A mechanical speedo-meter to assess swimmer’s intra-cyclic velocity: validation at front-crawl and backstroke.

The aim of this paper was to validate the system for the assessment of horizontal intra-cyclic velocity while swimming front crawl and backstroke. 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 (Front-crawl and Backstroke). The speedo-meter (f = 50 Hz) 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 and thereafter the hip was digitized. It was 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 apparatus for the variables selected, except for maximal velocity. Linear regression models where very high. More than 80% of the Bland-Altman plots were with the 1.96 standard-deviation criteria used on regular basis as rule thumb for techniques validation