A mechanical speedo-meter to assess swimmer’s intra-cyclic velocity: validation for breaststroke and butterfly stroke.

The aim was to validate a system for the assessment of horizontal intra-cyclic velocity while swimming the breaststroke and butterfly stroke. 12 boys and 11 girls with at least 4-y of experience participating in regional and national level competitions undertook a set of maximal 2x25 m swims (Breaststroke and Butterfly stroke). The speedo-meter cable was attached to the subject’s hip and data was acquired on-line. At the same time, subjects were recorded in the sagital plane with an underwater video camera enabling the hip to be digitized. The following were analyzed the : (i) maximal velocity; (ii) minimal velocity; (iii) difference between maximal and minimal velocity; (iv) coefficient of variation. There were no significant differences for the mean values between methods, except for the coefficient of variation (p