Jumping jacks are almost the perfect exercise: They work every major muscle group in your body and don't require any special equipment. If you were to spend an hour doing jumping jacks vigorously, you could burn up to approximately 700 calories, depending on your weight. But jumping jacks also involve a fair amount of impact and require good range of motion through the shoulders. If you can't handle the pounding or arm movement required, it's time to explore some effective alternative exercises.
Your Typical Low-Impact Jack
The standard low-impact variation on jumping jacks is also known as a side jack. Instead of jumping to spread your feet, then jumping to bring your feet back together, substitute a heel tap to the side for each jump out. So instead, your foot movements are right heel out, feet together, left heel out, feet together.
More Lower-Body Variations
You could substitute almost any low-impact, lower-body movement with a lateral component into jumping jacks. Try doing squat jacks -- step to one side and squat as you swing your arms up and then go back as you bring your arms back down. You could even do lunging jacks.
To do lunging jacks, step into a back lunge, rotating your torso toward the side of your back leg and swinging your arms together overhead; rotate back to the middle as you stand back up, switch leading legs and then twist your torso toward the side of your back leg. This requires good core strength and awareness. If you don't already know how to rotate your torso as one unit, ask someone for help with this exercise or eliminate the twist and just swing your arms straight overhead.
If your shoulders aren't stable or mobile enough for the arm motion required for full jumping jacks, you have two options. The first is to limit yourself to a safe, comfortable range of motion -- for example, swinging your arms out to shoulder level instead of overhead. Or substitute any upper-body motion that you can do into your jumping jacks. Examples include doing biceps curls or shadow boxing as you continue doing the lower-body portion of a jumping jack.
Other Types of Calisthenics
If you're just tired of doing jumping jacks, you can get similar benefits by doing other types of calisthenics. Try mountain climbers, burpees or star jumps. To do star jumps, stand with your feet shoulder-width apart. Squat down, bend forward slightly at the hips and then explode upward, jumping off the ground as you spread both arms and legs to form the "star."
If you enjoy jumping jacks but find they aren't challenging enough, do them faster or substitute tuck jumps with your arms out to the sides. To do tuck jumps, start by standing with your feet shoulder-width apart; then jump as high as you can, tucking both knees to your chest before you land again with both feet. This is an extremely intense exercise that even very fit individuals will be able to maintain for only a short amount of time.