Monitoring HRV: Why the Orthostatic Stressor is Best and How to Make it Practical
Tips for athletes interested in HRV monitoring
Heart rate variability (HRV) is widely used to assess our stress response, recovery needs, and training adaptation. However, there are important considerations to make in relation to the best way to measure HRV for this specific application (i.e. for athletes of all levels).
Recent research (Gronwald et al. 2024) suggests that morning HRV is the more effective option, due to the orthostatic test.
In this blog, I will provide an overview of what the orthostatic test is and add practical tips to exploit this mechanism during your morning measurements without adding unnecessary complexity.
I was just having this same conversation with my co-authors for our upcoming “HRV book”, and I think it could be useful to the many people using our tools as well, hence I am elaborating on this here as well (as it will take a little longer to get that book done!).
The only way to exploit the orthostatic stressor is in the morning
Morning HRV provides additional value when measured after a postural transition. This is referred to as an orthostatic stressor, i.e. the autonomic response to a change in body position.
Gronwald et al. describe the physiological response to posture change as follows:
When transitioning from lying to sitting or standing, parasympathetic activity is rapidly suppressed, leading to an increase in heart rate.
This is followed by sympathetic activation, which stabilizes blood pressure and cardiac output.
In healthy individuals, vagal tone is gradually restored, but the timing and magnitude of this response can vary based on fatigue, training status, and overall autonomic balance. This is really what we are after here with our measurement.
The key point is that this response does not occur at night (obviously). Nighttime HRV measurements do not include a postural change, which means they lack this additional source of physiological information.
Several studies support the use of morning HRV over nighttime HRV when tracking training adaptation and recovery.
Kiviniemi et al. (2007) found that morning HRV recordings more accurately reflect physiological stress and recovery compared to nighttime data. As reported by Gronwald et al.:
“Thus, a sitting or standing body position possibly implies an autonomic stressor of interest, with enhanced sensitivity compared to a measurement in supine position. For example, in the case of highly trained endurance athletes (especially with high volume of low-intensity aerobic training), despite high parasympathetic activity, this cannot be meaningfully represented via supine HRV analysis“.
Schmitt et al. (2015) reached a similar conclusion, noting that morning HRV, particularly when incorporating an orthostatic stressor, was a better predictor of training adaptation and fatigue than nighttime HRV.
“In this context, Schmitt et al. (2015a) argued that HRV values obtained only from supine position do not provide information about the preserved or altered ability of dynamic adjustment of the autonomic nervous system. They also suggested that especially HR(V) changes between supine and standing position as an orthostatic response assessment could better inform about cardiovascular autonomic functioning and fatigue state and may therefore potentially further enlighten non-functional overreaching and chronic overtraining response processes“.
In other words, if the goal is to assess autonomic function in response to training stress, measuring HRV after waking—while incorporating an orthostatic stressor—provides a clearer signal. None of this should be news to you, as I’ve been discussing it a few times in previous blogs. However, the point of this post is that there are differences between the original Orthostatic Test and how I recommend measuring HRV outside of the lab, differences that have a practical origin and that I want to clarify below.
How to make it practical: measuring while sitting
The traditional orthostatic test involves measuring HRV in both lying and sitting or standing positions to track autonomic reactivity. This test is often performed in research settings using a tilt table, which standardizes the postural change and eliminates movement artifacts. However, this is not practical for daily HRV monitoring.
For home use, standing up introduces movement artifacts, breathing irregularities, and postural instability, all of which can distort HRV data. Measuring in both lying and standing positions also adds unnecessary complexity, requiring users to track multiple variables (supine HRV, standing HRV, HR change, HRV change, time to peak HR), which may reduce the actionability of the data rather than improving it.
Instead, I recommend a simplified approach that still leverages the orthostatic stressor but eliminates unnecessary steps:
Lie down for a few minutes upon waking (e.g. 1-2 minutes if you had to go to the bathroom first).
Sit up and start measuring within ~30 seconds.
Use this sitting measurement as your morning HRV value.
This method still captures the key autonomic response to a postural change while eliminating unnecessary steps, and is what I’d consider the best of both worlds: you are using state-of-the-art research recommendations to measure your morning physiology in response to training (and other) stressors, exploiting the orthostatic stressor, but also keeping it practical.
This approach is faster, easier, more actionable, and more reliable for daily tracking (in my opinion). It might still be worthwhile in certain research settings to explore the data and full Orthostatic Test protocol, but I think that would just be confusing for daily tracking.
I think that it is important - especially for athletes - to exploit the orthostatic stressor and measure shortly after sitting up - but not to perform and record the entire standard Orthostatic Test protocol.
Final thoughts
HRV is a valuable tool for monitoring training adaptation and recovery, but when and how it is measured matters. The research suggests that:
Morning HRV is more effective than nighttime HRV because it provides a clearer reflection of autonomic recovery, without the confounding influence of sleep-stage variability, and previous day stressors.
An orthostatic stressor enhances the sensitivity of morning HRV, as it captures the autonomic response to a postural change, something that cannot be captured with night data. As a result, night data tends to be less sensitive to important training-related changes (e.g. overtraining).
A simple morning HRV measurement after sitting up provides the benefits of an orthostatic stressor while avoiding the practical limitations of a full orthostatic test.
For those looking to incorporate HRV into their routine, a structured morning measurement protocol is likely to be the most effective approach. See here for more details about morning protocols.
Keep in mind that I do understand there are also practical considerations, but those do not make night data suddenly effective at capturing your training-related response. Research shows there’s only one reliable way to use HRV to track subtle training stressors—including overtraining, and that is via a morning orthostatic stressor - not with night HRV data collected with wearables. It seems that marketing and science keep diverging on this one.
That’s all for this post, I hope it was informative, and thank you for reading!
[Research] More Evidence in Support of Morning Protocols
![[Research] More Evidence in Support of Morning Protocols](https://substackcdn.com/image/fetch/$s_!N-NG!,w_1300,h_650,c_fill,f_webp,q_auto:good,fl_progressive:steep,g_auto/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Fdbcd4fb6-a5c1-4c1b-bf8b-cec3f7bf1713_2220x1658.png)
Today I was reading a few recently published papers, and I was glad to find one by Gregoire Millet and co-authors, led by Thibaud Pirlot. This is a group that has been doing very interesting research for decades, and that has been looking in detail at various protocols and metrics in the context of capturing autonomic nervous system changes in relation…
Related articles
How to Show Your Support
No paywalls here. All my content is and will remain free.
As a HRV4Training user, the best way to help is to sign up for HRV4Training Pro.
Thank you for supporting my work.
Endurance Coaching
If you are interested in working with me, please learn more here, and fill in the athlete intake form, here.
Marco holds a PhD cum laude in applied machine learning, a M.Sc. cum laude in computer science engineering, and a M.Sc. cum laude in human movement sciences and high-performance coaching.
He has published more than 50 papers and patents at the intersection between physiology, health, technology, and human performance.
He is co-founder of HRV4Training, Endurance Coach, guest lecturer at VU Amsterdam, advisor at Oura, and editor for IEEE Pervasive Computing Magazine.
He loves running.
Social:
Hi Marco, I’ve just started with the app & been taking an HRV reading sat-up with feet still in the bed (legs horizontal). Should I sit-up sat on the edge of the bed (feet on the floor) to create enough of an orthostatic stress? Thanks for your time.
Ok, hear me out.
For practical reasons, I'm thinking of getting up, going to the bathroom, sitting on the toilet to pee and then taking the HRV reading while sitting on the toilet
Is that enough time to get a good reading?
In the winter when it's chilly will this affect the reading?
Should I just go back to bed and sit up there?