Physiology, Frank Starling Law

The Frank-Starling relationship is based on the link between the initial length of myocardial fibers and the force generated by contraction.  There is a predictable relationship between the length between sarcomeres and the tension of the muscle fibers. There is an optimal length between sarcomeres at which the tension in the muscle fiber is greatest, resulting in the greatest force of contraction. If sarcomeres are closer together or further apart compared to this optimal length, there will be a decrease in contraction tension and strength. The greater the ventricular diastolic volume, the more the myocardial fibers are stretched during diastole. Within a normal physiologic range, the more the myocardial fibers are stretched, the greater the tension in the muscle fibers and the greater force of contraction of the ventricle when stimulated. The Frank-Starling relationship is the observation that ventricular output increases as preload (end-diastolic pressure) increases. See Frank–Starling Law.