Have you ever found yourself doing a strenuous weight training session after doing cardio or after having a physically-demanding day at work?

If you have, then you’ve probably realized something:

It can be grueling, and it can feel like you’re putting too much stress on your body that will lead to muscle loss.

And, to some degree, that’s true.

Now, the question is, does cardio after lifting weights kill gains?

Cardio After Weight Training – Gains Killer or Fat Destroyer?

Eh, most likely neither. Even if we can see some increased fat-burning from doing cardio after weight training, the effects would be negligent in the long-run. In other words, sure, doing cardio after weights might lead to slightly better fat burning. But that slight increase wouldn’t lead to significant results over the months.

We do know that there is an interference effect, especially if we lift and do cardio in the same workout – there is simply no way around it. For example, in one study, researchers looked at endurance performance after strength training (1). They concluded:

These results suggest that endurance performance may be impaired when preceded by strength-training, with no oxygen uptake or heart rate changes during the exercise.

So, you can expect your cardio to suffer a bit if you do it after lifting weights. But, it comes down to what your goals are. If you primarily care about muscle and strength gain, this shouldn’t concern you.

Other research has shown that doing too much cardio can interfere with resistance training-induced adaptations (2). In one meta-analysis from 2012, researchers concluded (3):

Our results indicate that interference effects of endurance training are a factor of the modality, frequency, and duration of the endurance training selected.

No, cardio after lifting does not kill gains, but you should expect your aerobic performance to be lower. You should avoid going overboard with it in order to maximize muscle gain / prevent muscle loss. 

Why You Shouldn’t Do Cardio Before Weight Training

Okay, so what about cardio before weights? Well, if you want to optimize your lifting performance and muscle growth, you should avoid it.

For example, in one study, researchers examined the effects of strength training performance following aerobic training (4). They concluded:

It was concluded that when aerobic training precedes strength training, the volume of work that can be performed is diminished for up to 8 hours. This impairment appears to be localized to the muscle groups involved in the aerobic training.

So, you should either do your cardio at least eight hours before weight training, do it after lifting, or do it on a rest day to avoid any potential interference.

Suggestion: If you are enjoying this article, you might like another article on Pump Some Iron: “Should You Do Cardio On Leg Day?” Click this link if you want to check it out. 

Cardio After Weights – Three Important Considerations

Say that you want to do cardio after weight training. Here is what you should keep in mind:

  1. What type of cardio do you plan on doing?

The type of cardio work you choose to do after your lifting session matters. For example, if you’ve done a push workout, it might not be the best idea to train the battle rope afterward. Your upper body musculature would be fatigued, and you wouldn’t be able to train as hard, burn as many calories, and reap the same benefits.

The same goes for doing leg-based cardio (running, climbing the Stairmaster, etc.) after a lower-body workout.

So, if you can, choose a cardio activity that will involve different muscles from those you’ve trained.

  1. How long do you want the cardio session to be?

As we discussed, doing too much aerobic work can interfere with your strength training adaptations (2, 3). Researchers suggest that longer and more frequent cardio sessions can hinder muscle growth (5).

So, if you want to do cardio after lifting, it’s best to limit it to no more than 15-20 minutes.

  1. What do you want to get out of it?

And finally, you should get clear on what you’re looking to gain from it? Are you doing it to kill two birds with one stone? Is this all your schedule allows, and you can’t possibly do your cardio at another time? Do you expect to burn more fat and get lean faster?

If you’re doing it for efficiency or because that’s what your schedule allows, have at it. But if your primary reason to do cardio after strength training is to burn more fat, then you would be better off doing cardio on your rest days. That way, you’ll be able to do it in a fresher state, put more effort into it, and burn more calories.

Suggestion: If you are pushing the limits on cardio and want to preserve as much muscle as possible, I would supplement with HMB. HMB has been shown to reduce muscle protein breakdown by half. This, theoretically, will help you to hold on to your gains while burning off the fat. I buy nutricost brand on Amazon and use 5g per day. Click this link if you want to check it out.

Are There Any Exceptions to the Rule?

Of course. For example, if you care more about your cardio than weight training performance, then, obviously, you should go with cardio first. You should always start with what matters most.

But, don’t confuse the goal of fat loss with that of becoming more endurant. Many people use cardio primarily to aid in fat loss, and if that’s the case for you, then you should lift weights first.

Another exception here would be if you want to do cardio as part of a warm-up. In that case, jogging for, say, five to ten minutes at a low intensity shouldn’t negatively impact your lifting performance.

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