What is the duration of weight training?

In order to build muscle mass you should train for up to and no more than 45 minutes at a time, otherwise you are doing edurance training rather than building muscle. Try training upper body one day, have the next day off, then the day after tdo your lower body. This way your body has time to recover from the workout, and you train your whole body evenly. hope this helped =)

Alex, 17