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.
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.
Lastly, 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.
Special Consideration for Ectomorphs
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.
Absolute beginner ectomorphs are the only weightlifters who should not do cardio in the beginning of the bulking phase, according to strength and conditioning specialist Jason Ferruggia. For this group, often referred to as "hardgainers," Ferruggia recommends laying off cardio for eight to 12 weeks, getting your training and diet dialed in until you have put on 15 to 20 pounds of mass.
If you feel that you need to do some type of cardio, stick to two or three low-intensity sessions of 20 minutes a week.
Types of Cardio
After the initial period, beginner hardgainers should add in three 20-minute sessions of moderate-intensity cardio each week, advises Ferruggia. He recommends riding a bike to limit stress on the joints.
Everyone else should be doing two to three cardio sessions per week of either long, slow cardio; moderate-intensity cardio; or high-intensity intervals. Bodybuilding coach Sean Nalewanyj recommends one to two high-intensity interval sessions of eight to 20 minutes and one to two longer and lower-intensity sessions of 40 to 60 minutes.
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, bodybuilder Aaron Nimmo advises doing it no less than three hours prior to lifting to give your body a chance to recover. According to Nimmo, your best bet is to do your cardio as far apart from lifting as possible.