The purpose of the study was to determine the effect of 8 weeks pre-season training on body composition, physical fitness, anaerobic capacity, and isokinetic strength in collegiate taekwondo athletes. Thirty-four collegiate athletes (male: 22, female: 12) participated. Body composition, bone mineral density, physical fitness, anaerobic capacity, and isokinetic muscle strength were tested. After statistical analysis was performed the results indicated that there were significant decreases in body weight, percent body fat, and fat tissue after 8 weeks of pre-season training. Bone mineral density increased significantly only in males. There were significant improvements in the 50 m shuttle run and 20 m multistage endurance run in both males and females. The sit & reach test and standing long jump were not significantly changed after 8 weeks. Relative peak power and anaerobic capacity were significantly improved in males. Significant increases in angular velocity were observed for knee extension at both % BW 60°/sec and 180°/sec in both males and females. A significant increase in angular velocity was seen for right knee flexion at % BW 60°/sec for males, but it decreased at % BW 180°/sec for both males and females. In conclusion, this study suggests that 8 weeks of pre-season training has a positive effect on body composition, physical fitness, anaerobic capacity, isokinetic muscular strength, and endurance. Nevertheless, an exercise approach with the goal of increasing lean tissue, and improving power in knee flexors and flexibility of athletes, should be included in the training program.

This study examined the effects of resistance training on muscle quality, muscle growth factors, and functional fitness in older adult women with sarcopenia. Twenty-two older adult women aged over 65 with sarcopenia were randomly assigned to either resistance training (RT, n = 12) or non-exercise control group (CG, n = 10). The body weight-based and elastic band RT were performed three times a week, 60 min per session, for 16 weeks. Body composition and thigh muscle quality were estimated by dual-energy x-ray absorptiometry (DEXA) and computed tomography (CT), respectively. The muscle growth factors, including growth differentiation factor-8 (GDF-8), growth differentiation factor-15 (GDF-15), activin A, and follistatin, were analyzed via blood samples. Statistical analyses were performed using repeated measures multivariate analysis of variance (MANOVA), analysis of variance (ANOVA), and effect size (i.e., cohen’s d, partial eta square), and the significance level was set at 0.05. The RT group improved their functional fitness, grip strength, gait speed, and isometric muscle strength (p < .01, d > .99; large), while these variables did not change in the CG. An increase in intramuscular fat was only observed in the CG (p < .01, 1.06; large). Muscle growth factors such as follistatin were significantly increased in the RT (p < .05, .81; large), but other variables did not change following resistance training. Sixteen weeks of resistance training improved functional fitness and prevented age-related increases in intramuscular fat in the thigh area. However, there were only some changes in muscle growth factors, such as follistatin, suggesting that the effectiveness of resistance training on muscle growth factors is limited. Body weight-based and elastic band resistance training is an alternative training method for sarcopenia to minimize the age-related adverse effects on muscle function and quality.

Vitamin D insufficiency may be associated with increased risk of upper respiratory tract infection (URTI) in athletes. This study examined the effects of vitamin D3 supplementation on salivary immune functions and symptoms of URTI in vitamin D-insufficient taekwondo athletes. Twenty-five male taekwondo athletes, aged 19–22 years with vitamin D insufficiency [serum 25-hydroxyvitamin-D concentrations (25(OH)D, 31.3 ± 1.39 nmol/L)], participated in this study. They were randomized to receive 5000 IU/day of vitamin D3 (n = 13) or placebo capsule (n = 12) during 4 weeks of winter training. Blood samples were collected two times (pre- and post-tests) for analyzing serum 25(OH)D concentration while salivary samples were obtained three times (pre-, mid-, and post-tests) for secretory immunoglobulin A (SIgA) and lactoferrin analyses. The symptoms of URTI were reported daily during the intervention. Serum 25(OH)D concentration significantly increased by 255.6% in the vitamin D group, whereas in the placebo group it did not change (p < 0.001). While the significant increase in SIgA was observed in both groups (p < 0.001), elevated salivary lactoferrin level in response to winter training was found only in the placebo group (p = 0.011). The change in serum 25(OH)D concentration was negatively associated with total URTI symptoms (r = −0.435, p = 0.015). Vitamin D3 supplementation may be effective in reducing the symptoms of URTI during winter training in vitamin D-insufficient taekwondo athletes.

We investigated the effects of vitamin D supplementation on physical performance during winter training in vitamin D insufficient taekwondo athletes. Thirty-five collegiate male and female taekwondo athletes, aged 19-22 years with low serum 25(OH)D concentration (28.8 ± 1.10 nmol/L), were randomly assigned to a vitamin D group (n = 20) or a placebo group (n = 15). Subjects received either a vitamin D capsule (5,000 IU/day) or a placebo during 4 weeks of winter training. Blood samples were collected for analyzing serum 25(OH)D concentration. Physical performance tests included Wingate anaerobic test, isokinetic muscle strength and endurance, a countermovement jump test, sit-ups, agility test, and 20-m pacer. Serum 25(OH)D concentrations increased significantly in the vitamin D group (96.0 ± 3.77 nmol/L) after 4 weeks of supplementation, but no changes were found in the placebo group (F = 242.44, p = .000). There were significant interaction effects for anaerobic peak power (F = 7.49, p = .010) and isokinetic knee extension at 180 deg/s (F = 6.08, p = .019). Changes in serum 25(OH)D concentration were positively associated with changes in peak power and isokinetic knee extension at 180 deg/s. However, no significant interaction effects were observed in other performance variables. This study suggests that 4 weeks of vitamin D supplementation elevates serum 25(OH)D concentration to sufficient levels. Correcting vitamin D insufficiency improves some but not all aspects of performance. Thus, efficacy of vitamin D supplementation to enhance performance remains unclear.

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