In a previous article, I advocated for single-arm swimming as the most useful drill to improve a swimmer’s stroke efficiency. The reasons are plentiful: alternating sides lap-to-lap, glide position for body length, easier recovery and catch, better stroke leverage, coordination with kick, and easier breathing.

My examples were all related to crawl or “freestyle” stroking, but most apply as well to swimming back crawl and butterfly. Butterfly stroking is basically a double-arm crawl stroke, so the same advantages are gained. It is a whole lot easier to swim many lengths of single-arm “fly,” switching arms each lap, than it is to swim the same distance using both arms together.

Single-arm fly makes it easier to coordinate the arm stroke with an up-and-down “dolphin” kick. One downkick is simultaneous with recovery and the other with the propulsive arm as it levers against the water to move the body past.

What is different from the usual butterfly is that the body is tilted slightly to one side. Thus, it is easier to breathe on that side (as in crawl stroking) instead of facing down and forward. However, the advantages gained by using just one arm can be felt when the swimmer makes the switch to using the full two-arm fly.

Swimming on the back with a single arm is easier if you reach back, drop your arm under water, and imagine grabbing a pole rising vertically from the pool bottom, then propelling yourself past it. This can be taught with an actual pole being anchored by an instructor.

Another analogy is to think of throwing a ball at your feet to create propulsive force. A good throw accelerates from beginning to end, and so does a good stroke, from catch to finish.

A variation for all three strokes, especially the back crawl, is to swim single-arm with the non-stroking arm down at your side. This is, however, more difficult for fly and front crawl, and probably should be left to competitive swimmers.

How can a swimmer tell the effectiveness of this or any other drill?  Count strokes. If the drill helps to reduce the usual number of strokes taken per pool length, that’s greater efficiency, a worthy goal for every swimmer.

Dr. Bob Colyer of Bluffton is an actively retired college professor, coach and author of “Swim Better: A Guide to Greater Efficiency for Swimmers & Instructors,” directed primarily to non-competitors.