I have a jump rope, and my pulse sure goes up while jumping. But what am I exercising exactly?
Jump roping can be very effective in conditioning and strength.
Jump roping is a very helpful cardiovascular exercise. You're really exercising a complex system of muscles. You're not really isolating one muscle. You're exercising your upper body, core and lower muscles all in one action. You can't get more complete than that.
Because your arms are constantly working to move the jump rope, the upper body muscles are used extensively, including your deltoids (shoulders), back, forearms, biceps and triceps. If you use a heavier rope, your upper body will get more of a workout because it is like adding weight training to your jumping.
Core Jumping rope requires balance, which draws on your core muscles each time you jump and land with the timing of the rope. Abdominal, lower back and hip muscles are all used as they help stabilize and coordinate your movement.
Lower Body Because you are constantly on your toes and making vertical jumps, the calf muscles are used a great deal in jumping rope. It also uses the quadriceps (front of the thighs), hamstrings (back of thighs) and glutes (buttocks) for power and strength. Adding in different moves where you travel forward, backward or side-to-side as you jump, will also engage the smaller stabilizer muscles in your lower body.
If you are jumping on your toes tips then you are definetely working out your calves.
Also you can count that as a cardio if you can keep jumping for like 20 minutes. But if your heartbeat rate is going really high, no point to do that as a cardio exercise. You should be able to keep your heartbeat rate at a constant range, let's say 140-160 for most of the males.
Edit: Yep, i meant toes! :) Sorry, English is not my mother language.
I agree with the earlier answers that slow-paced jumproping can increase your cardio-respiratory endurance, but I think the primary benefit is increasing power and speed. This is why you see it used in any movie with a boxer getting ready for a fight.
Because of the rapid higher jumping required, double unders are the most effective way to use a jumprope.