This is an excerpt from Jump Rope Training-2nd Edition.
Biomechanics of Rope Jumping
Rope jumping involves three phases in each jump—load phase, flight phase, and landing phase—and you will perform each of these phases hundreds of times during each jumping session. The load phase requires you to balance your body on the balls of your feet with your knees slightly flexed. The flight phase consists of muscular contractions that propel your body high enough to clear the rope with each jump. In the landing phase, you return to the surface by allowing your body weight to balance on the balls of your feet with your knees flexed to help absorb the impact of the landing. Efficient recovery from the landing phase through the load phase to the flight phase is critical if you are going to enjoy the benefits of jump rope training.
Your body weight should be balanced on the balls of your feet, and your knees should be slightly bent in an upright version of the universal athletic position. This position prepares your body for the multijoint demands of rope jumping. Ideally, you should jump no higher than 1/2 to 3/4 of an inch (1.3 to 1.9 cm) from the jumping surface (the exception to this rule involves power jumping). This approach leaves you virtually no room for error and therefore reinforces your performance of precise movements. Jumping in this manner—rising less than an inch from the surface and landing lightly on the balls of your feet—requires you to exercise concentration, kinesthetic awareness, and perfect timing. This is a refined and highly skilled whole-body movement. Many people find that it is relatively easy to “give it all you've got” when asked to jump or leap, but it is quite a different matter to jump with control. In rope jumping, less is more. See figure 3.1 for a diagram of the muscles worked during this phase.
The flight phase consists of two stages: the propulsion stage and the airborne stage. Understanding what happens from the moment your feet push off the surface to the point when you are in the air is critical to maximizing your training benefits and reducing your risk of injury. You generate propulsion by means of a slight push from your ankles, calves, knees, and hips. Push through the jump rope surface from the balls of your feet and point your toes toward the surface as you become airborne (see figure 3.2a).
During the airborne phase, your feet should rise no more than 1 inch (2.5 cm) from the surface as the rope passes under your feet. Swinging the rope and jumping over it recruits muscles in your upper and lower body (see figure 3.2b). This movement is essential to enhancing your proprioception in your feet and ankles, so that you know where to plant your feet and how to balance so you don't topple over. Proprioception, known as an inner sense, is the ability of your central nervous system to communicate and coordinate parts of your body with each other. This movement also increases your balance, rhythm, and timing, while reducing your risk of injury. Repetition of these movements improves your body's kinesthetic awareness (known as the outer sense, the body's awareness of where it is in space and time) or the body's ability to coordinate motion knowing where the rope is in relationship to the body during jumping.
Your shock-absorbing joints (i.e., your knees, ankles, and hips) diffuse the impact of each landing you make during your jumping session. It is the frequency of jumping that poses your greatest threat of injury in jump rope training. If you use proper technique and jump on a surface that both absorbs impact and offers rebound properties, you reduce your risk of injury and enable yourself to derive the greatest training benefits from your rope-jumping program.
Regardless of which technique you are using, you must land softly on the balls of your feet. It is during the landing phase that you develop balance while subtle neuromuscular adjustments prepare your body for the subsequent load and flight phases (see figure 3.3).
Your landing should be soft and silent, forcing you to concentrate on perfect balance and on delicately positioning your feet during each jump. Your heels should not touch. If your heels hit the floor, or if your feet land with an emphatic slap, you are using an improper technique and thus reducing your training benefits and increasing your risk of injury. Intense concentration helps you keep your contact with the jumping surface as short as possible, which reduces stress in your hips, knees, and ankles.
When you do successive jumps, you draw on muscle groups throughout your body to reestablish balance and propulsion during each jump. In this respect, rope jumping is similar to resistance training, which requires subtle adjustments in several muscle groups in order to balance the weight as you lift and lower it. In many ways, rope jumping is also similar to running. If you fail to run with proper form, you risk fatigue and injury. Proper form allows you to maximize the benefits of the exercise and reduce your risk of injury. If you manage the multiple movements required for proper rope-jumping form, you not only enjoy aerobic and anaerobic training effects but also develop the kinesthetic sense that enhances your balance, rhythm, and timing while producing graceful movement.
Read more about Jump Rope Training, Second Edition.