Going heavy in your weight lifting routine is the key to building muscle size and density. Muscle cells will split and require a sufficient recovery period to grow back larger thereby making the muscle stronger. Forced reps will split more cells when pushing to failure and beyond. The critical balance here is between workout time and recovery time. Synchronizing these periods in your weight lifting routine will vary from person to person depending on one's body chemistry. People with higher natural testosterone levels will recover faster. This allows them to cycle faster and grow quicker. The rest of us have to program in one lighter high rep day into the three day a week weight lifting routines as a recovery aid to make the heavy days more effective. Heavy, usually means 4-5 reps to failure and going for maximum singles once a week.

For most people more sets get faster results i.e. as many as 8 sets on bench press and squats. This is because strength and endurance are inter- related and with fewer reps per set, you need more sets to achieve the proper endurance balance. At any rate it is a balancing act and very complex as any experienced body builder knows. With some people, doing endurance or light weight high repetition exercises on the rest day actually speeds up the recovery time and makes recovery more complete. This is because you are turning over the blood supply in your system more times during the rest period which more completely resupplies the split cells from you heavy day while not splitting any new cells. The result is, more fully recovered and larger cells making you stronger on your next heavy day.