The blood pressure response in sprinters and distance runners to isometric and dynamic exercise

The purpose of this study was to examine the cardiovascular responses of sprinters and distance runners to isometric (IE) and dynamic (DE) exercise in an attempt to understand the role that training and muscle fiber type play in the hemodynamic adjustments to exercise. Eighteen normotensive college-age males were selected as subjects based upon prior running performance and grouped accordingly: sprinter (n = 6) , distance runner (n = 6) or active control (n = 6) Each subject completed a DE (cycle ergometry) test (6 minutes) at 20%, 40%, and 60% of VO_2peak, three minutes of isometric handgrip at 30% of MVC, and a muscle biopsy. Blood pressure (BP), heart rate (HR), cardiac index (CI), oxygen uptake, and blood lactate were measured and systemic vascular resistance (SVR) was calculated during each stage of DE, while BP and HR were measured during each minute of IE. Needle biopsies of the vastus lateralis muscle revealed a significant difference in capillary density (capillaries per mm²between the sprinters and distance runners ( 323 ± 23 vs. 409 ± 27 , p = 0.0308 ) and approached significance for type I fibers ( (46.5 ± 4.4)% vs. (64.8 ± 6.7)% p = 0.06 ). The IE challenge elicited higher BP responses (SBP, DBP, & MABP) at minute-3 in the sprinters, which was due to their higher HR response. During DE, there were no significant BP or HR differences between the groups. However, at 60% of VO_2peak , the distance runners had a higher cardiac index (p = 0.0002) and a lower systemic vascular resistance (p = 0.0157) than the sprinters. The latter response is consistent with the greater capillary density in the distance runners. Taken together, these results indicate that fiber type, capillary density, and/or training influence the hemodynamic responses to exercise, even when intensity is normalized to a subject's maximal capacity.