The effect of prolonged cycling and running on selected cardiovascular responses
Date
1994
Authors
Donahue, Melissa Marie
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Abstract
To better understand the cardiovascular responses to prolonged exercise 10 male recreational triathletes performed three exercise sessions consisting of a 110 minute control cycle (CC), a 110 minute control run (RC), and a sequential cycle/run session (C/R) (a 70 minute cycle followed by a 40 minute run). Selected physiological responses were monitored every 15 min. After increases at the onset of exercise there were no significant differences in ventilation (VE), cardiac output (Q), and plasma concentration (PC) within any of the exercise sessions. For cc, oxygen consumption (VO₂), arteriovenous oxygen difference ((a-v)O₂diff), heart rate (HR), and rectal temperature (Tᵣ) all showed significant changes from those observed 3 min into the exercise session. The mean change in HR at the end of the CC was 9 ± 6 beats·min⁻¹. For the RC, HR, Tᵣ and stroke volume (SV) changed significantly between 3 and 110 min of the session. The mean change in HR at the end of the RC was 12 ± 6 beats·min⁻¹. When comparing sessions the first 40 min of RC did not yield significantly higher HR's than those observed for the run portion of the C/R. In contrast, the last 40 min of the RC elicited significantly greater HR's than the run portion of the C/R (means= 173 ± 8 beats·min⁻¹ and 162 ± 8 beat·min⁻¹, respectively. The smaller magnitude of cardiovascular drift during the cc was possibly related to the lower thermal demand of the activity reflected in the mean Tᵣ and stabilization at 60 min of the session. Although the absolute change in HR was greater for the RC than for the cc when expressed in terms of percent change both the RC and the CC sessions were very similar (7% and 6% change, respectively). The results indicate that the RC elicited greater cardiovascular and thermal responses than the CC and the C/R sessions.