The P90X home workout program designed by personal trainer Tony Horton features 12 weeks of workouts known for their intensity and difficulty. Workouts are completed six days per week, with each workout lasting about 60 minutes. The chest and back workout is scheduled for weeks one, two, three, nine and 11.
P90X is not designed for building mass, but for building overall fitness. Although you can expect your chest muscles to grow, there are better workout programs if your goal is to build size.
Building Muscle Mass
Building muscle mass requires that you complete high-volume resistance training. As you complete such workouts, your muscles are damaged, creating small tears in the fibers. This stimulates the healing process, during which your body adapts growing bigger and stronger muscles that are better equipped to handle the stress of weight training.
Increasing Chest Size
In order to build the size of your chest muscles, you need volume and the right weight. A minimum of eight sets of exercises that directly target the chest muscles is a good goal, but doing more than that -- 15 to 20 sets -- is often recommended.
To build mass -- also called hypertrophy -- the genral rule of thumb is to do sets of eight to 12 repetitions. The weight you choose should be heavy enough that you reach muscle failure -- you can't do another rep with good form -- between reps eight and 12 on each set.
P90X Chest and Back Workout
The P90X chest and back workout consists of six chest exercises, including standard push-ups, military push-ups, wide fly push-ups, decline push-ups, diamond push-ups and dive-bomber push-ups. Each of the six exercises is completed for two sets, meaning the workout consists of a total of 12 sets of chest exercises.
The volume of chest exercises in the P90X workout is adequate for building muscle mass, however the reps may be too high in some cases. This largely depends on your current fitness level. Each set of the P90X chest exercises are completed for about 60 seconds. While you may only be able to complete eight to 12 reps of the harder exercises, you'll likely be able to complete more than 12 of the easier exercises. You may be able to complete close to 20 repetitions of an exercise during this amount of time. Therefore, your reps will exceed the target range for hypertrophy.
Others will find P90X more challenging and may only be able to perform eight to 12 reps per set. In that case, hypertrophy is probable. On the flip side, if you find the workout so difficult that you're only able to complete one to six reps per set, you are not in the optimal range for building mass.
The P90X workout is highly effective for total-body conditioning. Most people will gain some size during the program simply due to the challenges placed on the muscles. If you want more, you can add in some higher weight, lower rep chest exercises on another day of the week -- preferably 72 hours after the chest and back workout.
Remember that adequate rest and nutrition are critical for building muscles. Follow the dietary guidelines provided with the workout, and never work out your chest more than once every two to three days.
Read more: What Equipment Is Needed for P90X Workouts?