Fascia

Fascia is the continuous web of connective tissue that encloses muscles, separates compartments and surrounds organs. It transmits some force between muscles, contains a dense supply of sensory nerve endings, and helps organise how the body moves as a whole rather than as isolated parts.

It matters partly because it is genuinely interesting tissue and partly because a great deal of unsupported claim has attached to it. Fascia is real, richly innervated and mechanically relevant; the popular idea that foam rolling or massage physically breaks up or lengthens it is not supported — the forces required exceed what hands or a roller can apply.

In practice the benefits people get from rolling and soft-tissue work are real but neural: reduced pain sensitivity and a short-term increase in tolerated range of motion. That is a useful effect described honestly, rather than a structural one described wrongly.