We’ve all seen it happen. Two athletes begin double-unders at exactly the same time. They both use good posture and wrist movements, and their foot heights and rope timing are essentially the same, but one finishes significantly ahead of the other.
Likewise, we’ve all seen two athletes begin box jumps together. They are both powerful and spend minimal time at full extension at the top. Yet one finishes far ahead of the other. How does that happen? Good question. Here’s a description of what is often the primary factor involved.
When we perform an exercise — like box jumps or double-unders — that uses landing movements, we employ a neuromuscular dynamic known as the “stretch-shortening cycle.” The cycle involves three distinct phases. In the first phase, the agonist muscles (in the case of box jumps and double-unders, the plantarflexors and knee extensors) are lengthened and contract eccentrically on the landing. Think of how an athlete’s gastrocs stretch at the bottom of a box jump. During this portion of the cycle, termed the “eccentric” (lengthening) phase, the activated muscles store energy coming from two main sources: the spring-like action of stretched tendons, called “series elastic component,” and a neurophysiological reflex in the muscles’ “spindles” — a mechanism that protects against the potentially dangerous forceful and fast stretching of a muscle.
Once the lengthening action is completed, there is a slight delay between the eccentric phase and the subsequent contraction. This pause is called the “amortization” phase, and it is often what separates the athletes described above. This phase must be kept as short as possible.
Think of it this way. When a person takes out a loan, the interest is accounted for — or spread out — over time. This is referred to as the “amortization” schedule. In the same way, the stored energy in the agonist muscles (the main ones involved in the exercise) is spread out over the length of the amortization phase. Therefore, the longer the amortization, the less energy is available for subsequent contraction, called the “concentric” (shortening) phase.
In other words, if an athlete wants to make the best use of the energy stored in the agonist muscles and exert a more powerful contraction during the movement, he or she must minimize the amortization phase; otherwise, all that energy will be dissipated and lost. This is critical, and we’ve all seen it whether we have recognized it or not. For instance, we’ve all seen a person performing box jumps who “bounds” instead of “landing, loading and jumping.” The difference between an immediate bound and loaded jump is one that ultimately separates athletes in a WOD.
So how does an athlete actually get better at minimizing the amortization phase? Three things. First, focus on technique to minimize loading time. For instance, in a box jump or double-under, athletes should land midfoot with a very quick subsequent touch of the heel before exploding upward. Avoid any amount of time on flat feet. Likewise, when performing wall balls or thrusters, athletes should remain in a stable foot position, avoid rocking on their heels or toes, and explode out of the bottom of the squat in a ballistic manner. Avoid even the slightest amount of time sitting at the bottom.
Second, train to be explosive. Research shows that the stretch-shortening cycle can be trained. So when performing other movements in the box, athletes should practice minimizing the amortization phase by exploding at the moment the stretch is completed. Virtually any movement in a box can be used to refine one’s stretch-shortening–cycle action
Third, remember that becoming more explosive and shortening amortization is, ultimately, a mental game. It all starts in your head. Athletes should concentrate on calling into contraction the agonist muscles immediately on the completion of the stretch or eccentric phase.