Since its first application to field and team sports in 2006, global positioning system (GPS) technology has been used to detect fatigue in matches, compare intensity profiles according to player position, compare competition skill levels, and identify the most intense periods of play.1 GPS is most commonly used and studied in the Australian Football League (AFL) but is gradually infiltrating such other sports as rugby, soccer, hockey, and American football.
With GPS data, coaches can design physical conditioning and plan appropriate recovery time following intense work according to the demands of each player’s position. As the technology continues to develop, it will become more useful for court-based sports, will help coaches determine appropriate training loads, improve recovery, and decrease injuries.
Quantifying Game Demands: Football
In contact sports like football, coaches using GPS can read real-time tackle and impact information instead of, or in addition to, time-consuming video analysis.2 A study by Wellman et al. (2016)6 examined the use of GPS and accelerometry with thirty-three NCAA Division I football players during their twelve regular season games. The researchers wanted to determine and quantify the differences in the demands of player positions during competitive games.
They found that wide receivers and defensive backs executed significantly greater total distance covered, high-intensity running, sprint distance, and intense acceleration and deceleration efforts compared to other offensive and defensive players.
Linebackers and defensive backs essentially covered the same total moderate- and high-intensity distance. Defensive backs, however, displayed significantly more sprint, maximal acceleration, and maximal deceleration efforts than any other defensive position.
Coaches can use this information to design physical conditioning specific to each player’s position and plan appropriate recovery after intense work.
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A similar study of AFL athletes found a substantial 11% decline in exertion per minute from a game’s first quarter to the fourth quarter, showing accumulated fatigue late in the game.7 During the four-year study, researchers tracked a significant increase in player demands. Mean velocity and intensity increased by 8-14%, possibly because of league rule changes made to increase the game’s overall speed.
Quantifying Game Demands: Soccer
There are few studies on GPS in soccer competitions because the International Federation of Football Association (IFFA) prohibits GPS use. A European study found that wide midfielders experienced the highest physiological demands in a match and center backs had the lowest.5 Wide midfielders and second strikers, the players with greater overall running performance, displayed a higher effort index (which shows mean speed on cardiovascular stress as measured with a heart rate monitor).
In elite soccer, GPS data showed maximal accelerations occurred six times as often as sprints, bringing into question the current belief that repeated sprint ability is essential to team sports.1 The data also showed clear differences in the players’ running performance when a game is tied or a team is behind or ahead of their opponent.1
GPS data can indicate player exhaustion and team fitness. Share on X
GPS can also track game fatigue by showing the difference between the highest running intensities during first and last fifteen minutes of the game. The differences can indicate player exhaustion and team fitness.2
Maximal Training Load: Injury and Illness
More studies need to be done to measure the maximum training load that athletes can sustain before increasing the possibility of injuries.2 Researchers have found that a spike in training load preceded 42% of illnesses and 40% of injuries.1
Maximal Training Load: Children
Load is especially important to monitor in youth athletes since they possess inherent differences in physiology, biomechanics, and metabolism.2 Unlike adults, children have smaller energy reserves between submaximal and maximal exercise; any given running speed is metabolically more expensive for a child than an adult. Many factors influence this including lower running economy (shorter legs = greater stride frequency, shorter stride length), less efficient mechanics (higher ground impact/braking forces, greater vertical “bounce”), and weak co-contraction of antagonistic muscles because the muscles are underdeveloped.
Since all movement is more costly and demanding for young athletes, their training must be adjusted accordingly. Using GPS can help monitor loads and intensities placed on kids in training to reflect their age and skill level accurately and decrease injuries.
Court-Based Sports
GPS technology has yet to be refined for court-based sports requiring rapid but confined movement patterns and continuous direction changes like tennis and basketball.4 A study by Duffield et al. (2010) sought to determine the accuracy and reliability of GPS devices for these types of sports. The technology was compared directly against a VICON motion analysis system. VICON is considered an accurate and reliable, although time-consuming, method of athlete tracking and analysis.
The GPS accuracy was measured at both 1 Hz and 5 Hz trials while the VICON output was 100 Hz. Both GPS trials showed the technology underreported distance, with error ranging from 2-25% depending on distance and speed. It also underestimated peak and mean speed, ranging from 10% to 30% during court-based movement drills.
There is clear evidence that the higher the movement velocity, the lower reliability of the GPS reading.1 Reliability should improve in the future as satellite communication and tracking becomes more precise. Cummins, Orr, and O’Connor (2013) found that increasing a device’s sampling rate from 1-Hz or 5-Hz to 10-Hz improved the GPS’ reliability during constant velocity as well as accelerating and decelerating movements.
We’ll need higher resolution technology before GPS can become mainstream in court-based sports.
Future Direction
During the next decade, we should see a miniaturization of devices, extension of battery life, and integration of other sensor data, including improvements in accelerometry heart rate, to help better quantify athletes’ efforts.1 Integrated technology refers to the combined use of GPS, heart rate, and accelerometry for a greater understanding of the metabolic cost and specificity of movement patterns.3
This integrated information will supply coaches with tactical data for play design as well as physiological data for fitness programming.1 Integrated data will also help coaches simulate competition demands in practice plays with appropriate intensities to avoid overloading their athletes.
Future researchers also may explore biophysical effects in pre- and post-game conditions, such as the effect of supplements on performance, core temperature changes, indirect calorimetry (to accurately measure calorie burn), and hormone responses to training and competition.3 With this information, coaches and athletes may be able to improve plans for recovery and subsequent training sessions.
References
- Aughey, R. J. (2011). “Applications of GPS Technologies to Field Sports.” International Journal of Sports Physiology and Performance, 6(3), 295-310. doi:10.1123/ijspp.6.3.295.
- Cummins, C., R. Orr, H. O’Connor, and C. West (2013). “Global Positioning Systems (GPS) and Microtechnology Sensors in Team Sports: A Systematic Review.” Sports Medicine, 43(10), 1025-1042. doi:10.1007/s40279-013-0069-2.
- Dellaserra, C. L., Y. Gao, and L. Ransdell (2014). “Use of Integrated Technology in Team Sports: A Review of Opportunities, Challenges, and Future Directions for Athletes.” Journal of Strength and Conditioning Research, 28(2), 556-573. doi:10.1519/JSC.0b013e3182a952fb.
- Duffield, R., M. Reid, J. Baker, and W. Spratford (2010). “Accuracy and Reliability of GPS Devices for Measurement of Movement Patterns in Confined Spaces for Court-Based Sports.” Journal of Science and Medicine in Sport, (13), 523-525. doi:10.1016/j.jsams.2009.07.003.
- Torreño, N., D. Munguia-Izquierdo, A. Coutts, E. Sáez de Villarreal, J. Asian-Clemente, and L. Suarez-Arrones (2016). “Relationship Between External and Internal Loads of Professional Soccer Players During Full Matches in Official Games Using Global Positioning Systems and Heart-Rate Technology.” International Journal of Sports Physiology and Performance, 11(7), 940-946. doi: 10.1123/ijspp.2015-0252.
- Wellman, A. D., S. C. Coad, G. C. Goulet, and C. P. McLellan (2016). “Quantification of Competitive Game Demands of NCAA Division I College Football Players Using Global Positioning Systems.” Journal of Strength and Conditioning Research, 30(1), 11-19. doi:10.1519/JSC.0000000000001206.
- Wisbey, B., P. G. Montgomery, D. B. Pyne, and B. Rattray (2010). “Quantifying Movement Demands of AFL Football Using GPS Tracking.” Journal of Science and Medicine in Sport, 13(5), 531-536. doi:10.1016/j.jsams.2009.09.002.
