Injury flare-ups often mean that the demand placed on a body region has exceeded what it can currently tolerate and recover from. That does not automatically mean you have caused new damage but does mean that something in the equation needs to change.
When demand exceeds capacity of a tissue by too much, that tissue is not going to be able to recover from that demand and can lead to flare-ups.
The best response is usually not to push through the activity unchanged, but it is also rarely to reduce demand all the way to zero. A better approach is to temporarily reduce the aggravating load, keep doing what remains tolerable, and progressively rebuild the capacity required for work, exercise and daily life.
What do capacity and demand mean during injury flare-ups?
Capacity is the ability of a body region, or person, to handle a particular task or load and recover before it is loaded again. It is specific to the tissue that is being loaded. For example: the ability of your low back muscles to maintain stability during a deadlift.
Demand is the total stress imposed by the task. It changes with weight, repetitions, duration, speed, range of motion, frequency, impact, novelty and recovery time. For something like a deadlift, it is the amount of weight on the bar, how much rest you had since your last set, and how full of a range of motion are you performing.
In this train of thought, flare-ups therefore often follow mismatch in the capacity vs demand equation rather than one obviously “bad” movement: the first tennis match after a quiet winter, an abrupt increase in weekly running volume, or a busy work week with less sleep. Demand may have risen, capacity may have temporarily fallen, or both.
The capacity vs. demand equation can also give us some insight in how to deal withe flare-ups once they occur: we need to tip the scales back in favour of capacity and let the tissue settle. This generally means a decrease in demand to let the tissue settle, before regaining capacity to the point where it can handle the previously overwhelming demand.
Does more pain always mean more tissue damage?
No. Pain can accompany tissue damage, and often does, but pain intensity is not a damage meter.
The International Association for the Study of Pain describes pain as an experience influenced by biological, psychological and social factors. This distinguishes it from nociception which is the the nervous system’s (pain receptors) processing of potentially threatening input. Pain may closely accompany an acutely traumatic injury like a new ankle sprain. But in something like recurring low back pain, symptoms may increase without a meaningful new injury as your nervous system is acting more to protect a tissue from a demand it thinks might exceed capacity vs. what actually produces injury.
Therefore, a flare-up should not automatically be treated as evidence that tissue is damaged, but it should not be completely ignored either. Pain needs context: what was the thing that changed the capacity vs. demand equation? Was there an increase in load? Is function reducing? How was my sleep? My stress? My recovery? Did I try a new exercise? All of these things can influence the capacity vs. demand equation and lead to pain. But not all of these things means that something bad happened on a tissue level.
Why complete rest is usually an incomplete answer
After a flare up, reducing demand can help to settle irritable symptoms. The problem is that while rest can reduce symptoms in the short term, it is counterproductive in the long term and will lead to more problems down the road.
Rest reduces demand but it does not rebuild capacity. Prolonged unloading reduces strength and tissue capacity, means that when you return to your previous activities after the pain settles, you have even less capacity than when you irritated the tissues in the first place. This flares up the issue gain, you try even more rest next time, and the downward spiral continues.
This is why current guidance for several common musculoskeletal conditions emphasizes remaining active and using exercise rather than waiting for complete symptom resolution. The 2024 clinical practice guideline for midportion Achilles tendinopathy recommends tendon-loading exercise even when painful and states that complete rest is not indicated. The World Health Organization also includes structured exercise among recommended approaches for chronic primary low-back pain. A large Cochrane review found that exercise probably improves pain in chronic low-back pain compared with no treatment, usual care or placebo, although the average effect on disability was smaller.
These findings do not prove that every painful condition should be exercised in the same way but they do support the broader principle that appropriate loading is treatment, not merely something to resume after treatment.
How progressive loading rebuilds tissue capacity
Biological tissues respond to load.
Muscle becomes stronger with resistance training, bone adapts to mechanical strain, and tendons can change their material and mechanical properties.
That does not mean more load is always better. But it does mean that some load is always better than no load. A useful rehabilitation dose must be large enough to stimulate adaptation but manageable enough to recover from. The appropriate exercise, intensity and progression depend on the diagnosis, stage of recovery and demands of the person’s life- but there is almost always some activity that is beneficial.
This is also why a few easy exercises performed indefinitely are not a complete rehabilitation plan. If your goal is to lift a child, work a physical job, run 10 kilometres or play tennis twice per week, rehabilitation eventually has to prepare you for those demands. As your capacity increases, your demand should also increase, so your tissues are constantly adapting to new demands and gaining more capacity.
How much should you reduce activity during a flare-up?
Reduce the smallest amount necessary to make the response manageable. Think relative rest, not automatic shutdown.
Start by identifying what changed: volume, intensity, speed, frequency, range, novelty or recovery. Modify one or two variables while preserving tolerable activity. A runner might replace hills with shorter, flat runs while maintaining appropriate strength work. A gym goer may choose to use machines vs. free weights to reduce some stability demands.
For many people in Toronto, eliminating walking, commuting, childcare or physical work is neither practical nor necessary. The plan has to account for unavoidable demand before deciding how much exercise to add.
There is no universal rule that a certain pain score is always safe. A more useful approach is to monitor the pattern:
- During activity: Are symptoms mild and stable, or escalating with each repetition?
- After activity: Do they settle reasonably, or continue to build for hours?
- The next day: Are pain and function back near baseline, or clearly worse than the day before?
- Over several sessions or days: Is your tolerable workload gradually increasing?
A small, short-lived increase in symptoms can be acceptable for some conditions. A progressive loss of strength or movement, increasing swelling, worsening neurological symptoms, or a flare that repeatedly lasts into the next day suggests that the dose or diagnosis should be reassessed.
When should a flare-up be assessed rather than self-managed?
You should always seek immediate medical assessment after significant trauma, or if you develop an inability to bear weight or use the limb, visible deformity, marked swelling, fever or unexplained illness, progressive weakness or numbness, or changes in bowel or bladder control. Protection or complete rest may be appropriate for fractures, tendon ruptures, certain postoperative restrictions and some acute inflammatory or medical conditions.
For muskuloskeletal conditions that are not emergencies, it is reasonable to try some self-management strategies for a few days following a flare up, especially if it is something that has happened and been assessed in the past and you have a plan on how to tackle your flare up.
However, if it is something that you have not experienced before, are having trouble managing the pain on your own, it is not getting better after a few days, or you just want some reassurance and guidance from a professional that you are doing the right things: that is where an assessment from a chiropractor can help.
An assessment can identify the likely pain mechanism, contributing demands and a starting dose that supports recovery. It can also help to create a plan that gets you out of your flare-up, into a progressive rehabilitation program to regain your capacity, and help you re-start your activities safely to reduce the chance that we have another flare-up from a demand mismatch.
