Adequate recovery time between training sessions allows your muscles to repair and grow, leading to increased strength and muscle mass. Rest times between weightlifting sets are just as important because they allow the muscles to recover and replenish the energy they need to perform the next set. Rest time between sets also helps prevent fatigue, which can lead to poor form and injury.
When you rest for too long, your body cools down and your muscles lose the activation and tension they had prior to the rest period. This means that the muscle fibers are not as stimulated and the next set will not be as effective as if you would have rested for a shorter period of time.
Additionally, waiting too long causes your heart rate to drop, and blood flow to the muscles decreases, which can impact the anabolic response that should be triggered by training. This can lower the muscle-building and muscle-toning effects of the workout.
The specific rest time needed can vary depending on the individual and the type of exercise being performed, but generally, rest times of 60 seconds to 3 minutes are recommended for weightlifting.
Endurance
Rest times of less than 60 seconds are typically recommended for exercises that target muscular endurance, such as circuit training or high-rep (20+) sets.
Hypertrophy
Hypertrophy training intentionally brings muscles to fatigue, causing them to grow larger in response to the stress of training, so 3-4 sets of 8-12 reps with 60 to 90 seconds of rest between sets have proven ideal. These shorter rest times help to increase muscle fatigue which can lead to an increase in muscle growth.
Strength & Power
Longer rest periods of 3-5 minutes are typically recommended for exercises that target maximum strength and power, such as heavy compound lifts like squats, deadlifts, and bench press. These exercises require high levels of energy and effort, and longer rest periods are needed to allow the muscles to fully recover and perform at their best.
But like everything else within the realm of weightlifting, everything comes down to the individual and their fitness level. It's always good to experiment and find the rest time that works best for you.