One hopes it doesn't only apply to adolescent girls.
For this study, researchers followed 99 adolescent girls between the ages of 12 and 14 years. Ward and her colleagues took blood samples to measure the girls' serum levels of vitamin D. Many of these girls were found to have low levels of vitamin D despite not presenting any symptoms.
Researchers used a novel outcome measure called jumping mechanography to measure muscle power and force. Jumping mechanography derives power and force measurements from a subject's performance in a series of jumping activities. Ward says this method of testing is ideal as the muscles required to jump are those most often affected in subjects with vitamin D deficiency. Girls without vitamin D deficiency performed significantly better in these tests.
"Vitamin D affects the various ways muscles work and we've seen from this study that there may be no visible symptoms of vitamin D deficiency," said Ward. "Further studies are needed to address this problem and determine the necessary levels of vitamin D for a healthy muscle system."