Mechanical work and efficiency in swimming crawl and back strokes

Summary1.The problem of the mechanical work done in swimming crawl and back stroke was investigated.2.A mathematical analysis of the motion in the crawl stroke was undertaken and substantiated by series of experiments.3.Experiments consisted of:a)Recording of the distance and duration of a glide, after the man has been towed a certain distance.b)Lifting a maximum weight using various strokes.4.A dynamometrical estimation of the propelling force in various strokes is given: overarm side — 13.6 kg., breast — 17 kg., back — 13 kg., crawl — 13.89 kg.5.Formulas for the calculation of work in swimming crawl and back strokes were derived:a)Swimming with a constant speed: $$w = kv^2 s = k\left( {\frac{s}{t}} \right)^2 s$$ b)Swimming from a dead start: $$w = k\left[ {(1 + \cdot 69\frac{m}{{ks}})\frac{s}{t}} \right]^2 s$$ c)Swimming from a dive or push-off start: $$w = ktr.\left\{ {\left[ {1 + \cdot 69\frac{m}{{ks}} - 2 \cdot 30\frac{m}{{ks}}\log _{10} \left( {\frac{{v_0 }}{{\frac{s}{t}}} + 1} \right)} \right]\frac{s}{t}} \right\}^2 s$$ The last two formulas should not be used for the distances less than 6 meters. For the distances more than 50 meters they become identical with the first one (a).6)A formula for the determination of the velocity with which the body enters water after a dive or a push-off start was given: $$v_0 = \frac{m}{{kt}}\left( {2 \cdot 718\frac{{ks}}{m} - 1} \right)$$ 7)Efficiency of swimming as a type of locomotion was estimated. It varied for the crawl stroke from 0.5% to 0.22% and back 0.88% to 1.35%.