training time
 

You can train long, or you can train intensely, but you can't do both. For every set completed, more, and more of the body's limited reserve of biochemical resources is used up in an attempt to merely recover from, or compensate for the exhaustive effects of the workout, leaving that much less left over for over-compensation in the form of more muscle mass. Long, drawn out training sessions decrease growth hormone, and testosterone levels, while increasing cortisole levels. This hormonal shift creates a very catabolic environment in the body that will result in muscle loss, and a reduced basal metabolic rate. If it's taking you several hours to get through a workout then you're wasting your time. I suggest never allowing any lifting session to exceed 45 minutes in duration.