SWOLF and swimming efficiency

SWOLF and swimming efficiency


Follow-up posts:

Swim golf – or SWOLF – is an interesting drill, intended to measure efficiency in swimming. 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?

 


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Please note:

  • “Number of strokes” means total number of hand entries – left and right combined. It is not the number of stroke cycles – as the Swimsense uses in its SWOLF calculation. H2oustonSwims and TI get it right; About.com gets it wrong. FINIS gets it right on its website but wrong on the Swimsense.
  • “One length of the pool” means one length of a 50-meter pool, starting from the wall. No long streamlines – that’s cheating. This doesn’t mean you can’t do SWOLF in a short-course pool. However, two lengths are necessary for a sufficient sample size (of strokes and seconds); and SWOLF scores are less meaningful if they include a turn.

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):

[youtube_sc url=PJtgTjU1RBE width=500 start=131]

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).

[youtube_sc url=4YrZXqBKwuc width=500 start=219]

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.

This fallacy can often be seen in the writing of certain swim gurus who fetishize Sun Yang’s stroke technique.

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.

14 Responses to “SWOLF and swimming efficiency”

  1. Sarah

    2012-04-06T12:35:13+00:00

    Ugh… we had to do that ALL THE TIME when I was in highschool. We just called it GOLFing though. You just brought back torturous memories of when I was forced to drill when all I wanted to do was swim endless laps. I really was the same at 16 as I am at almost 30….

    Reply
    • Evan

      2012-04-06T15:05:33+00:00

      Here is my rank order: (1) Actual golf. (2) SWOLF. (3) Swimming endless laps. Unfortunately for me, I’m better at #3 than either of the first two.

      Reply
  2. Mariano

    2013-01-24T14:29:03+00:00

    I am still at 75, is quite hard to improve once you have lost swimming for a long time

    Reply
  3. Terry Laughlin

    2013-02-01T13:16:09+00:00

    SWOLF was one of my favorite exercises in the 90s. While my best SWOLF score did not equate with my fastest swimming, it did help tune me up for the relaxed-but-strong pace I hoped to maintain in the early stages of distance events – say 800m to 1500m/1650y – that I aimed to negative split. I began using the Tempo Trainer in 2004 which provides a higher precision way to do the same thing. And is useful for tuning up far more brisker paces and tempos — such as the .85 tempo I use during the first 100m or so of open water races, before finding someone to draft off and dropping tempo to a more sustainable .95.

    Reply
    • Terry Laughlin

      2013-02-01T13:19:53+00:00

      PS: My best score, attained about 15 yrs ago when I was in my mid-late 40s, was 56 — 31 sec + 25 strokes. Today, during a Tempo Trainer set, I scored a 65 – taking 25 strokes and 40 seconds.

      Reply
    • Evan

      2013-02-01T14:02:55+00:00

      Thanks for the comment, Terry.

      Reply
  4. Swimming - Page 31 - London Fixed-gear and Single-speed

    2013-02-04T06:26:39+00:00

    [...] can use the SWOLF / efficiency as a training aid (write up here) – but you would need to use it in conjunction with drills / technique work to find what works [...]

    Reply
  5. Eventathon | My Olympic Challenge

    2013-08-14T03:20:39+00:00

    […] length and the number of stroked taken, and a lower score is better (like golf). There’s some more information here. So given I’m in a 25m pool, my score of 65 equals 130 for a 50m pool. An excellent swimmer […]

    Reply
  6. Countdown to Stowe. | My Journey to Ironman Bolton UK 140.6 – 2014

    2013-08-31T02:49:26+00:00

    […] am. Christine has volunteered to be the director and come film me. I just cannot seem to improve my SWOLF which seems to be hovering around the 55 – 60. I’m not too worried at the moment […]

    Reply
  7. Natation : intérêts et limites du Swolf Score | Trimes.org

    2013-11-24T13:25:21+00:00

    […] l’explique Evan Morrisson, pour prendre deux extrêmes, le nageur chinois Sun Yang (1m98) a un SWOLF SCORE de 59, là ou […]

    Reply
  8. steve s

    2013-12-06T10:20:56+00:00

    what’s up when my garmin 910 XT gives me a SWOLF of 35. I was swimming in a 25 yard pool, did 2800 yards in 45 minute swim. Is it basing it on 25 yards? is this good or bad?

    Reply
    • Evan

      2013-12-06T11:37:04+00:00

      Yes – it sounds like your 910xt SWOLF score is based on a 25-yard length. Standard SWOLF is one 50m length in a long-course pool.

      Reply
  9. Garmin 910xt – First Ride | AeroGeeks

    2014-04-17T06:01:49+00:00

    […] is calculated by total time plus strokes normalized to 25 meters. Average SWOLF (swim golf -http://marathonswimmers.org/blog/2012/04/swolf-swim-efficiency/) is the time in seconds plus the strokes it takes you to complete one pool length. A lower number […]

    Reply

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