Electromyography has been used for half a century as a method for evaluating muscle activity during swimming. In swimming research, surface electromyography is mainly measured, and from the data, it is possible to know which muscles at what timing and how much are active during swimming motions. In some previous studies, surface electromyography was also used to evaluate muscle coordination and muscle fatigue. In recent years, with the technological evolution of surface electromyography system, it has become much easier than before to measure muscle activity during swimming. Therefore, some recent studies have attempted muscle synergy analysis using data obtained by measuring multiple muscles. As the future prospect, it is expected that electromyography studies combined with other analytical methods, the studies focusing on swimming styles other than front crawl, and the ones analyzing the effects of trainings on muscle activity will be reported.