The capacity to exert force with speed is what makes an athlete effective, and that truth is perhaps more apparent in CrossFit than in many other sports. After all, CrossFit movements often must be performed explosively and with high velocity.
Some CrossFit movements are better at developing power than others, with the more traditional weight-training exercises tending to be those that are less effective at power development. But take the kettlebell swing, for example. That movement is performed quickly, so you’d think it necessarily develops power. Not true.
The reason is because of a phenomenon known as “compensatory deceleration,” which refers to the fact that an athlete must decelerate, or slow the movement of, the weight near the end (in this case, the top) of the movement.
Research has shown that in movements like the kettlebell swing, the bar or weight actually decelerates for a time period accounting for 24 percent of the entire movement. The faster the peak velocity of the movement, the longer the duration of the deceleration phase. So you may think you’re training for power, in which speed of movement is primary, but instead you end up spending a great deal of time slowing the weight down.
If you think about it, it’s easy to see where and why the deceleration occurs. After peak power is produced (at the point when the kettlebell is approximately at the level of the abdomen), the athlete must slow the weight down in order to accommodate the kettlebell’s stop above the head and its subsequent descent. In this compensatory deceleration, not only are the agonists (muscles that are the prime movers) slowing their force production, but the antagonists (muscles that oppose the ascent) also are kicking in to slow the weight to a momentary stop.
So should you avoid kettlebell swings completely? Of course not. Kettlebell swings, like other exercises, are a great way to train for muscular endurance and hip extension; they’re just not the best choice for complete power production.
So how do athletes complement their training so they avoid compensatory deceleration and maximize their efforts to improve power? Enter the medicine-ball throw.
The med-ball throw is a type of exercise, called “load projection,” in which there is no deceleration phase. This type of training improves power output throughout the movement and is used in various ways: “take off” in jumping, ball release in throwing, impact in striking.
The med-ball throw uses the same mechanics as the kettlebell swing, in that power comes from hip extension. However, when the weight moves past the abdomen, the emphasis is on speeding up to the top of the movement, not slowing down, with the ultimate goal to maximize velocity so that it peaks at the top of the movement (above the head).
To execute the throw, start in a squatting position with a medicine ball between your feet. (Rx is 20 pounds for men, 14 for women.) The midline of the ball should be parallel with your forefoot. Grasp the ball on both sides and swing it in front of your body, fully extending your arms when the ball reaches hip level. At that point, lean back slightly and continue to accelerate the ball upward with your arms extended. (Avoid bending the elbows at this point, which is a biomechanical error.) When the ball reaches chin height, arch your upper back slightly farther backward, keep the arms straight, and explosively launch the ball high and behind you, letting it drop to the floor.
As a power exercise, med-ball throws should be performed after a substantial warm-up and before any slow-speed training (deadlifts, etc.). Because of the explosive nature of this exercise and the importance of maintaining good technique to maximize power production, med-ball-throw programming should be limited to no more than once per week, with a total of no more than 20 throws in a training session and 30 to 60 seconds between throws.