Swimming Watch Analysis – 10 x 100 Freestyle Swim Set

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

What can SWOLF tell us? Interpreting Swim Data from your GPS Watch.

Swimming watches have become an essential tool for triathletes, providing valuable insights into our performance in the pool. With built-in accelerometers, these watches accurately count strokes, track lap distances, and monitor our pace and time for every lap and repetition. But what can we actually do with all this information?

Currently, the most popular platform for tracking and reporting swim data is Garmin.  However there are a number of newer competitors on the market with both watches as well as goggles having the ability to track, report and visualize swimming information.

One of the most intriguing and easily accessible metrics provided is the SWOLF score. SWOLF, short for “Swim Golf,” is a score obtained by adding together the number of strokes per length and the time it takes to complete that length.

For example, if you swim 25 yards in 30 seconds and it takes you 20 strokes, your SWOLF score would be 50.

Take a look at the screenshot below, captured from Garmin Connect, showcasing this informative metric:


SWOLF Score Garmin 910xt GPS watch


And here is a similar example from Finis, the makers of the Swim Sense, which is no longer sold, but you can see another way the information is presented. (do you use another brand of watch or goggle to record your swimming?  Send a screenshot our way and we may feature it in an update to this series!).

SWOLF Score FINIS SwimSense Watch


Unveiling the Secrets of SWOLF: What Does It Really Tell Us?

When it comes to SWOLF, many coaches consider it a measure of efficiency, believing that a lower SWOLF score indicates a more efficient stroke. While striving for a lower SWOLF score is a common goal, there are two important factors to consider when analyzing SWOLF and its relationship to efficiency. Let’s explore these factors and uncover new ways to leverage SWOLF in your workout analysis.

Firstly, It’s essential to grasp the concept of efficiency in swimming. Efficiency refers to the ratio between the energy you invest in your strokes and the resulting forward movement. Accurately measuring efficiency would involve quantifying the amount of oxygen a swimmer consumes while swimming at a particular speed, which requires specialized tools for measuring oxygen consumption. Since swim watches cannot provide a precise efficiency value, we must explore alternative indicators that can offer insights into stroke efficiency.

Now, let’s delve into the second reason why SWOLF alone cannot provide a comprehensive picture of efficiency. While SWOLF is calculated by combining two parameters—Strokes per Length (SPL) and the time taken to complete the length—we still need independent knowledge of both SPL and time to make meaningful interpretations of the SWOLF score.

In essence, SWOLF offers valuable insights into stroke efficiency but should be analyzed alongside additional information to gain a comprehensive understanding. By examining factors such as stroke technique, stroke rate, and overall swimming mechanics, you can paint a more complete picture of efficiency and make informed adjustments to enhance your performance in the water.

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Exploring Swim Golf Variations: Understanding Time and SPL Matrix

Let’s explore different combinations of Stroke Per Length (SPL) and time in a simple two by two matrix to understand how they affect SWOLF and what it indicates. Take some time to go through each scenario, and it will provide you with new perspectives on these metrics.

Four Scenarios: A) High SPL and high time = High SWOLF and inefficient swimming B) High SPL and low time = Medium SWOLF and improved efficiency C) Low SPL and high time = Medium SWOLF and very efficient swimming D) Low SPL and low time = Very low SWOLF and inefficient swimming

If if SPL * rate = time, then we are curious about what SPL + time or SWOLF can tell us?

Four Scenarios:


A) SPL is high and time is high = high SWOLF and inefficient swimming
B) SPL is high and time is low = medium SWOLF and improved efficiency
C) SPL is low and time is high = medium SWOLF and very efficient swimming
D) SPL is low and time is low = very low SWOLF and inefficient swimming

A) When SPL and time are both high, it suggests a lot of drag or an inefficient catch. Swimmers in Scenario A can learn a lot by tracking SWOLF and observing its improvement. A decrease in SPL or an increase in speed indicates improved swim efficiency.

B) As speed increases, it’s normal for SPL to increase (SWOLF may remain the same) in efficient swimming. Swimmers in Scenario B can expect a lower SWOLF for slower swimming and a higher SWOLF for faster swimming. They should aim for a sustainable faster speed and be satisfied with a higher SWOLF while identifying their specific SPL and pace targets for different training distances or race settings.

C) Scenario C suggests a very low stroke rate with a significant amount of glide, indicating highly efficient swimming (SWOLF may be the same as in Scenario B). Swimmers in Scenario C should strive to increase their SWOLF by increasing their tempo since they already possess a highly efficient stroke.

D) Achieving a low SPL while swimming at a high speed requires considerable power and strength. Although SWOLF will be low, true efficiency may be compromised. However, in a race, the fastest time, not the highest efficiency, determines the winner. Swimmers in Scenario D are skilled and powerful, allowing them to adapt their strokes based on the task at hand.

Each scenario provides valuable insights into stroke efficiency, and understanding these variations can help swimmers refine their technique and optimize their performance.

Swimming Efficiency Comparison: Stroke Counts, Times, and SWOLF Scores

In this video, Jai demonstrates an interesting comparison between two lengths of swimming. In the first length, he completes it with 16 strokes in 31 seconds, resulting in a SWOLF score of 47. In the second length, he maintains the same 16 strokes but completes it in just 18 seconds, resulting in a lower SWOLF score of 34.

Despite the faster time in the second length, it’s important to note that the slower length is actually more efficient considering the amount of effort required relative to the forward movement achieved. While Jai could sustain the effort of the first length for a significant distance, the second length would likely be sustainable for a shorter distance, possibly around 100 meters or less.

SWOLF: More Than Just Efficiency

Let’s delve into an interesting aspect: the connection between speed and SWOLF. Imagine plotting different combinations of speed and SWOLF at various stroke rates. We might uncover a valuable self-coaching tool. My hunch, however, is that we can’t rely solely on SWOLF to gain insights. To truly analyze data and improve our swimming practices, we need to consider at least two out of three metrics: stroke count (SPL), time, and speed.

For me, SWOLF serves as a quick measure of consistency rather than an absolute measure of efficiency. When I review my athletes’ watch data, the SWOLF graph tells me if they are taking too much rest or swimming too easily. It also reveals if they are becoming more consistent in their performance during specific sets, such as a set of 10 x 100. While pace alone or SPL alone won’t provide the full picture, SWOLF alone doesn’t tell us much either.

Consider this: If I observe a set of 10 x 100 with a consistent SWOLF and unchanging SPL, it indicates that the swimmers are maintaining a steady level of performance, which is a positive sign. However, to truly understand their progress and enhance their performance as triathletes, I need to combine SWOLF with either pace or SPL. By reducing rest intervals, increasing the distance of each repetition, or ramping up the pace, we can aim for faster swimming and improved fitness, which may impact SWOLF in different ways.

Going Beyond SWOLF: Practical Strategies for Improving Swimming

I hope this discussion has shed light on the significance of various metrics and how to make the most of the information. In my experience, focusing on stroke count ranges, discovering your optimal SPL, experimenting with different SPLs, and maintaining your chosen stroke count—coupled with the use of a tempo trainer (steady, ascending, descending, etc.)—offer greater control and guidance compared to relying solely on SWOLF.

In an upcoming article, I will analyze specific watch data graphs to provide insights into executing swim sets and planning practice sessions for improved skill development. I’m eager to hear your thoughts and learn how you use the watch data you collect. Share your experiences and ideas in the comments section below. Together, we can continue to enhance our swimming performance.

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