If you have decided to take the P90X fitness challenge, you will need some dumbbells to get started. Created by Tony Horton and produced by Beachbody, the P90X program involves a blend of strength training, flexibility and cardio to improve your physical fitness level. Learning how to size your dumbbells for the P90X workout may mean the difference between a solid workout and a muscle injury.
Go to your local sporting good's store or find a friend with a complete set of dumbbells. At the sporting goods store, locate the area with free weights or dumbbells, usually included in the fitness section.
Select a starting dumbbell weight of 8 lbs. for a woman or 20 lbs. for a man, according to the P90X Fit Test at Decidetostayfit.com/p90xFitTest.pdf. These are the minimum starting weights suggested for the P90X program.
Complete a set of bicep curls with good form up to the point of failure. Both men and women should be able to complete 10 repetitions with the 20-lb. or 8-lb. weights, respectively, according to the P90X Fit Test.
Take note of how many repetitions you completed if you were able to surpass 10. If you could easily complete 15 or more repetitions, select a heavier weight. In a set of 15 repetitions, the last two reps should require maximum effort on your part.
Select the dumbbells that you can use to complete between 10 and 15 repetitions, with the last two requiring maximum effort to curl. Consider purchasing the dumbbell that is next size up as well, as your strength should improve over the course of the program.