30 Box Jumps
12 Hang Cleans
20 Box Jumps
9 Hang Cleans
10 Box Jumps
6 Hang Cleans
Squat Clean instead of Hang Clean
BURPEES for SANTA – DAY 11 = 11 BURPEES
Before we get into the science behind box jumps, it’s important to understand what a box jump is. If we break it down to the simple fact that box jumps are plyometric exercise, we can more effectively discuss the benefit they provide. In the 1970’s Plyometric’s or “jump training” began to gain popularity in the United States. For years the Soviet and European counties used this type of training to improve their athletes in sports like Weightlifting, Track and Field and gymnastics. A coach by the name of Veroshanski was one of the first to publish a series of these jumping drills. Over the last 30 years or so Plyometrics have become one of the staple exercises performed by both novice and high performance athletes. Now that our little history lesson is over, lets get into the science.
Muscle is truly an amazing structure, it is the only structure in the human body that can generate forces and drive movement. At the same time muscle provides tone and protection from our brutal environment. Even more interesting, is the relationship between muscle and tendon. This relationship can be compared to that of a spring, when force is applied, its stored to be used at a later time. When you stretch a spring (or muscle for that matter), the energy you put into it is stored by the springs structure as elastic energy. When you release the spring, it snaps back into its pre-stretch condition. Under the right conditions a muscle can act the same way. This feature of the muscle – tendon relationship is helpful in understanding the theory behind box jumps (or any plyometric for that matter).
The amazing part about plyometric training is the benefits returned. Along with Olympic lifting, its one of the few training modalities that has been researched and repeatedly demonstrated to increase both the speed at which you can move a muscle and the maximal strength at which a muscle can perform at. (Last time I checked those two things are important for crossfitters)
Here’s how it Works:
The body uses the energy storage and release properties of muscle and tendon all the time. The best example is probably running (which in itself a form of plyometric). When you run, some energy is stored in the Achilles tendon and is stretched and returned to provide propulsion as the foot pushes off the ground. Now, intensify this process and imagine the amount of energy stored on the impact phase of a box jump.
In kinesiology we define the process of energy storage and the subsequent release of that elastic energy the Stretch Shorten Cycle (SSC).
Phase 1: of the SSC is known as the eccentric phase, where preloading and stretching of the muscle occurs. During this phase the rapid stretching process through the tendon stimulates muscle spindle. A message is then delivered to the muscle to contract. During a box jump, we experience this phase on the way down, once we have landed and energy is absorbed from the ground into the muscle.
Phase 2: Is the amortization phase. This can be further defined as the amount of time it takes to accept the load and reapply force into the ground to get you back off the ground. This phase is by far the most important and I feel this is where the majority of us can improve dramatically. This phase must be kept as short as possible to fully take advantage of the stored elastic energy. The longer you remain on the ground after you have made impact with the ground, the more potential energy escapes. This is also the point of the box jump where the muscle and tendon receive the most benefit. In actuality, jumping onto the box does nothing for you in terms of increasing your ability to generate power.
That’s right, Ill say it again. The act of jumping on a box has no plymetric properties; it’s the landing that provides us with all the host of strength and power benefits! It’s amazing to think that the small window of time between when your feet strike the ground and the time it takes you to jump back up is where we get all the benefits of a box jump. Sure jumping up on a box might get your heart rate and look cool, but so does break dancing…
Phase 3: is the concentric phase, where the voluntary action of jumping is combined with the neurologic, spring-like release of elastic energy. I fear this is where most crossfitters think they are getting the benefit of jumping. Plyometric training goes well beyond basic concentric muscle contractions.
Now how do we capitalize on all this gibberish? Next time you look up at the board and see box jumps keep these tips in mind.
- As your dismounting from the box have your arms back in what we call the ready position. This will assist with your timing and place you in a preparatory position.
- As you approach the ground, anticipate your landing and apply as much force as possible to the ground. Pretend your legs are two pogo sticks and you’re trying to get those springs to recoil as much as possible.
- Avoid heal contact! You are able to produce more force, at a greater rate of speed if you land on the balls of your feet. Your ability to capitalize on the benefit of storing energy in the Achilles tendon is also dependent upon your ability to stay on the forefoot.
Courtsey of CrossFit South Bay