Understanding Running Injury Flare-Ups

multiracial young athletes training run at school track

Therapeutic Associates

As a track athlete at the University of Washington, I was entering my final year of competition. This was to be the culmination of my collegiate career and years of meticulous training. 

I’d had a few injuries along the way but had stayed healthy recently, building up to the final year – until an old injury reappeared. 

I felt a familiar pain on the outside of my knee while increasing my volume on a hilly gravel road. The more miles I ran the more pain I felt. As the pain increased, I began to feel frustrated, which only increased when other old pain areas began to flare-up too over the next week. I took time off and still the pain persisted. Worried that I would not be able to return to running anytime soon, I could not understand – why was I in pain and was I making things worse with every step?

What is a flare-up?

What I needed to be reminded of in that moment is that running injuries are very common and, unfortunately, running reinjury is common as well. In one study, it was found that 85% of runners experienced an injury significant enough to miss one day of training. One of the strongest predictors of injury was history of previous injury in the last year.1

Though frustrating and disappointing, flare-ups are very common while returning to running. 

A flare-up is defined as an exacerbation or a return of a condition you have been experiencing. This often comes in the form of a setback in function or ability, reoccurrence of familiar symptoms, or pain you did not expect as you return to running and activity. This can be frustrating and disappointing, even scary.  

The intensity of a flare-up is often disproportionate to the amount of running and activity you have resumed. 

This is often because the return of symptoms does not correlate with new tissue damage. 

In short, a flare-up means that something is irritated, inflamed, or dysfunctional, again.

woman holds her painful hamstring during a running workout

Why do flare-ups happen?

A majority of flare-ups are related to modifiable risk factors that are connected to the original injury. Often, a flare-up provides an opportunity to address something unresolved from a previous injury. Consider the original mechanism of injury and if the primary and secondary contributing factors were appropriately addressed. If not, this may help explain why this injury has returned or become worse. 

If you are experiencing a flare-up and are unsure why, consider these five questions.

It is all too common to simply wait until the pain goes away and then attempt to run again. After all, the thrill of the run is ever-inviting and the call of training is insistent. However, this fails to address the underlying cause and the injury may actually feel worse the next time out the door due to the prolonged inactivity and subsequently lower tissue tolerance. This is why incomplete rehabilitation places you at risk for symptom return.

In overuse injuries, the demand or stress placed on the tissue exceeds its tolerance and ability to regenerate. When this occurs, the tissue is at risk for reinjury. The most common training error is too much too soon. If you recently increased either volume or intensity (or both), this is likely related to the flare-up you are experiencing. Did the tissue have the reserve for the activity demands you asked of it or did you fail to appropriately prepare the tendon, muscle, etc. prior to the training change?

Although running may the primary reason for a high level of demand on an overloaded tissue, activities other than running may be contributing. If you have introduced other forms of training, such as strength work or cross training, this may be contributing to tissue overload. New shoes, new surfaces, and new exercises are all things that can lead to a flare-up.

Tissues require appropriate nutrition and rest in order to effectively regenerate and heal. If deprived of nutrition and rest, a running volume and intensity that you have previously tolerated may lead to injury or a flare-up. Signs of inadequate recovery include feeling lethargic, general fatigue, early exhaustion during training, poor quality sleep, lack of energy or motivation, and disinterest in activities that you normally care about. These signs would indicate training overload and a high risk for a flare-up.

In contrast to tissue overload, tissue irritability can drive a flare-up as you return to running. This may be related to other factors, including a poor understanding of pain and what pain means, a high level of stress, and concurrent conditions. Your attitude toward your flare-up, including the apprehension and fear you feel, can impact the level of pain you experience while running. Pain that is poorly understood may linger and morph. Catastrophization, when you assume the worst will happen, and pain-avoidant behavior may lead to a delayed return to running, despite readiness to get back on the roads, track, or trail. The presence of other conditions or injuries can impact an old injury and flare up an otherwise resolved episode.

How do you manage and prevent flare-ups?

  • Progress running volume gradually – The general rule is no more than 10-20% a week
  • Make changes incrementally – This includes the addition of strength and cross training to the routine
  • Stay active – Establish a baseline of activity to prevent a boom-bust cycle that leads to injury flare-up
  • Scrutinize recovery – This should include an appropriate amount of high-quality sleep, planned days off, and nutritional planning
  • Be clear about your recovery expectations: Flare-ups happen!

Knowing that flare-ups have a high occurrence rate, we need to have a plan in place for when that familiar pain occurs. A flare-up plan should include strategies to manage the onset of symptoms and ways to keep making progress toward the goals that you have. Examples include:

  • Adjusting rest and recovery
  • Reflecting on contributing factors that may need to be addressed, like fear and stress
  • Maintaining a baseline of activity. Some running is better than not running at all!
  • Initiating safe, pain free exercise
  • Establishing clear expectations regarding acceptable symptom levels during and following running

Because flare-ups are often related to irritated tissues rather than tissue damage, there may be a level of acceptable symptoms during training. If you have seen a medical professional for the original injury, it can help you feel confident that you are not causing harm as you return to running. If you have not seen a medical provider, remember that sharp pain, pain seemingly disproportionate to the run or activity, and symptoms lasting longer than 24 hours without improvement are signs that additional evaluation is needed.

physical therapist works with patient on knee and hip mobility
physical therapist talks to a patient during an initial appointment

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As physical therapists, we know the importance of movement for overall health and well-being. From injury recovery to achieving optimal performance, our passion is to help every patient reach their goals and live an active, pain-free life. Get started with PT today!

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