Non-invasive evaluation of the isovolumic relaxation period during dynamic and isometric exercise

The purpose of the study was to evaluate non-invasively the response of the isovolumic relaxation period to different types of exercise--dynamic supine bicycle exercise (DSBE) and handgrip (HGP), in a selected healthy population. From simultaneous echo-polygraphic recordings, obtained in 30 young subjects at rest, during submaximal DSBE, during one minute of HGP (75% of maximal heart rate) and in the recovery period, the true isovolumic relaxation period (IRP) was determined. Systolic (SBP) and diastolic (DBP) blood pressure, aortic closing pressure (AoCP) and heart rate (HR) were also recorded. HR increased more markedly in DSBE (delta HR = +85% at peak load) than in HGP (delta HR = +29% at peak), while a greater rise of DBP (delta DBP = +25%) was observed in HGP. IRP shortened at both exercises as the workload progressively increased, with a maximum decrease by 54% in DSBE and by 42% in HGP. Moreover, at both exercises, an exponential correlation between IRP and HR was found. Correlating IRP with HR and AoCP by multiple regression analysis, it was found that IHP in HGP was equally affected by HR and AoCP, while during DSBE heart rate had a greater influence than AoCP.