CARDIOVASCULAR-RESPONSES TO EXERCISE IN SPRINTERS AND DISTANCE RUNNERS

The purpose of this study was to examine the cardiovascular responses of sprinters and distance runners to isometric (IE) and dynamic exerci se (DE). Normotensive males were selected and grouped according to pri or running performance: sprinter (N = 6) or distance runner (N = 6). E ach subject completed an incremental DE (cycle ergometry) test (6-min stages) at 20%, 40%, and 60% of V over dot O-2peak, and 3 min of isome tric handgrip at 30% of MVC. Blood pressure (BP), heart rate (HR), car diac output (Q over dot), oxygen uptake, and blood lactate were measur ed, while mean arterial blood pressure (MABP), cardiac index (CI), and systemic vascular resistance (SVR) were calculated during each stage of DE. BP and HR were measured during each minute of IE. Muscle biopsi es of the vastus lateralis revealed a significant difference in capill ary density (capillaries per mm(2) and capillaries per fiber) between the sprinters and distance runners (323 +/- 23 vs 409 +/- 27 and 2.2 /- 0.2 vs 3.2 +/- 0.3, P < 0.05) and for the percentage of Type I fibe rs (46.4 +/- 4% vs 64.8 +/- 7%, P < 0.05). The if challenge elicited a greater BP response at minute 3 in the sprinters, which was associate d with a greater HR response. During DE, there were no significant dif ferences in BP or HR between the groups. However, at 60% of V O over d ot (2peak), the distance runners had a significantly higher cardiac in dex and a lower systemic vascular resistance than the sprinters (P < 0 .05). These results suggest that fiber type and/or alterations in micr ovessel density induced by training may influence the hemodynamic resp onses to exercise, even when intensity is normalized to a subject)'s p eak aerobic power.