We've all seen it happen: finding the motivation to actually make it to 6 a.m. boot-camp with a friend; nailing the last round of squats when you see those around you powering through; or pushing ...

FIFA Medical Assessment and Research Centre, and Schulthess Clinic, Zürich, Switzerland Correspondence to Mario Bizzini, FIFA Medical Assessment and Research Centre, FIFA-Strasse 20, P.O. Box, 8044 ...