Are you a runner? Are you at risk for a running injury? As running is becoming a more common method of exercise during this time, more people are experiencing injuries. Approximately 19- 79% of runners experience an injury each year and approximately 80% of them are due to overuse .
Research suggests certain factors in runners increase the risk of injury, though evidence is stronger for some factors than others. Recognizing these factors is an important step in preventing running injuries so you can take the necessary steps to decrease your specific risk. Today, we will discuss what puts runners at risk for injury.
Risk Factors for Running Injuries
The most common risk factors for injury can be grouped into four categories:
1. Personal factors
Personal factors are factors that cannot be changed, and include a runner’s age, sex, height, and other genetic factors. There is mixed evidence on age as a risk factor, with running experience being a better predictor of risk. Beginner runners are at a higher risk of injury if they are older in age, over- or under-weight, have a history of prior injury, and/or have no history of previous running or sport experience. Experienced runners who are older in age and have a history of prior injury are at increased risk of injury .
Overall, there is little agreement in the research on how sex relates to running injuries. One article sought to determine the risk of running injuries based on sex and found that male and female runners have different risk profiles. These profiles include other personal and lifestyle factors.
For example, there is some evidence that women are at higher risk of injury if they are older in age, have a history of sport and/or endurance running, run on concrete surfaces, and have running shoes 4-6 months old . The same article found that men were at greater risk if they had less experience, recently restarted running, and/or ran 32-48.7 km or >64km weekly.
Statistically, the risk ratios reported for the above profiles have “moderate significance.” This means that they do not predict injury risk in a lot of cases. There are other factors that have higher significance, and can give better insight when it comes to finding ways to avoid injury.
2. Lifestyle factors
Lifestyle factors include health and health history, some which can be altered through behavioral changes. These factors include smoking, previous injuries, weight, and other comorbidities.
It goes without saying that overall health status, including nutrition, fitness level, habits, sleep, and medical conditions play a role in running performance. Performance is linked to the risk of injury in that repeated poor performance or overtraining can lead to injury. More on this in the training factors section (see below).
The strongest evidence we have is that previous leg injuries put runners at risk for future injuries . One article found that a leg injury in the past 12 months is a risk factor for knee injury in runners. The same article also found evidence that an injury anywhere on the leg was a risk factor for a calf injury. Other more specific injuries, such as shin splints and Achilles tendinopathy, were indicated for risk of re-injury .
3. Biomechanical factors
Biomechanical factors include everything from body structure to cadence to stride mechanics. As a quick review, biomechanics studies a set of measurements about how the body moves. This includes structures and forces both within and outside of the body. In the case of running, we look at how the hip, knee, ankle, and foot move and absorb and distribute forces.
The structures of the leg considered in biomechanics include the hip, knee, ankle, and foot joints. Scientists look at the alignment, angles, range of motion, and strength of those joints. The forces involved in the motion of running are calculated based on a runner’s weight, foot strike pattern, and the running surface.
Information about the structures and forces involved during running can be combined to shed light on running technique. Good technique, including posture, foot strike, cadence (the number of steps in one minute), etc. can help reduce the risk of injury from running.
Biomechanical Risk Factors
One article looked at several structural factors related to running, with evidence pointing specifically at foot structure and differences in leg length. It was determined that runners with high, stiff arches are at higher risk of injury. Runners with higher arches may have altered contact with the ground, affecting how force is absorbed in the rest of the body .
Leg Length Differences
The same article found that runners with different leg lengths were at a higher risk of stress fractures. Without correction, the runner’s stride mechanics are uneven, often leading to one leg doing more work than the other. Additional stress to one leg can lead to injury in that leg .
Leg length also comes into play with how long a runner’s steps are. Runners with shorter legs tend to have a higher cadence, taking more steps in one minute to complete the same distance as someone with longer legs. Increasing cadence can also be used as a strategy to increase speed. However, runners who increase their cadence too quickly may be at higher risk of injury as well .
Decreased Lower Body Strength
To learn about normal stride mechanics, check out this previously written blog post. Factors that may cause abnormal stride mechanics include decreased hip and thigh (specifically vastus medialis obliqus and gluteus medius) strength and poor eccentric strength. Eccentric muscle contraction occurs when a muscle lengthens in a controlled manner. The best example is running downhill or slowing down after a sprint. Those actions require controlled muscle lengthening to avoid injury.
Another specific example of an eccentric muscle contraction when we run is what our foot needs to do after it hits the ground. A muscle known as the posterior tibialis, located on the inside of our lower leg, needs to “slow down” the flattening of the foot. The runner seen below has excessive flattening (or pronation) of her right foot upon landing. This leads to her right knee collapsing inward and her left hip dropping. This repetitive movement places a lot of strain on her right leg including her foot, knee, and ankle.
Runners with previous or existing injuries are more likely to present with abnormal stride mechanics, such as the ones described above. It is very likely that those deficits contributed to their risk of injury .
4. Training factors
Training factors include mileage per week, training schedule, stretching, and footwear. These factors will be discussed in more detail in the next blog post. Here are some quick facts:
Excessive weekly running mileage puts runners at increased risk of injury . This is especially the case when there is a dramatic increase in a short amount of time. Excessive mileage can be the result of both increased running distance and increased frequency of running. These factors contribute additional repeated forces to the structures of the legs (bones, muscles, ligaments). Without appropriate rest or conditioning, these structures can fail leading to injury.
Both stretching and footwear are highly controversial topics. Research has found that runners who stretch either at every training session or not at all were at decreased risk of injury . Likewise, when considering footwear and orthoses, most injuries are seen in runners who make a drastic change. This change could be adopting minimalist shoes or adding an orthosis when there is no history of injury . An article distinguishing between different types of orthoses determined that custom orthoses (as opposed to off-the-shelf) decreased risk of injury in runners .
At the end of the day, knowing your body and your habits will help determine the best training factors to help you run safer. That, and checking out my next article on determining your training factors and footwear solutions to prevent injury and improve performance. As always, check out In Motion PT’s return to running page for more info. Make sure to give us a call to schedule your running analysis to address or prevent your lower extremity aches and pains!