A DIFFERENCE OF BLOOD LACTATE LEVEL IN FREESTYLE SWIMMG BETWEEN S-SHAPED AND I-SHAPED STROKE

Abstract

James Counsilman [1] established a foundation of the present front crawl swimming style. He proposed a S-shaped pull stroke by observing skillful swimmers' underwater images in 1968. The driving force generated from a palm in S-shaped pull stroke utilizes a dynamic lift and drag forces. One of the authors, Ito [2] analyzed a soft-shelled turtle's swim, and applied the propelling theory obtained from the turtle's stroke to the front crawl stoke of human swimming. The calculation results showed that S-shaped pull stroke was a movement which requires minimal energy. The stoke of the drag type is I-shaped stroke which produces the maximal thrust (speed). Comparing with the S-shaped stroke, the I-shaped stroke gained 11% more of the propelling force. But it had a disadvangate of 2.4% in the propelling efficiency. However, the mechanical efficiency does not necessarily corresond to the physiological inefficiency, namely fatigue which a swimmer feels. Physiologically, a direct energy source of the muscular shrinkage movement is ATP. As an exercise strength level becomes higher, glycogen in a muscular cell is decomposed into lactic acid as an energy source in an anaerobic state, and lactic acid accumulates in muscles. The blood lactate cannot always explain fatigue, but the blood lactate level (