by Andrew Flatt MS, CSCS

After purchasing my ithlete to monitor heart rate variability (HRV) well over a year ago I was unsure of whether to take measurements laying down (supine) or standing up. I don’t recall what it was exactly that prompted my decision, but I decided to measure standing. Since day one I’ve recorded my HRV in the exact same position (standing) after waking up for consistency. I often wonder however if this is the best way of measuring HRV for the purpose of monitoring training load and recovery status. Please understand that this article is simply my perspective on the topic based on my experience and research into the matter. Furthermore, I’ve yet to see this discussed in too much depth and therefore decided to investigate the issue myself.

In this discussion I wish to accomplish 3 objectives;

1. Briefly discuss the role of the autonomic nervous system (ANS) in controlling heart rate at rest and in response to orthostasis (standing up)
2. To  briefly review some of the research I have read pertaining to this issue
3. To present and discuss some data I collected over a two week period comparing my morning supine resting heart rate (RHR) and HRV score vs. my morning standing RHR and HRV score.

Heart Rate Mediated by ANS

Within the wall of the right atrium of the heart is the sino-atrial node (SA node). The SA node randomly initiates impulses that cause the heart to beat. The cardiovascular center of the autonomic nervous system located in the brainstem governs the SA node via parasympathetic and sympathetic innervation. More specifically, the cardiac accelerating center (sympathetic) and cardiac decelerating centers (parasympathetic) of the medulla are responsible for sending sympathetic and parasympathetic impulses to the heart in response to altered blood distribution and pressure requirements (exercise, stress, standing, laying down, etc.)

Sympathetic impulses increase heart rate by exciting the SA node while parasympathetic impulses reduce heart rate by inhibiting it. Thus, with parasympathetic predominance we can expect heart rate to be less frequent and less consistent (more variability between beats) while sympathetic predominance would result in more beats with less variability.

During supine rest, heart rate and blood pressure are lower as the body is in a relaxed state. From supine (a state of high parasympathetic activity and low sympathetic activity) to standing, there is a shift in sympathovagal balance characterised by a withdrawal of parasympathetic activity and a concomitant increase in sympathetic activity (Montano et al. 1994, Mourot et al. 2004). Naturally, the body needs to accommodate for postural change forcing the heart to beat harder and faster to pump blood to the brain; a task much less strenuous in the horizontal position.

Some Pertinent Research

Kiviniemi et al. (2007) provides a very through explanation of why HRV might be better measured in a standing position as opposed to seated or standing. Essentially, HRV is susceptible to saturation of the parasympathetic nervous system in subjects with low heart rates. Therefore, in athletic populations, changes in parasympathetic activity may be harder to detect. The authors state “In the present study, endurance training increased HF power measured at standing position but did not change HF power measured at sitting position. This supports our notions that orthostatic stimulus may be more favorable condition than sitting or supine positions to obtain specific information on the status of cardiac autonomic regulation in exercise intervention settings among relatively high fit subjects.”

Mourout et al (2004) saw decreased HRV in overtrained athletes compared to not overtrained athletes in the supine position. Similar results were found when HRV was measured after 60 degree tilt. The non-OT group always had higher HRV in the standing position and saw greater reactivity to the postural change.

Uusitalo et al (1999) saw similar results to the work mentioned above by Mourot. Overtrained athletes saw an increase in LF power in the supine position; lower HRV in the standing position; and decreased reactivity to postural change. Additionally, changes in maximal aerobic power were related to decreased HRV in the standing position.

Gilder and Ramsbottom (2008) wanted to test whether volume of training load resulted in changes in HRV in response to orthostasis. The authors findings in their words; “Women reporting higher volumes of physical activity had significantly higher levels of parasympathetic HRV than less active women while supine, but also demonstrated a much greater change in parasympathetic HRV in response to standing. It is of interest to note that short-term vagal measures of HRV for HV while standing are similar to those for LV while supine.”  *LV=Low Volume HV=High Volume

Grant et al. (2009) found that standing HRV indicators showed significantly more correlations with cardiopulmonary fitness indicators compared to supine measurements. The authors did however urge practitioners to use caution when attempting to measure fitness via HRV.

Hedelin et al. (2001) found that during a 70 degree head up tilt, LF power correlated to measures of strength and aerobic capacity. A greater shift toward LF power in the tilted position correlated to reduced performance. Changes in LF were linearly related to changes in performance suggesting a reflection of adaptation to training.

Hellard et al. (2011) measured HRV in swimmers to model a relationship between HRV and illness. The main results of this study were the following:

 “1) In winter, national-level swimmers showed a greater risk of pathology than international-level swimmers. 2) The weeks that preceded the appearance of URTI and pulmonary infection but also MA were characterized by an increase in autonomic parasympathetic activity in supine position. Conversely, in orthostatic position and in winter, the weeks that preceded the appearance of AP were characterized by a drop in parasympathetic activity. 3) During weeks characterized by URTI and pulmonary infection, a shift was noted in the autonomic balance toward sympathetic predominance in supine position and a drop in parasympathetic drive in orthostatic position. And 4) in winter and in orthostatic position, a drop in parasympathetic drive associated with an increase in sympathetic drive was linked to an increased risk of MA.” MA= Muscular Injury, AP=All type pathologies, URTI=Upper Respiratory Tract Infection

Huovinen et al. (2009) measured HRV and Testosterone-Cortsiol ratios in army recruits during a week of basic training (class room based). The authors stated; “In the present study, the correlation between the

testosterone-to-cortisol ratio and changes in heart rate, SDNN, and high-frequency power expressing an association between circulating ‘‘stress’’ hormones and cardiac vagal activity was apparent in the standing condition only. Thus, based on the results of the present study, measures of heart rate variability should be done not only at rest but also during a controlled sympathetic stimulation (e.g. during an orthostatic challenge).”

I will add that there is plenty of research that has demonstrated a detection of overtraining in athletes from measuring HRV in the supine position. The focus of this article however is on standing measurements.

I summarize my thoughts and conclusions on the research at the end of this article.

My Experiment: HRV Supine vs. Standing

Protocol:

• Wake up and go pee
• Return to bed and record HRV once HR stabilized from postural change
• Stand up and record HRV once HR stabilized from postural change

sRPE is my rating of perceived exertion of my workout from that day. Workouts rated as 8 or above were higher in volume and intensity while workouts rated as 7 were lower volume and intensity. A score of 5 or below represent active recovery work. Therefore it is the following day that will reflect quality of recovery. Keep in mind that workouts rated as 5 or above were resistance training based while workouts rated below 5 were more aerobic in nature to facilitate recovery.

I have highlighted four instances that showed conflicting scores. On all four occasions supine HRV is high while standing HRV is low. Each of these conflicting scores occurred on days following a higher intensity workout. Based on my trends and perception of stress I find that the standing scores to be a more accurate reflection of my training load. Generally after an intense workout I’m sore the next morning and fatigued from the workout.When reviewing my overall trends (not just these two weeks) usually HR goes up and HRV decreases in response to a high loading day (sRPE 8+). Likewise, HR will decrease and HRV will increase in response to a lower loading day. However, I’ve found this to be subject to change based on sleep quality and other lifestyle factors that can promote a change in HRV.

Non-training related stressors are not documented. This is a huge limitation as various forms of stress (mental, physical, chemical) can affect HRV.

Thoughts and Wrap Up

First and foremost, consistent measurements are more important than position. This is because each position appears to provide important data regarding training status. Therefore, pick a position and stick to it 100% of the time for your values to be meaningful. Switching positions from day to day will provide skewed data and affect daily ithlete colour indications.

In my opinion, endurance athletes and individuals with low resting heart rates are probably better off measuring HRV in a standing position to avoid the potential affect of “parasympathetic saturation”. A colleague pointed out an important point after I ran this experiment; a standing HRV measurement will produce a larger sample size of R-R intervals which decreases margin for error.

Nearly every paper I’ve read on HRV stresses that HRV varies a great deal between individuals. This means that you should not be comparing your data to others. In a team setting, it is important to always compare daily values to baseline (of each individual) for meaningful interpretations. A score of 80 may be high for one individual and low for another.

I like the standing test for the simple reason that it provokes a small stress response. This removes the issues of parasympathetic saturation from the supine position. Seeing how your body responds to standing appears to give you a good idea of how your body can/will handle stress that day. If HRV remains high after standing (given time to stabilize) then you are likely in an adaptive state. If HRV is low after standing (given time to stabilize) you are likely less adaptive (currently under higher stress).

HRV test length may influence positional preference. The ithlete measurement is a 1 minute test and therefore I don’t find the standing position to be a nuisance. However, I did prefer the supine measurements simply because I only needed to focus on breathing and nothing else. When measuring HRV with devices of longer duration I preferred the supine or seated position.

Ultimately, you should experiment for yourself to determine positional measurement preference. Try recording data in both positions, compare it to perceived stress (training, mental, chemical, etc) and determine what method you like best.

References

Gilder, M., & Ramsbottom, R. (2008) Change in heart rate variability following orthostasis relates to volume of exercise in healthy women. Autonomic Neuroscience: Basic & Clinical, 143(1-2): 73-76

Grant, C. et al. (2009) Relationship between exercise capacity and heart rate variability: supine and in response to an orthostatic stressor. Autonomic Neuroscience: Basic & Clinical, 151(2): 186-188

Hedelin, R.  et al. (2001) Heart Rate Variability in athletes: relationship with central and peripheral performance. Medicine & Science in Sports & Exercise, 33(8), 1394-1398.

Hellard, P. et al. (2011) Modeling the Association between HR Variability and Illness in Elite Swimmers. Medicine & Science in Sports & Exercise, 43(6): 1063-1070

Huovinen, J. et al. (2009) Relationship between heart rate variability and the serum testosterone-to-cortisol ratio during military service. European Journal of Sports Science,9(5): 277-284

Montano, N. et al. (1994) Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt. Circulation, 90: 1826-1831

Mourot, L. et al (2004) Decrease in heart rate variability with overtraining: assessment by the Poincare plot analysis. Clinical Physiology & Functional Imaging, 24(1):10-18.

Uusitalo et al. (1999) Heart rate and blood pressure variability during heavy training and overtraining in the female athlete. International Journal of Sports Medicine, 20: 45-53

Author Profile

Andrew Flatt currently resides in Toronto, Ontario, Canada. He holds a Master’s Degree in Exercise Science with an interest pertaining to HRV and its application to monitoring training status in athletes. Andrew is a competitive powerlifter and former collegiate football player.

For more information about Andrew, visit his blog hrvtraining.com, read his ithlete case study or follow on twitter @andrew_flatt