Association between muscle fiber composition and blood pressure levels during exercise in men

Normotensive individuals with a magnified blood pressure (BP) level during exercise have an increased risk for developing hypertension. The purpose of this study was to determine if skeletal muscle fiber type is related to th e BP level during exercise. Peak BP was determined in 35 normotensive, midd le-aged (mean +/- SE, 46.0 +/- 1.8 years) men during maximal treadmill exer cise. Fiber distribution (I, IIa, IIb) was measured in muscle samples (perc utaneous needle biopsy) from the vastus lateralis and lateral gastrocnemius . The systolic BP during exercise was significantly (P < .05) related to th e percentage of type IIb fibers in both the vastus lateralis (r = 0.37) and gastrocnemius (r = 0.38). Mean arterial pressure BP was also related to th e percentage of type IIb fibers in the gastrocnemius (r = 0.39, P < .05), w ith a similar trend evident in the vastus lateralis (r 0.31, P = 0.08). The percentage of type IIb muscle fibers in both muscle groups was associated with (P < .05) body fat (vastus lateralis, r = 0.44; gastrocnemius, r = 0.4 3). There were no relationships between the relative percentage of type I o r IIa fibers with any BP parameters. Maximal oxygen consumption was negativ ely related to BP, but only when expressed relative to body weight (mL . kg (-1) . min(-1)). These data suggest that muscle morphology is related to th e blood pressure level during exercise and provides insight into factors th at may predispose individuals toward the development of hypertension and ca rdiovascular disease. Am J Hypertens 2000;13:586-592 (C) 2000 American Jour nal of Hypertension, Ltd.