Muscle fibre composition in relation to blood pressure response to isometric exercise in normotensive and hypertensive subjects.

A positive relationship was demonstrated between the blood pressure and the fibre composition of the vastus muscle at rest in 17 hypertensive and 17 age- and sex-matched normotensive subjects. The hypertensive group had a higher proportion of fast twitch (FT) fibres (p less than 0.1). The circulatory response was measured during isometric exercise (IE) and cold pressor test (CPT). During IE the blood pressure increase was positively related to the percentage of FT fibres. No such relationship was demonstrated during CPT. It was thus found, particularly in hypertensive subjects, that an individual's muscle fibre profile is of importance for the blood pressure response during IE.