Concerning the relationship between physical activity and 25OHD levels, as was to be expected, we found no association between indoor activities and hypovitaminosis D. Although it would seem obvious that indoor physical activity does not modify 25OHD levels, some authors have suggested that physical activity per se may raise vitamin D levels [20], [21], possibly by means of a transient exercise-induced increase in PTH levels [22]. This evidence concerns the gene PTH and rickets.