Resistance Training 7 Step Approach - Step 7: Rest Periods
Strength and Power
For a quick refresher, strength and power exercises usually involve maximal and near-maximal weights with repetitions of 6 or lower. Research has shown that there are much greater strength gains from individuals who rest for 2-5 minutes rather than 30 seconds.
The fact that when your training goals are for strength and power, and you are literally pushing your muscles to the limit should be no surprise that longer rest periods are necessary.
Studies have shown that 30-90 second rest periods facilitate the greatest gains for hypertrophy training goals (6-12reps). The theory behind this time frame is that you actually want to start another set of exercises for the same muscle group before it has completely recovered. This can increase the metabolic demand and damage within the muscles to facilitate muscular growth.
Muscular endurance training (12+ reps) has a goal to increase the aerobic capacity of muscles. In doing so, and the fact that muscular endurance training is training with lighter resistance, rest periods between sets should be as minimum as possible (30 seconds or less).