Q: When doing strength training, what is the optimal rest time between sets?
A: There is no single optimal rest interval. It depends on your goals, as well as your level of training, the type and intensity of exercise, and the main muscle groups being worked. But generally speaking, while serious weightlifters and other people trying to “bulk up” may need to consider their rest intervals carefully, this is not a concern for most exercisers training for general health and fitness, for whom resting anywhere from one to three minutes between sets is fine.
The best way to build muscle mass and strength is to do progressive resistance training (using dumbbells, weight machines, elastic bands, or other forms of resistance), in which the resistance is increased over time. This is usually done in sets of 8 to 12 “reps” in a row, using enough resistance to leave the muscles very tired at the end of each set. The standard number of sets is three for each exercise, though trained lifters often do five or six sets.
Why rest fatigued muscles between sets? It takes a little time to restore intramuscular blood flow and oxygen delivery, which allow for replenishment of the muscles’ energy supply, removal of metabolic byproducts, and restoration of acid-base (pH) balance.
Shorter rest intervals (30 to 90 seconds) are best for building muscle endurance (the ability of a muscle to repeatedly contract over a period of time) and help keep your heart rate up, thus providing something of a cardiovascular workout. Muscle endurance is important if you are training for tennis or skiing, for instance.
Longer rest intervals (two to five minutes) are recommended for building strength (the maximum amount of force a muscle can produce) and power (the ability to generate as much force as fast as possible), though there is some disagreement about what’s optimal. If one of your goals is to develop a more powerful golf swing, for example, muscle strength and power are keys.
For most people, somewhat longer rest intervals may be better than shorter ones. For instance, in a small study in the Journal of Strength and Conditioning Research in 2016, fit young men engaged in full-body strength training three times a week for eight weeks, with half resting for one minute between sets, half for three minutes. Though both groups had gains in muscle size, strength, and endurance, the three-minute group had greater increases in muscle size (thickness) and strength.
Bottom line: Find the rest interval that works best for you.