Cardiac outputs of post-myocardial infarction patients during swimming and cyclic.

We compared the cardiovascular response of post myocardial-infarction (MI) patients and inactive normal subjects at submaximum and maximum intensities of tethered swimming and upright cycling. At any given oxygen uptake (VO2), the inactive normals had similar cardiac outputs (Q) and heart rates (HR) during swimming and cycling, whereas the post-MI patients had lower Q's and higher HR's during swimming compared to cycling. The maximum response of inactive normals were not significantly different during swimming and cycling, but during swimming the post-MI patients had a 21% lower VO2. The lower VO2 swimming was due to a lower Q. While swimming at any exercise rate including maximum, the stroke volume (VS) of the post-MI patients did not increase above resting VS seated. Therefore, any increase in Q during swimming was due solely to increases in HR. Since the HR's of the post-MI patients were not significantly different during maximum effort swimming and cycling, the intensity of swimming can be safely prescribed from the maximum HR achieved cycling.