The Relationship Between Training Load & Injury (Part 2 of 3)
Before reading this blog, T3 Physiotherapy highly recomends you read part 1 of this series to assist with understanding load, load progression and potential load related injuries.
Normally training load is split into acute and chronic loads. Acute load is the sum of the current week’s training (i.e. duration x intensity x frequency of that week i.e. fatigue). Chronic load is the average weekly training load over the previous four weeks i.e. fitness.
So to simplify this:
Duration can be measured in minutes
Intensity can be measured in a lot of different ways, however to keep things simple, we’re going to use the modified RPE (Rating of Perceived Exertion) scale. This scale ranges from 0 (at rest, no perceived exertion at all to) to 10 (maximal exertion).
Frequency being the number of sessions per week.
To exemplify how to calculate your training load - we will use a beginner to running training - Fred. In week 1 of Fred’s training plan, he runs x5/week, for 30 minutes per session at an RPE of 7/10.
We can take these numbers and multiply them together to create an acute training load = 1050 units.
Now we need to figure out Fred’s chronic training load. Chronic training load can depend on multiple factors e.g. training history, amount of time taken off between training periods, genetics etc. IDEALLY, if you’re new to running or returning to running after an extended period off we want to be starting this first week with a total load of ~450 units, preferably 2-3 training sessions of 20-30 minute runs at an RPE of 5/10.
This gives us an idea of our ideal starting chronic training load of ~450 units.
3 x 30 x 5 = 450 units (ideal starting chronic workload).
Now we know Fred’s ideal starting chronic load, we can calculate his acute to chronic workload ratio which will determine if Fred is overtraining and at risk of load-related injuries.
Acute-chronic workload ratio is calculated by dividing the acute workload units by the chronic workload units.
Acute workload units / Chronic workload units = Acute-Chronic Workload Ratio
Evidence within scientific literature shows that an acute-chronic workload ratio of 0.85 - 1.3 is the ideal range to prevent injury and improve performance.
Graph reproduced from British Journal of Sports Medicine
Going back to Fred. His acute workload of 1050 units can be divided by his ideal starting workload of 450 units, which equals a high acute-chronic workload ratio of 2.3 - way above the recommended range of 0.85 - 1.3. If Fred were to continue his current training routine, he will likely experience load-related injuries over the next 1-2 months.
In summary, if you’re new to training, write down your acute training load you’re performing currently. Apply it to the equations above and see if you’re acute-chronic workload ratio is a little above, between or below 0.85 - 1.3!
Next week’s blog will cover how to increase your chronic workload! Stay tuned for more evidence based resources so you can prevent injury and perfect your performance!
Resources:
Bourdon, P., Cardinale, M., Murray, A., Gastin, P., Kellmann, M., Varley, M., Gabbett, T., Coutts, A., Burgess, D., Gregson, W. and Cable, N., 2017. Monitoring Athlete Training Loads: Consensus Statement. International Journal of Sports Physiology and Performance, 12, pp. S2-161-S2-170. http://journals.humankinetics.com/doi/abs/10.1123/IJSPP.2017-0208
Carey, D., Blanch, P., Ong, K., Crossley, K., Crow, J. and Morris, M., 2016. Training loads and injury risk in Australian football—differing acute: chronic workload ratios influence match injury risk. British Journal of Sports Medicine, 51(16), pp.1215-1220. http://bjsm.bmj.com/content/bjsports/early/2016/10/26/bjsports-2016-096309.full.pdf
Gabbett, T., 2016. The training—injury prevention paradox: should athletes be training smarter and harder?.British Journal of Sports Medicine, 50(5), pp.273-280. http://bjsm.bmj.com/content/early/2016/01/12/bjsports-2015-095788?__hstc=196135283.0bb2ae1552d2dda845881b6516c33848.1481673600081.1481673600082.1481673600083.1&__hssc=196135283.1.1481673600084&__hsfp=528229161
Impellizzeri FM, Rampinini E, Marcora SM. Physiological assessment of aerobic training in soccer. J Sports Sci. 2005 Jun;23(6):583-92. doi: 10.1080/02640410400021278. PMID: 16195007.
