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The purpose of this study was to investigate the effects of caffeinated chewing gum on the cognitive tasks, strength and military performance of tier 1 special forces soldiers in Taiwan. Sixteen male serving special forces soldiers (age: 34 ± 7 years; height: 172 ± 4 cm; BMI: 25.4 ± 2.7 kg/m²) completed the caffeinated chewing gum (CAF) trial and the placebo (PL) trial using a randomised crossover experimental design. After chewing the caffeinated chewing gum containing 3 mg·kg− 1 of caffeine (CAF trial) or placebo gum (PL trial), participants completed the cognitive tasks, grip strength, weighted vertical jump and the special forces military performance tests which included rapid-fire test and close-quarters battle (CQB) tests. Before, during, and after the experiment, the heart rate variability and salivary α-amylase were collected. Grip strength (increase 4.4 ± 7.1 kg; P = 0.037), weighted vertical jump height (increase 1.3 ± 2.1 cm; P = 0.032), cognitive tasks (simple response times, stroop task and visual search reaction time in 20 items) (P < 0.05), shooting scored in rapid-fire test (increase 1.0 ± 2.1 points; P = 0.030), the CQB tests (increase 1.1 ± 1.8 points; P = 0.044) and the completion times of CQB tests (increase 9.8 ± 7.2 s; P = 0.015) of the CAF trial were significantly better than those of the PL trial. The values of LF, LF/HF, salivary caffeine and α-Amylase concentration in the CAF trial were significantly higher compared to the PL trial (P < 0.05). Caffeinated chewing gum may improve military performance and cognitive performance by increasing sympathetic nervous system activity, as indicated by heart rate variability and salivary α-amylase concentration in CAF trials. The study was registered at ClinicalTrials.gov ID NCT06638372.
Optimizing training intensity and volume is crucial for adolescent swimmers, as excessive high-intensity exercise may cause fatigue, overtraining, and hinder recovery. Research has shown that training load affects immune function and sleep. This study examined how progressively increasing training intensity impacts salivary immunity, sleep quality, perceived fatigue, and performance in adolescent swimmers. Eighteen male swimmers participated in a three-week protocol with daily 100-min sessions at 70%, 80%, and 90% of maximum heart rate, respectively. Saliva and questionnaire data were collected twice weekly to assess cortisol, testosterone, α-amylase, immunoglobulin A, lactoferrin, and perceived exertion. Sleep was measured using actigraphy. Performance was evaluated weekly through 200-m freestyle and 25-m lap counts within 16 min. Results showed a significant weekly increase in maximum heart rate (p < 0.001). Muscle soreness and perceived exertion were significantly higher after training at 80% and 90% intensities (p < 0.05) compared to rest days. Sleep quality and most salivary immune markers did not significantly change over time. However, the testosterone/cortisol ratio decreased after 5 days at 80% intensity (p < 0.01). Performance significantly improved at 80% and 90% intensities compared to 70%. In conclusion, a progressively incremental training program enhanced athletic performance without negatively affecting sleep or immune markers. These findings support controlled intensity increases for improving performance while maintaining physiological balance in adolescent swimmers.
Background 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.Methods 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.Results 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.Conclusion 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.
Background:Obesity is a major global health concern, leading to increased risk of metabolic diseases and mortality. Swimming, as a low-impact exercise, may provide metabolic benefits. However, the influence of water temperature on the metabolic and physiological responses remains underexplored. This study investigated the effects of water temperatures on muscle and adipose tissue adaptations in high-fat diet-induced obese mice. Methods:Obese mice were subjected to swimming at different water temperatures: 15°C, 25°C, or 32°C. Changes in body and tissue weight, grip strength, exhaustive swimming performance, and key metabolic parameters were assessed. Epididymal fat pads (EFP) and gastrocnemius muscles were collected for histological analyses (muscle fiber composition and adipose tissue remodeling), gene expression (Ucp1, Pgc-1α, Prdm16, Cidea), and western blot analyses (SIRT1-PGC-1α-FNDC5 pathway). Results:Swimming at 25°C and 32°C significantly reduced body weight and EFP weight, improved metabolic profiles and grip strength, whereas cold-water swimming (15°C) enhanced endurance performance. Histological analysis revealed reduced adipocyte size in the 25°C group, accompanied by increased oxidative (Type I) fibers across all swimming groups. Elevated Pgc-1α expression in EFP was particularly prominent at 25°C, and FNDC5 in muscle was most pronounced at 15°C. These findings highlight distinct temperature-dependent metabolic and muscular adaptations during swimming in obese mice. Conclusion:Moderate (25°C) and warm (32°C) water temperatures are optimal for reducing obesity-related metabolic dysfunctions and enhancing muscle strength, while cold water (15°C) improves endurance through oxidative muscle adaptation.
Athletic training and menstruation both contribute to iron depletion and anemia in female athletes. We hypothesized that oral iron supplementation during the menstrual period would increase the hemoglobin (Hb) level and reduce fatigue in female athletes. Twenty-two female athletes were randomly assigned to either the control (CON) or experimental (EXP) groups. Participants in the EXP group received one capsule of ferrous bisglycinate chelate (equivalent to 20 mg of elemental iron) daily during their menstrual periods in the second, third, and fourth menstrual cycles (M2-M4), whereas those in the CON group took a placebo. Blood samples from each subject were collected after each menstrual period, and Hb, hematocrit, and blood cell counts were analyzed. The results indicated that iron supplementation significantly increased the levels of Hb, hematocrit, and red blood cell (RBC) count from the first menstrual bleeding period (M1) to the fifth menstrual bleeding period (M5). The immune-related cell populations and rating of perceived exertion fatigue indicators showed no significant differences from M1 to M5. In conclusion, daily supplementation with ferrous bisglycinate chelate during the menstrual period significantly increased Hb levels, hematocrit levels, and RBC counts in female athletes.
