Are jumping jacks good cardio workouts?
If you are out of breath and your heart rate goes up, you are getting a cardiovascular workout. Generally, you would want to do if for at least 20 consecutive minutes. I can’t imagine staying in one place while doing jumping jacks for 20 minutes because of how repetitive that would be. If you can force yourself to do it, go for it. Sit-ups alone aren’t a particularly useful exercise. If you can do more than about 15 reps of a movement, you are not actually building any muscle (you may build some at first if you were completely sedentary before). Also, if you work your abs, but not your spinal erectors and obliques, you can cause muscular imbalances which could lead to injury. The abs are such a small set of muscles compared to the rest of your body; if you really want to build some calorie building muscle mass, do full body workouts including the abs.
