Physical Activity and Injury Risk

Summary of article

• Being physically active, in general, reduces risk of pain and disease

• Acute injuries occur where the force applied to a tissue exceeds its ability to tolerate that force

• Cumulative injuries occur where a tissue is repeatedly exposed to stressors that exceed capacity for adaptation

• Activities with higher risk include contact sports and change of direction sports

• To reduce the risk of injury, build up activity intensity and volume gradually

Article

So, you know that you can use physical activity to improve your health, but you’re concerned about the risk of pain and injury? Firstly, it’s important to distinguish between those two things, as they are not the same.

Pain vs Injury

Pain is defined by the International Association on the Study of Pain (IASP) as: “An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage” (1). Note that tissue damage is not necessary for there to be pain. Some people who experience excruciating pain will not have tissue damage demonstrated on scans. Similarly, many people will have scans of various body parts showing what might be considered tissue damage, but not have any pain. Pain is more complex than structure alone.

The good news is, in short, that being active is protective against pain. People who engage in regular activity are at a 11-16% reduced risk of developing chronic low back pain (2). For people with hip and knee osteoarthritis, being physically active can significantly reduce pain (3). Despite the big picture positives, it is worth acknowledging that injury does occurs when engaging in physical activity.

The definition of injury is an area of debate in scientific research. However, a commonly accepted definition is: “A physical complain or observable damage to body tissue produced by the transfer of energy” experienced due to being active (4).

How Injury Occurs

Broadly, injury occurs when tissue capacity is exceeded by the stressors applied to those tissues (5). Injuries can occur acutely (suddenly) or can be cumulative (occurring over time).

Acute injuries result from an excessive force acting on a tissue (5). For example, when a novice gym goer attempts to pick up a heavy weight, and their lumbar extensor muscles are exposed to forces they are not prepared for, some muscle fibres may tear (commonly referred to as a muscle strain). Cumulative injuries, such as bone stress fractures and tendinopathies, result when a tissue is repeatedly exposed to stressors that exceed capacity for adaptation (5). For example, a person who takes up tennis and starts playing several times a week exposes the tendon on the side of their elbow to more cumulative load than it can adapt to, the structure becomes diminished and painful over the course of several weeks.

Injury Risk in Different Activities

Different types of physical activity stress the body in different ways, and therefore the risk of sustaining an injury, and the type of injury sustained, can vary. One way of quantifying risk of injury for a particular activity, is by looking at the number of injuries sustained per 1,000 hours of activity participation. Below is a brief summary of research comparing rates of injuries in some different, common activities:

• Running (6)

  • Novice runners (little or no running experience) – 17.8 injuries / 1,000 participation hours

  • Recreational runners (some running experience) – 7.7 injuries / 1,000 participation hours

  • Sprint athletes – 5.8 injuries / 1,000 participation hours

  • Long distance athletes – 2.5 injuries / 1,000 participation hours

• Weight training sports (7)

  • Bodybuilding – 0.24-1 injuries / 1,000 participation hours

  • Powerlifting – 1.0-1.1 injuries / 1,000 participation hours

  • Strongman – 5.5 injuries / 1,000 participation hours

• Tennis – 0.04-3 injuries / 1,000 participation hours (8)

• Professional Football / Soccer – 8.1 injuries / 1,000 participation hours (9)

• Swimming – 2.6-3 injuries / 1,000 participation hours (10)

• Rugby Union (11)

  • Youth / adolescent – 26.7 injuries / 1,000 participation hours

  • Amateur adult – 46.8 injuries / 1,000 participation hours

  • Professional adult – 81 injuries / 1,000 participation hours

When comparing the above information, it is important to remember that different definitions of injury (is it defined as any pain at all, or only when it results in time away from sport, or only when it becomes significant enough that medical attention is sought?), can affect the data. It means that it may be challenging to directly compare different studies. However, some general takeaways include:

• No activity has zero risk of injury.

• Although weight training is often viewed as having a high risk of injury, it may well result in fewer injuries than running, which is often seen as relatively safe.

• Contact sports likely have much higher rates of injury than non-contact sports.

Injury Prevention

With injuries representing a big problem for people who are recreationally active, for professional athletes, and for public health, there has been large amounts of research generated to answer the question: how do we reduce injury risk?

A systematic review of research looking at injury prevention strategies determined that “injury prevention programs are effective and can reduce injuries by at least 40% in both youth and adults” (12). Some of the effective strategies include:

• Progressive strengthening and balance programs

• External braces and joint supports

• Sport rule changes to limit player contact

There was less evidence in support of stretching and warming up (12). This doesn’t mean there is no benefit to stretching or warming up. But for injury prevention there has not been adequate research to demonstrate this. The clear message, however, is that to prevent injury the best strategy is to avoid exposing tissues to forces they aren’t ready to deal with. In other words: don’t do too much too soon.

In Summary

While being physically active has many health benefits, and is broadly protective against pain, injury does occur. To reduce the risk of injury, avoid rapidly increasing the intensity or volume of physical activity, and use exercise to build up the capacity of your tissues.

References

1. Raja, S. N., Carr, D. B., Cohen, M., Finnerup, N. B., Flor, H., Gibson, S., ... & Vader, K. (2020). The revised International Association for the Study of Pain definition of pain: concepts, challenges, and compromises. Pain, 161(9), 1976-1982.

2. Shiri, R., & Falah-Hassani, K. (2017). Does leisure time physical activity protect against low back pain? Systematic review and meta-analysis of 36 prospective cohort studies. British journal of sports medicine, 51(19), 1410-1418.

3. Kraus, V. B., Sprow, K., Powell, K. E., Buchner, D., Bloodgood, B., Piercy, K., ... & Kraus, W. E. (2019). Effects of physical activity in knee and hip osteoarthritis: a systematic umbrella review. Medicine and science in sports and exercise, 51(6), 1324.

4. Timpka, T., Alonso, J. M., Jacobsson, J., Junge, A., Branco, P., Clarsen, B., ... & Edouard, P. (2014). Injury and illness definitions and data collection procedures for use in epidemiological studies in Athletics (track and field): consensus statement. British journal of sports medicine, 48(7), 483-490.

5. Kalkhoven, J. T., Watsford, M. L., & Impellizzeri, F. M. (2020). A conceptual model and detailed framework for stress-related, strain-related, and overuse athletic injury. Journal of science and medicine in sport, 23(8), 726-734.

6. Videbæk, S., Bueno, A. M., Nielsen, R. O., & Rasmussen, S. (2015). Incidence of running-related injuries per 1000 h of running in different types of runners: a systematic review and meta-analysis. Sports medicine, 45, 1017-1026.

7. Keogh, J. W., & Winwood, P. W. (2017). The epidemiology of injuries across the weight-training sports. Sports medicine, 47(3), 479-501.

8. Pluim, B. M., Staal, J. B., Windler, G. E., & Jayanthi, N. (2006). Tennis injuries: occurrence, aetiology, and prevention. British journal of sports medicine, 40(5), 415-423.

9. López-Valenciano, A., Ruiz-Pérez, I., Garcia-Gómez, A., Vera-Garcia, F. J., Croix, M. D. S., Myer, G. D., & Ayala, F. (2020). Epidemiology of injuries in professional football: a systematic review and meta-analysis. British journal of sports medicine, 54(12), 711-718.

10. Trinidad, A., González‐Garcia, H., & López‐Valenciano, A. (2021). An updated review of the epidemiology of swimming injuries. PM&R, 13(9), 1005-1020.

11. Yeomans, C., Kenny, I. C., Cahalan, R., Warrington, G. D., Harrison, A. J., Hayes, K., ... & Comyns, T. M. (2018). The incidence of injury in amateur male rugby union: a systematic review and meta-analysis. Sports medicine, 48, 837-848.

12. Stephenson, S. D., Kocan, J. W., Vinod, A. V., Kluczynski, M. A., & Bisson, L. J. (2021). A comprehensive summary of systematic reviews on sports injury prevention strategies. Orthopaedic journal of sports medicine, 9(10), 23259671211035776.