Central and peripheral circulation in relation to muscle-fibre composition in normo- and hyper-tensive man.

1. Fibre composition in the vastus lateralis muscle, and blood pressure, were determined in age-matched normotensive (n = 22) subjects and previously untreated patients (n = 19) with essential hypertension. 2. In all subjects the muscle fibres were classified, as fast-twitch (FT) and slow-twitch (ST), and blood pressure was recorded. Eleven patients and seven of the normotensive subjects participated in an extended haemodynamic study with intra-arterial pressure measurements and determinations of leg blood flow. 3. In both normo- and hyper-tensive subjects, ambulant and intra-arterial blood pressure and leg vascular resistance were negatively correlated to the percentage of ST fibres; no significant correlation was found to total leg blood flow. 4. The findings show that muscles with a high proportion of FT fibres have a higher resistance than muscles rich in ST fibres and suggest that the type of fibre in skeletal muscle might be of importance for the development of the hypertensive disease.