To increase muscle mass in the bulking phase, you have to increase your caloric intake to supply your body with the raw materials for muscle growth. For some people, this can lead to fat gain instead of muscle gain, especially if the calorie intake is too high.
A moderate amount of cardio exercise will help you stay lean while you bulk, and it's good for your health, so plan to include a few cardio sessions per week. The only exception is if you're a beginner weightlifter who has problems putting on muscle mass. In that case you may want to lay off cardio for the first couple months of your training program.
Doing too much high-intensity cardio while bulking can interfere with your goals.
Benefits of Cardio Exercise
Almost everyone should be doing some type of cardio during the bulking phase. To build mass you have to eat a large amount of calories; regular cardio will enable you to eat more calories without gaining a lot of fat.
Cardio exercise also increases blood flow, delivering more oxygen to your muscles and removing waste products, such as carbon dioxide and lactic acid. The increase in blood flow to the muscles promotes muscle building by delivering fresh nutrients to the muscles needed for growth and aiding in recovery.
Last, you probably do more in your daily life than just lifting weights. To have the stamina to play a football game with friends, or even climb a long flight of stairs, you need to keep up your cardiovascular fitness with cardio exercise.
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Cardio While Bulking
People with an ectomorph body type are naturally skinny and have trouble keeping on body weight and building muscle mass. They can often eat whatever they want without gaining fat. These people have a tough time building mass. If you're one of them, you know it.
According to the American Council on Exercise, ecotomorphs are individuals with a naturally fast metabolism. This can be a disadvantage if you are trying to bulk up. ACE recommends only doing the minimal amount of cardio required to maintain your cardiovascular health — three times per week for 30 minutes.
If you are part of this group, often referred to as "hardgainers," keep your cardio at minimum for eight to 12 weeks, getting your training and diet dialed in until you have put on 15 to 20 pounds of mass.
According to an article published in the February 2017 the European Journal of Translational Myology, performing high volumes of aerobic exercise negatively impacts muscle growth — the primary goal during the bulking phase.
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When to Do Cardio
When you do your cardio depends on your training schedule. If you're on a three-day training schedule, you can do cardio on your off days. Lower intensity cardio is great active recovery. If you're on a four or five day training schedule you'll probably need to do cardio on the same day, at least some of the time.
You can do your cardio after lifting, but not before. You want to devote most of your energy to making every lift count. If you have to do cardio before consider doing it no less than three hours prior to lifting to give your body a chance to recover. Your best bet is to do your cardio as far apart from lifting as possible.