Vaart, A. J. M. van der, Savelberg, H. H. C. M., Groot, G. de, Hollander, A. P., Toussaint, H. M. and Ingen Schenau, G. J. van (1987). J. Biomech. 20, 543-546.
Propulsive arm forces of twelve elite male swimmers during a front crawl swimming-like activity were measured. The swimmer pushed off against grips which are attached to a 23 m tube at 0.8 m under the water surface. The tube was fixed to a force transducer. Since at constant speed, mean propulsive force equals mean drag force, this method also provides the mean active drag on a moving swimmer. The mean propulsive force at a speed of v = 1.48 m/s appeared to be 53.2 ± 5.8 N which is two to three times smaller than what is reported by other authors for active drag, but which is in agreement with values reported for passive drag on a (towed) swimmer who is not moving. Discrepancies with indirect active drag measurements are discussed