The topic of athlete monitoring has garnered a lot of attention from both coaches and sport scientists in recent years. This is partly due to a greater appreciation of the fact that individual training responses differ substantially among athletes. By tracking fatigue and recovery status, coaches can make strategic training interventions for individuals by increasing or reducing training loads, prescribing recovery modalities and so forth. One of the most common and useful monitoring variables that team-sport coaches track is neuromuscular function because of its strong involvement in athletic performance. The countermovement jump is often used as a key performance indicator for sports such as soccer, rugby and basketball because it is a convenient marker of lower body power. It’s hypothesized that a reduction in countermovement jump performance correlates with decrements in on field performance markers such as sprinting speed and distance coverage. However, research on this topic is quite limited.
A new study published ahead of print in the Journal of Strength and Conditioning Research sought to determine whether markers of lower body power and muscle damage predicted training outputs in elite male soccer players. Thirty players from an elite team performed a countermovement jump test and provided blood samples for creatine kinase analysis (a marker of muscle damage) prior to practice throughout a training period. During all training sessions, global positioning system (GPS) devices were worn by all players. The training outputs derived from GPS included total distance, sprint distance, high speed distance, accelerations, decelerations, explosive distance and maximal velocity.
The results showed significant main effects for both countermovement jump and creatine kinase Z-scores (normalized values). A reduction in countermovement jump performance by 1 Z-score resulted in decrements in various training outputs (total high speed distance, very high speed distance, accelerations, decelerations, explosive distance, and maximal velocity running) by an average of -2— -5.6%. Similar decrements in training outputs for the same variables were observed with an increase in muscle damage corresponding to a Z-score increase of 1 for creatine kinase. These results suggest that pre-training countermovement jump scores may provide insight to coaches regarding performance potential in soccer players.
Malone, S., et al. Decrements in neuromuscular performance and increases in creatine kinase impact training outputs in elite soccer players. Journal of Strength and Conditioning Research. In press.