Abstract
The ultimate purpose of this study is to develop a system of measurement of swimming motion. Using tri-axes accelerometer attached swimmer's wrist. we tried to estimate stroke frequency and divide one stroke in freestyle swimming into three phases : stretching phase, propulsive phase and recovery phase. We examined the relationship between stroke frequency or time rate of each stroke phase and swimming speed. The results shows that it is possible to estimate stroke frequency easily from accelerations of swimmer's wrist, and that their swimming speed is controlled by the change of time rate of stroke phases and the stroke frequency.
