Does Cardio Kill Gains? How Much Cardio Is Too Much?

It’s an observable fact that the average sprinter has larger muscles than the average distance athlete. While the self-selection of sports and exercises has something to do with this difference, the bottom line is that both sets of athletes are usually engaged in similar weight training regimens, yet one group ends up with significantly larger muscles when it’s all over with.

Observations like these have led to the belief that doing too much cardio can effectively kill the gains that you might otherwise make in muscle mass. Is this true? More importantly, if it is true, what is the point at which my cardio is actively preventing me from gaining muscle at a faster rate?

Protein Intake

First of all, before we get into the precise number of calories you should be consuming, if you are engaging in both resistance training and considerable amounts of cardiovascular exercise, you should probably be following the protein intake guidance provided for athletes-in-training. 

Specifically, you might consider targeting the uppermost limit of protein intake associated with gains in muscle mass, which is 1.6 grams per kilogram of body weight, or 0.72 grams per pound of body weight. Studies have shown that maintaining a positive nitrogen balance through protein consumption even in caloric deficit can still result in muscle mass gains. (1) (2)

To be clear, your level of cardio will not detract from the work protein is doing to restore your muscles and potentially help them grow, so it is important to ensure that you are consuming ample protein to support your training efforts.

Caloric Intake

Once you’re certain you’re ingesting enough protein to ensure that you’re achieving a positive nitrogen balance and maintaining an optimal internal environment for muscle growth, you can now focus on the amount of calories you’re ingesting during a day. 

Based on the results of research, once you establish what your baseline is for daily calorie consumption and size maintenance, it is advisable that you ingest 1,500 to 2,000 calories above that caloric baseline every day in order to create a system conducive to building muscle mass at a rapid rate. (3)

So here’s where it gets tricky: Chipping away at this figure through cardio will absolutely deplete your body of the available calories it needs to accelerate the creation of new muscle. So if you are engaging in a lot of cardio and desire to gain muscle, you are advised to offset the caloric burn to some degree if you are prioritizing muscle growth over the loss of body fat and other potential training goals.

Individual changes due to caloric intake

Certainly, there will be metabolic changes that occur in your body as a result of increases and decreases in calories. One of the changes that is often considered to be a negative consequence of eating too many calories is the storage of unburned calories as fat tissue, and this can vary based on a number of factors, including the type of food you’re consuming, the type of training you’re doing, and your individual metabolism.

Because different people’s bodies respond in different ways to the same combinations of factors, you should be diligent about monitoring your physical responses to your training and dieting regimen, and be prepared to make changes if you find that the net effect on your physique isn’t something that you can live with. 

In this specific case, if you’re only doing a little cardio after making a dietary adjustment, you may still find that it’s too much cardio to help you grow your muscles at the rate you want depending on your body’s unique characteristics.

Cardio doesn’t have to kill your gains

The short answer to the question of whether or not cardio can hinder your muscle gains is a resounding “yes,” but that doesn’t mean you have to like it, and it certainly doesn’t mean you have to live with it. Boosting the amount of calories you're consuming, and especially the amount of protein in your diet, can result in significant muscle growth in your physique despite an aggressive training regimen that includes a high volume of cardiovascular training.

Summary:

1. No matter how many calories you consume or burn, the presence of a positive nitrogen balance caused by sufficient protein intake can still enable you to build some muscle even in a calorie deficit. 

2. Muscle grows more rapidly in bodies that are consuming 1,500 to 2,000 calories about their baseline threshold, and cardio can chip away at this figure and prevent faster muscle gains.

3. Because people’s bodies respond differently to the same types of nutrients and exercise, you should monitor the response of your body closely and be prepared to tinker with the amount of cardio in your workout to ensure optimal muscle growth.

Sources:

1. Pikosky MA, Smith TJ, Grediagin A, Castaneda-Sceppa C, Byerley L, Glickman EL, Young AJ. Increased protein maintains nitrogen balance during exercise-induced energy deficit. Med Sci Sports Exerc. 2008 Mar;40(3):505-12. doi: 10.1249/MSS.0b013e31815f6643. PMID: 18379214.

2. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial12, Longland, Thomas M et al. The American Journal of Clinical Nutrition, Volume 103, Issue 3, 738 - 746

3. Ribeiro AS, Nunes JP, Schoenfeld BJ, Aguiar AF, Cyrino ES. Effects of Different Dietary Energy Intake Following Resistance Training on Muscle Mass and Body Fat in Bodybuilders: A Pilot Study. J Hum Kinet. 2019 Nov 30;70:125-134. doi: 10.2478/hukin-2019-0038. PMID: 31915482; PMCID: PMC6942464.