Recently, a particular exercise selection during the Crossfit Games created more than a little controversy from coaches and athletes concerned about its possible dangers to some competitors. The exercise in question was the Box Jump, or rather the "extreme" number of repetitions during the scheduled workout. Whether or not you're familiar with the exercise or not isn't necessarily relevant to the rest of the post, but if you've ever strung a few of these together you may have an opinion of your own on whether or not this level of concern is warranted.
The box jump itself is just a simple matter of jumping from the floor to the top of a box of a certain height, and has been used by strength and conditioning coaches for many many years in order to train explosiveness and agility in their athletes. The problem that can arise from this movement is when an individual attempts to complete multiple jumps in succession. In the case of Crossfit, and the controversy in question, this happens in order to complete a greater number of jumps than the next competitor in a short amount of time. Doing them in quick succession can turn the box jump into what's called a Plyometric movement, which is a style of training that's also used by coaches to train explosiveness and power. Depending on the athlete and the manner in which they've been training this CAN present an increased risk of injury. However with responsible training, preparation, adherence to a tissue quality protocol (SMR, massage), and proper warmup this risk can be minimized.
To complete rapid box jumps, two different methods can be used. The first, somewhat slower method, involves landing on the full surface of the foot and building up tension in the legs, hips, and shoulders to explode back up onto the box. This method, while still Plyometric in nature uses much more muscle stretch a and contraction than the second method. The second method, and basis of the controversy, involves landing much more on just the ball of the foot and uses the combination of the calf muscles (mostly gastroc and soleus), and more importantly the Achilles tendon to stretch and contract to rocket the athlete back up for the next repetition. So far these may seem just like two different ways to skin the box jump cat. There is quite a difference from a bio mechanics standpoint however. When landing flat footed the athlete is able to use all of the large powerful muscles of the lower body, such as the glutes, hamstrings, quads, and all their respective tendons and connective tissues, in addition to the calves, to jump back upward. This means that the force of their bodyweight and reversal of movement gets spread out through much more tissue. It is, however, also a bit slower. So when completing a large number of repetitions that slightly slower pace can begin to add up pretty quick.
The risk of the second method lies in the fact that over so many repetitions if an athlete's lower leg muscles and/or connective tissue aren't strong or elastic enough to decelerate/reverse all the forces involved some pretty nasty injuries can occur. This risk is inherent in any speed or agility movements of this type when an athlete must decelerate and reverse the movement of their entire body. Some other examples of this would be during sprinting, jumping rope, or the quick side to side motions of a football, basketball, or soccer player. So is there a risk from a physics standpoint? Sure. But as life is an inherently risky endeavor in itself, a little extra recreational danger shouldn't necessarily be such a big deal.
As I mentioned earlier there are a number of ways to reduce risk in this situation, and those same precautions can help reduce risk of quite a few other sport injuries as well. If those precautions are not taken, then clearly the risk increases, and when considering the entire pool of injuries of a certain type the number of athletes who Were taking all those precautions is most likely extremely small. Because of this fact, to say that a certain exercise is inherently to dangerous and should be removed from competition is being a bit hasty. One other problem that can increase the risk of injury is athletes disregarding their training and deciding to attempt exercise styles or methods that they've not been proudly expired to. In the case of the box jump, any experienced coach will always start their athletes jumping down safely from a box and landing with their entire lower body in order to build the necessary strength, nervous system reflexes, and tissue elasticity to prepare for a more advanced style. In addition, a good coach will be able to recognize that certain athletes may not be candidates for the faster style no matter how they train and prepare. For example, larger athletes will create a much greater amount of force in decelerating their box jumps, and because of this may be advised to always land more flat footed, and in some cases step down from the box rather than even actually jumping down. Older athletes as well may be coached to perform safer styles. The point here is that if an athlete has always been coached to a certain style or ability level it's not exactly fair to shun a certain exercise if that athlete decides to ignore their training and attempt something being their capabilities.
At the end of the day, it's not necessarily a valid argument to criticize a certain exercise or movement of of context. Given proper training, preparation, and recovery, the dangers of any sporting endeavor can be minimized to allow for the realization of the highest capabilities of each and every athlete brave enough to attempt them. The lack or ignorance of any degree of due diligence can easily lead to injury and heartbreak, and is the duty of both the athlete AND the coach to observe. If you're not ready, don't push it. To Thine Own Self be True!
Play how you practice! And if you desire to achieve a certain level of achievement, ensure you have the right coach, and the right training to get you there. Be safe, be smart, and kick some ass!!