Author: Troy Theodosiou

Performing “cardio” too frequently, too intensely or for too long can certainly prevent you from gaining muscle from your strength training workouts. A bodybuilder wanting to pack on muscle will not achieve optimal training results when half of his or her workouts consist of excessive cardio training. Just as a marathon runner will not improve his or her running performance by pumping heavy weights in the gym every day.

Consider all the necessary resources required by your body to build muscle. You need good nutrition to provide protein for muscle growth, and carbohydrates and fats to fuel and enhance recovery from your intense workouts. You also need rest and recovery time between workouts to allow your body to rebuild and increase your muscle mass.

Decades ago, it was shown that 10 weeks of cardio plus resistance training interfered with muscle growth relative to resistance training alone. However, if you take a closer look at the training volume used in that study—six days a week of cardio plus five days a week of strength training—you can see it was quite high. Few of us today are going to be doing 30-40 minutes of cardio six days week.

More recent research suggests that moderate amounts of cardio can actually boost the effects of strength training. Studies have shown that resistance training coupled with 2-3 days of cardio can lead to greater gains than strength training alone.

Common forms of cardio include walking, jogging, swimming, cycling, and fitness classes. Cardio machines may include a rower, elliptical, stair climber, upright or recumbent bike, and treadmill.

According to the Center for Disease Control and Prevention (CDC), a 154-pound person can burn anywhere between 140 and 295 calories in 30 minutes doing cardiovascular exercise. Here are some different methods of cardio and the number of calories you can burn in 30 minutes:

  • Hiking: 185 calories
  • Dancing: 165 calories
  • Walking (3.5 mph): 140 calories
  • Running (5 mph): 295 calories
  • Cycling (>10 mph): 295 calories
  • Swimming: 255 calories

Aerobic exercise (regardless of intensity) will help to:

  • Strengthen the muscles involved in respiration, to assist lung function.
  • Increase the total number of red blood cells in the body, to enable greater oxygen facilitation throughout the body.
  • Strengthen the heart muscle, which will improve resting heart and pumping efficiency.
  • Reduce stress and tension, and increase mental well-being.
  • Increase circulation throughout all areas of the body.
  • Increase self-esteem.

Lower-to-moderate intensity aerobic activity (50-75 percent of MHR) will:

  • Typically provide less impact on the joints, making it ideal for the obese and/or unfit.
  • Burn fat directly (as opposed to total calories) and can be done for a longer period.
  • Can be used as active recovery from more intensive training systems.

Higher intensity aerobic activity (70-85 percent of MHR) will:

  • Will burn more total calories and more total fat as a result.
  • Will increase the metabolic rate (during and after training) to a greater degree than will lower intensity aerobics.
  • Offer fitness benefits such as improved endurance, strength, and athletic performance.
  • Help with the prevention of osteoporosis.

According to Tommy R. Lundberg and his Swedish research team, endurance training not only indirectly benefits muscle building, it can even directly contribute to muscle growth. In a study published in 2013 in the Journal of Applied Physiology, he comes to the conclusion that a combination of endurance and resistance exercise leads to greater muscle growth than strength training alone. These findings are further supported by a new study published in 2016, once again by a Swedish research team headed by Zuzanna Kazior. The results of this study, however, contradict the findings of several other research papers showing that a combined training program does indeed interfere with muscle growth.

The takeaway here is that too much cardio can interfere with muscle growth—but so can too little. Performing cardio 2-3 days a week seems to be the sweet spot for complementing your training gains without putting your muscle at risk.