One area that a personal trainer or strength coach can really improve upon to increase their value to a client or team is to become a little savvier with statistics. There are some very basic statistical procedures that coaches can use to determine practically meaningful changes in performance. Communicating these results to the athletes and other coaches with visuals (i.e., charts and figures) can really show them how performance is affected by the training program and/or competition schedule.
The smallest worthwhile change (SWC) developed by Will Hopkins, is considered 30% of the standard deviation (SWC = .30*SD) in elite athletes. With this formula, we can determine what change in a performance marker is practically meaningful, and not necessarily within the daily “noise” of a measure. For lower level athletes a higher value (i.e., .50*SD) may be necessary as these athletes will likely have less consistency in performance and higher “noise”.
To perform these calculations in excel, you will simply need to calculate the mean and standard deviation and then calculate 0.3 or 0.5 (whichever is more appropriate in your situation) by the standard deviation to get your SWC value. You can then add the SWC to the mean and subtract it from the mean to get your upper and lower thresholds for what is above, below or within the SWC.
The following screen shots in excel demonstrate some examples of applying the SWC to a set of performance data. Amber shading indicates a meaningful decrease in performance while green shading indicates a meaningful increase in performance.
Below is an example of bar velocity changes in submaximal squats over 10 different days of measurements
Below is an example of vertical jump changes over 10 different measurements.
Lastly, we can see the evolution of performance in 40 yard dash over 10 different measures.
Determining the changes in performance can be useful for assessing daily readiness, or recovery status of your athletes. If their vertical jump is below the SWC it is likely that they are experiencing fatigue and therefore training can be adjust accordingly. Alternatively, scores above the SWC indicate positive adaptation to training and likely quality recovery. Being able to show this to the coaching staff or your clients can show them that you are closely monitoring performance and can therefore determine the effectiveness of training.