Time of measurement

We recommend taking your ithlete heart rate variability (HRV) reading first thing in the morning, preferably right after waking. There are several reasons behind this recommendation…

Following a full night of rest

It’s a well-known fact that the body’s rest and repair functions are most active during sleep (which is why it is so important for a good recovery!). During sleep the parasympathetic branch of the ANS is dominant, rebuilding and improving muscles from workouts and fuel stores. So following a nights rest is the best time to measure what your body can handle today.

Informed daily decisions

Measuring first thing in the morning allows you to adjust your day’s training plans according to the ithlete colour coded recommendation. So a morning measurement is practical; you can make your training plans based on your body’s readiness to train after a full night of recovery!

Additionally overtraining can affect almost every aspect of life, including appetite, sleep (both need for and ability to) and perceived stress. For more on overtraining symptoms check out our full post here. With this in mind morning measurement is even more important, helping you eat and behave in the way your body needs.

Before the day gets going


Heart rate variability is the most accurate window to your autonomic nervous system (ANS) activity – a great measure of stress. Monitoring ANS activity with heart rate variability allows users to get a snapshot of their body’s current stress level, but it’s important to remember your body – and readiness to train – is affected by much more than the physical stress from yesterday’s workout.

Stress comes in three main forms, physical, mental and chemical; and all stimulate the same reaction from the ANS. So to bring this back to the importance of measuring heart rate variability in the morning, the impact of a quick coffee, or a rush getting children off to school, for example, will significantly increase your body’s short term stress levels and so ANS activity and affect your reading. You wouldn’t want to base your training session on skewed results.

Whilst this is something we will look at in more details in future Tuesday Tips essentially variable external factors have a considerable impact on your heart rate variability, so measure in the morning to avoid misleading readings.

How heart rate variability behaves throughout the day

In the past users have asked us why their measurement is higher than they would expect compared to normal morning readings – surely, as in the paragraph above, daily stressors would lower your HRV?

Heart rate variability is actually counter-intuitive, the higher the variance between heartbeats the better your body is prepared to respond to demands placed upon it. So you would expect the number to decrease throughout the day as cumulative stress (physical, mental & chemical) increases right? Well yes, but we must take in to account one other thing… The Cortisol Awakening Response (CAR).

CAR is the term given to the body’s process of waking you each morning, flooding the body with cortisol to wake you. However, cortisol is also well known to be a stress hormone, raising blood pressure and heart rate. So your body is under perceived stress first thing in the morning due to the CAR. This is also why a larger number of strokes and heart attacks take place in the first morning hours after awakening.

The reason we suggest measuring first thing in the morning despite the effect of CAR is to avoid the influence of variable external factors such as life stress, work stress, caffeine etc. (above). CAR is a constant influence placing the same amount of stress on the body each morning – so it won’t impact your daily change from baseline and training recommendation.

On the other hand, if you get up especially early one day before the CAR has had time to kick in, you may find your HRV considerably higher than normal. Just something to be aware of!

Be consistent!

Although we recommend measuring right after waking some people do prefer to go to the bathroom first, some users even do some gentle morning exercise or shower before taking their reading. If this suits you best that’s fine, but take a couple of minutes to relax before your measurement and above all be consistent.

Other users have contacted us to ask about how to cope with shift work and when to take their ithlete measurement. We’d recommend picking a point in the circadian rhythm (such as upon waking) and stick with that. The shift work may have some impact, but this is the best way to minimise disruption.

The most important piece of advice we can give to any ithlete user is to be consistent with your measurement practice, ensuring the daily recommendations are always meaningful!

We hope you found this post useful and would love to hear what time of day you take your ithlete HRV reading and why – leave us a comment below!