Muscle as an Endocrine Organ, Not Just an Engine

Contracting muscle releases signalling molecules that act elsewhere. The catalogue is growing faster than the clinical evidence.

Muscle secretes proteins during contraction that act on liver, fat, bone, and brain. This reframes training as a systemic intervention rather than a local one, and it is one of the more genuinely interesting findings of the past two decades.

The enthusiasm outruns the evidence. Most individual myokines have been characterised in cell or rodent models, and human studies rarely link a specific molecule to a specific outcome.

What the human data does support is that skeletal muscle mass and strength track with better outcomes across many endpoints, independently of body weight.

The practical conclusion has not changed with the molecular detail: train the muscle you have, twice a week, and progress the load.

Editorial note: this article summarises published research for general information. It is not medical advice. Discuss any intervention with a qualified clinician.