One problem with research looking at concurrent resistance training and cardio is it’s hard to cover all the variables. For example, a person who does 90 minutes of cardio and 15 minutes of resistance training every day will likely have problems developing lean muscle mass. On the other hand, someone who does 20 minutes of cardio and an hour of heavy resistance training on alternative days may not. So many factors come into play – type, duration and intensity of the cardio and resistance training being performed. Then there are nutritional factors. If you’re doing cardio every day and not consuming enough protein, you’ll have trouble putting on muscle no matter how hard you resistance train. As you can see, it’s not an easy thing to study.
What Does Recent Research Show About Cardiovascular Exercise and Muscle Growth?
One study published in the Journal of Strength and Conditioning Research looked at concurrent strength and endurance training. One group did a serial strength and aerobic workout. They began by doing resistance exercises and then proceeded to do an aerobic workout before cooling down. The second group did the same exercises but did them in an integrated manner, like a circuit workout. They performed an aerobic exercise followed by a strength exercise to keep their heart rate up through the entire workout. By the end of the study, both groups had made greater than expected gains in upper and lower body mass. Interestingly, the group that did integrated strength and cardio experienced more muscle gains than those that did the two forms of exercise serially. The researchers point out that concurrent training may not interfere with muscle growth and may actually offer some synergy.
It’s an intriguing thought that cardio could work synergistically with resistance training to help build lean body mass. Why might that be? No one knows for sure, but there are some possibilities. Consider the adaptations your body undergoes when you do aerobic exercise. Endurance training increases the number of ATP-generating mitochondria inside muscle cells and the number of capillaries that carry blood to your muscles. In addition, cardio improves cardiac stroke volume so you’re pumping more blood with every beat. That means your muscles are capable of getting more oxygen and nutrients to your muscle cells when you’re resistance training. That could work in your favor if you’re trying to develop strength or increase the size of your muscles.
Despite some research showing synergy, the issue is far from resolved. A meta-analysis published in 2012 also looked at this issue. It showed no significant difference in muscle strength or hypertrophy between groups that did concurrent resistance training and cardio compared to those that did resistance only. What they did find was concurrent training appears to reduce power. They also found that the type of cardio matters. Running as a form of cardio interfered with lower body muscle and strength development while cycling did not.
Nutrition is a Factor Too
Nutrition enters into the equation too. If you’re doing long periods of endurance training and not consuming adequate protein and carbs, your cortisol level will rise. This creates a catabolic state as your body breaks down muscle tissue so the liver can use it to make glucose. If you do more than 30 minutes of endurance training, make sure you’re not in a protein or carb-depleted state. Fasted morning cardio could interfere with the gains you’re trying to achieve from resistance training.
The Bottom Line?
There’s no real consensus as to whether cardio and resistance training interfere with one another or whether there could be some synergy between the two. Based on what’s known, here are a few tips.
Understand what your primary goal is – is it to increase your endurance or build lean body mass? If you’re around your ideal weight and want to develop muscle definition, make resistance training your main focus – without ignoring cardio. Keep your cardio sessions short and intense. Interval training works well because it gives you a good cardiovascular workout in a short period of time. You don’t need to work out for more than 20 minutes when you keep the intensity high. Limit cardio to three times a week – not every day. Running is probably not your best choice for cardiovascular exercise if you’re trying to build lean body mass.
When you resistance train, make sure you’re challenging yourself. You should be doing a hypertrophy workout, not a muscle endurance one. Just as importantly, make sure you’re consuming enough calories and protein and you aren’t working out in a carb-depleted state. Be sure you’re including adequate rest and recovery time. Overtraining will limit the ability of your muscles to grow. Maintaining a proper balance between the two forms of exercise is important. Reduce the risk of interference by emphasizing the one that best helps you reach your goals.
References:
J Strength Cond Res. 2008 Sep;22(5):1487-502.
J Strength Cond Res. 2012 Aug;26(8):2293-307.
European Journal of Applied Physiology, 45, 255-63.
Related Articles By Cathe:
5 Hormones That Impact Muscle Growth and How They Work
Is Muscle Damage Necessary for Muscle Growth?
A Different Approach to Training: Integrated Concurrent Training
Can You Build Muscle Size Through Aerobic Exercise?
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Great information. However, what if you are trying to trim down, what is the best balance between cardio and resistance training?
In case you check this article again Kathy, here is a link to one of Cathe’s articles that addresses your question:
https://cathe.com/5-tips-for-strength-training-to-lose-weight