-nutrition prescriptions for optimal aging.Trial registrationKCT 0010756 (Retrospectively registered; July 15, 2025).

This exploratory metabolomics pilot study employed non-targeted liquid chromatography-tandem mass spectrometry (LC‒MS/MS) to characterize serum metabolic profiles in elite male water polo athletes, thereby assessing physiological adaptation to high-intensity training. We aimed to provide a scientific basis for evaluating physical fitness and optimizing performance capacity in elite athletes. Sixteen male water polo athletes of the Chinese national team were recruited. All athletes underwent a one-week complete break following the end of the previous competitive season to mitigate accumulated fatigue and establish a true resting metabolic baseline. Fasting venous blood samples (5 mL) were collected at 7:00 AM on two time points: the first sample (E1) was collected before commencement of the official training week, and the second sample (E2) was collected immediately after the completion of that week of training. The data were analyzed via XCMS, MetaboAnalyst 6.0, SPSS 21.0, and GraphPad Prism. (1) Metabolomic analysis identified 363 metabolites in total, 33 of which were differentially expressed between pre- and post-training time points. After one week of routine training, 11 metabolites were significantly up-regulated (p < 0.01), and 22 were significantly down-regulated (p < 0.01). (2) KEGG pathway analysis identified the top eight metabolic pathways, with MetPA further highlighting lysine degradation (p < 0.01) and vitamin B6 metabolism (p < 0.05) as key altered pathways. (3) Three metabolites were identified as potential markers associated with the training week changes in water polo athletes on the basis of significant alterations post-training. N6, N6, N6-trimethyl-L-lysine (p < 0.01) and 2-aminoadipic acid (p < 0.01) were significantly decreased, whereas 4-pyridoxic acid (p < 0.01) was significantly increased. Non-targeted LC‒MS/MS provides a valuable tool for monitoring metabolic adaptations at the molecular level in aquatic athletes. In this exploratory study, we observed associated changes in the serum metabolome following intensive training, pointing to adjustments in amino acid and lipid metabolism. These findings offer preliminary insights for guiding fitness and performance optimization.

ABSTRACTBackgroundWith increasing altitude, the partial pressure of oxygen and oxygen saturation (SpO2) decrease, reducing physical performance. This study investigates whether the nutritional supplement Sanopal® (5-hydroxymethyl-2-furfural and α-ketoglutaric acid) increases hemoglobin-oxygen affinity and SpO₂ during exercise at moderate altitude.MethodsNineteen healthy young sports students (12 females, 7 males) participated in a single-blinded, placebo-controlled crossover study investigating the effects of Sanopal® at low (590 m) and moderate altitude (2900 m). Participants received Sanopal® or placebo in a randomized order, with measurements of SpO₂, heart rate, and blood parameters taken before and after ingestion, as well as before and after exercise at altitude.ResultsUnder resting and acute hypoxia conditions, Sanopal® did not increase hemoglobin-oxygen affinity or SpO₂. At altitude and post-exercise, Hb-O₂ affinity decreased by approximately 5% in the PL trial but increased by approximately 2% in the SA session (interaction effect: p = 0.030). There were no significant differences in SpO₂ or heart rate between the Sanopal® and placebo groups.ConclusionsSanopal® did not alter hemoglobin-oxygen affinity or SpO₂ under resting conditions in normoxia or acute hypoxia. After exercise at altitude, it slightly increased Hb-O₂ affinity without significantly affecting SpO₂ or other measured blood parameters. The modest increase in Hb-O2 affinity following exercise may have limited the exercise-induced decrease in Hb-O2 affinity. However, this increase was likely too small to significantly raise SpO₂ in this cohort at a relatively low altitude.

Nordic skiing, an energy-demanding endurance sport, may be particularly susceptible to low energy availability (LEA) and relative energy deficiency in sport (REDs). The objective was to examine the nutritional practices and physical symptoms associated with (REDs among young elite Norwegian Nordic skiers during the off-season, with particular emphasis on energy and CHO intake, in the transition from the competitive season to preparation for the subsequent season. Thirty female and thirty male Nordic skiers participated in a 24-week controlled clinical trial. The daily dietary intake variables were carbohydrates (CHO), protein, and calcium (Ca) intake and weekly training hours. The blood variables were vitamin D, total osteocalcin (tOC), procollagen type 1 N-terminal propeptide/cross-linked C-telopeptide type 1-collagen (PINP1/CTX1) ratio, heart rate (HR), resting metabolic rate (RMR), bone mineral density (BMD), lean body mass (LM), visceral adipose tissue (VAT), and body fat percentage (BF%). Energy intake increased by 25%, and CHO increased by 14.5% for both sexes during the study, and training volume increased by 41% for female athletes and 83% for male athletes, respectively. There were positive correlations between higher BMD, bone markers, RMR, and LM and negative correlations between VAT and REDs symptoms. VAT was correlated with RMR and bone markers. LM emerged as a key predictor for health variables, explaining variability across multiple REDs markers. Nordic skiers seem unable to increase energy intake sufficiently during the preparation period, leading up to the competitive season, as demonstrated by a large discrepancy between changes in energy intake, especially CHO, and exercise volume. The correlations between energy intake and BMD, RMR, VAT, and HR underscore the clinical consequences of insufficient energy intake, which may arise if individuals focus on low body mass and body fat percentage without sufficient knowledge. VAT, tOC, and the P1NP/CTX-ratio are promising indicators for monitoring dietary interventions in individuals with REDs and should be considered in future research on REDs treatment strategies.

Following a comprehensive review, the International Society of Sports Nutrition (ISSN) has developed an official position on the role of dietary antioxidants in exercise and sport. Antioxidants play a complex, context-dependent role in vivo; they can facilitate recovery from exercise but may also hinder training adaptations when consumed at supraphysiological doses. While endogenous antioxidant systems can effectively maintain redox balance, dietary sources, particularly whole foods, can help mitigate excessive oxidative stress following intense/heavy training or inadequate recovery. The influence of dietary antioxidants depend on timing, dosage, type, and individual factors. The ISSN's official position encompasses the following: (1) Redox balance exists on a spectrum, with mild oxidative eustress driving beneficial physiological adaptations and excessive oxidative distress impairing health, recovery, and performance; (2) Moderate levels of exercise-induced reactive oxygen and nitrogen species (ROS/RNS) can support training adaptations but excessive levels can result in muscle damage, inflammation, and reduced physical performance and immune function; (3) Endogenous and exogenous antioxidants protect cells by neutralizing free radicals and reducing oxidative damage to biomolecules; (4) FDA labeling for "antioxidant" claims applies to nutrients with established RDIs and demonstrated antioxidant activity; this typically includes vitamins C and E, β-carotene (a source of vitamin A), selenium, zinc, copper, and manganese; (5) While dietary antioxidants show potential for both direct and indirect effects, the evidence varies, and their use should be tailored to individual performance or recovery goals; (6) Long-term exercise augments endogenous antioxidant defense and should be the primary strategy for enhancing redox capacity before considering supplementation; (7) Whole foods and beverages rich in flavonoids, polyphenols, carotenoids, vitamins, and minerals are preferred antioxidant sources; (8) Dietary supplementation is best reserved for nutrient insufficiencies or deficiencies, inadequate dietary intake, or periods of high training distress; (9) Responses to supplementation vary by individual factors, such as training status, baseline antioxidant capacity, demographics, diet, and injury risk, with some antioxidant compounds offering cognitive, behavioral, or physical-related benefits; and (10) Creatine monohydrate (i.e. 0.1 g/kg/day), omega-3 fatty acids (1000-6000 mg/day EPA+DHA for 6-12 weeks), tart cherry (480 mg powder or 60-90 mL juice/day for 7-14 days), and astaxanthin (4-12 mg/day for 4-12 weeks) rank among the top nutrients for their antioxidant effects, with moderate- to high-quality evidence supporting their use in recovery or performance without interfering with training adaptations. Most others show weak or low efficacy. This position promotes an individualized, evidence-based approach, recognizing that small to moderate exercise-induced oxidative stress aids adaptation, while excess oxidative stress causes harm; it also emphasizes food-forward and dietary supplementation strategies.

A growing body of evidence supports the use of supplements to enhance cycling performance through both direct and indirect mechanisms. This review was informed by a structured literature search conducted in PubMed, Scopus and Web of Science for peer-reviewed studies published up to May 2025. Studies were included if they involved human participants, were published in English and evaluated outcomes related to endurance performance, recovery or physiological function. Direct enhancement with ergogenic supplements is primarily achieved via modulation of skeletal muscle energy metabolism. During exercise, adenosine triphosphate (ATP) resynthesis is driven by the phosphagen system, glycolysis, oxidative phosphorylation and beta-oxidation, with each system contributing according to the intensity and duration of the effort. Supplements such as beta-alanine, caffeine, carbohydrates, carnitine, creatine monohydrate, dietary nitrates, electrolytes, exogenous ketones, N-acetylcysteine and sodium bicarbonate support these energy systems by improving substrate utilization, buffering capacity, energy availability or resistance to fatigue. In addition to ergogenic supplements that directly enhance performance, medical supplements play an important indirect role by supporting bone health, connective tissue integrity, inflammation management, micronutrient status, muscle repair and gut function. Evidence-based options for cyclists include calcium, cherry juice, collagen, curcumin, iron, multivitamins, omega-3 fatty acids, pickle juice, probiotics, protein, vitamin C, vitamin D and zinc. Each contribute to either improved recovery, immune support or long-term physiological adaptation. Evidence quality varied substantially across supplements, with strongest support for Australian Institute of Sport (AIS) Group A compounds. The integration of physiological testing including assessments of maximal oxygen consumption (VO2max), lactate threshold, metabolic substrate utilization and blood biomarkers may inform the development of individualized supplementation strategies tailored to training demands and competitive goals. This evidence-informed approach underscores the synergistic relationship between nutrition, training and performance optimization in cycling. Future research should explore personalized nutrition frameworks, interactions between multi-supplement protocols and the molecular mechanisms underpinning adaptation to endurance training and nutritional interventions.

BackgroundPsychological resilience significantly influences immune function and health outcomes in high-stress populations, yet mechanisms underlying nutrition-psychology-immunity interactions remain poorly understood. This study developed an individualized prediction model integrating dietary patterns with psychological and immune adaptations to inform personalized therapeutic approaches.MethodsA retrospective cohort analysis examined 200 endurance athletes over 12 months using integrated datasets from NHANES athletic subcohort, UK Biobank, and training monitoring databases. Athletes were categorized into three dietary pattern groups (high-carbohydrate, high-protein, balanced micronutrient) based on their naturalistic dietary intake. This observational design examined associations between dietary patterns and health outcomes without manipulating participant diets. A hybrid LSTM-XGBoost machine learning architecture with SHAP analysis predicted individual responses based on psychological variables, immune markers (IL-6, TNF-α, CRP, IgA), and performance metrics. Statistical analyses controlled for multiple comparisons using Bonferroni correction. Non-normally distributed variables were log-transformed or analyzed using non-parametric methods. Mediation analyses examined psychological pathways linking dietary patterns to immune outcomes.ResultsPsychological resilience emerged as the primary predictor of dietary pattern response (SHAP importance = 0.342), with psychological improvements consistently preceding immune function recovery by 1-2 months. Three distinct resilience-based subgroups demonstrated different response trajectories: high resilience athletes achieved superior improvement rates (0.43 vs. 0.10 points/month) and reached plateau phases earlier (6.8 vs. 11.2 months) compared to low resilience individuals. The predictive model achieved exceptional performance metrics (91.2% sensitivity, 87.6% specificity) for identifying non-responders to dietary patterns. Mediation analysis revealed that 42.4% of the associations between dietary patterns and immune function operated through psychological pathways, with cortisol reduction serving as a critical mechanism.ConclusionsPsychological resilience predicts responsiveness to dietary patterns through psychoneuroimmunological pathways. Baseline psychological assessment should guide personalized nutrition strategies in clinical populations experiencing chronic stress and immune dysfunction.