A Comparative Study on Effects of Exercise Intensity and Duration on Left and Right Ventricular / 中国运动医学杂志

ABSTRACT

Objective To examine the effects of exercise intensity and duration on the structure,function and fibrosis of the left and right ventricular,and to discuss the potential mechanism in these processes.Methods Forty-eight male Sprague-Dawley rats were randomly divided into a sedentary(Sed)group,a moderate exercise(ME)group and an intensive exercise(IE) group,each of 16.Rats in Sed group were not given any training,while those in ME group and IE group run on treadmill at the speed of 15.2 m/min with the slope gradient of 5° and 28 m/min with the slope gradient of 10 degree 1 hour per day,5 days per week.Eight and 16 weeks after the training,we recorded the body weight and measure end-diastolic diameter,end-diastolic wall thickness,and ejection fraction of both ventriculars using the ultrasonic testing.All rats were then sacrificed after blood sampling.Elisa was used to measure serum cTnI concentration,and sirius red staining was applied to evaluate collagen volume fraction of both ventriculars.Results Eight or sixteen weeks after the training,the average bi-ventricular end-diastolic diameter of ME and IE rats was bigger than Sed group.There were no differences in end-diastolic diameter of both ventricular between ME group and IE group after sixteen-week training,but the left ventricular end-diastolic diameter of IE group was greater than ME group.As exercise intensive increased and time accumulated,the end-diastolic wall thickness of both ventriculars increased but without statistical significance.At sixteen-week intervention,the bi-ventricular ejection fraction of IE rats was significantly lower than Sed and ME groups,while there was a decreasing trend eight weeks earlier without significant differences.After 8 or 16 weeks of training,the serum cTnI was significantly higher in IE rats than Sed group or ME group,but there was no significant differences between ME group and Sed group.After 16 weeks' exercises,the average bi-ventricular collagen volume fraction of ME or IE group was greater than that after 8 weeks' exercises.The average collagen volume fraction of the right ventricular was greater than Sed group at the same time points,and after sixteenweek training the right ventricular collagen volume fraction in IE group was significantly greater than ME group.However,there were no significant differences in the measurement of the left side among different groups.The serum cTnI was negatively correlated with the left and right ventricular systolic function(r=-0.327,P=0.029 and r=-0.582,P=0.000).Moreover,it was positively correlated with the right ventricular collagen volume fraction moderately,but had no correlation with the left ventricular collagen volume fraction.Conclusion(1)Sixteen-week moderate and intensive exercise result in left ventricular dilation,and the dilation increases with the increase of the exercise intensity.Only 8 weeks' exercise at the same intensity can lead to right ventricular dilation,but exercise intensity has little influence on the right ventricular dilation.(2)Long-term moderate or intensive endurance exercises may cause bi-ventricular hypertrophy potentially.The left ventricular hypertrophy and dilation may not be synchronous with hypertrophy followed by dilation,while the right ventricular hypertrophy and dilation is synchronous.(3)The temporary decrease in bi-ventricular systolic function after intensive endurance exercise may be caused by ventricular injury,with more serious injury in the right ventricular than in the left.Moderate exercises don't cause ventricular injury,thus there is little or no influence on ejection fraction.(4) Long-term (8 or 16 weeks)moderate or intensive endurance exercises can increase the right ventricular collagen volume fraction,which may indicate cardiac fibrosis following right ventricular injury but not in the left ventricular.The bi-ventricular collagen volume fraction at sixteenth week in ME and IE rats are greater than corresponding rats at eighth week.It may result from the hypertrophy of bi-ventricular cardiomyocyte after 8-week training,followed by increase in the extracellular matrix but not cardiac fibrosis.