Rest and recuperation are major players in the size game. Your body does most of its growing during the sleep phase. You need adequate sleep when you are working out, especially if your goal is to get bigger. The advantages of longer rest periods between workouts are just being realized by many bodybuilders. When you lift heavy iron you really shock your system. It needs time to recuperate. If you don't pay attention to getting enough rest and recuperation your body will soon hit a state of overtraining. If you fall into this state, your body will rebel and your progress will stop. If you spend too much time in an overtrained state your body will actually start to lose muscle size. And you definitely don't need that.
Give your body lots of rest and recuperation between workouts. Get enough sleep at night. The amount necessary varies from person to person, but most people need 7 or 8 hours, and some need even more. Take naps every now and then, and in general take it easy between workouts.
Should you engage in aerobic/cardiovascular workouts while on a mass muscle-building program? Most trainers will say no. They believe that the extra effort for the aerobic/cardiovascular work depletes the system too much. And it can. But the problem is that you need to keep up your lungs and heart and overall endurance condition. Additionally, you need to be careful of putting on bodyfat, and aerobic/cardio work is the best way to deal with this.
Power walking is the perfect exercise for burning off bodyfat while still gaining massive muscle size. Power walking is such a great exercise because it is effective for burning off fat and improving aerobic/cardiovascular fitness while not pushing the body too hard. Porter Cottrell says, "I've discovered that if your goal is to build solid muscle, you have to keep your metabolism primed. In this respect, I've learned that my body responds best to two forms of aerobic exercise: the stair-stepper and fast walking. These are the two best exercises to burn bodyfat ... I usually alternate these walking sessions with bouts on the stair-stepper - but in consecutive shows like this, you have to be very aware of what's going on, and I felt that if I did the stair-stepper too intensely, I'd end up burning muscle tissue along with the fat, which I definitely didn't want to do! So I relied more and more on the walking and less upon the stair-stepper to bring me into the contest without sacrificing any muscle tissue." What Porter used for contest preparation can also be used for building mass because the power-walking workout will not burn muscle tissue as do most other cardiovascular workouts. Power walking is an awesome exercise for the person who wants to pack massive muscle onto his physique without adding extra fat. There is less risk of injury with power walking. If you can get in 2 or 3 sessions of power walking for 2 to 4 miles per session you will notice that the muscle mass you are putting on doesn't come with that unwanted marbling of bodyfat. The pace of your walking should be 3-1/2 to 4-1/2 miles per hour. This pace is just right for using fat as fuel instead of the more precious glycogen stores. Make power walking the cornerstone of your aerobic/cardio conditioning during your mass muscle-building program. There is no better aerobic/cardiovascular exercise to use while putting on muscle mass than power walking.
Aerobic/cardiovascular fitness is important to your body-training program. If you neglect it the capacity for intensity in your workouts decreases. You will perform your workouts at a lower level, and run out of steam sooner. It is important to use some aerobic/cardio work that conditions the body without digging too deep into the body reserves. Power walking is perfect for meeting this criteria.
Another trio of good exercises that will build the aerobic/cardio condition without wiping out the recovery system too much are stair-stepping/climbing, bike riding (stationary or regular) and swimming. Swimming also has the extra effect of really stretching out the body. Some lifters swim right after working-out and report less stiffness and soreness from the effect of the weights than if they didn't swim. The key to using these aerobic/cardiovascular exercises is to get in a good brief workout (20 to 40 minutes) 2 to 3 times a week. Don't push yourself too hard on your aerobic/cardiovascular workouts - just enough to burn off bodyfat and challenge the lungs a bit.
Choose to use power walking or stairstepping, swimming, or biking to maintain a good level of aerobic/cardiovascular fitness. Or use a mixture of all of them. But don't do too much while on a mass muscle-building program - a couple of workouts per week should be enough. If you find that you are putting on a little more fat than you want, add a third aerobic/cardio workout to your weekly routine. But take it easy and keep the focus on the muscle-building program.
One mistake that some people make is not building enough muscle mass before they move on to other "fancy" style specialty workouts. Or they give their physique just one main cycle of mass-building and then move on. If you do not have sufficient muscle mass, then you should not be focusing on other training approaches. Michael Francois points out that a lot of bodybuilders start to get into advanced speciality workouts before they have built a good base of muscle mass. What if you fall into that category? What if you realize that you do not have sufficient muscle mass? You need to go back and re-establish your muscle mass base. Too many people wrongly assume that you only have one shot to put on muscle mass. That is not necessarily true at all. There is no law that says you cannot go back and rebuild your size base. Put together a "second-stage" size program. Go back to the basics and add the extra muscle mass you need to get to the size you want for your physique.
Making your muscles larger is an art and a science. Use the known science of muscle-size expansion for informational purposes, and develop the art to fit it to your unique physique. Focus on the muscle size you want (as opposed to just body size) and stick with the basics - a nutritious and size-specific diet, heavy-metal training, and plenty of rest and recuperation.