Stroke count games

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:

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)?

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?

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; 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):

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.

Swim slow slower, Swim fast faster

There’s a possibly-apocryphal story about Matt Biondi (one of the fastest swimmers ever) that he always made a point of being the slowest person in the pool during warm up, no matter the skill level of the other swimmers surrounding him.

Matt BiondiI think there’s something to this idea. In training, most swimmers succumb to laziness from time to time. It’s been my observation (in myself and others) that swim-laziness comes in two basic forms:

  • not swimming slowly enough, when you’re supposed to be swimming slow
  • not swimming fast enough, when you’re supposed to be swimming fast

There’s an important purpose to slow swimming and drilling: Ingraining perfect technique, and being mindful of each part of your stroke by reducing it to its components. Drilling well requires focus and concentration, and the path of least resistance is to do it sloppily – or just skip it altogether. Sloppy drilling is, of course, self-defeating.

There’s also an important purpose to fast swimming. As my college coach Rob Orr liked to say: You’ve got to swim fast to swim fast. When the coach assigns a 100% effort, the path of least resistance is often to give a bit less – perhaps 90%. People prefer to avoid pain – and 100% is painful. The problem with giving only 90%, though, is the last 10% is where a lot of the improvement happens.

Don’t be lazy! Swim slow slower. Swim fast faster.

In praise of backstroke

photo credit: Santa Barbara News-Press, 1997.

Is there any good reason for a marathon swimmer to train strokes other than freestyle?

It’s fairly uncontroversial, I think, that training in multiple strokes makes one a better athlete, in a general sense. Each stroke works a unique set of muscles, giving swimmers more “balanced” power in the water. Eddie Reese (multi-time U.S. Olympic coach) is well-known for promoting IM training for all swimmers, including sprinters and single-stroke specialists. Multi-stroke training is also less likely to lead to over-use injuries.

Think of it as in-water cross-training.

What about open-water and marathon swimming? Or triathlon? Is there any point to training other strokes when you’ll never race anything but freestyle? If (like most working adults) you have limited time to train, isn’t that precious time best spent optimizing your freestyle? That certainly has been my approach. Not surprisingly, since I started focusing on open water, my other strokes have suffered.

Recently, I’ve been rethinking this position – especially with regard to backstroke. For one, there are technique benefits. The principles of balance, body position, and core rotation are much the same between backstroke and freestyle. To the extent you can develop efficient backstroke technique, your freestyle should benefit.

But I’m thinking of a more practical reason. Specifically, backstroke is a natural recovery motion for freestyle. While similar muscles are engaged in the two strokes, they’re moving in opposite directions. After a hard freestyle effort, backstroke helps you almost literally “unwind” your shoulders.

At Point Vicente. It was all I could do to raise my arms even this high...

How is this relevant to marathon swimming? Two words: shoulder fatigue. For me, this was the limiting factor in all my big swims this year – Tampa, MIMS, Catalina, and Ederle. My cardiovascular fitness was never an issue; my energy levels stayed high, thanks to a well dialed-in nutrition plan. The only thing holding me back was shoulder pain.

(Re: shoulder “pain,” I should clarify: I’m not talking about rotator cuff inflammation, which is dangerous and typically the product of technique flaws. Just fatigue/over-use of the shoulder muscles.)

This is especially true for shoulder-driven swimmers such as myself. So… what can I do to get beyond the brick wall of shoulder fatigue? A few obvious ideas:

  1. Train more – so my shoulders are better able to tolerate the abuse. (But do I have time?)
  2. Take more (or stronger) drugs. (Is that safe?)
  3. Develop more of a hip-driven stroke – distributing the effort away from my shoulders, toward my core and legs. (But how much speed will I sacrifice, given my short stature and weak kick? — not ideal for hip-driven technique.)
Backstroking somewhere in the Harlem River. Photo credit: Hannah B.

Here’s another idea: do more backstroke. I already do some backstroke during marathon swims – usually a few strokes after each feed. At MIMS, I backstroked under every bridge.

How far can I take this idea? What if, instead of just a few strokes per hour, I swam on my back for an entire feed cycle? Unnecessary for a 5-10 hour swim, perhaps, but what about a 15-20 hour swim? Could I extend the useful life of my shoulders by “unwinding” them for 20 minutes each hour?

It seems even more relevant in my case, because I used to be a backstroke specialist. In my younger, pool swimming days, my main event was the 200 Back. Compared to most, I give up relatively little speed on my back.

To quantify this, I went through my results archive and compared my backstroke and freestyle times through the years at the 100 (yards+meters) and 200 (yards+meters) distances. At both distances, I consistently gave up about 6% of my speed in backstroke, compared to freestyle. (This estimate includes a 2-second correction for the disadvantage of an in-water start in backstroke.) By comparison, the difference between the world records in the 100m freestyle (46.91) and 100m backstroke (51.94) is 9.4%.

6% is really not that much. If my ultra-marathon freestyle pace is 2.5 mph (just under 1:30 per 100m), that means theoretically I should be able to swim backstroke at 2.35 mph – still a very reasonable pace. I give up 6% of my speed, but I’m willing to bet it’s more than offset by delaying shoulder fatigue.

Food for thought…

On over-training

When I was younger, I swam in a near-constant state of over-training. To improve fitness, hard work is necessary but not sufficient. You also need rest – time for your body to recover and rebuild. Indeed, it’s during recovery that you get stronger. If you don’t rest enough, you don’t improve. If you’re over-trained – like I was for most of high school – increasing training load can ironically lead to decreased fitness.

My training load back then – 50K for an average week – wasn’t unusual for an elite age-group program. The problem was that I was only getting about 6-7 hours of sleep per night during the school year. (My natural sleep duration is 9 hours.) Over the course of a week, that produced a sleep debt that even a 14-hour “coma” on Saturday night couldn’t make up for.

I cut corners on my sleep because, well, I was busy. I don’t necessarily regret this choice… but I was naive about just how much it was affecting my swimming performance. When you’re that age, it easy to think you’re invincible. But over-training is very real – even for 16-year olds.

What are the symptoms of over-training? My intuitive sense is: If, for more than 30% of your training sessions, you feel crappy for most of the workout, you’re probably over-trained. For me, at times, that number was more like 60%. I didn’t understand how bad that was until years later, when I decided to respect my sleep needs and brought my “crappy workout ratio” down to 10-20%.

Dave Salo – legendary former coach of the Irvine Novaquatics and currently head coach at USC – is more scientific about it. To test for training adaptation (fitness improvements) vs. over-training, he recommends a set of 8×100 on a 4-minute interval. For the first 4, descending from 70-100% effort; for the second 4, ascending from 100-70% effort. After each swim, you take your pulse for 10 seconds, three times: immediately after finishing, then again after 30 seconds, then again after another 30 seconds.

Then, you take the sum of the three pulse measurements for each of the 8 swims, and make a chart like this:

From Salo & Riewald, Complete Conditioning for Swimming, pg. 16

The chart above shows three series of data, from three separate test sets. The circles show the baseline; the triangles show adaptation (improvement); and the squares show over-training.

I graduated college less than 10 years ago, but my sense is that even since then, swim coaches have become much more sophisticated about exercise physiology. One hopes these coaches are now more likely to recognize signs of over-training – leading to more athletes achieving their potential.

For more on this and other essential topics of swim training, I highly recommend Dave Salo’s book, Complete Conditioning for Swimming.

In praise of the pool

Pools sometimes get a bad rap among open water swimmers. Marathon swimmers who live outside the Sun Belt are known to bemoan long winter hours in the “concrete prison.” David Barra memorably quipped to the New York Times:

The free spirits want to be outdoors, and have a relationship with a body of water…. You don’t have a relationship with a chlorine box.

Hearst Castle. San Simeon, CA.

But pools have their uses – even for marathon swimmers. Especially if one of your goals is to get faster. Alex Kostich was a U.S. National Teamer, an All-American distance swimmer at Stanford, and a training partner of Janet Evans in her prime. Now 41, Kostich is possibly the fastest Masters open-water swimmer in the country at the short distances (up to 5K). In the July/August issue of USMS Swimmer, here’s what he had to say about pools:


The easiest and most efficient way to get faster in open water is to do quality work in the pool.

Kostich is an open water specialist. He lives in Los Angeles. Yet he doesn’t train in open water.

He isn’t unique in this regard. Friend-of-the-blog Mark Warkentin, who also lives on the California coast, did nearly 100% of his training for the 2008 Olympic 10K in pools. Take a poll of the current open-water National Teamers, and you’re likely to find that all of them do the vast majority of their training in pools.

Pools are useful because they make training quantifiable, measurable, and precise. In pools there is accountability and objectivity. Ironically, many of the factors that make open water enjoyable – its freedom and unpredictability – are the same ones that make it less than ideal as a training environment.

The two best ways to get faster are to (1) improve your technique, and (2) improve your cardiovascular conditioning. In the pool, it’s easier to monitor and adjust technique. In the pool, it’s also easier to do the “quality” work necessary to improve your conditioning. That said, training in open water is useful, I believe, in three regards:

  1. Cold water acclimation. There simply is no substitute (including ice baths). If you want to swim in cold water, swim in cold water.
  2. Rough water acclimation. This is an area where I’ve really improved since I moved to Chicago last year. My success in the choppy first few miles of Tampa and the choppy last 10 miles of MIMS was probably due, in part, to my training in Lake Michigan (which is, more often the not, choppy).
  3. Over-distance training. For the long (10K+) swims that are an essential (if only occasional) element in the marathon swimmer’s training regimen, I find open water preferable to the pool. It’s easier, psychologically – time passes more quickly in open water. That said, I still think my 25K pool workout in March better prepared me mentally for Tampa and MIMS than anything else I did.

See, the chlorine box isn’t so bad! Especially if the chlorine box looks like this:

Los Baños del Mar Pool. Santa Barbara, California.

No shortcuts in marathon swimming

As a sort-of counterpoint to my post on Kevin Murphy, I want to highlight this item about Andrew Gemmell, winner of this past weekend’s Crippen SafeSwim 10K. Munatones writes:

He took off time from his collegiate career at the University of Georgia to train with world 10K champion Chip Peterson and coach Jon Urbanchek who has developed 28 Olympians winning 5 gold, 6 silver and 4 bronze medals.

“I have tried to break [Andrew] down,” commented Coach Urbanchek. “But he is tough. He keeps coming back ready for more.”

Notice Coach Urbanchek doesn’t harbor any illusions about minimalist training or competing on “efficiency.” You don’t make it to that level without already being efficient.

What Coach Urbanchek does say is: “I am trying to break him.

Marathon swimming is now an Olympic sport, so objective standards become necessary – in particular, speed. At the elite level, “willpower” is necessary but not sufficient. To be an Olympic marathon swimmer, you have to be fast. And to swim a 10K fast, you have to train your butt off. There are no shortcuts.

You might be able to survive a marathon swim on “less than 20,000 yards per week… with most sets being 3000 yards or less” (to be clear, I’m not talking about Kevin Murphy here). But it probably won’t be very pleasant, and you definitely won’t be fast.

No shortcuts. That’s another reason I’m a marathon swimmer.