The general recommendation for muscle fitness exercises for teens depends on several factors. First, it is important to know whether you want to build muscular endurance or muscular strength. Second, it is important to know your age. Finally, it is important to know if you are a beginner or a person who has been doing regular muscle fitness exercise. Strength exercises should be performed two or three days a week and not on consecutive days. For muscular endurance, the exercises can be done three to six days a week. For preteens (11 to 12), younger teens (13 to 14), and older teens who are just beginning, two days a week would be a good place to start. Preteens, younger teens, and beginners should do fewer sets and repetitions than older teens and those who have been doing regular muscle fitness exercises. Check table 7.2 on page 81 and the information on page 82 of the middle school textbook and pages 218-226 of the high school textbook for more information on the number of sets and repetitions to perform.