Stroke volume changes during cross-country skiing to allow the heart to work more efficiently. It has become in-creasingly clear that with near-maximal and maximal rates of work, stroke volume is a major determinant of cardiorespiratory endurance capacity. Let's examine the basis for this.
Stroke volume is determined by four factors:
The first two factors influence the filling capacity of the ventricle, determining how much blood is avail-able for filling the ventricle and the ease with which the ventricle is filled at the available pressure.
The last two factors influence the ventricle's ability to empty, determining the force with which blood is ejected and the pressure against which it must flow in the arteries.
These four factors directly control the alterations in stroke volume in response to increasing exercise in-tensity in cross-country skiing. As a result of increased training, the cross-country skier exhibits a greater stroke volume (240) compared to untrained (110), trained (150), and highly trained (210) individuals during exercise.
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