An at-home workout program designed to get you in the best shape of your life, P90X pushes you to your limits. What those limits are depend on your fitness level and are measurable by increases and decreases in your heart rate as you work out. However, that doesn't mean you should spend a lot of time monitoring your heart rate.
In fact, Steve Edwards, vice president of fitness and nutrition at Beachbody, the company that produces P90X, states in a blog on the company's website that the workouts don't target a particular heart rate zone, and monitoring your heart rate in each workout isn't necessary. However, it can be helpful for tracking your progress and recovery as you go through the 90-day program.
Maximum Heart Rate
Any talk of heart rate zones should first begin with an explanation of maximum heart rate. Your max heart rate is the limit of your cardiorespiratory system during exercise — the highest number of beats per minute your heart can handle for any period of time.
Max heart rate varies from person to person and depends on many factors, including genetics, age, gender and fitness level. A rough estimate can be calculated by subtracting your age from 220. You can get a more accurate reading in a clinical test, or by conducting your own field test wearing a heart rate monitor.
Heart Rate Zones
Max heart rate is important to understand because it's the basis for the target heart rate zones. These zones refer to varying levels of intensity from low to high, depending on how close they get you to your max heart rate.
Zones 1 and 2 are the lower-intensity zones, with recommended heart rates between 50 percent and 70 percent of max heart rate. In these zones, the perceived exertion difficulty is 2 to 5 on a scale of 10.
Zone 3 is the aerobic zone, with a perceived exertion rate of 5 to 7 and a heart rate between 70 to 80 percent of your max heart rate.
Zones 4 and 5 include the threshold zone and the redline zone. In the threshold zone, you are at 80 to 90 percent of your max heart rate with a perceived difficulty of 7 to 9. In the redline zone your heart rate is between 90 and 100 percent of max with a perceived difficulty of 9 to 10.
Read more: Is P90x a Good Workout for Beginners?
P90X Workout Intensities
During the 90 days of the P90X program, you should spend some time in all of these heart rate zones. During the cardio, kenpo and plyometrics workouts, you'll spend a lot of time in zone 3 and some time in zone 4 and even zone 5. These workouts are meant to get your heart rate up and keep it up to improve cardiovascular conditioning and burn calories.
These high-energy workouts utilize interval training, which involves alternating periods of high-intensity effort with periods of recovery. During the high-intensity periods, you should be working close to your limit. These are the periods where your heart rate will be highest, in zones 4 and 5.
During the resistance training workouts, you may start out in zones 2 and 3 if you're a beginner. The idea is that you will continue to increase the resistance and repetitions of the exercises to increase the intensity as you get fitter.
During the yoga, stretching and abs workouts, which are less demanding, you'll primarily be in zones 2 and 3.
Why Heart Rate Is Important
A lot of emphasis is put on these heart rate zones, but the truth is they're not really important for recreational exercisers who just want to get fitter, leaner and stronger.
According to Edwards, P90X is designed so that you go as hard as you can during the high-intensity efforts and ease off during the lower intensity periods. You'll know when you're pushing your hardest without looking at your heart rate or worrying about zones. Edwards writes that only athletes or those training for a particular race or event need worry about heart rate zones.
But, that doesn't mean your heart rate isn't important. It can be very helpful in measuring your progress in P90X. As you become more aerobically conditioned, you should start to see your heart rate decrease during the program, compared to when you first started. You should also see your heart rate increase as you do the strength-training workouts, because you should be continually challenging yourself with increased reps and weight.
You can also use your heart rate to judge recovery and make sure you're not overtraining. As you follow the program, you should start to see your resting heart rate become lower first thing in the morning. If consecutive days go by where your heart rate is higher than normal first thing in the morning, it could be a sign that you're getting sick or that you're overtraining and not getting adequate recovery between workout sessions.
Read more: P90X Workout Program Pros & Cons