Rest periods between sets is a important for the replenishment of the energy systems in the body. Depending on the training loads and exercise programs, rest periods can be from 30 seconds to 5 minutes based on the goal of the athlete. Traditional strength training athletes use longer rest periods 3-5 minutes. Due to heavy work rate (1-6 reps) the body’s ATP-PC system uses the phosphogens to produce energy quickly. It takes about 3 minutes to fully replenish the system allowing strength athletes to continue lifting very heavy weight. Hypertrophy training athletes rest 1-2 minutes on average. Hypertrophy training athletes use the ATP-PC system and the glycolytic system to produce enough energy as well as the aerobic system (small part).
Short rest periods (90 seconds or less) has been found to increase metabolic stress. Schoenfeld found that metabolic stress is one of the primary mechanisms for muscle growth (Schoenfeld, 2016). Longer rest periods (3 minutes or more) has the ability to achieve more total volume and increase the ability to lift heavier weight and perform more reps.
So which is better?
According to the Schoenfeld findings, the longer rest period group saw an increase in muscle growth and an increase in strength gains due to the total volume being a more effective mechanism for performance. A Senna et al. study found the same conclusion. Senna et al. found that 2 minute rest periods are effective for single joint exercises, while 3 minute rest periods are optimal for compound movements (Senna et al. 2016). There have been no current studies that have found any negative effects on greater rest periods than 3 minutes, leading many to believe that 3-5 minutes are an optimal rest period. The fear among many professionals about 5 minute or more rest periods is the “cooling” of the muscle after a long rest which can increase the lead to injuries. There is no scientific studies to claim this, however longer rest periods do decrease blood flow to the muscle and slows down the hormonal response to hypertrophy and strength response which can decrease the effectiveness of the exercise.
Schoenfeld, B. J., Pope, Z. K., Benik, F. M., Hester, G. M., Sellers, J., Nooner, J. L., ... & Just, B. L. (2016). Longer interset rest periods enhance muscle strength and hypertrophy in resistance-trained men. Journal of strength and conditioning research, 30(7), 1805-1812.
Senna, G. W., Willardson, J. M., Scudese, E., Simão, R., Queiroz, C., Avelar, R., & Dantas, E. H. M. (2016). Effect of different interset rest intervals on performance of single and multijoint exercises with near-maximal loads. The Journal of Strength & Conditioning Research, 30(3), 710-716.