The year 2016 is an Olympic year. Developments in high-performance swimwear for swimming continue to advance, along with other areas of scientific research. One area of research has focused on which type of crawl stroke is more effective—when the arm draws a curve in the water (S-stroke) or moves straight (I-stroke)—long a matter of debate in the world of competitive swimming. A research team has carefully investigated this matter in terms of fluid mechanics, examining the ideal crawl stroke from every angle, based on the latest measurement and analysis data from Japan and around the world.