What is Acceleration Load?
Acceleration load is calculated from smoothed velocity data. From the smoothed velocity data, resultant acceleration values are calculated at 0.2s intervals. The acceleration load value is the accumulation of acceleration values over the specified period. Acceleration Load treats all acceleration (+ve) and deceleration (-ve) activity as a positive value and as such, the acceleration and deceleration values accumulate and contribute equally to the overall and absolute value of the acceleration load.
Acceleration Load was developed following a research paper by Duthie and Delaney (2015) titled "Acceleration-Based Running Intensities of Professional Rugby League Match-Play." The research used average acceleration values to better reflect the work of athletes in small spaces in comparison to open spaced performances. Please see the References section of this article for more information.
Acceleration Load versus Acceleration (Gen2) effort detection?
Acceleration Load is designed to capture discreet changes in speed that would potentially be missed when using an effort detection assessment where a duration threshold (Dwell Time) must be met in order for an acceleration to be detected (typically 0.4 – 0.6s). In addition to this, acceleration effort detection uses a set of ‘rules’ to quantify an acceleration effort and categorizes them into effort bands whereas Acceleration Load is calculated and accumulates using all acceleration values.
Acceleration Load and Inter-unit Reliability
Investigations have shown an inter-unit reliability of 2-3% when assessing average acceleration values and these are lower than typically seen between devices using the traditional effort detection based approach to acceleration assessment. This is primarily due to the complexities of the ‘Yes / No’ nature of acceleration count detection algorithms, especially when we consider frequent changes in speed within small areas.
Console (Non-Banded) Acceleration Parameters
|Acceleration||Displays instantaneous Acceleration|
|Acceleration Density||Average acceleration values over the specified period (i.e Average Acceleration Load). Acceleration Density is most effectively used alongside average speed (m/min) to assess drill or period intensity.|
|Acceleration Density Index||It is the average amount of acceleration activity performed per 10m of distance covered. (Acceleration Load/ Distance). It is designed to reflect the density of acceleration activity during the locomotive work periods, rather than the overall time period.|
|Sum of the acceleration values for the specified period. Acceleration Load is a marker of acceleration volume or the total amount of speed change activity. It can be used to quantify session and weekly loads.|
Console (Banded) Acceleration Parameters
|A1 Dur||Amount of time spent in a designated acceleration band.|
|A1 Efforts||Counts the # of times an athletes reaches the designated acceleration band for a specific amount of time (as defined by the Acceleration Dwell time).|
|A1 Per Dur||Displays the percentage of Acceleration Load spent in a specified Acceleration zone for the duration of the Period or Activity.|
A Practical Example
The table below shows a series of drills with differing acceleration demands. The table is sorted using the Acceleration Density Index and does an effective job of sorting the drills from highest to lowest acceleration demands per 10m of distance covered.
Acceleration load and smoothed GPS / LPS data
It is important to understand that Catapult uses a smoothed velocity stream to calculate acceleration and therefore Acceleration Load and derivatives.The image below provides an example of why we use smoothed and not ‘raw’ velocity data. As is well documented, raw forms of positional data can be susceptible to noise, and the smoothing of this signal ensures we can eliminate as much of this noise as possible, giving a more realistic representation of changes in speed.
The raw velocity as displayed above is showing many sudden peaks and troughs representing a potentially unrealistic representation of changes in speed. When used in conjunction with the acceleration load calculations, this would provide much higher numbers. The smoothed velocity data (as shown above) is used to calculate Acceleration Load and is a representation of a less noisy data stream.
How do I get the Acceleration Parameters on my OpenField Account?
New users have Acceleration Parameters by default and can begin using this feature in OF 1.18 or above.
- Delaney, J.A., Duthie, G.M., Thornton, H.R., Scott, T.J., Gay, D., Dascombe, B.J. 2015. Acceleration-Based Running Intensities of Professional Rugby League Match-Play. International Journal of Sports Physiology and Performance.