male triathlete swimming in a pool

In this post I’ll discuss one way to analyze a swim set using the data from a Garmin 910xt Swim Watch. Similar data and graphs can be obtained from the Finis Swim Sense but the graphs look slightly different. Understanding the concepts of how pace, strokes per length and rate fit together is the most important key…if you understand that you can analyze the data in just about any system…or even by hand, tracking the information with paper & pen after each repeat.

Step 1: What is the intention of the set?

This is a 1000 yard set of 10 x 100yds freestyle posted by a triathlete early in his season. Like most folks, his goal is to get faster for his race distances. So lets take a look first at the dashboard and look at the key pieces of information.

10x100 Swim Set All

The first thing I look for, if I don’t already know is a sense of what the set represents. It’s easy here to see this is a set of 10 x 100 yard repeats with short rest intervals.  Essentially this is a “broken 1000 yd swim” due to the short rest, as opposed to a series of ten 100-yard efforts.  The less rest between repeats, the more continuous the energy demand is, and the better it reflects demands of a triathlon swim leg or open water race.


Step 2:  How is the pace control?

Next, the list if intervals on the left hand side shows us the distance and the pace of each interval. if yo don’t own a swim watch, this same data can be easily tracked with any sort of sports watch with a timer that allows you to start and stop each interval.  Because pace is usually listed as pace per 100 yards, and these are 100 yard repeats, the pace and the time are identical for each repeat.  You can see that his pace remained in a tight band of 1:28 – 1:32 seconds/100 yds for 1000 yards.  While the rest interval isn’t show in the left hand panel, you can see from the blue & red panel on the lower right that the rest period looks to be about 10 seconds per 100 or less, just by comparing the width of the rest interval to the known 1:30 min:sec swim time.

So the second piece of data we collect is a gestalt of the overall pace, and how consistent the athletes pace is.  He gets an A on pacing for sure.  Do you agree?

Step 3:  How is the Stroke Length Control, ie Technique or Skill Endurance?

The next thing we will look at his how this athlete constructed his pace, and is a reflection of how well his current skills hold up with fatigue and distance. This is the part that can really help accelerate improvements, because if we try to increase pace or performance before we are ready, the athlete can stall in his technique development which makes overall development limited (even if still he is still improving )

The top right panel shows us strokes per length for the entire set.  I like this panel because it gives me a good feeling for stroke length control, which reflects skill, coordination and neuromuscular movement patterns.   Since I already know this set is a 1000 yard broken set, ideally what I’d like to see in a well developed swimmer is a steady SPL for the entire set, and that’s exactly what we see here:


10x100SwimSet SPL

There are a few variations  on his 8 stroke cycle average. Overall, rarely more than 1 stroke cycle variation from his average, and those variations are occasional, not on every length.  For clarity, these swim watches count stroke cycles which is a full left and right arm cycle.  The watches do not measure 1/2 cycles or an odd number of strokes.   For that reason I prefer to have swimmers get into the habit of couting their own strokes when possible so they can begin to understand and feel the difference between say a 16 stroke length (8 cycles) and a 17 stroke length (8.5 cycles).

So now we have 3 pieces of vital information:

  1. What type of set 
  2. Overal pace control
  3. Overall stroke length control (skill or technique endurance)

For this athlete we have gathered just by reviewing the watch data

  1. Type of Set: Aerobic Endurance, broken 1000yd Freestyle as 10×100 with short rests
  2. Overall Pace Control:  Average pace of 1:30 with a range of 1:27 to 1:33
  3. Technique Endurance:  Average Stroke Cycles per length of 8, with variation of 1-2 cycles in some repeats. (note that the watches are not always accurate in cycle counting either, sometimes adding a cycle or not completing a cycle depending on how you turn at the wall and what are you swim with or touch the wall with) 

At this point you have everything you need to make a determination of how well the athlete performed this set, and what changes if will help contribute to the next stage in improving his racing speed.

There are a few other data points it would be nice to know in the big context, but this is enough information for a quick “microcycle” scope review of a standard type of swim set.   Before you read the rest of this article series, think about any other data you’d like to know in order to make plans for the athlete in a larger time scope.

What do we do with SWOLF?

The next chart is the SWOLF chart.  I present this here because it seems like there should be a gold mine  of data here…but I’ll just go out on a limb and say at many times, this is fool’s gold.  We have to ask our selves if we are really asking the right question.  What does the sum of two different units represent? Do I want my SWOLF to be as low as possible? If I lower my SWOLF am I improving?


10x100Swim Set SWOLF


It’s far more important that you understand the concepts and meaning of the 3 data points we have already collected, but Several different patterns can emerge with this chart so it is worth at least thinking things through. SWOLF is the sum of strokes per length (stroke cycles) plus time in seconds per length. This number has no units and conceptually we can’t place an absolute value on it’s meaning. What we can see in this graph is that that number is steady as well…but we knew that it would be. In a differently paced set, or a less consistent swimmer, this chart would have a different “shape”.

Where do we go next? What’s my next workout, coach?

Since we’ve already extracted the important bits of data in the first 3 steps so let’s continue with what happens next! The next part of this article will discuss how to interpret the information we’ve gleaned from the watch data and plan future sets. Before reading it, think about what makes sense here to continue the athletes aerobic abilities, skill/techinque endurance and overall speed. What would you recommend this athlete do next? Several different options are available so lets’ brainstorm a little.

You can find additional articles about SWOLF and swim watch anlaysis in the following links