Constant-load versus heart rate-targeted exercise: responses of systolic intervals

Abstract

Eight normal male volunteers were studied during bicycle ergometry at constant work loads of 50, 100, and 150 W for 4 min each and heart rate-targeted exercise to rates which matched those during the end of the 4th min at each constant work load. Systolic intervals measured prior to and during exercise included: Q-IM, isovolumic contraction time (IVCT), preejection period (PEP), left ventricular ejection time (LVET), ejection time index (ETI), PEP/LVET, and pulse transmission time (PTT). Directional changes during both exercise methods were consistent with previously reported results. Comparable control values indicated equivalent starting points for each bout and confirmed recovery from preceding exercise. There was striking similarities within each matched exercise set for Q-IM, IVCT, PEP, and PEP/LVET. LVET was significantly shorter for rate targeted exercise. We conclude that either constant-load or rate-targeted bicycle ergometry may be employed with choice of method determined by the purpose of the protocol and that systoloc intervals (except LVET) should not be importantly altered owing to the method chosen.

Recovery from exercise at varying work loads. Time course of responses of heart rate and systolic intervals.

“…The uniform response patterns and the directional results, which parallel their invasively measured physiological correlates (Lindquist et al, 1973;Lance and Spodick, 1975), showed that these non-invasive techniques were an appropriate means for determining cardiac responses during actual exercise performance. Various invasive techniques, both in anaesthetised animals and in human subjects, have shown that the heart rate, blood pressure, stroke volume, left ventricular end-diastolic volume (LVEDV), sympathetic activity, and other variables change rapidly immediately after stopping exercise.…”

“…Recovery proceeded from exercise-induced changes in systolic time intervals, all of which were in the expected ranges (Pigott et al, 1971;Lance and Spodick, 1975;Xenakis et al, 1975). These in- Symbols: X, mean; SD, standard deviation; SE, standard error; PA(4'), significance level of difference between indicated measurement and four-minute exercise measurement; % A(C), per cent difference between indicated measurement and resting control measurement (C).…”

“…With the onset of the QRS ('q') of the electrocardiogram as zero time, the following phases of the cardiac cycle were measured as previously described (Pigott et al, 1971;Spodick and Quarry-Pigott, 1973;Lance and Spodick, 1975): electromechanical systole, left ventricular ejection time (LVET), pre-ejection period (PEP), isovolumic contraction time (IVCT), preisovolumic period (q-Im), pulse transmission time (PTT), and PEP/LVET. All measurements were made to the nearest 5 ms. Heart rate (HR) was calculated from the RR intervals of the electrocardiogram (RR in ms/60 000 =HR in beats/min).…”

“…Changes in pre-ejection period were determined by changes in isovolumic contraction time; the degree of return toward control of pre-ejection period and isovolumic contraction time from their exercise nadirs was load-dependent throughout recovery; loaddependent differences in their rate of return were pronounced in thefirst 30 seconds. The rates of change in the ejection time index and in the ratio pre-ejection period/left ventricular ejection time (PEPILVET) were virtually independent of load throughout most of recovery.Polygraphic recording of systolic time intervals (STI) has been successfully applied during upright exercise (Miller et al, 1970;Pigott et al, 1971;Lindquist et al, 1973;Lance and Spodick, 1975;Xenakis et al, 1975). The uniform response patterns and the directional results, which parallel their invasively measured physiological correlates (Lindquist et al, 1973;Lance and Spodick, 1975), showed that these non-invasive techniques were an appropriate means for determining cardiac responses during actual exercise performance.…”

“…Polygraphic recording of systolic time intervals (STI) has been successfully applied during upright exercise (Miller et al, 1970;Pigott et al, 1971;Lindquist et al, 1973;Lance and Spodick, 1975;Xenakis et al, 1975). The uniform response patterns and the directional results, which parallel their invasively measured physiological correlates (Lindquist et al, 1973;Lance and Spodick, 1975), showed that these non-invasive techniques were an appropriate means for determining cardiac responses during actual exercise performance.…”