Dave and I are the epitome of tech dinosaurs.

 

Neither of us use social media (yes you read that correctly).

 

My credit card was just compromised for the first time and I had to try and log in to the website it got stolen from over the phone. The person on the other end literally laughed at me when I gave him what I thought my password may be. He quipped back “did you change that from 1, 2, 3, 4?”

 

Ouch!

 

Our technophobia also transfers to health. We were extremely early adopters of the Whoop Band. We both loved the utility of it, but I abandoned it because all of the sleep data was actually making me sleep worse. The data would show I had a bad sleep and it would ruin my day because the wrist band said I hadn’t slept well.

 

Technology has also crept into strength training. I’ve worked out in and been employed by many gyms through my years and noticed you can generally categorize trainers into a number of broad categories. Here are three of the worst categories.

 

• You have the ‘motivators’: Those with little thought to structure, but great at yelling uplifting things to get you going.
• You have the ‘technique mongers’: Those that convince you that every movement you do is somehow wrong and correct everything from the position of your lowest rib, to the way you are breathing.
• Then you have the ‘technology adopters’: Those that use fancy gadgets for feedback and often even time your rest intervals between sets using a stopwatch.

 

For some odd reason, the timing of rest intervals has always struck me as odd.

 

It seems like common sense to me that the person exercising would be able to tell when they feel ready to perform their next set.

 

For instance, if the person is training a more endurance type of session with maximal volume of sets but at lighter weights, they likely do not need a ton of rest in between sets. If they are going for maximal strength, or trying to improve their heaviest lifts, a little more rest is likely in the cards.

 

Either way, the person doing the lift must somehow ‘intrinsically feel’ when they are ready for their next set……right?

 

My hypothesis is simple – there is no such thing as a ‘proper rest interval’ and being as stubborn as my wife often accuses me of being I’ll stick to that assertion until proven otherwise.

 

So obviously my next step was to try and prove myself otherwise.

 

Lucky for me, Brad Schoenfeld and his excellent team of researchers just a few weeks ago answered the rest interval question for me in the journal of strength and conditioning research. And as usual I was wrong.

 

Much to my surprise there has already been a fair bit of research on optimal rest time between strength sets but each study I looked at had issues. Sometimes it was the exercise choice, sometimes it was the study design, sometimes it was the patient population.

 

The recent Schoenfeld study addressed all of these.

 

They had 16 subjects perform 2 lower body exercises: the leg extension and the back squat with 3 different rest interval lengths (one, two and three minutes) in a randomized fashion. To ensure recovery was full, they separated the exercise days by at least 48 hours.

 

To standardize the lifts, everyone did a ‘familiarization’ workout with the researchers where subjects were made to complete a 10 rep max of the back squat on a smith machine (to ensure technique standardization instead of doing a free weight back squat), and a leg extension machine. This just means they had to lift a weight they could do 10 reps of and no more.

 

Since the researchers were interested in optimal rest intervals, the obvious outcome measure would be performance – meaning how many reps of their 10 rep max weight could they perform in subsequent sets.

 

Let’s take the back squat for instance. If subjects performed 10 reps on set one, and on the day they used 1 minute rests their subsequent 3 sets had 8, 6, and 4 reps then we know there was a significant performance decline. If done 2 days later with 3 minute rests and their rep range was 10 reps, then 9, 8 and 8 reps, the conclusion would be that longer rest was optimal. Simple.

 

The reason I liked this study though, was the other data that they included. They had subjects use a rating of discomfort scale from 0-100 at baseline, immediately after each work set and then 5 minutes after completing their exercise. To me, this is extremely interesting. It would tell us subjectively how ready subjects felt to perform their next set and researchers would then be able to compare this with their objective strength outcomes.

 

Additionally they measured something called blood lactate. Ever heard of the term ‘lactic acid’? Blood lactate kind of measures that.

 

In brief, you need something called phosphocreatine (PCr) to generate rapid energy (ATP) in the first 15 seconds or so of intense exercise. The acute acidosis from increased usage of glucose, results in the buildup of lactic acid which can hinder PCr regeneration. It takes a certain amount of time to buffer out the acid (typically thought to be 120 seconds or more to reach full recovery). Lactate testing is an objective measure of this – how much acid there is in your body that needs to be buffered out.

 

Like I mentioned…..well thought out, great study.

 

Before I share the results, what is your hypothesis? Let’s take overall strength measured by ability to do the most reps in subsequent sets. What do you think would have the best outcome? One minute of rest in between sets? Two minutes? Three? What about the difference between one and two minutes versus the difference between two and three?

 

Mine was simple. I assumed there would be a straight line linear relationship for rest period meaning that one minute would be the worst, and three minutes between sets the best, with two minutes nestled right midway in between. Nice, tidy results.

 

As usual, stubborn old me was wrong.

 

It does in fact turn out that longer rest duration allows for more repetitions versus short rest. This was more pronounced for the back squat compared to the leg extension exercise (likely because the back squat is multi joint, and takes a lot more energy, building up more lactic acid along the way).

 

But here is the kicker.

 

There is a large difference for rest intervals of 1 and 2 OR 3 minutes but very trivial differences between 2 and 3 minutes.

 

Read that again because it is confusing.

 

This means you gain an advantage (if you are working out for strength or hypertrophy) if you wait 2 minutes in between sets compared to waiting just one minute. BUT, you gain negligible improvement by waiting an additional minute (3 minutes total in between sets). Most of the benefit is by waiting for at least 2 minutes.

 

Here is the chart showing the data if you are interested.

 

 

 

Here was the interesting part. Psychologically, as rated by someone’s perceived exertion, there WAS an impact on greater rest intervals where the longer people waited, their rating of exertion went down. So they felt more ‘ready’ to perform subsequent sets the longer they waited. BUT, we know from a physiological standpoint (strength and performance output) you certainly are…..after just 2 minutes! Yet another way the mind tricks us.

 

The blood lactate component was a bit of a disappointment. Essentially it showed an increase through subsequent sets regardless of rest intervals, and even was elevated at 5 minutes after the subjects completely stopped exercising. It turns out that blood lactate takes a REALLY LONG time to clear.

 

 

So what have we learned?

 

 If you are looking to build strength or muscle size you should rest 2 minutes instead of 1 for optimal output, but adding to 3 minutes had minimal change.
 Building on this, we know there is a direct correlation with exercise volume (how many total reps and sets you do) and hypertrophy and strength improvements. By waiting 2 minutes instead of 3, you can add over 30% more to your hour long workout.
 Despite the fact you may feel like you are not recovered after 2 minutes, you probably are. Just lift the darn weight!

 

Maybe there is something to using the stopwatch between sets after all.