Dj. Torok et al., CARDIOVASCULAR-RESPONSES TO EXERCISE IN SPRINTERS AND DISTANCE RUNNERS, Medicine and science in sports and exercise, 27(7), 1995, pp. 1050-1056
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.