Measurement of active drag during crawl arm stroke swimming

TLDR

The study aimed to measure active drag during front crawl swimming by designing, building, and testing a specialized measurement system. A 23‑m tube with a force transducer on the pool wall measured instantaneous propulsive forces while swimmers crawled with legs fixed and buoy support, and the signals were filtered, digitized, and averaged over a lane at constant speeds of 1–2 m s⁻¹. Regression of force versus speed was nearly quadratic, with a mean force of 66.3 N at 1.55 m s⁻¹ and a 4.1 N accuracy across days, matching passive drag values and published propulsive forces, and the system did not noticeably interfere with normal front‑crawl technique, proving useful for studying active drag and its relation to anthropometry and technique.

Abstract

Abstract In order to measure active drag during front crawl swimming a system has been designed, built and tested. A tube (23 m long) with grips is fixed under the water surface and the swimmer crawls on this. At one end of the tube, a force transducer is attached to the wall of the swimming pool. It measures the momentary effective propulsive forces of the hands. During the measurements the subjects' legs are fixed together and supported by a buoy. After filtering and digitizing the electrical force signal, the mean propulsive force over one lane at constant speeds (ranging from about 1 to 2 m s‐1) was calculated. The regression equation of the force on the speed turned out to be almost quadratic. At a mean speed of 1.55 m s‐1 the mean force was 66.3 N. The accuracy of this force measured on one subject at different days was 4.1 N. The observed force, which is equal to the mean drag force, fits remarkably well with passive drag force values as well as with values calculated for propulsive forces during actual swimming reported in the literature. The use of the system does not interfere to any large extent with normal front crawl swimming; this conclusion is based on results of observations of film by skilled swim coaches. It was concluded that the system provides a good method of studying active drag and its relation to anthropometric variables and swimming technique.