Using the ‘Acute To Chronic Training Ratio’ for runners: prevent or predict injuries
The "acute to chronic training ratio" is a modern approach that offers an improvement over the traditional ten percent rule, helping athletes stay injury-free.
When training for an event, runners often worry about the risk of injury, sometimes attributing it to overtraining. However, recent insights from sports science suggest that it's not just about how much training is done, but about finding the right balance. In some cases, intensive training might actually help in building resilience against injuries.
A note to ensure that runners use this ratio to understand when they are spiking AND under-loading; Both can cause issues longer term.
Therefore, understanding the fine line between "too much" and "too little" training becomes crucial. The acute to chronic training ratio calculator aids in determining safe training thresholds.
This method focuses on the balance between current and past training loads. By monitoring this ratio, athletes can avoid the dangers of both over-training and under-training. The acute-to-chronic training ratio is calculated by dividing the distance of the last week by the average weekly distance of the past four weeks. For instance, if the distance over the past four weeks was:
Week 1 = 35km
Week 2 = 40km
Week 3 = 42km
Week 4 = 51km
Week 5 = 49km
The ratio would be 49km (last week's distance) divided by 42 (average of the previous four weeks), equating to 1.17
Research indicates that the risk of injury increases when this ratio exceeds 1.30, with a significant rise in risk when it surpasses 1.50. This method offers a more nuanced view than the old "10 percent rule" by taking a longer-term perspective and helping prevent overexertion after periods of reduced activity or injury.
This ratio can be used also for measuring specific metrics, such as your “long run” distance or your pace that you are trying to improve each month. You would simply do the same thing; jot down your previous 4 “long run distances” or your “pace”, determine an average and divide by the current week to get your ratio for that metric.
Applying a traffic light system to this ratio can be helpful
A ratio of 0.80-1.30 represents a green light (safe),
1.30-1.50 a yellow light (caution),
1.50 or above a red light (high risk).
However, individual differences mean that each athlete's response to training varies. By tracking changes in the ratio over time and noting any injuries or discomfort, athletes can identify patterns that reveal their personal thresholds.
Being cautious is particularly important when increasing mileage or intensity. A low ratio helps ensure safe training progression. Observing patterns at the lower end of the ratio can also be insightful; for example, a drop in mileage might lead to a spike in the ratio when training resumes, potentially leading to injuries.
While not all injuries can be prevented, understanding the acute to chronic training ratio can help athletes avoid repeating past mistakes.
Below is a basic calculation table to help you determine your ratio. Sharing this information with coaches and practitioners can aid in planning safe training and return-to-sport strategies.
Week 1 =
Week 2 =
Week 3 =
Week 4 =
A - Add together then divide by 4 (this is your average) =
B - Current or planned week =
B Divide by A = C (your ratio)
If “C” equals 0.80-1.30, that week is planned correctly
