Ideal rest is a vital component of exercise, not only between training sessions but also between sets during a workout. Following the completion of a set of exercises, the body must “clear out” the metabolic by-products incurred from the trauma of the lift; we refer to this as muscular recovery. As a general rule, rest time between sets is a function of the amount of weight being lifted. According to the American Council on Exercise (ACE), different goals dictate the paradigm of sets, volume and rest intervals.
Ideal Rest Interval for Endurance Training
If a client is attempting to increase sports-specific muscular endurance, as is often the case with runners and cyclists, keeping rest intervals less than 30 seconds will facilitate the conditioning required for prolonged workouts. In this scenario, weight is typically lowered while volume is quite high, such as sets of 20-30 repetitions.
Conventional endurance workouts draw energy from aerobic metabolism, as the body burns carbs and fats in the presence of oxygen. Since endurance training is aimed at creating muscles that successfully resist fatigue, another goal of this scenario is to minimize lactic acid accumulation. The buildup of this by-product contributes significantly to fatigue. A regular program of endurance training results in a higher level of efficiency at clearing lactic acid from the muscles by boosting the body’s hormonal and vascular systems.
The Classic Hypertrophy Model for Between-Set Rest
Typical bodybuilders and clients invested in hypertrophy to achieve a lean, muscular physique tend toward lifting above average-to-heavy weight loads, with repetitions ranging from 6-12 per set. In this scenario, athletes favor rest intervals of 60-90 seconds. Muscles recruit energy for resistance training from a substance called creatine phosphate, as well as from carbohydrates consumed and stored as glycogen. Rest intervals allow creatine phosphate levels to return to normal, re-establishing pre-lift homeostasis. In this type of training, aerobic metabolism plays a very minor role.
To a large extent, the quantity of anabolic hormones produced by the body following weight training dictate muscular growth. Short rest periods (1 to 2 minutes) cause a greater release of these hormones than periods of longer duration. Shorter intervals also induce other muscle-building bonuses such as increased lactate production and improved blood flow.
Powering Up For Pure Strength
By contrast, powerlifters often perform 1-3 repetitions per set of near-maximal weight loads expending their ATP stores which need to be replenished, thereby necessitating rest intervals of 2-5 minutes. As previously mentioned, the process of serious strength training causes micro-tears in the muscle tissue (trauma) accompanied by metabolic products that the body must safely eliminate. Further, it is important to approach maximal strength training sets ready to take on as much weight as possible requiring the body to be as “fresh” and ready to tackle the weight again. Thus, it is understandable that such hefty weight loads will require longer rest periods.
These intense workouts require not only a dedicated time commitment but attention to detail in the kitchen as well. Sufficient protein in addition to adequate amounts of branched-chain amino acids will facilitate the building of abundant lean muscle mass.
Every Body Is Different
Every trainer needs to take into account the client in front of them whose physiological makeup and grit may vary wildly from another. The above are guidelines to accomplish a goal but if someone seems to demand more rest, it can be a struggle for a fitness professional to grant it if they fear they aren’t pushing their paying client quite enough.
Always keep the goal in mind: Someone wanting to gain muscle would be working at higher intensities requiring more rest, while someone in it for weight loss should be moving less weight at lower intensities and utilizing shorter rest periods.
The NFPT training approach dictates that the same number of reps should be completed for every set of each exercise regardless of goals (and assuming that you are aiming for the same intensity in each set). So if your client got 12 reps on set one, but only 10 on set two and 8 on set 3, that is a pretty good indication that rest periods need to be increased!
Certainly for clients first starting out, rest periods may need to be longer until they adjust to the demands of their program.
The NFPT recommends gauging heart rate between sets in order to accommodate these goals. Allowing the resting heart rate to return to a particular threshold will dictate help dictate how long the rest period should be. A heart rate monitor would come in handy here, but good old fashioned pulse-checking is still a reliable method.
Ideal heart rate during between-set rest periods according to goals:
Hypertrophy and Strength Clients: 100 BPM
General Fitness Clients: 115 BPM
Weight Loss Clients: 125 BPM
It may only take a conditioned strength client a minute or so for their heart rate to return to 100 BPM, so this rest period may not correlate all that well with the suggested 2-5 minutes for strength and power athletes. You just have to time and wait those out.
But for the general fitness and weight loss clients, you might find that their heart rates take a while to return to the suggested ranges above until they are more conditioned, making rest periods slightly longer at first. By knowing the goals your client has set forth, you can create the ideal training program in terms of exercise selection, time under tension, and ideal rest intervals to ensure his success and satisfaction.