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  • Jung, Hyun Chul  (2)
  • Kim, Jung-Hyun  (2)
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  • 1
    Online Resource
    Online Resource
    The Associations of Vitamin D Status with Athletic Performance and Blood-borne Markers in Adolescent Athletes: A Cross-Sectional Study
    MDPI AG ; 2019
    In:  International Journal of Environmental Research and Public Health Vol. 16, No. 18 ( 2019-09-14), p. 3422-
    Details
    In: International Journal of Environmental Research and Public Health, MDPI AG, Vol. 16, No. 18 ( 2019-09-14), p. 3422-
    Abstract: The purpose of this study was to examine the associations of vitamin D status with athletic performance and blood-borne markers in adolescent athletes. This cross-sectional study included forty-seven Taekwondo athletes, aged 15–18 years old. Athletic performance was assessed using maximal oxygen consumption (VO2max), Wingate anaerobic power test, vertical jump, agility T-test, lower limb muscle strength, and fatigue resistance. Blood samples were collected to assess serum 25-hydroxyvitamin D [25(OH)D], free-testosterone, cortisol, creatine kinase, and urea. One-way ANOVAs were applied using Bonferroni adjusted alpha levels, which was 0.02 (i.e., 0.05/3). Multiple linear regressions analyses as well as Pearson and partial correlation analyses were used to examine the relationship among 25(OH)D concentration, athletic performance, and blood-borne markers. The participants 25(OH)D concentration were ranged from 16 to 73.25 nmol/L, indicating that 74.5% of the adolescent athletes have vitamin D insufficiency or deficiency. The vitamin D status did not show any significant effects on the performance factors or blood-borne markers. Serum 25(OH)D concentration was positively correlated with mean power output (r = 0.359, p 〈 0.05) and relative mean power output (r = 0.325, p 〈 0.05) after adjusting for bone age, height, weight, training experience, lean body mass, and fat mass. However, 25(OH)D concentration was not associated with other performance-related factors and blood-borne markers. In addition, multiple linear regressions analyses revealed that serum 25(OH)D concentration were not significant predictors of athletic performance in adolescent athletes. In conclusion, vitamin D status is weakly correlated with anaerobic capacity; moreover, the underlying mechanisms of how vitamin D influence anaerobic performance is unclear in the present study. Nevertheless, the importance of vitamin D on health benefits should not be underestimated, especially during growth periods.
    Type of Medium: Online Resource
    ISSN: 1660-4601
    URL: Article
    DOI: 10.3390/ijerph16183422
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2175195-X
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  • 2
    Online Resource
    Online Resource
    Does Online Social Connectivity Promote Physical Activity in a Wearable Tracker-Based Intervention? A Pilot Randomized Controlled Study
    MDPI AG ; 2020
    In:  Sustainability Vol. 12, No. 21 ( 2020-10-23), p. 8803-
    Details
    In: Sustainability, MDPI AG, Vol. 12, No. 21 ( 2020-10-23), p. 8803-
    Abstract: Wearable activity trackers have gained popularity among individuals who want to track their physical activity (PA). The features of wearable tracking technology that are known to facilitate positive behavior changes such as self-monitoring and social connectedness) are well documented; yet, the existing evidence is not conclusive in the literature requiring further investigation. This study was an 8-week pilot randomized controlled study examining the effectiveness of PA intervention incorporating a wearable activity tracker’s online connectivity feature. Forty participants were equally randomized into either an individual-based (n = 20) or a connected group (n = 20). A Jawbone UP24 tracker was provided to all participants in both groups as a means of self-monitoring PA for eight weeks, but the connected group was additionally instructed to share their PA levels with the others using the accompanying smartphone application. Participants’ weekly step counts were evaluated each week to examine the change in PA. Participants’ biometric variables such as body weight, body mass index, waist circumference, blood pressure, and psychological status, including self-efficacy (SE) and exercise motivation (EM), were measured from both groups before and after the intervention period. Additionally, the social support questionnaire (SSQ) was measured among the connected group. The statistical significance level was set at 〈 0.05. The average step counts for eight weeks were significantly increased only in the connected group (p 〈 0.001). Significant differences in step count improved from the baseline to week 8 in the connected user group (p 〈 0.01), but only baseline vs. week 7 in the individual users. Also, no significant interaction effects for biometric variables, EM, and SE were founded. However, SSQ was significantly improved in the connected user group (p 〈 0.001). PA intervention combining a wearable activity tracker and online social connectivity feature shows a greater effectiveness of promoting PA than a wearable tracker alone
    Type of Medium: Online Resource
    ISSN: 2071-1050
    URL: Article
    DOI: 10.3390/su12218803
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2518383-7
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