This study is a randomized, double-blind study evaluated the effects of 90 days of vitamin D supplementation, with or without calcium, on bone mineral density and sports performance in indoor female semiprofessional athletes.
Vitamin D and calcium are essential for bone health, with vitamin D also influencing muscle function, immunity, and inflammation. The primary source of vitamin D is skin synthesis via UVB exposure, though deficiency is common, especially in indoor athletes. There are current mixed evidences on whether vitamin D supplementation improves sports performance, despite its role in muscle physiology and bone health. Female triad athletes are particularly vulnerable due to risks of low energy availability, bone loss, and menstrual irregularities. Therefore, the purpose of this study is to investigate the effects of vitamin D and calcium supplementation on bone mineral density and performance in female athletes. A randomized, double-blinded study was conducted, including a total of 37 young female semiprofessional athletes. The participants were divided into three groups of one) vitamin D supplements (5000 IU, 125 μg/day), two) vitamin D (5000 IU, 125 μg/day) and calcium supplement (600 mg/day), and three) control group (medium-chain triglycerides) intervention for 90 days. Blood draws, bone density test, and other values were used to assess the changes in the bone and nutritional status. Subjective and objective values were used to evaluate the sports performance.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
37
Participants received 12 oral drops of vitamin D3 (cholecalciferol), providing a total daily dose of 5,000 IU (125 μg).
Participants received 12 oral drops of vitamin D3 (cholecalciferol), providing a total daily dose of 5,000 IU (125 μg), together with one 600 mg calcium tablet taken orally once daily.
Participants received a placebo which does not contain vitamin D (contains medium-chain fatty acid oil), and a calcium placebo.
Fu Jen Catholic University Hospital
New Taipei City, Taiwan
isokinetic muscle strength Biodex
Using the Biodex System 4 QuickSet, the players performed the maximum extension and flexion muscle strength test of the knee joints at 60∘ per second and 180∘ per second angular velocities. The action range is from 90∘ to 0∘. The maximum eccentric contraction was repeated five times, and the sequence was from slow to high angular velocity
Time frame: From enrollment to the end post-test at 90 days.
Star excursion balance test
The players stood in the center of the star with bare feet. With their hands placed firmly on their hips, the left foot stood at the center point to control their balance while the right foot was used as a reaching foot, directing their positions onto another point. They must extend the right foot as far as possible in a straight line, lightly touch with their toes at the farthest distance, and then return to the center point and rest for two to five seconds. They have to repeat this step eight times in a clockwise direction, and then repeat this same test by changing the sides of their foot counterclockwise direction in a sequence. Finally, the testers recorded the length of each direction (with a minimum unit of 0.5 cm), and recorded the best distance for subsequent analysis. This test was done three times. The scale is reach distance (CM). Minimum is 0CM, and there is no fixed macimum. If greater reach distance is achieved, that means better dynamic balance.
Time frame: From enrollment to the end post-test at 90 days.
Vertical jump test
The players hold a piece of tape, standing on the sideway of the wall. They then have to squat down, swing their arms, and jump up vertically as high as possible, extending their legs and arms. The scale is jump height in cm. Minimum score is 0cm, and there is no fixed maximum. If higher jump is reached, that means they have a better lower-limb power.
Time frame: From enrollment to the end post-test at 90 days.
T-shape agility test
The players ran back and forth on four T-shaped angular cones. They 17performed a total of three tests and were recorded for the best speed for the subsequent analysis. Lastly, on the sport performance test, a 20-meter sprint test was recorded. The players started to sprint when instructed from a static position on a basketball court. Players performed three times with the best time recorded for subsequent analysis. The scale is measured in times (sec), minimum is 0 sec and there is no fixed maximum. When lower time is achieved, that means they have better agility.
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Time frame: From the entrollment to post-test at 90 days.