Metabolic Health and Tendinopathy: Why Load Alone Does Not Explain Tendon Pain

When we think about tendinopathy, the usual explanation is simple:too much load, too soon, for too long.

And while training load absolutely matters, it is no longer enough to explain why:

• Some people develop persistent tendon pain

• Some struggle to improve despite “perfect” rehab

• And some tendons fail at surprisingly low loads

Increasingly, research is pointing to something else playing a major role:

👉 metabolic health

Diabetes, obesity, and lipid disorders do not just affect the heart and blood vessels. They also change how tendons are built, how they adapt to load, and how well they heal.

Tendinopathy is not just a mechanical problem. It is a mechanical plus biological problem.

Tendons Adapt to Load, But Only If the Biology Allows It

Under normal conditions, tendon responds to loading by:

• increasing collagen synthesis

• improving stiffness and strength

• maintaining organised fibre structure

This is the principle behind eccentric training, heavy slow resistance, and graded loading programs.

But tendon adaptation depends on a healthy cellular environment.

Metabolic disorders interfere with this process by:

• altering collagen cross-linking

• impairing blood supply

• promoting low-grade inflammation

• disrupting tendon stem cell function

As a result, tendons exposed to the same training load may respond very differently depending on the person’s metabolic status (Kuliś et al., 2025; De Luca et al., 2025).

Diabetes: One of the Strongest Risk Factors for Tendinopathy

Among all metabolic conditions, diabetes shows the most consistent association with tendon disease.

A large systematic review and meta-analysis found:

• people with diabetes had around a 7-fold higher risk of Achilles tendinopathy

• higher rates of trigger finger, medial epicondylitis, and shoulder tendinopathy

• poorer healing and higher re-tear rates after tendon surgery

(De Luca et al., 2025; Abate et al., 2013)

Why?

Chronic hyperglycaemia leads to the formation of advanced glycation end-products (AGEs).These molecules:

• Stiffen collagen fibres

• Make tendon tissue more brittle

• Impair cellular repair mechanisms

Histological studies show diabetic tendons have:

• Disorganised collagen

• Reduced elasticity

• Poorer vascular supply

In simple terms, the tendon becomes structurally inferior before loading even begins.

Obesity Is Not Just About Body Weight

It is tempting to think obesity affects tendons simply because heavier bodies load tendons more.

But this is only part of the story.

Adipose tissue acts as an endocrine organ. In obesity, it releases:

• TNF-α

• IL-6

• Leptin

• Other inflammatory mediators

This creates a state of chronic low-grade systemic inflammation that directly affects tendon tissue (Lui and Yung, 2021).

This inflammatory environment promotes:

• Collagen breakdown

• Disorganised tendon matrix

• Impaired healing

• Persistent pain signalling

This explains why obesity is linked to:

• Higher rates of Achilles and rotator cuff tendinopathy

• Worse post-surgical outcomes

• Higher recurrence rates

(Abate et al., 2013; Lai et al., 2024)

So obesity affects tendons through:

1. Mechanical overload

2. Inflammatory biology

Both matter.

Cholesterol and Lipids: The Overlooked Tendon Risk

Dyslipidaemia is another underappreciated contributor.

High cholesterol has been associated with:

• Achilles tendon thickening

• Xanthomas, which are lipid deposits within tendons

• Collagen disorganisation

(Abate et al., 2013; De Luca et al., 2025)

Lipid disorders appear to:

• Disrupt tendon stem cell activity

• Alter collagen turnover

• Reduce tensile strength

This is why:

• Achilles tendinopathy is common in people with familial hypercholesterolaemia

• Lipid abnormalities are frequently found in chronic tendinopathy populations

While statins remain controversial, the metabolic condition itself appears to carry intrinsic tendon risk.

Metabolic Syndrome: When Risks Stack

Metabolic syndrome combines:

• Central obesity

• Insulin resistance

• Dyslipidaemia

• Hypertension

It represents a perfect storm for tendon pathology.

Studies show that people with metabolic syndrome:

• Have significantly higher rates of Achilles tendinopathy

• Respond less favourably to traditional loading programs

• Experience more persistent symptoms

(Kuliś et al., 2025; Lai et al., 2024)

This helps explain why some patients:

• Follow rehab correctly

• Progress load sensibly

• But still plateau or relapse

The tendon is being loaded in a biologically hostile environment.

Why “Perfect” Rehab Sometimes Fails

Traditional rehab models assume:

apply load, tendon adapts, pain improves

But metabolic disease changes this equation.

Evidence suggests:

• Eccentric and heavy loading programs are less effective in metabolically unhealthy patients

• Collagen remodelling is slower

• Flare-ups are more common

• Adaptation thresholds are lower

(Kuliś et al., 2025)

This does not mean loading is wrong. It means loading alone may be insufficient.

Clinical Implications: What Should Change in Practice?

For clinicians, metabolic health should become part of tendon risk stratification, especially in:

• Bilateral tendinopathy

• Recurrent cases

• Slow or incomplete rehab response

• Atraumatic onset

• Middle-aged and older runners

Key screening considerations:

• HbA1c or known diabetes

• Lipid profile

• BMI and waist circumference

• Features of metabolic syndrome

(De Luca et al., 2025)

Rehab still needs mechanical loading. But it should be paired with:

• Education about metabolic contributors

• Coordination with GP or physician where appropriate

• Realistic timelines

• Conservative progression strategies

What Runners Should Take From This

For runners, the message is not “don’t train”.

It is:

your tendons adapt based on both training and biology

Training matters. So does:

• Sleep

• Nutrition

• Body composition stability

• Blood sugar control

• Lipid health

You can have an excellent training structure and still struggle if your metabolic health is working against your tendons.

Healthy metabolism improves:

• Tissue quality

• Recovery

• Load tolerance

• Long-term durability

Bottom Line

Tendinopathy is not just about overload.

It reflects:

• how much load you apply

• and how capable the tendon is of adapting

Metabolic health influences:

• tendon structure

• healing capacity

• rehab response

• recurrence risk

Ignoring this leaves part of the problem untreated.

The future of tendon care is not:

load or biology

It is:

load plus biology

References

• Abate, M., Schiavone, C., Salini, V. and Andia, I. (2013) ‘Occurrence of tendon pathologies in metabolic disorders’, Rheumatology, 52(4), pp. 599 to 608.

• De Luca, P. et al. (2025) ‘The interplay between metabolic disorders and tendinopathies: systematic review and meta-analysis’, Journal of Experimental Orthopaedics, 12, e70429.

• Kuliś, S. et al. (2025) ‘Beyond mechanical load: metabolic factors and advanced rehabilitation in sports tendinopathy’, Journal of Clinical Medicine, 14(21), 7480.

• Lai, C. et al. (2024) ‘Metabolic syndrome and tendon disease: a comprehensive review’, Diabetes, Metabolic Syndrome and Obesity, 17, pp. 1597 to 1609.

• Lui, P.P.Y. and Yung, P.S.H. (2021) ‘Inflammatory mechanisms linking obesity and tendinopathy’, Journal of Orthopaedic Translation, 31, pp. 80 to 90.