“…In a recently-published study of football players in the Norwegian, Swedish and English Premier Leagues, Bjørneboe et al 5 found that illness is only a minor contributor to the total health burden, with players getting sick on average once every two seasons. In contrast, surveillance data from the Norwegian Olympic and Paralympic team show that, in certain sports, such as swimming, rowing and cross-country skiing, common illnesses have a far greater impact on athletes' participation and performance than do injuries (unpublished data—for methods) 6.…”