The Science Of Rest Intervals
Updated: Jul 5, 2019
The science of rest periods by Dan Eiden
Rest periods are one of the most overlooked factor in any exercise program but one of the most important. Most people never track the rest periods in their workouts and they do themselves a huge disservice by not doing so. Even workouts in health and fitness magazines rarely have rest intervals written in to the workout. The fact is there is a science to rest intervals and why you would to rest a certain period of time between sets of an exercise and between exercises. It depends on a number of factors including the number of reps you are performing in that specific exercise, the type of exercise, the size of the muscle you are working, the goal of the workout program and the person.
Now there are always exceptions to rules but these are the general rules to the science of rest intervals. The lower the number of reps the more recovery is needed and the higher the number of reps the less recovery is needed. Basically there is an inverse relationship between the number of reps and the rest time it takes to recover. Low reps = long rest periods, high reps = short rest periods. One of the reasons for this is that training with lower reps is more taxing on the bodies central nervous system and the cells of the nervous system take 5 to 7 times longer to recover then muscle cells. This is why you may see big power lifters and Olympic lifters training with near maximal poundages and really low reps resting several minutes in between sets. Rest periods can range from several minutes to 30 seconds to no rest at all between sets.
Another rule is the bigger the exercise the longer recovery you need. Bigger exercises like squats, dead lifts and chin ups require a lot longer recovery then smaller exercises like abdominal crunches, calf raises and bicep curls. These bigger movements have you moving at multiple joints which involves more muscles, larger muscles, which in turn require you to lift heavier poundages and this is much more taxing on the body than smaller movements like abdominal crunches, calf raises and bicep curls which are moving at just one joint and working less muscles, often times smaller muscles and in turn requiring less weight to be lifted in those movements.
Now this rule ties into the previous on but the bigger the muscle you are training the longer the recovery you need. The smaller the muscle you are training the less recovery you need. Bigger muscles like the muscles in the thighs, the quads, hamstrings and the bigger muscles in the back like the traps and the lats require more recovery then smaller muscles like the calves, forearms and abdominals.
Rest periods are also dependent on the goal of the workout. If a person is training for strength as their main goal they would want to use longer recovery to maximize the heaviest amount of weight they can use and allow for complete recovery between sets to do so. On the opposite end of the spectrum if someone is training for muscular endurance they would want to use shorter recovery periods and incomplete recovery in an attempt to build up their endurance and work capacity. Also someone looking for fat loss as their main program goal may use shorter rest intervals and recovery to produce a hormonal response more favorable to fat loss.
Rest intervals can also be very individualized as well. A person who is a beginner may need longer recovery than an advanced trainee because the advanced trainee’s conditioning and overall work capacity is much greater and they can probably tolerate shorter rest intervals and shorter recovery periods than a beginner. Also a person who is bigger and stronger with more muscle can require more recovery time then someone who is smaller and not as strong and with less muscle.
As you can see rest periods can vary depending on many factors and because rest intervals are one of the many things the body adapts to in a workout varying them so that the body doesn’t adapt to the same rest period time is important to continue making progress.