Jumping jacks may be a throwback to elementary school gym class, but they are also a surprisingly effective cardiovascular workout. In addition to burning as many calories as jogging, they provide a great workout for your lower body. Unfortunately, while jumping jacks certainly help tone your arms, they do not build much in the way of muscle.
Jumping jacks are an easy, equipment-free calisthenic exercise that works several major muscle groups at once while simultaneously giving you a solid aerobic workout. While there are countless variations to this exercise, the basic jumping jack is very simple: begin by standing with your feet together, your arms at your sides and your knees slightly bent. Jump up while raising your arms in an arc and spreading your legs to either side. You will land in a "star" position with your legs spread wide and your arms overhead. Jump again from this position, bringing your legs back together beneath you and your arms back to your sides.
Jumping jacks primarily work the muscles in your thighs, particularly the quadriceps, which contract to straighten your knee and give you the power to jump, and your adductor and abductor muscles running down the inner and outer sides of your thigh, which move your legs laterally as you jump. Your hamstrings and calf muscles also get a workout as stabilizer muscles and when they contract to soften your landing. The deltoid and latissimus dorsi muscles that control your shoulder get a workout from moving your arms up and down. Additionally, the connective tissue in your knee, hip, ankle and shoulder joints is stretched and lengthened as you jump.
Unfortunately for those seeking 20-inch pythons, jumping jacks do not have much effect on your arm muscles. Your biceps will generally contract slightly if you bring your hands together over your head as you jump, but for the most part your shoulder muscles are the ones moving your arms. Jumping jacks do, however, tone your arm muscles by providing an excellent cardiovascular workout. This is an exercise that relies on short, explosive and repetitive movements, which require plenty of oxygen for your muscles, leading to an increased heart rate and caloric burn. On average, a 150-pound woman doing jumping jacks for 20 minutes will burn around 190 calories, and that number rises to about 565 calories for an hour of jumping jacks.
While you could also add wrist weights to your jumping jacks, this will not affect your arm muscles much either. The added weight will definitely increase your heart rate and resistance for your shoulder muscles, but too heavy a weight can stress your wrist, elbow and shoulder joints. Holding a pair of small dumbbells while performing jumping jacks can help build a small amount of muscle in your forearm, as the muscles used to grip the handles will be worked out.
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