Tendon Stiffness Comes First

01The evidence

• Athletic training has been shown to affect the uniformity of muscle and tendon adaptation, with tendon properties changing alongside muscle and not always in step with them.Journal of Applied Physiology
• Musculoskeletal adaptations to resistance training have been documented across muscle and tendon, with the tendon adapting on a different timescale from the muscle.Manual Therapy

02The tension

Strength is attributed to muscle cross-sectional area, and training programmes are designed around hypertrophy. Early strength gains occur before any measurable change in muscle size, and the usual explanation is neural, which is a label rather than a measurement.

03The theory

Force generated by muscle is transmitted through tendon to bone. If the tendon stretches, part of the muscle's shortening is lost and the rate of force development falls, so the effective strength at the bone depends on tendon stiffness.

Training stiffens tendon over weeks, faster than muscle grows. That makes stiffness a plausible mechanism for early gains, and it predicts that force should increase before cross-sectional area does.

The prediction is that tendon stiffness should predict strength gains better than muscle size in the first weeks, and that training which loads tendon should produce earlier gains than training which does not.

The practical consequence is that strength programmes should include tendinous loading, and that strength testing should include rate of force development rather than peak force alone.

04What this is not

05Predictions

• P1Tendon stiffness should predict early strength gains better than muscle size.
• P2Force should rise before cross-sectional area changes.
• P3Tendon-loading programmes should produce earlier gains.

06What would refute it

Early gains tracking hypertrophy at controlled tendon stiffness would leave the muscle account adequate.

07What it would change

It would change strength programme design and testing.