I, personally, am not a fan of using fins or paddles during swim workouts. Fins caused pain and tenderness in my ankles and paddles created, what I felt, was unnecessary stress on my shoulders. Plus, when it comes time to race, fins and paddles are not allowed, so I prefer to know how I’m performing and progressing in the water without the aid of swimming tools.
However, according to my husband, who was a competitive swimmer for years and who can still post world-class times in the swim leg of a triathlon, “Fins and paddles can be useful training tools early in the season to improve technique and teach your body what it feels like to move fast through the water.”
When used sparingly and correctly, fins can indeed help swimmers increase speed, build leg and kick strength, teach proper stroke technique, and improve body position, cardiovascular endurance and ankle flexibility, which, according to swimming.about.com, “will result in a more efficient flutter kick through better angles of attack on the water.” Fins also helps athletes feel the difference between kicking from the hips as opposed to kicking from the knees. But fins also increase stress on the knee joints so they should not be worn by swimmers with knee pain or while swimming breaststroke.
Since 90 percent of swim propulsion comes from the upper body, hand paddles are used to increase shoulder strength and power, and to create a better feel for the water by helping a swimmer to improve stroke technique and efficiency.
Paddles should be no more than 10 percent bigger than your hand and, as with fins, should not be used for more than 25 percent of your workout. If used incorrectly or too often, paddles can cause shoulder soreness and even lead to shoulder injuries. Swimmers with technical stroke deficiencies should not use paddles until the deficiencies are corrected.
As trainright.com notes, if you want to improve your stoke, focus on technique first and strength second. “The goal is always to do it right, and then do it powerfully.”