Why is GPS such an important part of athlete training and improving athlete performance?
GPS devices have become a regular inclusion in measuring and monitoring athlete’s training and match performance, it has become common place to watch matches on the television and to see players wearing GPS devices under their team shirts.
Wearing GPS devices started with elite clubs using systems like Catapult and has trickled down to semi-professional clubs, universities, colleges and schools using more affordable systems.
Before we look at the information we can get from GPS devices we need to understand “what is GPS” and how do these devices work?
What is GPS?
GPS is an acronym for “Global Positioning System” which is a space based navigation system owned by the United States government. GPS provides geo-location and time information; the GPS devices receive the geo-location and time information from the satellites, they do not transmit data like mobile phones.
They use trilateration (a more complex version of triangulation) to determine the athlete’s position on the surface of the earth. Once a GPS device receives information from a minimum of three satellites it can perform the trilateration calculations.
The GPS device needs a clear line of sight to the satellites it wants to receive information from, because of this GPS devices work better when used in open spaces like playing fields etc.
One quick observation: GPS is not the only satellite system available, there are many. For example the Russian’s have a system called GLONASS, the Chinese have a system called BeiDou-2 and the European’s have a system called Galileo to name a few.
Some devices combine the information from different systems, an example of this is combining the GPS, GLONASS, BeiDou-2 and Galileo systems – this is known as “Global Navigation Satellite System” (GNSS).
Having acquired GPS information from the satellites the GPS device calculates and logs an athlete’s position.
If the athlete is wearing a watch to measure distances and performances, position information is logged on a “once a second” basis. More professional devices log position information on a “five times a second” basis and the very professional systems like Catapult and iSportsAnalysis log position information on a “ten times a second” basis giving the most accurate results.
Calculating the metrics
Once we know the positions of an athlete’s movements along a time line (at a point in time the athlete is at point “A” and at another point in time the athlete has moved to point “B” etc.) we can work out metrics like distances covered, speed, fastest speed, acceleration and deceleration.
This information is incredibly useful; for example, it is vital to understand the efforts made by athletes in both training and in matches.
Using the metrics
Measuring distances combined with the number of times an athlete sprinted is a great start to understanding the exertion an athlete has made.
If we split the acceleration and sprints into speed bands based on an athlete’s profile information, which includes their fastest running speed, we can ascertain the the “load” an athlete has experienced.
This gives coaches and sports scientists insights into how the athlete’s training is effecting their match performances and can be a good indicator of possible over training and under training.
If we put deceleration readings into speed bands, once again based on an athlete’s profile, we can start to predict possible injury and fatigue.
Deceleration can require a massive effort; if an athlete takes time (usually measured in seconds) to reach a maximum speed and then stops immediately this can put a massive strain on muscles, tendons and knee joints.
If we take into consideration body weight as well as the deceleration (measured in m/s^2) we can start to understand the “load” put on the body. If an athlete’s GPS information indicates this is a regular part of their performance it is worth looking at changing the way the athlete slows down as this will help to decrease fatigue and possible injury.
Heart rate, the bigger picture
These measurements can be even more useful when combined with heart rate information. If we know an athlete’s threshold and maximum heart rate we can work out the times the athlete is in a threshold state and in an anaerobic state. This combined with the above GPS information is invaluable. For example, if an athlete sprints and quickly decelerates in an exhausted state they are a lot more prone to both fatigue and injury. If an athlete has spent most of their session in a threshold state and an anaerobic state they will need more rest that the athletes that haven’t.
This article is not about understanding heart rate information, this article is about why GPS information is so important in measuring and monitoring athlete’s training and performances.
I wanted to point out that the combination of GPS and heart rate data is incredibly helpful, in fact iSportsAnalysis.com calculate 107 metrics for an athlete on a per session basis using GPS and heart rate data.
To conclude – knowing the distances, speeds, accelerations and decelerations an athlete has experienced in any given session is invaluable information in understanding performance and “loads” on the body. If this article has been of interest you can have a look at www.iSportsAnalysis.com for more athlete and match analysis.
About the Author: Anadi James Taylor
I am expert in helping sports clubs, schools, colleges and universities improve their sporting performances using Sports Video Analysis and GPS Performance Analysis.
I developed iSportsAnalysis.com with world class sports scientists, coaches and trainers and university lecturers to help optimise, maximise and realise the performance of athletes and teams.
iSportsAnalysis has helped over 120 universities, private schools and clubs to reach their true sporting potential; whether that has been from them using the iSportsAnalysis online video streaming services, our online sports video analysis, coaches corner or our GPS performance analysis, the results speak for themselves!
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You can find out more at iSportsAnalysis.com.