The Science of Rest Periods for Strength Training

Written by; Beth Tobin (Bach Ex.Sci – Current)

Including rest periods between your weight training sets is one of the training variables you must change to trigger a varied physiological change within your body.

Rest periods are just as important as some of the other training variables you need to manipulate to achieve your training goals. 

The amount of weight (intensity), or the number of sets and repetitions (volume) we prescribe in your strength training program is closely related to your training goals and outcomes for your program.   These training variables are just as important as how we program your rest periods.

Physiological Responses following Rest Periods

  • Replenish short term energy supplies like creatine-phosphate, an anaerobic energy source
  • Allow the nervous system time to recover so power output does not decrease, and correct technique remains stable
  • Clear metabolites such as lactate and hydrogen ions from the blood stream
Rest Periods for weight training
Rest periods in weight training

Rest periods for Different Training Goals

Rest Periods for Strength and Power

If your goal is to increase strength, or increase power your program should include heavier weights, low repetitions, and a long rest period between your sets.  Around 2-4 minutes of rest period for these training goals.

This is because when you do high intensity exercise, your body switches to anaerobic metabolism to provide fuel for the working muscles, and this energy source becomes depleted quite quickly, and causes an increase in metabolites like lactate and hydrogen ions to build up. This lowers the pH of blood, leading to acidosis, neuromuscular fatigue and a decrease in power. The rest period is designed to give the body time to get rid of these from the blood, and the muscles to replenish their fuel stores before the next set.

Over time, this allows the body to adapt to heavier loads.  The longer rest period will also help your nervous system to recover from the set and maintain your power and technique.

If you shorten your rest period whilst undertaking power and strength training work, you may not be recovered for your next set.  This may lead to less power gains and deteriorating technique, which in turn increases your risk of injury.

This is especially true for neurologically demanding exercises such as Olympic power lifting, which is highly technical, and compound exercises that use most major muscle groups.

Rest Periods for Weight Loss and Endurance

If your goal is to lose weight or improve muscular endurance you would generally undertake weight training using lighter weights and a higher number of repetitions such as 15-20.

With these training goals your rest periods between sets should shorter (30 – 60seconds). By using a shorter rest period, you are not as recovered. What this does over time is improve your ability to clear lactate as it is formed, and make you less susceptible to changes in blood pH. By improving this, it also improves your aerobic fitness, because one of lactate’s precursors can be moved into the aerobic energy pathway, during sub-maximal exercise and provides aerobic energy.

Shorter rest periods help increase total calories expended, build muscle, and burn fat.

Another way we can manipulate the rest period, so you are not waiting around for minutes during your workout, is to do what we call non-competing supersets.  This is achieved by undertaking two opposing exercises with a shorter rest period.

An example of this could be to perform a seated row for one set, and then superset with a chest press or bench press for the next. The exercises use opposing actions and allow the working muscles to recover.

If your workout has several exercises that you rotate through doing one set of each, it may employ this same strategy of non-competing supersets.

The rest periods you undertake will depend on what goals you have for your workout. This is one of the areas our Exercise Physiologists at Inspire Fitness will be able to advise you with and ensure your rest periods are appropriate for your goals.

Rest Periods Between Training Sessions

Another variable of strength training rest period is the time (days) we take between training sessions.  This usually refers to the days training where you are not working the same body part on consecutive days.

This is important because we need to give the body time to recover and adapt to the stimulus the session has triggered. This adaptation usually takes a few days.

You might be aware of the progressive overload principle your workout is based on.  This principle states that by overloading your muscles, small amounts of damage occur, and in response to this your cells are told that it needs to have bigger or stronger muscle fibres or needs more mitochondria (the power house that uses energy for contraction) for energy.

Progressive overload triggers a physiological adaptation, where the nucleus of the cell makes temporary instructions (transcription) to make more proteins (gene expression), whether they are more mitochondria, or bigger muscle cells. It takes up to 24 hours after a training session for those instructions to developed, and then up to 48 hours after that, for the body to make the protein the instructions are requiring.

This is why rest days between working the same area of the body are important. Similarly for using super sets within a workout (as discussed above), we can also manipulate them there, by working upper body one day, and then lower body the next day. You are still giving your body time to recover in between sessions, which is the important point.

So to make the most of your workout, talk to your Personal Trainer or Exercise Physiologist about what rest periods are best for your goals and don’t limit the results of your workout!