title: GPS Data Analytics in Football: A Spotlight on Deceleration
Creators: name: Newans, Timothy Jamie
Publisher: name: Griffith University
Year: 2018
Subjects: subject: Global Positioning System (GPS)
subject: Football
subject: Deceleration
subject: Acceleration
subject: Logarithmic curves

description: Background: As technology has improved, the ability to gain data from player monitoring devices has become more prevalent in sport science, especially with the introduction of Global Positioning System (GPS) technology. We know that the ability to rapidly increase velocity is a key element of field-based sports such as football, which require repeated sprint efforts throughout a game. What is less intuitive is the importance of negative acceleration or “deceleration” to team-sport performance. Deceleration is important because it affords players the ability to change direction and avoid collisions. Furthermore, deceleration may be a significant contributor to muscle fatigue and damage, which is an important consideration for performance and recovery. The two predominant metrics used to describe deceleration profiles are the frequency of deceleration efforts and the distance covered whilst decelerating; however, there are flaws with both metrics when considering the deceleration movement. Similarly, as deceleration is a secondary movement to a preceding acceleration, deceleration is opportunistic and cannot be analysed in isolation. Methods: Activity profiles were collected from twenty male football players competing in the Australian Hyundai A-League during 58 matches throughout two seasons (N = 368 observations). Match data were organised into ten 9-minute periods (i.e., P1: 0 - 9 min) and the time spent accelerating at moderate (1 to 2 m·s−2) and high (&gt; 2 m·s−2) acceleration (ACCM and ACCH, respectively) and the time spent decelerating at moderate (-1 to -2 m·s−2) and high (&lt; -2 m·s−2) deceleration (DECM and DECH, respectively) were quantified. Additionally, deceleration:acceleration and deceleration:high-velocity running ratios were also quantified to interrogate the opportunistic nature of deceleration activity throughout match play. A linear mixed model was used to determine the effects of time on the duration spent accelerating and decelerating, as well as the effect of position and formation on the duration spent accelerating and decelerating. Results: All four acceleration and deceleration metrics decreased between 23 – 26% from the first 9-min interval to the last 9-min interval. There was a significant effect of time on each metric and each displayed negative logarithmic curves within both halves of football match play. When examining the ratios of deceleration to acceleration and high-velocity running, there was no change in the ratio between DECH duration and total acceleration duration (ACCH + ACCM), while the ratios between DECM duration and total acceleration duration, DECM duration and high-velocity running distance (&gt; 14.4 km·h1), and DECH duration and high-velocity running distance increased as the match progressed. Discussion: Using negative logarithmic curves to illustrate the acceleration and deceleration decay provides a novel methodological approach to quantify the high-intensity actions during football match play. The decrease in the duration of deceleration efforts throughout match play could simply be attributed to a lack of opportunity, as evident by the increase in the ratio of deceleration:acceleration and deceleration:high-velocity running. This conflicts with the conclusions of previous studies which suggest that deceleration ability is compromised in the latter periods of match play. Practical Applications: Researchers and practitioners should consider the frequency and intensity of deceleration before making inferences regarding a decrease in a player’s ability to decelerate. By utilising negative logarithmic curves, practitioners can model the decay in acceleration and decelerations profiles. Finally, researchers and practitioners must be aware of the opportunistic nature of deceleration and monitor changes in the ratios of deceleration:acceleration and deceleration:high-velocity running, rather than relying on deceleration values in isolation.