The purpose of this systematic review and meta-analysis is to investigate the effects of vitamin D3 supplementation on skeletal muscle strength in athletes. Vitamin D3 supplements or vitamin D3 fortified foods always have claims for bringing people health benefits including bone and muscle health. An up-to-date rigorous systematic review and meta-analysis is important to better understand the effect of vitamin D3 supplementation on muscle strength. English written randomized controlled trials (RCTs) that looked at effects of vitamin D3 supplementation on muscle strength in healthy athletes were searched using three databases (PubMed, Embase and Cochrane Library). Serum 25(OH)D above 30 ng/mL is considered to be sufficient in this systematic review and meta-analysis. Five RCTs with 163 athletes (vitamin D3 n = 86, placebo n = 77) met inclusion criteria. Fourteen athletes were lost to follow-up and 149 athletes (vitamin D3 n = 80, placebo n = 69) were documented with complete result. Among athletes with baseline serum 25(OH)D values suggesting insufficiency, vitamin D3 daily dosage at 5000 IU for over 4 weeks led to a serum 25(OH)D concentration of 31.7 ng/mL. Athletes with sufficient serum 25(OH)D level at baseline were recruited in only one study, and the participants of which were assigned to either vitamin D3 at a daily dosage of 3570 IU or placebo for 12 weeks, their serum 25(OH)D sufficiency (VD: 37.2 ± 7.6 vs. 45.6 ± 7.6; PL: 38 ± 6.8 vs. 32 ± 8.4) was well maintained above the cut-off boundary. One repetition maximum Bench Press (1-RM BP) was not improved significantly (SMD 0.07, 95% CI: − 0.32 to 0.47, P = 0.72) and there was no significant increase in maximal quadriceps contraction (SMD -2.14, 95% CI: − 4.87 to 0.59, P = 0.12). Furthermore, there was no significant overall effect of vitamin D3 intervention on muscle strength in this meta-analysis (SMD -0.75, 95% CI: − 1.82 to 0.32, P = 0.17). Although, serum 25(OH)D concentrations after supplementation reached sufficiency was observed, muscle strength did not significantly improve at this point of current meta-analysis. Additional well-designed RCTs with large number of participants examined for the effect of vitamin D3 supplementation on serum 25(OH)D concentrations, muscle strength in a variety of sports, latitudes and diverse multicultural populations are needed.

(1) Background: Probiotics in the form of nutritional supplements are safe and potentially useful for strategic application among endurance athletes. Bifidobacterium animalis lactis BL-99 (BL-99) was isolated from the intestines of healthy Chinese infants. We combined plasma-targeted metabolomics and fecal metagenomics to explore the effect of 8 weeks of BL-99 supplementation on cross-country skiers’ metabolism and sports performance. (2) Methods: Sixteen national top-level male cross-country skiers were recruited and randomly divided into a placebo group (C) and a BL-99 group (E). The participants took the supplements four times/day (with each of three meals and at 21:00) consistently for 8 weeks. The experiment was conducted in a single-blind randomized fashion. The subject’s dietary intake and total daily energy consumption were recorded. Blood and stool samples were collected before and after the 8-week intervention, and body composition, muscle strength, blood biochemical parameters, plasma-targeted metabolomic data, and fecal metagenomic data were then analyzed. (3) Results: The following changes occurred after 8 weeks of BL-99 supplementation: (a) There was no significant difference in the average total daily energy consumption and body composition between the C and E groups. (b) The VO_2max and 60°/s and 180°/s knee joint extensor strength significantly increased in both the C and E groups. By the eighth week, the VO_2max and 60 s knee-joint extensor strength were significantly higher in the E group than in the C group. (c) The triglyceride levels significantly decreased in both the C and E groups. In addition, the LDL-C levels significantly decreased in the E group. (d) The abundance of Bifidobacterium animalis increased two-fold in the C group and forty-fold in the E group. (e) Plasma-targeted metabolomic analysis showed that, after eight weeks of BL-99 supplementation, the increases in DHA, adrenic acid, linoleic acid, and acetic acid and decreases in glycocholic acid and glycodeoxycholic acid in the E group were significantly higher than those in the C group. (f) Spearman correlation analysis showed that there was a significant positive correlation between Bifidobacterium animalis’ abundance and SCFAs, PUFAs, and bile acids. (g) There was a significant correlation between the most significantly regulated metabolites and indicators related to sports performance and lipid metabolism. (4) Conclusions: Eight weeks of BL-99 supplementation combined with training may help to improve lipid metabolism and sports performance by increasing the abundance of Bifidobacterium, which can promote the generation of short-chain fatty acids and unsaturated fatty acids, and inhibit the synthesis of bile acids.

Background: Physical activities play an important role in alleviating the aging problem and improving the physical fitness of middle-aged and elderly people. Blood flow restriction (BFR) training, also known as pressure training, has been widely used to improve athletes’ performance and rehabilitation, which is a relatively novel exercise method for improving the physical fitness of middle-aged and elderly people. The purpose of this study is to conduct a systematic review and meta-analysis of domestic and foreign randomized controlled trial studies on BFR training for middle-aged and elderly women, further explore the impact of BFR training on health status.Methods: Meta-analysis was performed according to PRISMA standards, and charts were drawn using Review Manager 5.4 and Stata 17 software. In this study, the keywords such as “pressure training”, “blood restriction training”, “elderly women”, “KAATSU”, “blood flow restriction training” were used on CNKI, China Science and Technology Journal Database, PubMed, Embase, Web of Science, Cochrane Library, EBSCO, Scopus, and randomized controlled trials were searched in all languages. The search was performed from the establishment of database to 2 January 2024. The results of the combined effect were represented by standard mean differences.Results: Among the 681 literature retrieved, six eligible English articles were included in this meta-analysis. The overall effect test of the combined effect was performed on 10 groups of data, and the results were SMD = −0.18 (95%CI: −0.91 to 0.56; p > 0.05), the maximum dynamic force of 1RM SMD = 0.97 (95%CI: 0.35 to 1.58; p < 0.05), leg compression force SMD = −0.10 (95%CI: −0.78 to 0.57; p > 0.05), heart rate SMD = 0.33 (95%CI: −2.50 to 3.17; p > 0.05), systolic blood pressure (SBP) SMD = −1.44 (95%CI: −2.17 to −0.70; p < 0.05), diastolic blood pressure (DBP) SMD = −0.69 (95%CI: 2.54 to 1.15; p > 0.05).Conclusion: BFR training had a significant effect on the increase of the maximum dynamic force of 1RM and decrease of blood pressure in middle-aged and elderly women, but there was no significant difference found in heart rate and leg compression force.Systematic Review Registration:https://www.crd.york.ac.uk/prospero/, identifier CRD42024491642.

Objectives: This study investigated the efficacy of wheat peptide supplementation compared to regular proteins in elite cross-country skiers, providing insights into the metabolic and performance effects of these supplements in order to guide athletes in selecting optimal energy sources for training and competition. Methods: Nineteen healthy male cross-country skiers were enrolled and assigned to either the peptide group (PEP, n = 9) or the protein group (PRO, n = 10). A four-week intervention study involving supplementation with wheat peptides/regular proteins was conducted, and pre- and post-intervention assessments were performed to evaluate exercise capacity and metabolic profiles. Results: The study found that the PEP group and the PRO group showed distinct within-group effects on exercise performance. The PEP group demonstrated improved aerobic capacity, including better performance in 10 km roller skating, an increased lactate threshold, and reduced resting blood lactate levels. The PRO group enhanced anaerobic capacity, such as improved sprint time, hexagon test performance, and lactate clearance. Metabolomic analysis revealed specific metabolic pathways affected in each group, with the PEP group showing impacts on the α-linolenic acid pathway and the PRO group on ketone body synthesis and degradation as well as vitamin B6 metabolism. Conclusions: Our findings indicate that wheat oligopeptides and regular proteins have comparable effects on exercise performance. However, the wheat peptides may offer greater advantages in enhancing aerobic capacity. No significant variations were observed in blood metabolite profiles between the two groups, but distinct metabolic pathways exhibited different responses.

Background: Remote ischemic preconditioning (RIPC) is a non-invasive intervention involving brief, repeated limb ischemia and is suggested to enhance muscle performance. However, findings in healthy men remain inconsistent, and few studies have examined upper-limb strength. This meta-analysis provides the first quantitative synthesis of acute RIPC effects on upper-body strength in healthy male adults, aiming to clarify its efficacy and practical relevance. Methods: English (PubMed, Web of Science, Embase, Cochrane Library) and Chinese (CNKI, Wanfang, VIP, CBM) databases were systematically searched up to March 16, 2025. Randomized crossover trials examining acute RIPC effects on upper-limb strength in healthy male adults were included. Primary outcomes involved maximal, explosive, and endurance strength measures. The review was registered with PROSPERO (CRD420251184757). Data were pooled using random-effects models, and heterogeneity was assessed via the I² statistic. Prespecified subgroup analyses examined moderators such as RIPC protocol (cycle number/duration) and strength outcome type (maximal, explosive, endurance). Results: Six randomized crossover trials involving 84 participants met inclusion criteria. The meta-analysis showed a small, positive, but non-significant overall effect of RIPC on upper-limb strength (SMD = 0.24, 95% CI: -0.02 to 0.51, p = 0.07) with low-to-moderate heterogeneity (I² = 32%). Subgroup analyses revealed no significant effects for maximal (SMD = 0.03, p = 0.85) or explosive strength (SMD = 0.13, p = 0.75). A moderate but non-significant improvement was observed for strength endurance (SMD = 0.54, 95% CI: -0.01 to 1.10, p = 0.054) with moderate heterogeneity (I² = 60%). Neither the number of ischemia–reperfusion cycles ( p = 0.40 for subgroup difference) nor the test time window (< 30 min vs. ≥ 30 min, p = 0.37) significantly moderated the effects. Conclusion: This first meta-analysis on RIPC and upper-limb strength suggests that acute RIPC does not reliably improve upper-body strength in healthy male adults. Despite a moderate effect size observed for strength endurance, the lack of statistical significance and the 95% confidence interval crossing zero indicate considerable uncertainty in this finding. Together with the limited and heterogeneous evidence, this indicates that current protocols do not consistently enhance strength performance. RIPC should therefore be regarded as a theoretically promising but practically unverified approach. Larger, well-controlled trials are needed to determine whether specific RIPC parameters or time windows can produce reproducible performance gains.

Article: Does leptin associate with testosterone and exercise-induced muscle damage among professional athletes? - Medicina dello Sport 2024 June;77(2):213-25 - Minerva Medica - Journals