Addressing Deceleration Demands in Training Through Global Positioning System

Deceleration is an intensive movement that requires the use of large forces to change velocity at a rapid rate. In the team sport setting such as soccer, lacrosse, or football, decelerations are measured using global positioning systems (GPS). When measuring this action, it is common to measure deceleration quantity above a -3m/s/s or a band 3 as it is often referred to. This is considered a high band deceleration, however, in most cases a change in velocity of <3m/s2 is usually not close to the basement as far as maximal decelerations are produced. Even at an under 17 age group it is likely to see changes of velocity of approximately <6m/s/s. This is a substantially large margin of variance that is not been given its own consideration. Therefore, are sport science practitioners who are strictly measuring the quantity of band 3 decelerations undervaluing what a deeper analysis could offer?

Decelerations must be analysed in isolation. When assessing the physical outputs that the GPS data presents following a match it is clear to see that there has been a significantly greater quantity of decelerations than accelerations. In a research paper comparing deceleration to acceleration quantity of an English League 2 club showed that an average of 330 <3m/s2 decelerations and only 165 >3m/s2 accelerations occurred during an average match (Rhodes et al., 2021). This means that each metric is required to have their own respective training target. It is not uncommon to see practitioners apply the use of a conjoined metric called “explosive actions” by categorizing decelerations and acceleration together. The use of data in this way will hinder the ability to adequately prepare the players. For example, if explosive actions were a metric that was being analysed there would be no way of identifying discrepancies in deceleration quantity in comparison to acceleration. Usually, to increase the deceleration load moderate to large sided competitive games will be required in comparison to acceleration that can occur across a whole host of nonspecific drills. This means that the use of this conjoined metric may lead to a lack of preparedness for high intensity decelerations.

The first data point that should be assessed is maximum deceleration. This data point should be compared to group and positional averages to rank the capacity and determine if it is a strength of weakness for the individuals. Training that produces improvements in maximal deceleration should be promoted within program design. Deceleration capacity is critical in sports where high-speed pressing and evading opponent successfully will improve situational outcomes. This is only one of a few reasons that it is a key performance indicator for team sports (KPI). Like how having a greater maximum speed in comparison to the positional average will allow the individual to run at reduced velocities more efficiently or utilize that speed to leverage an advantage. To possess an increased capacity of this physical quality will allow for improved efficiency in actions that are below maximal.

Not all actions that create a change in velocity are created equal. In a research paper assessing the difference between maximum decelerations and maximum accelerations showed significant difference in the change of velocity. According to these reports maximal decelerations ranged from -5.7-6.3m/s2 and maximal accelerations ranged from 4.4-4.7m/s2 (McBurnie et al., 2021). The disparity between each of these maximum values is because of the forces available to use during these specific actions. To rapidly accelerate will require large net forces to propel the centre of mass forward, this action is limited to concentric muscle action. In comparison to deceleration which will also require the production of large net forces, however, these forces are created eccentrically to reduce the momentum. If there are significant difference between the rate that athlete increase and decrease velocity, why is it common to see high band acceleration and deceleration corresponding to <-3m/s2 or a >3m/s2. It is with these difference that practitioner must begin the review a more effective approach to interpreting loading data. The commonality between these actions is restricted to the fact that they are both involve a change in velocity. All other variables relating to how these actions are produced are different. Sport scientist should be encouraged to review these actions with their own respective standards.

With intensive decelerations being more common during match play and possessing a greater margin in variance regarding velocity change it would make sense to account for this variety through an accumulated loading metric or intensity band system. It is common for practitioners to monitor metabolic stress through using acceleration density and index. Surely accounting for the mechanical stress that decelerations produce is insightful in how training can be better designed to prepare for such demands. This is not to say that monitoring metabolic stress is any less important, however, the analytic potential of deceleration is currently limited relative to its concentric counterpart. Deceleration data would possess greater utility if bands were plotted across 6 bands (>1m/s2->6m/s2). This will allow practitioners to identify where the most common decelerations to occur during match play and then better align drills to target these bands as necessary as possible.

Deceleration is a movement that is critical for team sport athletes. It is that it is being addressed through on-field training prescription for the purposes of preparation and injury prevention. While it must be analyses as a part of the performance puzzle to ensure that the training process is adequate for the outcomes, it is also important to that it is process with its own respective assessment. Deceleration should be assessed in three layers: workload targets, maximal outputs, and how a variety of intensities is reflected in different bands.

References

McBurnie, A. J., Harper, D. J., Jones, P. A., & Dos’Santos, T. (2021). Deceleration training in Team Sports: Another potential ‘vaccine’ for sports-related injury? Sports Medicine, 52(1), 1–12. https://doi.org/10.1007/s40279-021-01583-x

Rhodes, D., Valassakis, S., Bortnik, L., Eaves, R., Harper, D., & Alexander, J. (2021). The effect of high-intensity accelerations and decelerations on match outcome of an elite English League Two football team. International Journal of Environmental Research and Public Health, 18(18), 9913. https://doi.org/10.3390/ijerph18189913