Experimental preparations to understand the cardiovascular effect of training: in situ preparation.

Although exercise training is generally thought to exert a beneficial effect on the cardiovascular system, additional experimental work is required to determine the mechanism(s) by which training influences cardiovascular function. The utilization of an in situ preparation for cardiovascular studies should provide valuable information since both peripheral circulatory and myocardial performances can be evaluated. However, this paper specifically considers functional evaluation of the intact, in situ heart. The underlying physiological basis for ventricular pump performance evaluation in the intact heart is presented. Isolated muscle mechanics (force-velocity) principles are discussed and their application to the intact heart is illustrated. Proposed biochemical correlates of total tension development, the maximal rate of tension development, and maximal velocity of shortening are presented. The methods and procedures currently available for functional evaluation are described. Finally, the results of previous exercise studies where in situ cardiac functional evaluation has been utilized are reviewed.