When analyzing coordinative patterns in sports maneuvers such as a baseball pitch, tennis serve, or volleyball serve, it has been shown that the kinematic and temporal patterns show less variability as skill level increases. This is a linear hypothesis. What this really means is that the range of movement and the timing of each movement are more consistent in skilled players. This is certainly not surprising.
However, sport movements involving a moving target such as a volleyball spike or a tennis rally hit has made researchers wonder which aspect of coordination the athletes adjust in order to execute with consistent success. With these types of movements not every hit can be exactly the same…yet the outcome is consistent. Did they alter the kinematics? Or did they alter their timing? Researchers have hypothesized a U-shaped model, where unskilled players show high variability, skilled players show less variability, but when players reach a certain level of expertise, variability actually increases (while still producing a successful execution). This difference has been attributed to the unpredictability of the object when high precision is demanded. Expert-level players have developed an optimal degree of adaptability and precision whereby performance outcome variability is low, yet coordination variability can be high.
Goossens and Baeyens (2016) studied the performance outcome and variability for a volleyball attack amongst both top-level youth players and professional players. It was not surprising to see that the male players had a higher ball impact speed and jump height than females. Interestingly, with jump height the male players showed significantly less variability than their female counterparts, with the lowest variability being among the professional male players. However, with impact speed, the professional level players showed higher coordination variability. The real question is what is an acceptable range of variability when training young athletes? Is it better to teach “perfect” technique and allow natural variability? Or is it wise to encourage a certain range based on the individual athlete and the outcome? This research is the tip of the iceberg, and larger subject pools need to be analyzed before any concrete conclusions are reached.
What this could mean for injuries…
Although low variability has been strongly associated with skill level, it has also been suggested as a causative factor to overuse injuries. Minimal variability and high repetition can produce significant wear and tear on the body. Perhaps an athlete’s ability to execute a skill consistently with a functionally higher degree of variability may help to preserve the joints.