Sure, it's not necessary, but it is convenient. Athletes train in the off-season, so teams and sportspeople alike would not want their training disrupted knowin

Sure, it's not necessary, but it is convenient. Athletes train in the off-season, so teams and sportspeople alike would not want their training disrupted knowing that it would probably negatively impact their performace next season when it really matters. May as well measure while sportspeople are travelling between time zones, rather than having a scary coach shouting "give me thirty, kid" at 3am.