You shouldn’t skip your cardio workouts, even if you’re looking to build muscle.
In my day-to-day life as a personal trainer, clients often pick my brain about how certain workout methods — cardio, strength training, you name it — impact your body, for better or worse. But lately, as I scroll through the fitness realm of social media, I’ve seen questions specifically surrounding whether performing heart-healthy cardio can derail your muscle growth.
My opinion? Cardio enhances your muscle gains.
In case you need a refresher, cardio is any activity that raises your heart rate and helps your cardiovascular and circulatory systems become more efficient. The better you are at circulating nutrient- and oxygen-rich blood, the more efficient you will be at building muscle. Over time, cardio also enhances the functioning and number of mitochondria (organelles that use oxygen to create energy in the form of ATP) in skeletal muscle, an attribute that’s positively linked with exercise capacity in healthy humans.
Scientific literature backs this idea up, too. Research from 2014 suggests that aerobic exercise training can induce muscle hypertrophy in sedentary individuals between the ages of 20 and 80. The study authors also state that aerobic exercise training may be a viable exercise option to alleviate age-related reductions in muscle mass.
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Still, based on the science I’ve read and my own philosophy, I believe cardio can negatively impact muscle growth — if there are bad behaviors involved. Not fueling yourself with the right nutrients before and after a workout, running short on sleep, and overtraining can all potentially lead to muscle loss. But cardio isn’t necessarily the root cause.
Overtraining is the big one. Generally, to support your health, 80 percent of your weekly cardio makeup should be zone two work — steady-state cardio that builds your aerobic capacity and is easy enough that you’re still able to hold a conversation. The other 20 percent should be training in zones four and five, work that builds your anaerobic capacity and is so difficult you can’t speak. I often see people not spending enough time training in zone two; they don’t go easy on their easy days. If you spend more of your time working at a higher intensity than necessary, you might start to plateau in your resistance training routine, your rating of perceived exertion may go up when working with a weight that once felt easy, and you could experience more delayed onset muscle soreness. All of those changes are signs your body isn’t firing on all cylinders.
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So when your goal is building or maintaining muscle but you still want to reap the health benefits of cardio, follow this game plan: During your workouts, make sure to strength train first — when you can complete your reps with the most energy and focus — then do your cardio. (A 2022 review found that performing aerobic exercise before resistance training resulted in moderate declines in muscle strength.) The type of cardio you perform might involve quickly moving a load, such as kettlebell swings or power sled pushes, to further challenge your muscles.
What’s most important, though, is doing an activity you enjoy. Play pickleball with your friends. Read a book while riding the stationary bike. Swim in a local pool. Prioritizing the cardio you find fun — not the ones you dread — will lead the way to better gains in the long run.
Mike Owczarek is a Tier 3+ Coach and group fitness instructor at Equinox Hudson Yards. A basketball player turned runner, Owczarek is now on his journey of healing and running a second marathon, and he loves all things movement and exploring what is new. In addition to strength and conditioning, Mike specializes in stick mobility, nutrition, and pre- and post-natal coaching.