Current status of body composition assessment in sport: review and position statement on behalf of the ad hoc research working group on body composition health and performance, under the auspices of the I.O.C. Medical Commission - Ackland, T R; Lohman, T G; Sundgot-Borgen, J; Maughan, R J; Meyer, N L; Stewart, A D; Muller, W (Sports Med, 2012)