While appearing on the on-line Triathlon Summit this evening, I answered a question on what’s the right stroke count. I explained that the "right" count was highly individual and promised to publish a blog that gave more explanation and included a formula to learn your own optimal count. 

There is no single SPL (Strokes Per Length or stroke count) that’s "right" in all circumstances. A shorter swimmer will generally take more strokes than a taller one. Your SPL for a 400 will be higher than for a 100. It will also be higher when swimming a 50 in 40 seconds, than in 45 seconds. But counting strokes regularly gives you the information to make strategic choices: If your count increases dramatically as you go farther or faster, ask yourself whether that was the best approach, or set a goal of doing it more efficiently next time. Every lap that includes stroke counting automatically gains in awareness and purpose.

Your goal is not to achieve a single "best" count, but to learn the range of counts at which you can swim effectively. For Freestyle, my range in a 25-yard pool is usually between 11 and 15 SPL (12 to 16 SPL in a 25-meter pool and 30 to 40 SPL in a 50-meter pool.). Each count represents a different effort or emphasis level for me. Any count I use is always a conscious choice, never by accident or happenstance.
• At 11-12 SPL my emphasis is Swimming Perfectly, and my effort level is controlled enough to give me a chance at "perfection."
• At 13 SPL, I’m swimming at what I call Cruise Speed, the equivalent of conversational running. I could maintain this speed all day without tiring.
• At 14-15 SPL, I’m at what I call Brisk pace. Still sustainable but definitely "breaking a sweat." Another term might be Easy Speed.
• At 15-16SPL I’m swimming at what I call Race speed. This equates much more to a sensation than to a particular time on the pace clock. That sensation is how I’d like to feel at a specific stage of a specific race – say from 400 to 1200 m in a mile race. And not just any race, but the race of my life. You might call this an "aspirational" pace as I try to use it to create both a neuromuscular and psychological "zone of success."

Is a low count always better?
I’ve often seen swimmers who have been working on their Stroke Length, swimming with an impressively low SPL – let’s say 12 strokes for 25 yards – but a thoroughly inefficient style. They’re actually working harder at the lower count than they would if they allowed a few more strokes, because they strain so much to do it. It takes more effort to maintain a stroke count that’s too low for your skill level.

Your object is to find the optimal rather than minimum SPL. Your lowest SPL should be fluid, effortless, and silent, because the real goal is to minimize energy cost, not stroke count. By practicing mindfully, your SPL range should improve over time.

At age 20, when I focused on harder and faster training, my low count for Freestyle in a 50-meter pool was about 50 strokes. By age 30, it was 40 SPL. At age 40, it had dropped to the low 30s. In my 50s – when the stars are aligned and the moon is full — I’ve managed a relaxed, flowing 50-meter lap in 26 strokes, meaning I’ve approximately doubled my Stroke Length while doubling my age. If, on the other hand, you were taking 25 strokes for 25 yards last year, and this year you’re trying to maintain 13 SPL you may be exceeding your capacity for adaptation. If you make relaxation your primary goal, increases in efficiency will follow naturally and almost effortlessly. And by the way, if you use my stroke counts as your standard, remember, it’s taken me over 30 years to achieve them.

A Formula for SPL
An optimal stroke count – the one that should have the lowest energy cost for any distance or speed – is fairly individual. But there is a formula, based on arm length and the distance of your usual push off that allows you to predict your own personal "highly efficient" stroke count for Freestyle – the one you should aim for when swimming short distances at low speed. Allow 2 to 4 additional strokes per length for higher speeds.

For a 25-yard pool: High Efficiency SPL = 12 x (L-P)/A.
For a 25-meter pool: High Efficiency SPL = (L-P)/A

SPL = strokes per length
L = Length of pool (in feet or meters)
P = distance traveled in pushoff before stroking (in feet or meters)
A = Armspan from wrist to wrist (in inches or meters)

I’m 6′-0" tall with a 57-inch wingspan and I usually surface after pushoff at the 15-foot mark in a 75-foot pool, so according to this formula it should take me 12.6 high efficiency strokes to cover the remaining 60 feet (20 yards.) Indeed, when I practice low speed, high mindfulness swimming I take about 12 strokes so the formula works in my case. But I’ve also worked for decades, with drills and mindful swimming, on my efficiency.

How to Choose SPL Effectively
Some guidelines for making effective choices on stroke count:
Your lowest SPL should be:
a) Almost effortless
b) Flowing and quiet
c) With a relaxed kick
It should, however, require concentration to maintain it for more than a lap or two.

Swimming in the lower half of your SPL range, though slower, still produces benefits:
a) Makes a longer stroke more of a habit.
b) Helps you stay efficient at higher speeds
c) Helps you stay efficient for longer distances

When you choose to increase SPL to go faster it should be:
a) Something you can do with flow and control
b) A choice that adds more speed with little additional effort
c) An exercise in coordination, not in "going harder."

 This blog/article is excerpted from Extraordinary Swimming.