Cardiovascular Responses to Swimming

Abstract

The authors examined cardiovascular responses to long-distance fin swimming as compared to freestyle swimming. Elite male fin swimmers (n=17) swam 8 km in the open sea (group A) and 17 top freestyle endurance swimmers (group B) swam 6 km in the open sea. The swimming times of the 2 groups did not differ significantly. The heart rate and mean blood pressure were higher in group B than in group A after exercise. As estimated from the systolic time intervals (STI), total electromechanical systole index (QS₂I) and electrical systole index (QTI) increased and QT-QS₂ decreased in both types of swimming. These changes were more marked in fin swimmers. Moreover, the preejection period (PEPI) and the preejection period to left ventricular ejection time ratio (PEP/LVET) significantly decreased in both groups, while LVET remained constant in the 2 swimming events. Likewise, the amount of change in PEP/LVET was more pronounced in group A. Finally, only the QT-QS₂ changes were associated with performance efforts in both groups. Therefore, there are quantitative cardiovascular differences between these types of swimming that should be primarily attributed to the different muscle mass effort involved.