All about recovery
Did you know that when your heart beats at, say, 60bpm, each beat isn’t evenly spaced out at 1 second? In fact, the beats vary by milliseconds, and the more they vary the better. That variation, or Heart Rate Variability, is indicative of a lot of things, including your health and state of recovery.
ithlete is an iPhone app that measures HRV down to 1 millisecond, giving athletes an objective method of monitoring their recovery and planning their training accordingly. You take a reading each morning and ithlete gives you a score, as well as a green, white, amber, or red reading, telling you whether you should train hard, ride easy, or rest. The underlying principle is that improvements from training take hold during recovery, so if you don’t allow yourself to recovery properly you’re not reaping the full rewards of your training. This article is a good intro into the science of HRV.
While the motivated type A racer can also use the ithlete to prevent overtraining, I’m far too lazy and undisciplined to be in danger of that. The ithlete instead has served to kick my ass. It’s a fun game to play – you train super hard to earn a rest day, then you try to rest really well to drive your score back up. Once you get into the swing of things you can start to chart your training a week or two ahead so you can plan a peak. The feedback really gives your training a framework so you’re not thrashing about in the dark. It also really makes you focus on all aspects of recovery in an attempt to drive your score up.
Put on the chest strap and ithlete prompts you to breathe as it measures your HRV.
A color coded score tells you what you should do that day.
The white daily plotline goes up and down with training and recovery, while the blue long term trendline lets you know when you’re due for a block of rest.
I did my personal FAQ with ithlete inventor Simon Wegerif.
AS: First of all, why measure and monitor HRV? How highly does it rank as a physiological parameter?
SW: I believe HRV ranks highly for the following reasons:
1. Whilst we have many objective ways of measuring workouts (miles, hours, TSS, TRIMP, etc….), we get stronger during recovery, and recovery was difficult to measure until simple tests using HRV came along.
2. Research is now confirming what we have been hearing from users – that high HRV predicts high athletic performance.
3. HRV allows us to create a balance of good athletic performance whilst still maintaining excellent health.
AS: What’s your background, and how did you discover HRV and come to develop an app for measuring it?
SW: My professional background is in signal processing, having been a pioneer of digital broadcasting at the BBC in London and Philips Electronics in the UK and Silicon Valley, where I managed a number of technology startup activities. Recreationally, I have been a keen, but not very talented endurance athlete most of my adult life, firstly in rowing, then running, triathlon and nowadays I am a competitive cyclist.
I first came across Heart Rate Variability in an article by coach and Wattbike physiologist Eddie Fletcher, who had been using HRV with elite athletes for some time. This started me on a journey to find out a lot more about HRV, and I started reading a lot of original research papers (I’m now up to about 700!) and reaching out to some of the authors to gain a deeper understanding. Eventually I concluded that a simple but scientifically valid phone app was possible, and I filed US & international patents for the novel techniques I had developed.
From the first working app, it was 9 months until the testing was complete and Apple approval for ithlete on the iPhone in November 2009, at which point I decided to found HRV Fit Ltd as the commercial company, initially just myself but now with a dedicated and very talented small team.
Since launching ithlete, we have developed a research collaboration for heart failure rehabilitation and also made custom versions of ithlete available to business customers, both in tele health applications as well as elite sports. One of these also stimulated us to develop a novel finger pulse sensor, which has been validated & refined by University of Sydney.
HRV has been a journey for me personally as well. Since starting to monitor myself at least once a day (my ithlete database has over 1200 entries), I have discovered a number of things about my own health & body that have been revealing. One is the impact of mental stress, which can lower your HRV (and hence your body’s reserves) as much as intensive sports training. Thanks to a suggestion by my Wife, Lindy, I discovered that deep breathing was far more effective in relieving mental stress than I would have thought – it sent my HRV to new highs which were sustained over the longer term, and stimulated me to create another app for what’s termed ‘coherent breathing’ that I have teamed up with an old friend to bring to market this year.
AS: I’ve heard that Polar used to have a watch that could measure HRV, and there was an algorithm that could take that and give a good estimate for VO2max. Is there a correlation with HRV and VO2max?
SW: There is a correlation between HRV and VO2 max, but it is not very good. See attached chart below. Although I have yet to be convinced that HRV alone can be used to calculate VO2 max for an individual, I have seen convincing evidence that when an individual’s HRV baseline changes over a period of weeks, their aerobic capacity also changes.
AS: I’m self-coaching by doing what my morning readings tell me to do on a daily basis, with an eye to the long term trendline. When the long term trend drops too far I rest for a few days, bring it back up, and go back to it. Is this an appropriate use of the app?
SW: There are several different ways you can use the app, and yours is certainly one of them. For myself, I’ve started adding very intensive sessions on the bike just twice a week, and I pick days when I’m well recovered, preferably with HRV above baseline to do these. Also, when I get daily amber readings, I restrict myself to aerobic training only, and when I get a red I have learned the hard way that it’s not a good idea for me to train!
AS: I’ve been using Azumio’s heart rate app, which measures HR with the phone’s camera. Any chance ithlete could do the same?
SW: I have evaluated using the camera as a sensor, but these take max 30 fps, which equates to an accuracy of 33ms, i.e. 33 times lower than we can get from the strap. I’ve not heard anyone argue that it is good enough to measure HRV, but a pulse sensor similar to a doctors office pulse-ox can be made good enough, and we have one we are going to release in the next few weeks.
AS: ithlete gives a score of 1-100. Is that a medical standard or your proprietary scoring system?
SW: The scale is based on a medical standard, called RMSSD (which is a robust parasympathetic time domain measure often used in research) but log transformed and scaled in a novel proprietary way to make it convenient & intuitive. The scale does not stop at 100 – the highest I have every seen is 116 (in a professional athlete, not myself I hasten to add! ).
AS: My baseline is sadly around 52, Dan’s around 78, He’s also faster than me. Is the score relevant in comparing different people, or is it more for measuring an individual’s relative fitness/health?
SW: The score is only partly relevant in comparing people – it’s much more important to compare daily changes & weekly / monthly trends.
AS: What accounts for variations in readings taken in succession? Is it that your HRV is actually changing from moment to moment, or is there a margin for error in the measurement?
SW: The variation between readings is actually caused by changes in your HRV, and in back to back readings is also affected by knowledge of the previous readings (which is subliminally stressful). The math we do uses your own statistical spreads to figure out what is significant and what is not. All biological tests have spreads – blood pressure measurements similarly to HRV, and it does not mean the equipment is inaccurate or unreliable. A statistician called Will Hopkins is much respected for his understanding of expected spreads in sports science & uses the concept of ‘smallest worthwhile change’ being 0.5 x standard deviation, in other words, any change in a test that has a spread less than this is not meaningful. Some people have a hard time getting to grips with this, but we have been misled all these years by heart rate monitors that actually average typically 7 heartbeats to make everything look (fairly) smooth.
End of interview
I’ll leave you with a little anecdote. I asked Greg LeMond about HRV, and while he didn’t know about ithlete, he was very well versed on HRV. He told me that you can spike your score with several quick sprints, so I gave it a shot to see if I could top Schmalz. I got a 92 the next day, but with an amber (ride easy) score. Turns out the spike is due to adrenaline depletion which requires rest, not a miraculous spike in fitness. So once again there’s no substitute for hard work and I’m still slow.
Nice article. Now I want to try this stupid app.
Look at the lengths Andy will go to just to try and beat me.
Two thumbs up for a good interview.
What hardware are you guys using? I’m convinced that this is worth trying, but I see that one can use Bluetooth with an appropriate HRM strap or a little ithlete receiver with an analogue HRM strap. Are either of you using the little ithlete receiver, and if so would you recommend ponying up for the Cardiosport HRM strap that ithlete is selling? I have several Polar straps lying around from my pre-Ant+ days that are compatible, but ithlete implies that the results are better with a Cardiosport model.
Dan’s using the original strap + dongle, I’m using the Viiiiva strap.
https://nyvelocity.com/content/equipment/2013/4iiii-viiiiva-hr-strap
The Viiiiva works better and it’s nice to not need the dongle. The Wahoo bluetooth strap won’t work, that one transmits bpm instead of individual beats. Have no experience with ithlete’s bluetooth strap.
I was impressed by the review; my ithlete receiver just arrived. If anyone else is curious, the shipping time to the middle of the USA (from the UK, where ithlete is based) was 8 days.
saw an article in outside magazine and wanted to give HRV a try.
how does this affect training routines? i’ve been following the time-crunched cyclist interval training.
Not dismissing but what is the causation?
You are more likely to have a hip fracture if you live near citrus trees. That is a FACT. But it is only a correlation – old people move to Florida for the warm weather. Orange trees grow in Florida but don’t CAUSE hip fractures.
Call me when you’ve sorted out the HR data