[1] North Dakota State Univ, Dept Hlth Nutr & Exercise Sci, Fargo, ND 58108 USA
[2] Univ Utah, Dept Hlth Kinesiol & Recreat, Salt Lake City, UT 84112 USA
[3] Univ Hong Kong, Sch Publ Hlth, Li Ka Shing Fac Med, Div Kinesiol,Pokfulam, Room 301D 3-F, Hong Kong, Peoples R China
[4] Univ Cambridge, Sch Med, MRC Epidemiol Unit, Cambridge, Cambs, England