Why Tendons Flare When Training Ramps Up—and How Sports Physiotherapy Helps

 Sudden changes in hills, speed or weekly distance can increase tendon demand.

A tendon that has tolerated years of running, football or gym training can become stiff and painful after only a few weeks of increased activity.

A footballer may begin pre-season and add sprint sessions to weekend matches. A runner preparing for a half-marathon might introduce hill repetitions during the same week as a longer Sunday run. Each session can appear manageable on its own, while the combined workload exceeds what the tendon currently tolerates.

This is particularly easy for recreational athletes who train in several settings. A club coach sees scheduled practice but may not know about additional gym sessions, social matches or hilly runs around Toowoomba’s Picnic Point.

Not every painful tendon has the same cause, and pain does not necessarily mean that the tendon is tearing. However, a sudden increase in volume, intensity or frequency is a common factor worth reviewing.

Quick Answer

A tendon flare may occur when running, jumping or strength demands increase faster than the tendon’s current capacity. Management usually involves identifying the aggravating loads, modifying them temporarily and introducing progressive strengthening. Complete rest is not routinely recommended for tendinopathy, but suspected tears and severe symptoms require prompt assessment.

Key Takeaways

• Tendon pain often appears after changes in training volume, intensity, frequency or terrain.

• Sprinting, jumping, rapid changes of direction and hills can create substantial tendon demand.

• Pain that improves during a warm-up does not necessarily mean the tendon is ready for extra work.

• Rehabilitation usually involves load modification rather than complete inactivity.

• Progressive tendon-loading exercise is a first-line treatment for many cases of Achilles tendinopathy.

• Pain-monitoring rules should be individualised rather than applied as universal limits.

• Recovery should be guided by symptoms, strength and function—not a fixed calendar.

• A sudden pop, marked weakness or difficulty walking needs urgent assessment.

Table of Contents

1. Why Can Tendons Flare When Training Increases?

2. What Is Reactive Tendinopathy?

3. What Does a Load-Related Tendon Flare Feel Like?

4. Why Can a Tendon Feel Better After Warming Up?

5. Does a Sore Tendon Need Complete Rest?

6. How Does a Sports Physiotherapist Assess Tendon Pain?

7. What Does Tendon-Loading Rehabilitation Involve?

8. How Long Does Tendon Rehabilitation Take?

9. When Should Tendon Pain Be Assessed Promptly?

10. Frequently Asked Questions

Why Can Tendons Flare When Training Increases?

Tendons connect muscles to bones and help transfer force during movement. The Achilles tendon contributes to walking, running and jumping, while the patellar tendon helps transmit force through the knee during squatting, landing and acceleration.

Tendons respond to training, but their tolerance depends on several factors:

• Recent training history

• Strength and conditioning

• Previous injuries

• Recovery between sessions

• Age and general health

• Medication use

• Sleep and nutrition

• Running surface and terrain

• Changes in footwear

• The speed and type of movement

The idea that tendons always adapt more slowly than muscles is an oversimplification. A more useful principle is that cardiovascular fitness, muscular strength and tendon capacity do not necessarily improve at the same rate.

You may therefore feel fit enough to complete a harder session before a tendon has developed the capacity to tolerate repeated high-force loading.

Our guide to personal training and gradual exercise progression explains why training load should reflect recent activity, recovery and individual ability.

Which Training Changes Place the Greatest Demand on Tendons?

Not all kilometres or training minutes create the same physical demand.

Activities involving rapid force production can be particularly challenging:

• Sprinting

• Jumping

• Hopping

• Hard acceleration

• Sudden braking

• Changes of direction

• Hill running

• High-volume strength training

• Returning to sport after a break

A runner who increases distance, introduces hills and adds speed work in the same week has changed three variables simultaneously. A footballer who returns to full training after a quiet off-season may experience a similar jump in demand.

Training workload research suggests that sudden changes may be associated with injury risk. However, the acute-to-chronic workload ratio should not be treated as a precise injury calculator. It has received significant statistical criticism, and no single ratio can predict whether an individual athlete will be injured.

The practical message remains useful: build training progressively, consider all sporting activity together and avoid changing several demanding variables at once.

Expert Tip: Record running, gym work, matches and informal exercise in the same training diary. The tendon responds to the combined physical demand—not to how the sessions are labelled.

What Is Reactive Tendinopathy?

The tendon-continuum model developed by Cook and Purdam describes several possible stages of tendon pathology, including reactive tendinopathy, tendon disrepair and degenerative tendinopathy.

A reactive response may follow an unfamiliar or increased load and can involve pain, stiffness and temporary changes in tendon structure. However, the model is a clinical framework rather than something an athlete can use to diagnose their own condition.

The word “reactive” should not be interpreted to mean that:

• The tendon is definitely undamaged

• Every recent pain episode will resolve quickly

• Imaging can identify the precise stage perfectly

• All tendon pain follows the same biological pathway

A physiotherapist or doctor may need to distinguish tendinopathy from a tear, bursitis, joint pain, nerve-related symptoms or another condition.

What Does a Load-Related Tendon Flare Feel Like?

Achilles Tendon Symptoms

Midportion Achilles tendinopathy commonly causes:

• Pain several centimetres above the heel

• Stiffness during the first steps after waking

• Pain when beginning to walk or run

• Discomfort with hopping or calf raises

• Local tenderness

• Reduced calf strength or endurance

• Symptoms that improve during activity but return later

Insertional Achilles pain occurs closer to where the tendon attaches to the heel and may require different exercise modifications. Exercises performed with the heel dropping below a step, for example, may aggravate some insertional presentations.

The Australian Physiotherapy Association distinguishes between midportion and insertional Achilles tendinopathy and highlights education and prescribed exercise as important parts of physiotherapy management.

Patellar Tendon Symptoms

Patellar tendinopathy usually causes pain around the tendon immediately below the kneecap. Symptoms may be provoked by:

• Jumping

• Landing

• Sprinting

• Squatting

• Stairs

• Sudden deceleration

• Repeated changes of direction

Knee pain in this area is not always patellar tendinopathy. Patellofemoral pain, fat-pad irritation and other knee problems can produce overlapping symptoms, making assessment important.

Why Can a Tendon Feel Better After Warming Up?

Tendon pain sometimes decreases after several minutes of movement. Athletes may interpret this warm-up effect as evidence that the problem has resolved.

The tendon may then become more painful:

• Later in the session

• That evening

• During the next morning

• Following several consecutive training days

Pain during one moment is only part of the picture. The response over the following 24 hours, changes in morning stiffness and overall function can provide additional information.

This does not mean everyone should perform a daily heel-raise or single-leg-squat test without guidance. Repeated testing can itself add load, and the appropriate movement depends on the suspected diagnosis.

A physiotherapist may instead select a consistent monitoring task suited to the individual.

Does a Sore Tendon Need Complete Rest?

Complete rest may reduce pain temporarily, but it does not automatically rebuild strength or load tolerance. For many clinically diagnosed tendinopathies, the longer-term plan includes appropriately dosed exercise.

The 2024 clinical practice guideline for midportion Achilles tendinopathy recommends tendon-loading exercise as a first-line intervention, performed at a load that is appropriately tolerated.

However, “keep moving” is not suitable advice for every injury. Temporary protection or medical treatment may be necessary when there is:

• A suspected tendon tear

• Severe pain

• Marked weakness

• Significant swelling

• Inability to walk normally

• Recent surgery

• Another acute injury

• A clinician-imposed restriction

The Silbernagel pain-monitoring study found that selected patients with Achilles tendinopathy who continued some running and jumping during rehabilitation did not have worse outcomes than participants who temporarily stopped those activities.

That study used a structured programme and a pain-monitoring model. Its frequently quoted threshold of five out of ten should not be turned into a universal rule for every tendon, athlete or stage of recovery.

How Does a Sports Physiotherapist Assess Tendon Pain?

A sports physiotherapist will normally begin by reviewing:

• When the symptoms began

• Recent training changes

• Weekly running and sporting activity

• Pain behaviour during and after exercise

• Morning stiffness

• Previous tendon or joint problems

• Medication and health history

• Strength and movement capacity

• The athlete’s sport and performance goals

The physical assessment may examine local tenderness, tendon-loading movements, calf or quadriceps strength, hopping ability and sport-specific tasks.

Imaging is not always required. Tendon changes can appear on ultrasound or MRI in people without symptoms, while the degree of structural change does not always match pain severity. Imaging may be considered when the diagnosis is uncertain, symptoms are atypical or a tear is suspected.

In Toowoomba, the Optimise Health physio team manages tendinopathy and other sporting injuries. Coordination between the physiotherapist, athlete, coach and trainer may be helpful when club sessions and independent training are contributing to the total load.

How Can Training Be Modified Without Stopping Everything?

The objective is usually to reduce the loads that provoke a sustained flare while maintaining tolerable activity.

Depending on the diagnosis and symptoms, temporary changes might include:

• Reducing sprint volume

• Limiting repeated jumping

• Replacing hill running with flatter routes

• Shortening the long run

• Increasing recovery between hard sessions

• Using cycling or pool training temporarily

• Continuing unaffected strength exercises

• Separating demanding sessions rather than stacking them

A physiotherapist may monitor morning symptoms, function and the response during the following day. A single pain score should not determine progression by itself.

Response after training	Possible interpretation
Symptoms remain stable and settle promptly	Current load may be tolerable
Morning stiffness gradually increases	Recovery may be insufficient
Pain rises across several sessions	Training may need further modification
Strength or function declines	Reassessment may be needed
Sudden sharp pain or loss of function	Stop and seek prompt assessment

This table is general guidance, not an individual exercise prescription.

Tendon rehabilitation normally progresses from controlled strength work to faster, sport-specific loading.

What Does Tendon-Loading Rehabilitation Involve?

A programme may progress through several overlapping stages.

1. Symptom-Tolerable Strength Work

Early exercises may use isometric contractions or controlled calf, squat or leg-press movements. Isometrics can provide short-term pain relief for some people, but the response is inconsistent and they are not uniquely effective.

2. Progressive Resistance

Resistance is gradually increased to develop calf or quadriceps strength and tendon capacity. Programmes may use slow isotonic, eccentric or heavy resistance exercise.

Research has not identified one loading programme that works best for every person.

Exercise choice should reflect the tendon involved, pain response, equipment, goals and ability to progress.

3. Energy-Storage Exercise

Later rehabilitation may introduce faster tasks such as:

• Skipping

• Small hops

• Jumping

• Landing

• Bounding

• Controlled acceleration

These activities prepare the tendon for the rapid force demands of running and field sport.

4. Sport-Specific Loading

Full-speed running, cutting, kicking and repeated jumping are normally reintroduced

progressively. Feeling comfortable during slow strength work does not prove readiness for maximal sprinting.

The broader principles resemble other forms of joint rehabilitation: progression should consider pain, strength, movement quality and function rather than relying on time alone.

Does Shockwave Therapy Help Tendinopathy?

Extracorporeal shockwave therapy may be considered in selected persistent cases, particularly when exercise and load management have not produced adequate improvement.

Evidence varies according to:

• The tendon involved

• Symptom duration

• Treatment protocol

• Comparison treatment

• Whether shockwave is combined with exercise

Shockwave should not replace a progressive rehabilitation programme. Passive treatments may help some people manage symptoms, but they do not provide the strength and sport-specific capacity developed through exercise.

How Long Does Tendon Rehabilitation Take?

There is no reliable universal timeline.

Some recent flares improve after several weeks of appropriate load modification. Longer-standing or recurrent tendinopathy may require several months of progressive rehabilitation.

Recovery can be influenced by:

• Symptom duration

• Tendon location

• Training demands

• Previous injury

• Strength deficits

• General health

• Consistency with rehabilitation

• Ability to modify sport temporarily

The goal should not be to become pain-free by an arbitrary date. A safer return considers whether the athlete can tolerate strength work, running and sport-specific loading without a sustained deterioration.

When Should Tendon Pain Be Assessed Promptly?

Seek urgent assessment after a sudden injury if you experience:

• A pop or snapping sensation

• Sudden severe pain

• A feeling of being kicked behind the ankle

• Immediate swelling or bruising

• Difficulty pushing off the foot

• Inability to stand on the toes

• Marked weakness

• Difficulty walking

These can indicate an Achilles rupture or another significant injury.

Arrange a non-emergency assessment if pain persists, progressively worsens, interferes with walking or repeatedly returns whenever training resumes.

Mention recent fluoroquinolone antibiotics or corticosteroid exposure to the clinician because these can be relevant to tendon health.

Myth Versus Fact

Myth	Fact
Pain means the tendon is tearing	Tendon pain can occur without a tear, but sudden severe symptoms need assessment
Warming up makes the session safe	Symptoms may temporarily ease and return later
Complete rest is always best	Many tendinopathies benefit from modified activity and progressive loading
Everyone can train through pain up to 5/10	Pain limits must be individualised
An abnormal scan explains the pain	Imaging findings and symptoms do not always match
Shockwave replaces exercise	It is generally considered an adjunct, not a substitute for rehabilitation

Frequently Asked Questions

Can I keep training with a sore tendon?

Sometimes, but the answer depends on the diagnosis, symptom severity and sport. A physiotherapist may preserve tolerable activity while temporarily reducing sprinting, jumping, hills or other aggravating loads. A five-out-of-ten pain threshold is not appropriate for everyone.

Is rest and ice enough?

They may provide temporary symptom relief, but they do not rebuild tendon capacity. Ice is optional for short-term comfort rather than a treatment that repairs tendinopathy. Progressive loading is usually more important for longer-term function.

Should I stretch a painful Achilles tendon?

It depends on where the pain is located and how the tendon responds. Deep dorsiflexion or dropping the heel below a step may irritate insertional Achilles pain. Ask a physiotherapist which range is appropriate.

Do I need a scan?

Not always. Achilles and patellar tendinopathy are often diagnosed clinically. Imaging may be helpful when symptoms are atypical, progress is poor or a tear or different condition is suspected.

Do I need a referral to see a physiotherapist in Australia?

You can generally book a private physiotherapist without a doctor’s referral. Healthdirect confirms that physiotherapists are accessible without GP referral, although Medicare-funded services, insurance and compensation schemes may have separate requirements.

How quickly can I return to full training?

There is no fixed schedule. Progress depends on symptoms, strength, functional testing, sport demands and the response to progressively faster loading.

Final Takeaway

A tendon flare after a new running block or pre-season programme often reflects a mismatch between recent training demands and current capacity. The solution is rarely to ignore the pain or stop all movement indefinitely.

Review the combined workload, temporarily reduce the most provocative activities and rebuild capacity with progressive exercise. Monitor the response during the following day rather than trusting the warm-up effect alone.

Most importantly, obtain a proper assessment when symptoms are severe, persistent or accompanied by sudden weakness or loss of function.

References

1. Cook JL, Purdam CR. Is tendon pathology a continuum? British Journal of Sports Medicine. 2009;43(6):409–416.

2. Gabbett TJ. The training–injury prevention paradox. British Journal of Sports Medicine. 2016;50(5):273–280.

3. Silbernagel KG, et al. Continued sports activity during Achilles tendinopathy rehabilitation. American Journal of Sports Medicine. 2007;35(6):897–906.

4. Malliaras P, et al. Achilles and patellar tendinopathy loading programmes. Sports Medicine. 2013;43(4):267–286.

5. Chimenti RL, et al. Achilles Pain, Stiffness and Muscle Power Deficits: 2024 Clinical Practice Guideline. Journal of Orthopaedic & Sports Physical Therapy.

6. Australian Physiotherapy Association—Physiotherapy Management of Achilles Tendinopathy.