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What is the Optimal Rest Interval Between Sets?

People who are serious about weight training tend to become quite detail oriented, fixating on every aspect of training.  In that regard, a common question is what the optimal rest interval between sets is. That is, how long should a trainee rest between sets of the same exercise to best achieve their goals.

There is actually no single answer to this question.  Rather, various factors go into determining what/if there is an optimal rest interval between sets to begin with.  To examine this issue, I want to look at a recent review paper on the topic:

Willardson, J.M. A brief review: Factors affecting the length of the rest interval between resistance exercise sets. J. Strength Cond. Res. 20(4):978-984. 2006

The Optimal Rest Interval is Context Specific

As I mentioned above, the optimal rest interval, which I will express here in either minutes or seconds, depends entirely on the context.  Primarily it depends on goal of the trainee in that this tends to define the type of weight training being done to begin with.

For the purposes of this article, I’ll look at four specific goals:

  1. Maximal strength
  2. Power output
  3. Hypertrophy/muscle growth
  4. Local muscular endurance

For each I’ll define the goal of the type of training along with how that training tends to be “generically” set up.   I’ll look at the paper cited above within that context in terms of what an optimal rest interval between sets would appear to be.

Rest Interval for Maximal Strength Training

As its name suggests, the goal of maximal strength training is to increase maximal strength.  This is generally defined as 1 repetition maximum strength, the maximum weight that can be lifted once and once only.  There other definitions to be sure but, in a weight room context, 1RM is the end metric that it used.

Traditionally maximal strength training is structured around lower repetitions, often 5 or less, and a high intensity, generally 80-85% of 1RM or higher.  So someone who could lift 100 lbs maximum would be using 80-85 lbs or heavier in their sets.     Almost without exception multiple sets are done of any given exercise.

As the paper points out, maximal strength training has a general emphasis on maintaining a high training intensity across all of the sets which are done.  This means avoiding any sort of cumulative fatigue build-up between sets, the lifters wants to be nearly or fully recovered between sets with only occasional exceptions.

Examining a variety of studies along with some theoretical concerns involving ATP regeneration and the nervous system, the review recommends a fairly standard rest interval of 2-5 minutes between sets for maximal strength work.  This recommendation is certainly consistent with real-world experience and systems such as the 5X5 program and others typically recommend 3-5 minutes between heavy sets.

Exceptions to the Rule

The paper suggests, however, that when the intensities go above 90% of maximum (generally 3 reps per set or less) short intervals can sometimes be used without harming the workout.   The premise is that sets of 1-3 repetitions will generate very little metabolic fatigue.  Thus they may allow slightly faster recovery than sets of 5 repetitions which generate proportionally more fatigue.  Some studies even used short rest intervals when testing a maximum single.

In a real-world practical sense, I question this.  Most people testing a true 1 RM tend to take fairly long rest intervals.  5 minutes or longer isn’t uncommon and some very large powerlifters may need 10 minutes between a true maximum effort.   I would note that women, by and large, don’t seem to need as much rest between heavy sets as men although this can depend heavily on the specific woman.

I think the disconnect here is that even if less metabolic fatigue occurs, there may be additional neural fatigue in addition to the psychological factor that is required to give a maximum effort.   Testing a true 1RM requires laser focus and I prefer longer recoveries between repetitions on test days for this reason.

Other Factors Impacting RI for Maximal Strength Training

There are other factors that play a role here.  A primary one is the type of movement being done.  Olympic lifters often lift near maximum loads with relatively short rest intervals.  This is assuredly due to the fact that there is no grind component to Olympic lifting outside of perhaps the front squat recovery on the clean.   Repetitions in the OL’s either go or don’t go.

Sets are very short, there is no eccentric component and the explosive nature of the movements put them at a different point on the maximum strength curve.  A maximum clean and jerk might be 80-85% of someone’s best deadlift, a snatch 80% of that.  Simply, a maximum single in an OL isn’t the same as a maximum single in the deadlift.

In contrast, maximum singles in traditional weight training movements can become very grindy.  Powerlifters may spend multiple seconds grinding through the sticking point of a squat, bench or deadlift and this causes a very different kind of fatigue to occur.  After a true maximum repetition in the deadlift, a lifter may need 10 minutes to have any chance of recovering.  If it’s a true grinder of a lift, they may be done for the day.

Can the RI be Too Long?

While not explicitly mentioned in the paper, I have known trainees for whom a rest interval can be too long between sets of maximum strength training.  This tends to be especially true in the Olympic lifts where lifters may lose their snatch groove if they rest too long.

Others seem to cool down with too long between maximum sets.  I have a female powerlifting trainee like that now.  For her, anything more than perhaps 2 minutes between heavy repetitions and she looks worse than with a shorter RI.

Rest Interval for Muscular Power Training

Power training is done to improve a muscles ability to generate force quickly.  This is critically important for almost all performance sports where athletes may only have two tenths of a second to generate force.  Slow grindy strength isn’t helpful here since the athlete doesn’t have a full 1-2 seconds to generate force.

Traditionally power training takes the form of moving sub-maximal weights fairly rapidly.   This can include bodyweight movements such as plyometrics and jumps, medicine ball work or the Olympic lifts.  Traditional movements such as the squat or bench can be done explosively although they have their own issues in terms of the physics involved (a discussion of this is beyond the scope of this article).

In the same way that the focus of maximal strength training is on intensity, the focus of power training is on quality and speed of movement.  For this reason, sets are generally stopped when or before the movement speed slows.  This invariably means doing less than the maximal number of repetitions possible.  As well, fatigue between sets should be avoided here as well.

Similar to maximum strength training, a RI of 3-5 minutes between sets of power training.  This allows for maximal quality in each set without accumulated fatigue hampering movement speed.   This is especially true for higher rep efforts such as high rep bounding or higher rep sets of power weight training.

Someone performing power endurance work, performing 10 or more fast repetitions per set needs to be fully rested for each set to ensure that movement speed doesn’t slow down.  That requires full recovery between sets.

I’d note that when the Olympic lifts are used for power training, sets of 5 or less are usually used.  Since this will generate proportionally less fatigue than a set of 10 bounds, a short RI, perhaps 2 minutes may be appropriate.   The ultimate determinant should always be bar speed and explosiveness.

In this vein, Westside Barbell is famous for its “speed work” which is typically 8-10X2 in the squat, 8-10X3 in the bench with 45-60 second rest intervals.  Since this is typically done with as little as 60% of the lifter’s max or lower, there is little fatigue generated per set.  This allows a high quality of work to be maintained even with short rest intervals.

Rest Interval for Hypertrophy/Muscle Growth

The goal of training for muscle growth is, well, muscle growth.  Duh.  This can actually entail a number of factors including growth of the actual contractile parts of the muscle along with increasing in the non-contractile/sarcoplasmic part.  To discuss both in detail would take too long.

Focusing only on contractile growth, a primary factor is high muscular tension although volume and metabolic stress also play a role.  Simply, a muscle must be exposed to some number of high tension contractions to activate the pathways that make the muscle get bigger.  Yes, there is more to it.

To be honest, the section on rest intervals for hypertrophy is the part of the paper I had almost total disagreement with as it argues for relatively short RI’s of 30-90 seconds between sets.   Most of their argument revolves around the hormonal response to training but frankly this plays a small approaching irrelevant role in anything.

We’ve known that high muscular tension is the key to stimulating growth for decades and, flatly, short rest intervals compromise tension as fatigue accumulates and the weight on the bar has to be lowered too much.  The reality is that most of the bigger athletes, including bodybuilders and powerlifters, use longer RI’s for hypertrophy training.

It needn’t be as long as for maximal strength training and there should be some accumulated fatigue occurring for optimal growth.  In general, I’d set 2 minutes as an average “optimal” rest interval for this type of training although it can vary based on things such as the number of repetitions and the exercise done.  For a heavy set of 5 in the squat, 3 minutes might be required between sets.  For a set of 12-15 in the lateral raise, only 90 seconds should be required.  In all cases, 30 seconds will simply be too short.

I guess my point is that there is more to hypertrophy than giving a simple short or long rest interval can properly address.  The interaction of tension with fatigue/metabolic work and tonnage are all involved in the growth stimulus and by the time you get into issues of sarcoplasmic vs. myofibrillar hypertrophy, it starts getting complicated.  Some of those issues are addressed in the series on Periodization for Bodybuilders.

Put simply, I think that both longer (complete or near complete) and shorter (incomplete) rest intervals have their place in hypertrophy training.  In general, I’ll typically use longer rest intervals when the goal is primarily a tension stimulus (e.g. rest interval of 2-3 minutes for sets of 5-8 reps) and shorter rest intervals when the goal is a fatigue stimulus (e.g. 60-90 seconds for sets of 12-15 reps).

I should probably note that there are places, usually rest-pause training, where short inter-set rest intervals are used.  Here, after a primary set, as little as 10-15 seconds rest might be taken before the set is continued with another mini-set.   So someone might start with a heavy set of 8, rest 10-15 seconds, do 3-4 more reps, rest 10-15 seconds, do 2-3 more reps, rest 10-15 seconds and do 1-2 more reps before stopping.  But this is really just a single extended set. Between two of these types of sets, I’d recommend 2-3 minutes.

But overall, lifters who maintain a very short RI in order to “get a pump” are ultimately short changing themselves when it comes to hypertrophy.  A sufficiently high tension stimulus is required for growth and short RIs prevent that.  Not only do they not help growth, they tend to actively harm it.

Rest Interval for Local Muscular Endurance

Local muscular endurance refers to a muscle’s ability to resist fatigue, usually against accumulating waste products such as H+.  Improving this ability means exposing the muscle to those high levels of waste products so it can improve its ability to either buffer them or continue generating force in their presence.

As such, the goal of muscular endurance training is to generate fatigue and this is a more important stimulus than tension or intensity. Muscular endurance training generally revolves around multiple sets of high-repetitions (15-25 or more) with relatively short rest intervals of 30-60 seconds.  This prevents full recovery between sets so that the muscle is exposed to progressively increasing amounts of waste products.  It HURTS.

The Optimal Rest Interval Between Sets

As you can see, the optimal rest interval between sets depends on a number of factors.  The goal of the training is primary but other factors such as exercise selection or even sex/gender can also play a role.  I’ve summarized the above information in the chart below.

Optimal Rest Interval Between Sets

 

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