Stroke count games

by Evan Morrison. 28 May 2012.

What’s the fewest number of strokes you can take for a single length of the pool? (No streamlining past the flags; no more than three kicks per stroke.)

I can get down to 8 strokes per 25 SCY, but it’s tough to sustain for more than one length. 9 strokes per length (SPL) I can do pretty much indefinitely – but it’s incredibly inefficient. The inefficiency is readily apparent: a huge dead spot in my momentum as I glide (glide, glide…) after each stroke. The Swim Smooth guys have a term for this: Overgliding.

I swim most efficiently between 13 and 15 SPL, depending on pace. 13 for channel/marathon pace; 14 for “threshold” pace (from the mile up to about 5K); 15 for 200/500 pace. For an all-out sprint, I’ll add one more stroke (16 SPL).

Experienced pool swimmers have an intuitive feel for this… but what if you don’t? Is there a formula to identify the most efficient stroke count for a given pace? This question led me to try the following set:

8×100, as fast as possible, with about a minute rest between each. But there’s a twist: Within each 100, hold a constant SPL. The first should be your lowest sustainable SPL. On each subsequent 100, add one SPL. So for me, #1 is 9 SPL, and #8 is 16 SPL. Record all your times. The set is best done short-course (it’s tougher to control SPL so tightly in a long-course pool).

Here are my results:

**SPL time**
9    1:20
10   1:14
11   1:10
12   1:07
13   1:05
14   1:02
15   1:00
16   1:01

Further evidence of the inefficiency of minimum stroke-count: At 9 SPL, the fastest I could go was 1:20! Merely by adding two strokes per length (8 total), I was able to go 10 seconds faster.

[Warning: Geeky content ahead.]

Does this remind you of anything? That’s right - it’s sort of like SWOLF! So, let’s sum the two columns above to produce SWOLF scores:

**SPL time SWOLF**
9    1:20  116  [(9*4) + 80]
10   1:14  114  [(10*4) + 74]
11   1:10  114  etc.
12   1:07  115
13   1:05  117
14   1:02  118
15   1:00  120
16   1:01  121

SWOLF doesn’t quite get it right. According to SWOLF, my efficiency peaks at 10/11 SPL (1:14 & 1:10 per 100y) - which I know to be false. Even at cool-down pace, 10 SPL is more taxing than 12-13 SPL, due to the constant stop/start motion of overgliding.

The key here is: I already know my most efficient SPL is 13-15, depending on pace. I have the result; so what’s the formula that produces it?

Given the above data, the problem with the original SWOLF formula (time in seconds + total number of strokes) seems to be that it overvalues stroke count (and by corollary, undervalues speed). So I just tried the simplest thing I could think of: dividing stroke-count by two (thus reducing its importance in the final equation).

(Stroke Count / 2) + Time = modified SWOLF

**SPL time SWOLF(mod)**
9    1:20   98  [(9*4/2) + 80]
10   1:14   94  [(10*4/2) + 74]
11   1:10   92
12   1:07   91
13   1:05   91
14   1:02   90
15   1:00   90
16   1:01   93


What’s funny about my “discovery” is that there’s another term for “stroke count divided by 2” - stroke cycles. Which incidentally is exactly how the Swimsense calculates SWOLF. So perhaps our friends at FINIS were on to something?

If any readers out there want to try this set and report back, I’d be grateful for additional data. Does modified SWOLF find your most efficient stroke count(s)?

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Posted in: analysis , training Tags: SWOLF