Is It Okay to Do Cardio After Leg Day? What Science Says

To a lot of people, doing a cardio workout the day after training your legs makes no sense at all.

After a bout of heavy squatting, you may well find it difficult to walk down the stairs. The idea of getting on a treadmill to go for a run sounds completely outrageous.

Training your legs, then doing a cardio session the next day is just going to interfere with recovery and put the brakes on muscle growth.

Will doing cardio the day after training your legs kill your gains? Not necessarily.

Aerobic exercise certainly has the potential to put the brakes on muscle growth if you’re not careful.

However, the extent to which cardio blunts hypertrophy depends on a number of factors, most notably the type of cardio you’re doing, how hard it is, and how long it lasts.

In fact, there are instances where doing certain types of cardio after leg day may actually help rather than hurt muscle growth.

At the very least, it will often provide a degree of relief from severe delayed-onset muscle soreness (DOMS).

Let’s take a closer look at both sides of the story.

How Cardio After Leg Day Can Hurt Your Gains

Here’s a scenario where doing a cardio workout the day after training your legs is likely to interfere with your gains.

Imagine you’re following a 4-day upper/lower split. You train your upper body on Monday and Thursday, while Tuesday and Friday are leg days.

Here’s what your workout routine looks like:

• Monday: Upper Body
• Tuesday: Lower Body
• Wednesday: Off
• Thursday: Upper Body
• Friday: Lower Body
• Saturday: Off
• Sunday: Off

On top of that, you add a couple of 6-mile trail runs to your schedule. Both runs are done on Wednesday and Saturday, which is the day after training your legs. 

Let’s also assume each run is performed at a reasonably high intensity (85-90% of your maximum heart rate), and that the trail takes you up one side of a hill and down the other.

Running, downhill running in particular, generates a high level of mechanical stress on your leg muscles, which is likely to cause a significant amount of damage. Your knees, hips and ankles also take a pounding.

Problem is, your hamstrings, glutes, calves and quads are still recovering from and adapting to the leg workout you did the day before. 

Muscle growth doesn’t happen when you’re in the gym lifting weights. Rather, what you do in the gym triggers a series of adaptations that take place in the hours and days after your workout is over.

Muscle damage is being repaired, new muscle protein is being synthesized and connective tissue is being remodeled, all of which leaves your body better prepared for your next leg workout.

Not only are you interrupting that process by going for a run the next day, you’re also presenting your body with an additional stimulus it needs to recover from and adapt to.

Running on two of your rest days means that instead of working your leg muscles twice a week, they’re now being trained four times a week.

Some of the resources used by your muscles to recover and grow are now spread more thinly than they were before, which has the potential to hurt your gains.

What Type of Cardio Is Best After Leg Day?

It’s a different story if you were to replace the trail run with 30-40 minutes of moderate-intensity cardio (70% or so of your maximum heart rate) on a stationary bike or rowing machine. 

This type of cardio session is a lot less physically taxing than trail running, doesn’t cause as much muscle damage, and can be recovered from a lot more quickly.

As a result, it’s less likely to interfere with the adaptations to a prior leg workout.

So if you want to do cardio after leg day, I’d suggest something like cycling, rowing, or swimming.

With low-impact cardio, there’s far less muscle damage and joint stress compared to running. This means there’s less potential to interfere with the adaptations to weight training.

In fact, this type of cardio may well help recovery by promoting blood flow to the muscles without causing further damage. 

This increase in blood flow delivers more nutrients to the muscles, as well as clearing away some of the wreckage caused by all the squatting, deadlifting and leg pressing you did the day before.

Low-to-moderate intensity cardio (such as cycling) for 20-30 minutes the day after a heavy leg workout, for example, will often reduce delayed-onset muscle soreness (DOMS) and may accelerate the rate at which muscle damage is repaired [1, 2].

One of the other benefits of cycling is that it doesn’t seem to have any adverse effects on muscle growth. 

In one study, researchers from Finland’s University of Jyväskylä tested the effect of 21 weeks of aerobic exercise on muscle size, strength and power in a group of healthy men [3]. 

One group lifted weights twice a week, while group two performed the same workout but did an extra 30-60 minutes of cycling on separate days twice per week.

The result? 

Aerobic exercise had no negative effect on muscle size or strength. In fact, while the difference between the two groups didn’t reach statistical significance, muscle growth in the legs was greatest in the group combining cycling on a stationary bike and resistance training.

Interestingly, the addition of cycling to a resistance training program has been shown in some studies to actually improve rather than impair gains in muscle mass, albeit mainly in untrained novices rather than seasoned lifters [4, 5, 6, 7, 8]. 

Cycling is a form of low-intensity resistance exercise, and the resistance-like loading stimulus has been shown to increase the size of the slow-twitch type I muscle fibers [9]. 

Capillary Density and Muscle Growth

One of the other potential benefits of endurance exercise when it comes to building muscle is that it increases something known as capillary density.

Capillaries are tiny blood vessels, which deliver oxygen, nutrients and hormones to muscle cells, clear the metabolites that build up during a workout, as well as helping with repair and recovery from one workout to the next.

And there’s some interesting research to show that differences in capillary density partly explain why some people make gains faster than others [10].

That is, a higher capillary density was associated with a greater increase in muscle fiber size during resistance training.

Six weeks of endurance exercise has also been shown to augment muscle hypertrophy during a subsequent 10-week resistance training program [11].

The researchers found a link between the degree of capillarization and muscle growth. That is, muscle fibers with the greatest capillary density were the ones that grew the fastest.

In short, an increase in capillary density may have a small but positive effect on your ability to build muscle, possibly via an increase in the quality of your workouts (improved recovery between sets and increased ability to fight fatigue), a faster rate of recovery from one training session to the next, an increase in the supply of nutrients to the muscle, or some combination of the three.

And one of the best ways to boost capillarization is to do some cardio.

Most research shows that longer sessions of moderate-intensity cardio do a better job of stimulating capillary growth than shorter bouts of high-intensity interval training (HIIT) [12]. 

Frequently Asked Questions

What cardio is best for after leg day?

In most cases, stick with low impact moderate-intensity cardio. Cycling on a stationary bike for 20-30 minutes is ideal. As well as helping recovery, this will burn off a few extra calories and help to improve your overall fitness.

Avoid doing any high impact high-intensity interval training (HIIT) the next day, which is far more likely to interfere with your ability to recover and grow.

Should I finish leg day with cardio?

You can finish leg day with cardio. In fact, doing HIIT after lifting can serve as an effective supplement to your leg training, helping to improve your cardiovascular fitness without putting the brakes on (and potentially even contributing to) muscle growth.

And by HIIT after lifting, I’m talking about bike sprints.

By themselves, bike sprints aren’t a direct one-for-one replacement for resistance training. It’s not like you can ditch exercises like the squat, leg press or leg extension, start doing sprint intervals on a bike, and expect to gain the same amount of muscle.

However, I do think that high-intensity interval training can form part of an effective approach to training your thighs when it’s programmed alongside a weight training program.

Done immediately after training your legs, sprint interval cycling is like a supplement to your regular strength training program. Think of it like a “finisher” for your quads. You can read more about the benefits of finishing leg day with cardio here.

Is it OK to run after leg day?

Running tends to cause a lot more muscle damage than something like swimming, cycling, or even incline treadmill walking. There’s also a lot more wear and tear on your joints, specifically the knees, hips and ankles. As a result, going for a run after leg day has a much greater potential to interfere with recovery compared to low-impact cardio.

What should I workout after leg day?

That depends a lot on the workout routine you’re following. On a 4-day upper/lower split, for example, a leg day workout is typically followed by 1-2 days of rest. But on a 6-day push/pull/legs split, leg day is usually followed by a push day workout.

Should I do cardio before a leg day workout?

That depends a lot on what type of cardio you’re doing, and how long you’re doing it for.

Using low-intensity steady-state cardio as part of a general warm-up for weight training has the potential to improve your performance in the gym. That’s because a warm muscle tends to perform better than a cold muscle, as well as being more resilient to injury.

But it’s a different story with more intense and/or longer duration cardio.

In one study, performance during the high pull, squat, bench press, deadlift and push press was adversely affected when lifting was performed after cardio, with high-intensity interval exercise leading to the largest decline in exercise performance.

Over time, this dip in performance is likely going to mean slower gains in strength and size.

What should you do after leg day to help recovery?

The things that will help recovery after a tough leg day workout are the same things that will help recovery after any type of workout. Make sure to get as much sleep as you can, eat plenty of food (protein in particular), and avoid doing any intense and/or long duration cardio.

Using a foam roller the day after training has been shown, in some studies at least, to reduce post-exercise muscle soreness, and might be worth using if you’re feeling especially sore.

Personally, I prefer to ride on a bike for 30 minutes or so, keeping my heart rate somewhere between 60-70% of its maximum. This helps to reduce any lingering muscle soreness, and also helps to clear my head and leaves me feeling better.