Does cardio impair muscle gains?

You may be here because you’ve heard the phrase “cardio kills gains” – Not to worry, this is a meme, and not reality. This meta-analysis of 10 studies found that doing cardio before resistance training had no apparent negative effect on hypertrophy, though it did negatively impact leg strength. This article from Stronger By Science about how avoiding cardio can hold back your training is also a good resource.

The major caveat is that adding cardio, just like any other extra exercise, will use more calories and require that you eat more food to maintain the calorie surplus necessary to build muscle.