We always recommend taking your ithlete HRV reading first thing in the morning. Right after waking and certainly before eating / drinking / exercising or stressing. The only thing you should do first is to use the bathroom if needed.
There are a couple of good reasons for this:
1. Consistent conditions
The way ithlete can tell you how recovered you are, is by comparing today’s reading to yesterday’s, and the day before that and the day before that, and so on. Heart rate variability (HRV) is a holistic indicator of stress, which makes it very valuable when assessing total load. But it is important to reduce external influences to a minimum before your reading to get a consistent situation to compare from one day to the next. Total load is a combination of all stress from various sources (you can read more about that here).
Imagine for instance that you decide on just one day to have a large cup of tea or a double espresso first, then 20 minutes later you get to do your ithlete reading. The caffeine in your system will alter your HRV quite significantly up or down depending on how your body reacts to caffeine (this post on energy drinks offers some interesting insights) by let’s say +5 points on the ithlete scale. Not only will you get a false perspective on today’s reading (which is 5 points higher than it would have been), but your baseline (which is a moving average of all daily readings) will be distorted, making future comparisons less precise.
As another example, let’s say you decide to check your Twitter feed before doing your reading. You see something you really don’t agree with, and it causes you some stress which lowers your HRV by -4 points. You might actually have recovered fine overnight, but that transient stress (which you will probably forget all about in an hour) could cause an amber reading, making you think you can’t do the demanding workout you planned.
We could make other examples but I’m sure you get the point! Our preference is to roll out of bed, put the sensor on and breathe in a gentle relaxed way without thinking about anything – that gives the most unbiased reading.
Top tip:
One aspect you can delay if you prefer, is the subjective measures – waiting until you have moved around a bit or woken sufficiently to assess fatigue, mood or muscle soreness is no problem, and will probably lead to more accurate assessments.
2. Circadian rhythms
There are big fluctuations within the daily cycle regulated by hormones. At night, melatonin hormone influences put the body into parasympathetic dominant rest and digest repair mode: heart rate decreases and HRV increases. When we wake up cortisol is released to flush away the melatonin and get us ready for some ‘fight or flight’ daytime activity. The cycle is mostly driven by our built in clock, and leads to a natural variation in HRV as shown below:
You can see a sharp decrease in HRV around 7:30 – 8:00 when waking occurs. This means most of our daily HRV readings are done in the lower part of the curve. If however you have to get up much earlier than normal, say to catch a flight, you may well catch your body still in rest and digest mode, which will mean a significantly higher HRV than normal. Similar effects can happen if your body clock is out of sync due to shift work or travel across time zones. For this reason we’d recommend if you’ve woken more than 2 hours before or after your normal time that you don’t take an ithlete reading that day.
Summary
Try to find a consistent time of day when you can do your HRV reading uninterrupted and with a minimum of external influences, and you will be rewarded with more sensitive and accurate recommendations!
Simon, thanks for this very good briefing on such a fundamental point.
The curve, though pretty crude, is very useful. I look forward to more studies on that basic aspect. Wouldn’t it make sense to take the daily measure near a flat point of the curve ? If so 6 or 16 ? Thanks again.
Dear Yves-Marie. I agree there is a lack of studies on this very basic phenomenon, especially when many cardiac events occur between the hours of 6-10am. Although there are proponents of measuring HRV during sleep, I prefer the idea that we deliberately impose the small stress of standing in the morning, as our body’s reaction to that stress depends more on the current fatigue level than in the lying position. There is good recent research showing that the CV system behaves significantly differently when upright.
For anyone training, morning should be the best time to measure so that plans can be tailored to the readiness assessment that HRV provides.
Simon,
This is worth debating.
Yes your reasons make a lot of sense.
But on the other hand I see :
– On the very practical side
— The best measure is the fruit of a measurement…made ! That is one that you don’t forget to make…because it is automatic. Just like backups on personal computers.
— A good measure is one that is easy and cost as little time as possible.
From that point of view…night time measurement can’t be beaten!
— All these three arguments -unforgettable; easy; fast – to say that it could have HRV bring its benefits to a much broader audience than the very small “nerdy, very motivated athletes club”. Making morning HRV measure easier than oral temperature. Making HRV a data tele-medecine could easily use in therapy and prevention.
( I’m going to sign Dr Monfort ;-) )
– On the theoretical side
In a more recent article you acknowledge that patient/athlete self measures cant vary a lot from a moment to the other. Averaging measure over, let’s say the 60 mn after 2 hours from going asleep time , would radically eliminate this moment to moment variation
– On the prospective side
Fitbit whom you work with is introducing HRV to improve sleep quality assessment. Wouldn’t Fitbit devices give measures that Ithlete could crunch and interpret ? …
Yours
Yves-Marie
Dear Yves-Marie,
I hear you and I am with you! To become really commonplace, the HRV reading has to be done unobtrusively and without the need for a discrete sensor. This makes fitness wearables the obvious choice. The only problem (and it is a big one) is that the top of the wrist is simply not a good place to observe beat to beat HR. I have personally evaluated almost 10 different consumer devices, both general fitness and specialised, and none of these are even close to accurate enough. However I live in hope that they will get better over time, and that it will be possible for HRV to be used as a valuable health metric in the general population (which was the reason I became interested in HRV to start with).
Dear Simon, I’m thankful for your care and dedication.
Yes it is a road worth travelling on. Yes it will be a long road. As a small step , what do you think of placing the optical sensor on the inner, soft, blood irrigated part of the wrist ?
And yes not only are you one of a handful of HRV specialists but among them you might well be the one who succeeded the most to make it benefit a maximum of people.
Thank you Simon for bringing up this subject which is paradoxically of basic usefulness and understudied.
Thank you, Yves Marie for the feedback. As I said in the previous reply, I wish more research was done in this area. Perhaps it will come from analysis of data capture by wearables, as suggested here http://pages.himss.org/m000VZ30v2yR1GcpLeT0ZW0
At least for me, this Massachusetts Lyme successful prevention is a milestone in the beginning of the 21 st century. I hope money will flow in such studies. It would be a lot the NHS ‘s of the world could spare… with the “side benefits” on individual lives and life quality…Yves-Marie Monfort