The Science of Muscle Recovery: How Long Should You Rest Between Workouts?

Back in the day, I used to throttle myself in the gym. Russian squat routines. Deadlift specialization programs. And, of course, my high school days, when I benched three times per week and maxed out every Friday. (Because you never know—you may have gotten stronger that week!)

I’ve trained and pushed myself a lot over the years, and I’ve put countless thousands of people—of all shapes, sizes, and abilities—through training sessions, as well. If I’ve learned one thing over the years, it’s this: It’s not how hard you can exercise but what you can recover from that matters.

What Is Recovery and How Do You Monitor It?

One definition of recovery is “the ability to meet or exceed performance in a particular activity.”[1] While that’s a fine definition, recovery is not just about performance in the moment, but also your body’s ability to overcome and adapt to stress after exercise or competition.

When I first started learning about training theory and writing exercise programs, the experts were focused on the concept of homeostasis: The tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes. In simple terms, homeostasis is your body’s way of keeping itself in a state of balance. How does that apply to exercise? Let’s talk about the role of stress in upsetting that balance.

Training Is Stress, but It’s Stress You Control

When you go in the gym and crush arms for an hour, you’re stressing your system. It responds via various mechanisms to restore the body to its preferred “balanced” state. It increases protein synthesis—among other mechanisms—to build up the body bigger and stronger than before.

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Even so, you can’t just think about muscle recovery at the muscular level, you have to consider what it does for the body on a grander scale, as well.

Let’s use bodybuilding-style body-part splits as an example. The big issue when laying out a split is finding ways to avoid training the same muscle group too frequently. That puts the focus on local muscular fatigue and recovery. So, if you hit chest on Tuesday, you may not want to do arms or shoulders on Wednesday because you would be taxing some of the same muscle groups on consecutive days.

That’s good as far as it goes, but to get a true picture of the body’s response to exercise stress, you need to look at it from a global perspective.

What Drives Muscle Contraction?

Muscles don’t fire themselves. They need electrical impulses to drive that contraction, which means they need the nervous system.

The nervous system—namely, the autonomic nervous system, or ANS—consists of two branches:

The sympathetic nervous system, or SNS, is the fight-or-flight branch. If you want to run fast, jump high, or lift heavy things, you activate your SNS to help you do it.
The parasympathetic nervous system, or PNS, is the rest-and-digest branch. If you want to chill out, relax, and recover, you need to activate the PNS.

The goal is to have balance in your nervous system. When you want to train hard, you need to be able to crank up your SNS and push weight. But when it’s time to relax and get some deep, restful sleep, you need your PNS working at a high level.

The question becomes, how do you keep track of your nervous system balance?

Heart Rate Variability Monitoring

One of the best ways to keep an eye on your ANS is to track and monitor your heart rate variability, or HRV, with one of the various apps and monitors that are on the market. HRV systems measure the tiny differences in time that occur between your individual heart beats. They look at the balance between the SNS and PNS and give you a score. If you’re balanced and operating at a high level, you’ll typically get a green score, which indicates you’re recovered and ready to go. On the other hand, if you’re not recovering well, typically marked by an increase in sympathetic activity, you’ll get a yellow or red score.

How Does Training Affect Recovery?

When I’m designing workouts for new clients, there are three major factors I consider:

Their age and recovery ability.
Their primary training goal (i.e., strength focused vs. physique focused).
Other stressors they are dealing with in their lives.

The Age Factor

Someone who is 20 years old, whose only stress in life consists of getting up to go to class, getting to the gym five times per week, and recovering from extracurricular activities on the weekends, can take a lot of stress and recover from it. On the flip side, if someone is 50 and has teenage children at home, a full-time job, and money issues, their stress levels—and their ability to recover from exercise—are going to be vastly different.

When I write that first program, I start by considering how many sessions I want the client to complete in a given week, and from there I break down how much stress I can impose on any given exercise day. For most of my clients, 2-4 sessions per week works well. Younger clients typically trend toward the higher side, while my older clients trend toward the lower side. As we age, recovery between exercise sessions becomes even more critical, and we don’t recover as fast as we once did.

The Stress Per Workout

To consider how stressful a given exercise session is, you need to have some gauge as to how hard you trained. Many trainees track the workout volume (sets x reps), but a critical piece of the puzzle is the intensity.

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So, instead of sets x reps, the new formula is:

sets x reps x load

Using this equation, here’s how two different workouts done with the 5×5 scheme would look:

5 sets x 5 reps x 200 pounds = 5,000 pounds total workload
5 sets x 5 reps x 400 pounds = 10,000 pounds total workload

While each workout contains 25 reps (5×5), adding in the load gives you a much better measure of how challenging it is.

Don’t Overlook How the Workout Feels

Another way you can track intensity is to consider the rating of perceived exertion, or RPE. While it’s not perfect, a subjective score brings an added element of individuality into the mix.

For example, say you’re in the gym warming up on the squat. On some days, that weight is flying up and you feel amazing; you know it’s going to be a great day. At other times, you can’t seem to make it happen, and just having the loaded bar on your back feels like it’s going to crush you.

The RPE can give insight into not only how you’re feeling that day but also how you’re recovering from your sessions. I typically use a 1-10 scale to rate how difficult a session was, with 10 being a grueling workout, 9 being a really tough workout, 8 being a challenging workout, and so on.

Tracking RPE over the course of months (or even years) can tell you a lot about how your workouts are going and give you ideas for what you can do to squeeze even more gains out of every lift.

Building a Better Training Template

Once you have an idea of how hard a given training session was (or will be), you can plan the rest of your training week around it. When you’re young, it’s easier to go back-to-back days, simply because your recovery ability is so great. As you age, you will typically need to find a better balance, with time off between sessions.

As lifters get mature, they usually find that they need more volume or intensity to disrupt homeostasis and force the body to adapt. The combination of increased age, plus the increase in exercise stress forces you to take more time off between sessions to create an adaptation.

Yes, there are exceptions. Some people can train every day and get away with it. And yes, there are definitely ways to enhance your performance via pharmaceutical means. By and large, however, most people who are really pushing their body are going to train 3-4 times per week, taking a day off between workouts to rest, recover, and prep for the next session.

Let’s take this concept even further. At the famed Westside Barbell in Columbus, Ohio, you’ll find some of the most elite strength athletes in the world. Their system calls for four training sessions per week—two very high intensity max-effort days and two moderate intensity, higher volume sessions.

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A training week would look like this:

Monday: Maximum Effort, Lower Body
Tuesday: Off
Wednesday: Maximum Effort, Upper Body
Thursday: Off
Friday: Moderate Effort, Lower Body
Saturday: Moderate Effort, Upper Body
Sunday: Off

Here are a couple of key points about this program:

If you’re really pushing the intensity, you can probably only do a max effort twice per week, and you’re going to need 48-72 hours between sessions. Even if the muscles feel ready, the nervous system takes more time to recover.
Just because you have two high-intensity days doesn’t mean you take the rest of the week off. Whether it’s less intense, volume-focused workouts, recovery workouts, or some other plan, there are still options to keep you in the gym on the regular.

If your goal is to build more muscle rather than maximum strength, you will follow a traditional bodybuilding-style split. In this case, you’ll probably hit maximal levels only on leg day, and potentially on your back and/or chest day.

Furthermore, if you use a bodybuilding split, you should give yourself a day off after those heavy workouts to ensure that you maximize your ability to recover. Something like this may work well:

Monday: Legs
Tuesday: Off
Wednesday: Chest
Thursday: Off
Friday: Back
Saturday: Shoulders and Arms
Sunday: Off

As discussed, your leg workout would be the most intense of the week, with your chest/back days coming in second, based on the load and intensity you can handle for those muscle groups.

The Bottom Line on Recovery

Your goal is to find a training approach that lets you train hard each and every time you’re in the gym. If your goal is to lift heavy things and look good for as long as possible, make recovery a key part of your training when you lay out your workout schedule.

Before I let you go, here are a few pointers on several factors that can also help maximize the post-workout recovery process.

Hydration is a critical piece of the puzzle. Make sure you’re hydrating not only throughout the day, but especially after your training session. A quality hydration and recovery supplement can be helpful here.
Your body doesn’t grow when you train—it grows when you recover. Shoot for 7.5-9 hours of sound sleep every night.
Stretching may not necessarily make you more flexible, but it helps relax your body and kick-start the recovery process. After your workout, pick 3-5 main areas and hold for five full breath cycles.
A shake is the easiest thing to digest immediately after your workout. Focus on protein first and foremost, but if you’re training long and hard enough, get some simple carbohydrates in there, as well.
If you want to build your body bigger and stronger, you need to fuel it properly. Drink your shake within an hour of the workout, then work to get a balanced meal in within two hours after training.

References

Bishop, P. A, Jones E., & Woods A. K. (2008). Recovery from training: a brief review. Journal of Strength and Conditioning Research, 22(3), 1015-1024.

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