❤️ What Your Heart Rate Profile Tells You About The Effectiveness of Your Training
Top tips for what to look for in your training data after each swim
In Summary (TL;DR)
Celebrating 20 years as the world’s largest and longest-running swimming blog, Swim Smooth unveils a refreshed interface with over 750 articles and a new blog on heart rate profiling, available to read or listen to as a podcast.
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Discover the power of heart rate profiling in today's blog to optimize and elevate your swim training effectiveness.
Four scenario graphs from real sessions illustrate different training approaches demonstrating our approach to a gradual heart rate build and sustained effort as key for optimal performance.
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Celebrating 20 Years of Swim Smooth: A Fresh Look, New Features, and a Vibrant Online Swimming Community
Hi Swimmers,
As Swim Smooth approaches it’s 20th birthday, we have listened to your feedback and are excited to bring you a refreshed and cleaner interface for your reading enjoyment. With over 750 articles produced in the last two decades, and as the world’s largest and longest running blog on swimming, our commitment to helping you swim better remains unwavering.
To that end, we've gone all out this week to bring you an insightful blog on heart rate profiling to evaluate your training effectiveness. For the first time, thanks to a new spin of some technology, I'm sharing a cornerstone of my own training and progress—blending the art and science of swim coaching with detailed graphs and examples—that has allowed me to swim as fast and as efficiently now as I did 25 years ago. I know you're going to find it really useful for your own training as we geek out together!
With the revamped blog, you’ll continue to receive your emails directly in your inbox, but now with a heap of extra features! Enjoy community chat to discuss each post just like you would if you were here with me on the deck in Perth with all your squad buddies. This is also why I’m now recording each blog for you as a podcast, to capture all its nuances, as only a coach can.
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❤️ What Your Heart Rate Profile Tells You About The Effectiveness of Your Swim Training
I studied Sport & Exercise Science at the University of Bath between 1997 and 2001, a period when heart rate training was a prominent focus in the fitness world. This was largely influenced by the release of Sally Edwards' "Heart Zone Training: Exercise Smart, Stay Fit and Live Longer"1 in 1996. Like many other aspiring triathletes at the time, the idea of controlling your intensity via set heart rate zones and monitoring your recovery resonated with our Type-A analytical minds.
For someone like me, who spent most of 1996 and 1997 battling glandular fever from over-training, heart rate training was a saviour. It played a crucial role in my return to top health and fitness and inspired my career path in evidence-based coaching.
Studying heart rate in physiology classes made me realize how individualized sports performance truly is. The simple but flawed equation of "220 minus your age" for maximum heart rate was thoroughly debunked in Sally Edwards' white paper "The One-Size-Fits-All Age Adjusted Maximum Heart Rate Equation Fits No One"2 around 2000. Reflecting on this now, I see how Edwards' work must have influenced our Swim Types approach and our ethos of
"Coach the swimmer, not the stroke - there is no one stroke to fit them all!"
The Challenges with Heart Rate Monitoring
Heart rate monitoring, while revolutionary at the time, is not without its issues. Heart rate is highly susceptible to fluctuation due to various factors, including:
Dehydration: Can send heart rate higher than normal.
Low Glycogen Levels: Can send heart rate lower than normal.
High Ambient Temperature: Can send heart rate higher than normal.
Ingestion of Caffeine: Can send heart rate higher than normal.
Onset of Sickness: Can send heart rate higher than normal.
These factors highlight the variability in heart rate response to workload. Heart rate, in essence, is a variable response that can be influenced by multiple external and internal conditions, making it a somewhat simplistic measure on its own.
Evolution of Training Metrics: Power Meters and GPS Devices
The advent of power meters in cycling and Garmin GPS devices in running brought a significant shift in how athletes measured their performance. These devices allowed for the measurement of actual workload, leading to more precise and reliable data compared to heart rate monitoring alone. Consequently, many athletes began to favour these devices over traditional heart rate monitors due to their quicker response to changes in workload and their ability to provide consistent data unaffected by external variables.
However, it's essential to recognize that heart rate and power/pace metrics each have their place in monitoring the effectiveness of your training. In swimming, monitoring workload is straightforward: we use time or pace per 100m, and if you've been following Swim Smooth, you know we put this in the context of your Critical Swim Speed (CSS). By comparing your performance to your CSS, you can effectively gauge your training intensity and progress.
The Role of Heart Rate Variability (HRV)
Before delving into heart rate profiles, it's worth discussing the popularization of Heart Rate Variability (HRV) in endurance sports as a method to measure recovery response to training. HRV is the measure of the variation in time between each heartbeat, and it reflects the adaptability of the heart to stress and recovery. It was popularized around ten years ago, particularly through the influential article "Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring"3 by Dr. Dan Plews (et al.). Dr. Plews, a good friend of Swim Smooth, contributed significantly to the understanding of HRV. The website HRV4Training4 is also an excellent resource on HRV.
While we will explore HRV training in more detail in future blog editions, today's focus will remain on analyzing basic heart rate graphs and understanding what they can tell us about the effectiveness of your training sessions. If you have a Garmin, Apple, or other smartwatch device that you download after you swim, you've likely got all the tools you need to follow along with this simple, yet insightful, analysis.
Understanding Heart Rate Profiles in Training
While there are many ways to train effectively for endurance swimming, ultimately, defining your Critical Swim Speed (CSS) and working to improve this pace will be the single most determining factor in how well you perform over any distance of 400m and above. For this reason alone, we relate all of our training intensities relative to this pace. For example:
CSS +6s/100m: A relatively easy pace, six seconds per 100m slower than CSS or threshold pace.
CSS -4s/100m: A very quick pace, manageable for a number of 100 or 200m intervals with substantial rest, but unsustainable for longer durations.
We find a sweet spot for half and full Ironman athletes at about 3 to 4 seconds per 100m slower than CSS. An entire 4-5km swim session can average this pace, making it a very aerobic session. This type of session, when performed consistently over several weeks, can be highly effective as one of your key weekly workouts.
Scenario 1: Aerobic Session
During a session averaging around CSS pace, you’ll often see a gradual build in your heart rate curve. If the rest between intervals is short enough, there will be very few prolonged dips, effectively emulating a race environment. This sustained effort allows for significant aerobic conditioning, enhancing your endurance capacity.
Scenario 2: Short, Fast Intervals
Conversely, many swimmers aiming to get "faster" believe that very short, fast intervals with plenty of rest are the key. However, if the work-to-rest ratio is 4:1 or less (meaning more than 25% of your time is spent resting), you’ll see dramatic drops in heart rate between intervals. While this allows for quicker swim times during intervals, it doesn’t significantly improve your ability to sustain an aerobic pace over longer distances. You can see this in the last 7 intervals of this session where the recovery period was doubled in order to elicit greater speeds, however, the heart rate peaks are much less and do not build as much, and the heart rate dips are much greater too. This was a nice speed ego boost, but the most effective training in this particular session occurred before those intervals started.
Scenario 3: Continuous Swim
Another approach is a continuous swim, like the 2km swim I mentioned in a recent blog titled, "When 80% Perfect is Enough". In this regular 2km continuous swim, I aim to hold a steady pace about 4 to 6 seconds per 100m slower than my CSS. This type of training, often referred to as "maximal steady-state" or "tempo" in running, is the physiological point where you can buffer the onset of lactate build-up indefinitely.
A good way to check if you have this right is that after a slight build over the first 200 to 300m, your heart rate curve should level off. If it continues to rise upwards against a consistent pace, this so-called "decoupling" means that either you're not truly at your maximal steady-state, or other factors like dehydration, high water temperatures, or sickness might be affecting your performance.
Scenario 4: Classic Red Mist Session
A nice example of an effective aerobic training session is our Classic Red Mist session, which consists of 10 x 400m intervals as follows:
4 @ CSS +6s
3 @ CSS +5s
2 @ CSS +4s
1 @ CSS +3s
Observe the dips between each interval, representing just 20 seconds rest, with a work-to-rest ratio of 16:1. The gradual build of the heart rate over the 10 intervals as the pace increases exemplifies an effective and sustainable training approach.
Summary: Effective Training Strategies
We've found that the most effective strategy for a key swim session is to follow a structure that sees your heart rate gradually build over the course of the session, with few dips where the heart rate recovers "too much," and maintains this effort over a prolonged period of 20 to 90 minutes. That's not to say there's not a place for shorter intervals with more rest—like scenario 2—but we'd simply caution against too much of this type of training at the expense of more effective sessions. These types of CSS and Red Mist Endurance sessions can often seem a little daunting (and even a bit boring), but they are effective and will make a big difference to your performance when done consistently. Always think to yourself, how well is this session emulating what my race truly feels like?
Additionally, during key sessions, be observant of not taking too much rest between sets by adding unnecessary "faff" time, which can also reduce the effectiveness of the gradual heart rate build. I like to think of this as being aware of “keeping the engine running”.
A good way to monitor this is by comparing the total time for your swim against the total amount of time spent swimming:
Ideally, this would be a difference of no more than about 10% in your key sessions, but discipline is required to stick to this. For your less key sessions, if you've ever tried one of our Pure Technique or Technique/Endurance sessions, you'll note that we're much less strict—or even a bit ambiguous—about how much rest to take, simply because not every session wants to be super focused like this.
By understanding and applying these principles, you can optimize your training sessions to improve endurance, speed, and overall performance.
We hope you’ve enjoyed this first article here on Substack - please let us know if you have any comments or feedback below!
Sally Edwards' "Heart Zone Training: Exercise Smart, Stay Fit and Live Longer" available at https://www.amazon.com/Sally-Edwards-Heart-Zone-Training/dp/B01FIWTA0U
Sally Edwards’ "The One-Size-Fits-All Age Adjusted Maximum Heart Rate Equation Fits No One" chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://heartzones.com/wp-content/uploads/2016/03/hz-white-paper-1.pdf
“Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring.” Sports Med. 2013 Sep;43(9):773-81. Daniel J Plews 1, Paul B Laursen, Jamie Stanley, Andrew E Kilding, Martin Buchheit. Abstract at https://pubmed.ncbi.nlm.nih.gov/23852425/
Heart Rate Variability (HRV) insights to help you quantify stress, better balance training and lifestyle, and improve performance - https://www.hrv4training.com/
I would like to know what is your experience with hart rate monitoring during swimming. I use Garmin watch for tracking, for four years Tactix Delta and from December Tactix Amoled. In the first year the Delta with its built-in optical sensor measured the HR very well, I was satisfied with more than 90% reliability of the results. But something happened in mid of 2021, from this date, the result from the optical sensors are not reliable any more. This was the reason I changed to Tactix Amoled with the latest version of built-in sensor but it doesn't work either. I started to use Garmin HRM Swim what works correctly. But it is also not a perfect solution. I hate to wear it in a public swimming pool, not comfortable, it might be loosen during the swimming or after kicking off the wall. Furthermore after some months the chlorine ruins the strip completely.
Any other suggestion?
Thanks for the reply. I have done this for all my teams and also with a small group of “old geezer” masters swimmers when we workout together on off days.