Overuse injuries are one of the most common injuries seen in a Physiotherapy clinic. They are caused when tissues (tendon, muscle or bone) are unable to cope with the repetitive load placed upon them over a period of time.
Some examples of overuse injuries include tendinopathies such as tennis elbow or Achilles tendinopathy, bone stress injuries or it can be as simple as tightened muscles due to overactivity.
Factors that overload the body include:
- Rapidly increasing training and competition load
- Taking a break from the activity you are used to doing and going back to it where you left off
- Starting a new sport or activity
- Strength and fitness deficits
- Suboptimal movement mechanics
Often it is a combination of these factors which lead to overuse injuries. It is important to identify the causes of your overuse injury so they we can prevent them in the future.
This discussion will mainly focus on how training loads can lead to overuse injuries and how we can tailor them to prevent injuries.
Monitoring training load is vital in preventing these injuries. Recently, a new concept that has come to light is the acute: chronic workload ratio. The acute: chronic ratio compares your most recent 7 day training load to your training load over the last 28 days. It is calculated using the following equation:
Acute: chronic: Workload in the last 7 days (in distance or time)
Average weekly workload in the last 28 days (in distance or time)
For example, if a runner has been running 40km in the past 7 days and they averaged approximately 30km weekly in the last 28 days, their acute: chronic ratio would be: 40/30 = 1.3
Research has indicated that a training load leading to an acute: chronic ratio between 0.8- 1.3 is safe. Increasing your acute training load to result in an acute: chronic ratio of greater than 1.3 and in particular 1.5, puts the individual at risk of an overuse injury.
The takeaways from research on using acute: chronic ratio:
- Acute: chronic work load ratio is a simple way to gauge if you are progressing your training too quickly
- Make sure you keep changes to your training load within an acute: chronic ratio of 0.8- 1.3. This will help you safely progress your fitness whilst minimising the risk of injury
- Developing a high chronic workload can reduce the risk of overuse injuries i.e. give yourself more time to achieve your goals
- It is important that your training load matches the demands of the competition in intensity
So the next time you are preparing for an event or a race, schedule enough time to build up your training and fitness. Failing to do so can leave you underprepared, underperforming or have an increased risk of injury.
Drew, M., & Finch, C. (2016). The Relationship Between Training Load and Injury, Illness and Soreness: A Systematic and Literature Review.
Gabbett, T. (2016). The training—injury prevention paradox: should athletes be training smarter and harder?.
Hulin, B., Gabbett, T., Caputi, P., Lawson, D., & Sampson, J. (2016). Low chronic workload and the acute:chronic workload ratio are more predictive of injury than between-match recovery time: a two-season prospective cohort study in elite rugby league players.
Written by Dennis Tran, APA Physiotherapist