SWOLF and swimming efficiency

by Evan Morrison. 04 April 2012.

Follow-up posts:

SWOLF, an elision of “swim golf,” is an imperfect but useful metric of swimming efficiency. You only need a pace clock to measure SWOLF, although it is now included on many multi-sport watches such as the Garmin ???.

In brief: SWOLF is the sum of time (in seconds) and stroke count to complete a given distance.

Traditionally, that distance is 50 meters (or yards) - but there’s no reason you can’t get a SWOLF score for a longer distance. I once did a SWOLF face-off with David Barra for the buoy line at Lake Minnewaska, New York. I would not recommend measuring SWOLF for distances less than 50m (e.g., one length of a short-course pool) - the variability is too high.

Traditionally, “stroke count” means strokes (one arm = one stroke) rather than stroke cycles (two arms = one cycle) - but as I will argue later in this article, stroke cycles may be preferable.

In the interest of terminological precision, SWOLF is defined as the measure itself (40 seconds for 20 stroke cycles = SWOLF score of 60); and swim golf is defined as the process or exercise of trying different combinations of stroke rate and stroke length to find an optimally efficient stroke (lowest SWOLF).

It’s important to understand how to use it correctly. Here’s the drill:

  1. Swim one length of the pool
  2. Count the number of strokes you take
  3. Get your time (in seconds)
  4. Take the sum of (2) and (3). That is your SWOLF score.
  5. Repeat steps 1-4, trying different combinations of stroke rate, stroke length, and effort. Which combinations produce the lowest score?

Please note:

The golf analogy works better in a 50m pool, too. An excellent swimmer will score in the low-70s (e.g., 40 seconds in 32 strokes, or 35 seconds in 37 strokes) - just like a “scratch” or zero-handicap golfer. The (unofficial) world record for SWOLF is held by the great Russian sprinter Alexander Popov: 20 strokes + 25 seconds for a mind-boggling SWOLF score of 45.

Interpreting a SWOLF Score

SWOLF is an indirect measure of swim efficiency. Conceptually, swim efficiency can be thought of as [Speed / Effort]; however, measuring effort (% of max HR, V02, blood lactate, calorie burn, etc.) can be inconvenient in the pool. SWOLF uses stroke count as an indicator of effort - but it’s not a particularly good indicator.

An illustrative example:

Here is the famous final length of Sun Yang’s world-record setting 1500m last year (33 strokes in 26 seconds = SWOLF score of 59):

And here’s the final length of Janet Evans’ gold-medal winning 800m at the Seoul Olympics (49 strokes in 30 seconds = SWOLF score of 79).

Should we interpret Sun Yang’s much lower SWOLF score to indicate he is a much more efficient swimmer than Janet Evans? No. He is probably slightly more efficient, because he’s slightly faster - but we know nothing about their respective levels of effort. Sun Yang’s stroke count is lower than Janet Evans’ because he is 6’6” and she is 5’4”. He has a naturally longer stroke.

I can pretty easily hit the low-70s for SWOLF; does that mean I’m more efficient than Janet Evans? Not likely.

The point being: SWOLF is usually not meaningful in comparing different swimmers. It’s meaningful in comparing different data-points for the same individual. If I can move from a SWOLF of 75 to 70, that probably means I’ve improved my efficiency. But my SWOLF of 70 doesn’t mean I’m more efficient than someone else with an 80.

(Though, this rule has a limit: What about a SWOLF of 110? Most likely, I’m more efficient than that swimmer.)

At any given level of effort, each swimmer has a certain combination of stroke rate and stroke length that is most efficient in producing speed. SWOLF is a great drill to help swimmers zero in on that combination.

To watch a video of me doing SWOLF drill, see this post.

Evan Morrison coaches at Fog City Masters in San Francisco, California. He is a USMS Level 1 and Level 2-certified coach.

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