Personal trainers used to have the job of counting reps, but these days I see more and more counting total time spent training. Is this a valid way to have clients exercise – timing set length and stopping when a certain time count is reached? Let’s examine a study. John always reviews the full-text of every article, but you may view the free abstract by clicking here http://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1691&context=gs_rp