The beneficial adaptation of skeletal muscle function to strenuous exercise is partially attributable to the improvement of vitamin D status. The present study aimed to evaluate the effects of a 3-week vitamin D supplementation on serum 25(OH)D levels and skeletal muscle biomarkers (i.e. troponin, myoglobin, creatine kinase and lactic dehydrogenase) of endurance runners. A double-blind placebo-controlled study design was used and vitamin D supplementation was compared to a non-treatment control group. Twenty-four runners, competitors of the ultra-marathons held during the National Running Championships, were randomly assigned into two groups supplemented with the dose of 2000 IU vitamin D or placebo for three weeks. All subjects participated in three exercise protocols: (a) incremental exercise test (to determine the maximum oxygen uptake and the intensity of eccentric exercise), (b) eccentric exercise before and (c) after two dietary protocols. Venous blood samples were drawn at rest, immediately after the exercise and after 1 h and 24 h of recovery in order to estimate serum 25(OH)D levels, skeletal muscle biomarkers, proinflammatory cytokines and tumor necrosis factor-alpha (TNF-α) levels. A two-way ANOVA was used to test main effects and their interactions and Pearson correlation coefficients were analyzed to determine the effects of inter-variable relationships. Significant differences between pre- and post-intervention in baseline 25(OH)D levels were observed (34.9 ± 4.7 versus 40.3 ± 4.9 ng/ml, p = 0.02) in supplemented group. A higher post intervention 25(OH)D level was observed after vitamin D diet compared to placebo (40.3 ± 4.9 versus 31.8 ± 4.2 ng/mL, respectively; p < 0.05). The vitamin D supplementation decreased post-exercise (TN max) and 1 h post-exercise troponin (p = 0.004, p = 0.03, respectively), 1 h post-exercise myoglobin concentration (p = 0.01) and TNF-α levels(p < 0.03). 24 h post exercise creatine kinase activity was significantly lower in supplemented group compared to placebo (p < 0.05). A negative correlation was observed between post exercise 25(OH)D levels and myoglobin levels (r = − 0.57; p = 0.05), and 25(OH)D levels and TNFα (r = − 0.58; p = 0.05) in vitamin D supplemented group. Three weeks of vitamin D supplementation had a positive effect on serum 25(OH)D levels in endurance trained runners and it caused a marked decrease in post-exercise biomarkers levels. We concluded that vitamin D supplementation might play an important role in prevention of skeletal muscle injuries following exercise with eccentric muscle contraction in athletes.

Obstructive sleep apnea (OSA) is an underdiagnosed condition in athletes, strongly influenced by anthropometric factors such as body mass index (BMI) and neck circumference, which often reflect long-term sport-specific training and nutritional strategies. This review examines the impact of OSA on athletes’ recovery, injury risk, and performance, with emphasis on BMI and neck circumference as key risk markers. A comprehensive search was conducted in PubMed, Web of Science, EBSCO, and Google Scholar for studies published between 2015 and 2025. Eleven studies met the inclusion criteria. The findings indicate a substantial prevalence of OSA in athletes, particularly those involved in collision sports such as rugby and American football, where higher BMI and increased neck circumference were consistently associated with increased risk of OSA. OSA was associated with reduced sleep quality, hormonal disruption, excessive daytime sleepiness, and slower reaction times. These factors may collectively impair recovery, increase injury susceptibility, and negatively affect aerobic capacity, cognitive function, and sport-specific performance. The results highlight the need for routine sleep screening in athletes, especially those with elevated BMI or larger neck circumference. Early detection and management of OSA may improve recovery and performance. Further longitudinal studies are needed to evaluate the long-term effects of OSA treatment in athletic populations.

The level of post-exercise inflammatory response induced by oxidative stress may depend on the fatty acid content of red blood cells. Twenty-three ultramarathoners were randomly assigned to two groups: a lipid complex supplementation group (SUPL) (n = 12, 1200 mg/day for 30 days) and olive oil intake a placebo group (PL) (n = 11, 1200 mg/day for 30 days). Participants performed eccentric exercise (30 min of downhill running at 70% \(\:\dot{\text{V}}\)O₂ peak). Fatty acid composition in red blood cells, blood markers of antioxidant balance and inflammation were assessed at rest, immediately post-exercise, and 1-hour and 24-hour post-exercise. After supplementation, both the supplementation and placebo groups showed significant changes in the AA/EPA ratio (Z = −3.06, p = 0.002, r = 0.88 in SUPL and Z = −2.94, p = 0.003, r = 0.89 in PL), and the SUPL group showed lower malondialdehyde post-exercise level (5.2 ± 0.6 vs. 7.1 ± 1.7 µmol/L) compared to the PL group. The lipid complex in the SUPL group significantly increased superoxide dismutase post-exercise level (1371.6 ± 107.9 U/gHb vs. 1720.8 ± 312.0 U/gHb) and decreased catalase and reduced glutathione rest levels. Lipid complex supplementation derived from Perna canaliculus L. can induce beneficial changes in AA/EPA ratio and post-exercise superoxide dismutase activity in athletes’ blood.