Committing to work out every day is a big goal. Whether you do P90X or run, simply sticking with a challenging daily schedule is an accomplishment in itself. But if you want to know which is best for you, there are a few factors to consider. Take into account the energy requirements and convenience of the workouts as well as your need for rest.
According to research commissioned by the American Council on Exercise, the energy expenditure from P90X is "very comparable to jogging." Jogging has a metabolic equivalent task value of 8 -- meaning that your body burns eight times as much energy jogging as it does resting. The MET value for P90X ranges from a value of 6.7 for the "Chest, Shoulders & Triceps" workout to 10.8 for "Plyometrics." But if you're a fast runner you'll burn more daily calories running than with P90X; running at a speed of 8 mph has a MET value of 13.5.
Convenience and Equipment
P90X has the advantage of being an indoor workout. This can be a real advantage on rainy, cold or excessively hot days if you're committed to sticking with a seven-day-a-week schedule. If you run every day you will either need to deal with the elements or you'll need to have access to a treadmill. But aside from that you won't need any special equipment for running except for a pair of running shoes and appropriate clothing. For P90X you'll need to invest in dumbbells or resistance bands, a chin-up bar and a yoga mat.
You may not be able to run every day. According to the University of Rochester, most untrained runners can manage to run for at least 10 minutes everyday but according to Columbia Health's Go Ask Alice! website, some people may need multiple rest days per week. P90X includes one day of active recovery with a stretching routine. If you need a day to take it easy, P90X may be the better choice.
Deciding which activity is best for your daily routine comes down to your own personal needs and preferences. Both running and P90X offer health benefits; what's important is to choose the workout that you can stick with. Consult a doctor before starting either program. Your doctor can tell you if you're ready to workout on a daily basis. It can also be beneficial to talk to a personal trainer who can help you design your overall workout plan.