Training that causes fatigue is not necessary to grow large strong muscles. In a study from the University of Brighton in England, men and women aged 18-29 were assigned to either a high fatigue or low fatigue protocol. Those assigned to the high fatigue protocol performed four sets of 10 repetitions with 30 seconds rest between sets. That means that they lifted the heaviest weight that they could lift ten times in a row, rested for thirty seconds and then did three more sets of ten, each separated by a 30-second rest period.

The low-fatigue group lifted the same weight, rested for 30 seconds, then lifted again, for 40 single lifts each separated by a 30 second rest. To make sure that they were using proper training technique, they all used weights that were close to their one-repetition maximum. The heaviest weight that you can lift ten times in a row is usually equal to 78 percent of the heaviest weigh that you can lift once. So the participants lifted 73 percent of their one-repetition maximums, which is very close to the heaviest weights that they could lift in sets of ten.

What is the difference between lifting a weight 40 times in a row with 30 second rests between each lift, and lifting a weight ten times in row, resting 30 seconds and doing 3 more sets of ten, since both groups lift the heavy weights 40 times? There is no difference in strength gain, but there is a great difference in fatigue, pain and time spent lifting. When you lift a heavy weight several times in row, your muscles start to accumulate large amounts of lactic acid, which makes them feel like they are on fire and they hurt. If you lift a heavy weight slowly 10 times in a row, you will accumulate considerable amounts of lactic acid and your muscles will hurt. On the other hand, if you lift a heavy weight once, and rest for thirty seconds between each lift, you will not accumulate lactate acid, your muscles will not burn, and you will not hurt as much. Therefore, if both workouts give you the same strength gain, and one hurts far more than the other, you should pick the method that does not hurt. However, resting 30 seconds between each lift will make the workout seven times longer.