You started treatment – and the pain became worse. What is happening?
Have you had your first treatment at a specialist clinic, started physiotherapy or bought a home therapy device? Were you surprised to notice that the pain became worse instead of easing?
The frightening first thought is: “Am I harming myself?!”
The reassuring answer is: in most cases, no. A temporary increase in symptoms after starting treatment is a well-known, common and usually harmless phenomenon – research suggests that after manual therapies, for example, 20–40% of patients experience a mild to moderate, self-limiting reaction, while serious complications are exceptionally rare.1
But there is another side to the story: sometimes increasing pain really does indicate a problem – the wrong method, excessive dosing, poor technique, or an underlying condition that is not suitable for home treatment. This article separates these two situations: you will learn to recognise when the reaction is a natural part of recovery and when you need to stop.
Key point
Two rules decide almost everything. The time rule: a normal treatment reaction settles within 24–72 hours. The trend rule: it should become smaller from one session to the next. Anything that lasts beyond 72 hours or increases from treatment to treatment is not “healing kicking in”. It is a signal that something needs to change: the dose, the method, or the condition itself may be worsening and you need to see a doctor.
Normal reaction or warning sign? How to tell the difference
| Normal treatment reaction | Indicates an error or change in symptoms | |
|---|---|---|
| When does it occur? | During or immediately after the first 1–3 treatments, settling within a few hours | No close connection with the timing of treatment |
| What is it like? | Dull, muscle-soreness-like tenderness, mild tightness in the treated area | Sharp, throbbing or radiating pain; numbness, weakness |
| How long does it last? | Goes away on its own within 24–72 hours | Persists beyond 72 hours, or wakes you at night or at rest |
| What is the trend? | Becomes smaller from session to session, then disappears | Becomes worse even independently of treatment |
| What accompanies it? | Slow, gradual improvement | Swelling, redness, warmth, fever, deteriorating function |
If the left column sounds familiar: you can continue, usually with a reduced dose (more on this below). If even one item in the right column applies: stop and read the warning section at the end of the article.
Why can pain increase when everything is fine?
You have been protecting the painful part of your body for weeks or months: you barely move it, its circulation has slowed and its tissues are operating in “economy mode”. The first treatments – whether electrical stimulation, light, ultrasound, massage or exercise – shake this dormant state into action: blood circulation increases, muscles that have been resting for a long time start working and the repair process begins. A mild, temporary inflammatory response is a natural part of this process. You feel it as muscle-soreness-like tenderness.
The popular explanation that treatment “flushes out toxins” and “detoxifies the body” is not scientifically proven. What happens is that tissues receiving increased blood flow again after prolonged protection respond to the new stimuli – and this reaction fades after a few sessions as the area gets used to working again.1
Many people are surprised to feel pain during physiotherapy exercises – and stop because of it, although that is a mistake. Research into chronic musculoskeletal pain has specifically examined this question: according to a review of randomised trials, exercise programmes that allow, and even incorporate, tolerable pain produced slightly better short-term results than programmes designed to be completely pain-free – and did not cause damage.2 Feeling pain during exercise therefore does not equal tissue damage. The rule physiotherapists teach is this: pain during exercise should remain at a tolerable level and settle by the next day – within this framework, “it hurts, but I keep going” is not recklessness but part of the treatment. (Self-torture is not appropriate either.)
If your pain has lasted for months or years, your nervous system has adapted in the meantime: the pathways that process pain signals have become more sensitive and the alarm has been “turned up louder”. At first, stimuli that would hardly be noticed in healthy tissue can trigger pain – the first treatments and the first movements “sound louder” than they should. This is not imagined pain: it is real, but its source is not fresh tissue damage. It is the sensitised nervous system.
The good news is that regular, predictable, measured stimulation – exercise, TENS and gradual progression – gradually turns this alarm back down. That is why patience and consistency are essential, and why giving up after the first bad experience is a mistake.
When the treatment really is at fault – the three typical mistakes
1. The wrong method for the wrong problem. What worked for your neighbour may not be suitable for your problem. A classic example: heat therapy feels good for wear-and-tear and chronic joint symptoms, but can make a fresh injury or a swollen, inflamed joint worse by further stimulating an already overactive inflammatory process. The order cannot be skipped: diagnosis first, then method, finally the device. If you are unsure, the physiotherapy overview and which electrotherapy is suitable for what articles can help you find your way.
2. Excessive dosing – when more gives you less. With physical stimuli, the effect is not directly proportional to the dose but follows a bell-shaped curve: a low dose starts the cells’ repair activity, while too much inhibits it. Research calls this a biphasic dose response (the Arndt–Schulz rule), and it has been particularly well documented for soft laser therapy.3 It is like sunbathing: 20–30 minutes can be good for your skin, while several hours cause sunburn. In practice, using 30 minutes instead of a 5–10-minute daily laser treatment, leaving a treatment running all evening, or turning the TENS current up to maximum does not bring faster recovery. Paradoxically, it can cause more symptoms. Every method has its own dosage – I have described them precisely in the soft laser therapy guide and the ultrasound dosing article.
3. Poor technique. The most common example is therapeutic ultrasound: the treatment head must be moved continuously in slow circular movements. If it is held still at one point, the energy of the sound waves becomes concentrated in one place and may cause pain or tissue damage at the periosteum. This also includes an electrode stuck in the wrong place, a treatment head placed on damaged skin, or omitted contact gel. Reading the instructions for use and the method guides is not a formality: both the effect and safety depend on technique.
My advice – how to respond when symptoms increase
If a muscle-soreness-like reaction appears after the first treatments, do not stop the course and do not increase the dose “to get it over with sooner”. Instead, step back one level: shorter treatment time, lower intensity and less frequent sessions, then return to the prescribed level step by step over 1–2 weeks. Change only one thing at a time – if you change the method, dose and technique together, you will never know what the problem was. Keep a treatment diary (when, for how long, at what intensity and what you felt afterwards): three entries will tell you more than three weeks of guesswork.
When should you NOT treat yourself at home?
- Unexplained, new or worsening symptoms – medical diagnosis first, home treatment only afterwards
- Pacemaker or another implanted electronic device – electrotherapy and magnetotherapy must not be used
- Fever, acute infection, inflamed or swollen area – postpone treatment until your doctor advises otherwise
- Pregnancy – only after medical consultation
- Cancer – any physiotherapy treatment requires the approval of your treating doctor
- Recent thrombosis or suspected thrombosis – treatment is prohibited
When should you see a doctor?
Stop the treatment and seek medical assessment if the pain does not ease after 72 hours or increases from one treatment to the next; if it wakes you at night or at rest; if it is accompanied by swelling, redness, warmth or fever; if numbness, muscle weakness or altered sensation occurs; or if the function of the treated body part deteriorates. These are not treatment reactions. They may be caused by an undiagnosed injury, infection or another condition requiring treatment. The sooner it is identified, the simpler the solution is likely to be.
Frequently asked questions
If the symptom feels like muscle soreness, appears after the first sessions and soon eases or disappears: continue with a reduced dose; this is a normal reaction. However, if any item in the warning-sign column applies to you (it lasts beyond 72 hours, the trend is worsening, or swelling, fever or numbness occurs), then yes: stop and see a doctor. In the grey zone between the two, take a 2–3-day break, then restart cautiously at half dose.
Yes, at a tolerable level – research suggests that exercise programmes allowing pain performed slightly better in the short term than completely pain-free programmes.2 There are two limits: during the exercise, the pain should remain at a level you can accept comfortably, and it should settle by the next day. Anything beyond this – sharp, radiating pain or worsening the following day – means that the exercise technique or load needs to be adjusted with your physiotherapist.
No – this is a popular but scientifically unsupported explanation. Temporary tenderness after treatment is not caused by circulating “toxins”, but by the fact that tissue which has been protected for a long time and is now working again responds to mechanical and energetic stimuli with a mild, temporary inflammatory and repair response – similar to muscle soreness after exercise. The phenomenon is real, but the explanation is different. This is not hair-splitting: anyone who believes it is “detoxification” may be inclined to overdose the treatment so that it “clears faster” – when moderation is precisely what helps.
Because that is when the contrast is greatest between the tissue’s accustomed, protected state and the new stimuli. The first treatments “wake up” an area with slowed circulation that has become deconditioned – and this produces the greatest reaction. As the tissue adapts, the reaction becomes smaller from session to session and then disappears. That is why every method starts with a shorter time and lower intensity, increasing step by step – the reaction is gentler this way too.
This is the reverse of the same myth – and it is just as wrong. Most physical therapy treatments do not need to hurt at all: TENS feels like a pleasant tingling, while soft laser and magnetotherapy are practically imperceptible, yet they still do their work. The “no pain, no gain” principle applies at most to training load, and even there it has limits. Do not measure the treatment’s effect by how strong the sensation is. Measure it by the weekly trend: improvement in your pain-free range of movement and your ability to tolerate load.
What does the research say?
“Is it common for someone to feel temporarily worse after treatment?”
Yes, it is quite common – and it has been measured well. According to a review of the safety of manual therapies (massage, manual therapy and spinal treatments), 20–40% of patients experience a mild or moderate, temporary reaction after treatment – typically local tenderness, fatigue or a transient increase in symptoms – while the rate of serious complications is around 0.13%, making them exceptionally rare.1 Temporary worsening is therefore a known, familiar part of treatment – not a sign of failure.
“Is it not dangerous to exercise until it hurts?”
According to a review of randomised trials, no – quite the opposite. In chronic musculoskeletal pain, loaded exercise programmes that allowed pain produced slightly better short-term pain reduction than programmes designed to be pain-free, and the risk of harm did not increase.2 The researchers’ conclusion is exactly what we say in the clinic: pain during exercise is not an obstacle to successful treatment. The important points are that it remains tolerable and settles by the next day.
“Could I simply be treating myself too much?”
It is possible – and there is a sound physiological basis for this. Research into light-based treatments (soft laser) has described the biphasic dose response in detail: at a low dose, the cells’ energy production and repair activity increase; as the dose rises, the effect first peaks and then reverses – too much energy inhibits the same processes.3 This is the Arndt–Schulz rule. In practice, it means that treatment time and intensity must be set according to the instructions, not on the basis of “the more, the better”. Impatience here literally backfires.
Summary – Quick overview
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Scientific sources
- Carnes D, Mars TS, Mullinger B, Froud R, Underwood M (2010). Adverse events and manual therapy: a systematic review. Manual Therapy, 15(4), 355–363. DOI: 10.1016/j.math.2009.12.006
- Smith BE, Hendrick P, Smith TO, et al. (2017). Should exercises be painful in the management of chronic musculoskeletal pain? A systematic review and meta-analysis. British Journal of Sports Medicine, 51(23), 1679–1687. DOI: 10.1136/bjsports-2016-097383
- Huang YY, Chen ACH, Carroll JD, Hamblin MR (2009). Biphasic dose response in low level light therapy. Dose-Response, 7(4), 358–383. DOI: 10.2203/dose-response.09-027.Hamblin
