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.
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.
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!