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Studies have shown that many adolescents, particularly blacks, are deficient in vitamin D. Because severe vitamin D deficiency can cause myopathy, investigators studied jump mechanics in 99 healthy postmenarchal 12- to 14-year-old girls in the U.K. (68% South Asian, 12% black, 20% white) from a school that was previously found to have a high percentage of asymptomatic students with serum 25-hydroxyvitamin D [25(OH)D] levels <37.5 nmol/L. The investigators measured body mass index (BMI), ground reaction forces, peak jumping power, jump height, jump velocity, a fitness index (comparison of power per kg of weight to age- and gender-matched norms), 25(OH)D level, and parathyroid hormone (PTH) level.
Median 25(OH)D level was 21.3 nmol/L. After ad…