Left ventricular function in endurance runners during exercise

Abstract

Left ventricular function in elite runners and controls was compared by means of nuclear angiocardiography. Fifteen middle- or long-distance runners and a control group of 10 sedentary to moderately physically active subjects were studied at rest and during semi-sitting incremental exercise. Ejection fraction was higher in the runners than the controls both at rest and during exercise. At the transition from rest to exercise left ventricular end-diastolic volume initially increased similarly in runners and controls by an average of 14 and 12%, respectively, with an increase in stroke volume by approximately 25 and 23%. The parallel increase in stroke volume and left ventricular end-diastolic volume could at least partly be because of the Frank-Starling mechanism. With increasing workloads, left ventricular end-diastolic volume and ejection fraction remained fairly constant, resulting in an unchanged stroke volume from the lowest to the highest exercise intensity. This was in the runners accomplished by a 41% increase in peak filling rate and a 38% increase in peak emptying rate with similar changes observed in the controls. This has to be due to increased myocardial contractility paralleling the systolic shortening with increasing heart rate. We conclude that endurance-trained athletes have a better systolic function expressed as higher ejection fraction both at rest and during exercise than untrained subjects reflecting an enhanced myocardial contractility contributing to the maintenance of a large stroke volume during exercise. The regulatory mechanisms however, appear to be similar for athletes and healthy controls.

Myocardial Response to Incremental Exercise in Endurance‐Trained Athletes: Influence of Heart Rate, Contractility and the Frank‐Starling Effect

“…A consecutive decline in end-systolic volume has also been commonly observed during incremental exercise (Adams et al 1992;Kanstrup et al 1995). Others have reported maintenance of EDV throughout incremental exercise, with a concomitant reduction in end-systolic volume (Jensen-Urstad et al 1998). Both findings are suggestive of increased myocardial contractility leading to greater ventricular emptying.…”

“…The reduced end-systolic volume is thought to offset the decline in EDV, which allows SV to be maintained or slightly reduced during strenuous exercise. The increase in ÿ during the later stages of vigorous exercise is therefore thought to be related to the changes in heart rate and myocardial contractility (Higginbotham et al 1986;Plotnick et al 1986b;Ginzton et al 1989;Jensen-Urstad et al 1998). …”

“…Several investigators have revealed that SV reaches a plateau at submaximal exercise intensities at around 110-130 beats min _1 (Higginbotham et al 1986;Plotnick et al 1986b;Ginzton et al 1989;Adams et al 1992;McLaren et al 1997;Jensen-Urstad et al 1998). These investigators commonly reported an initial increase in EDV followed by a sharp decline at maximal exercise.…”

“…It has been postulated that this plateau occurs because tachycardia limits the time available for diastolic filling, thereby limiting EDV in both trained and untrained individuals (Higginbotham et al 1986;Plotnick et al 1986b;Ginzton et al 1989;Jensen-Urstad et al 1998). Increased myocardial contractility is thought to result in an increased ejection of blood (i.e.…”

Effect of Isometric Hand Grip Exercise Training on Cardiovascular and Echocardiographic Parameters Among Healthy Young Males

“…This improvement in cardiac contractility was indicated by the very highly significant decrease in left ventricular end-systolic diameter and volume with insignificant increase in end-diastolic diameter and volume (Table 5), as reported earlier. (36) The enhanced cardiac contractility may in turn be due to the improvement of intrinsic contractile properties of cardiac muscles and increased response to inotropic stimulation, which may be partly due to increase sensitivity of cardiac myocytes to calcium when stretched. (33) Future studies with larger sample size and longer duration are warranted to examine the long-term safety and efficacy of isometric hand grip exercise training on cardiovascular functions.…”