I've been getting a lot of questions about implementing heart rate variability monitoring with patients, so I wanted to write a quick post about it. Figuring out best practices is still a work in progress, but there are some simple, accessible means of tracking HRV in our athlete-patients.
We have a long way to go as far as understanding how to best utilize heart rate variability as an objective measurement in clinical practice. However, a great deal of research has been dedicated to monitoring athlete's training response using heart rate variability, and it seems that the field is nearing closer to a consensus on best practice. In this post I will explore a couple different means of utilizing HRV with patients who are training (runners, triathletes, cross fitters, body builders etc).
First, let's look at some of the literature surrounding measuring athlete HRV. The most common recommendation we see when it comes to measuring HRV is CONSISTENT METHODOLOGY. Above all else, consistency in measuring appears to be the most important aspect of checking HRV (1). Many of the studies that have been done, and much of the literature on the topic has athletes measuring their heart rate variability first thing in the morning within 5 minutes of waking up to get as close to an at rest measurement as is possible (1,2,3).
Given that there are many individual variations in HRV it is also very important to note that subjective measures must be taken into account including the athlete’s mental state (are they apathetic towards training), energy levels (are they experiencing lethargy), and, most important to the athlete, are they performing well (has their performance declined recently)? Correlating weekly variations in HRV with subjective changes as mentioned above is paramount to interpreting an athlete’s physiological response to their training stress (4).
For those of us in practice this poses significant challenges to monitoring a patient’s HRV. If the patient is presenting to your office at different times of the day, the challenge becomes interpreting HRV changes done at inconsistent times. This creates significant reliability issues when trying to interpret physiologic changes week to week. HRV is likely going to become a great tool for pre/post adjustment checks and re-examination tests as well, but like I said before, there is a long way to go in figuring out best practices.
Due to the need for consistency in methodologies, I have been advising patients to use HRV4Training. This is a smart phone app that does 60 second rMSSD readings in the morning using nothing more than the phone’s camera. This easy to use app makes daily HRV monitoring incredibly accessible to patients without the need for a chest strap heart rate monitor. Numerous studies have investigated whether or not rMSSD could be accurately measured using a smart phone camera and found it to be a valid measurement that tend to agree with readings obtained from a chest strap or ECG (5,6,7). The patients who have been regularly monitoring simply send me an email from the app and I’m able to view what their readings have been (as well as whether or not they have been consistent in checking).
Despite it’s ease of use, the issue we have been having is developing patient compliance. Patients tend to forget to do the reading each morning. That probably doesn’t surprise anyone reading this. These compliance issues tend to be resolved after we communicate to the patient the importance of monitoring HRV. I have found it effective (and very necessary) to explain to patients initially, that exercise is a stress on the body. In fact, exercise itself is actually BAD for the body. Think about it. Exercise and intense training is actually a fight or flight stress. It is the subsequent adaptation to exercise that has health benefits. If the athlete (patient) is not adequately adapting to the stress, or worse, maladapting, then exercise can actually pose a threat to the physiology and result in sometimes pathologic symptoms. Not adapting and not recovering from workouts is how patients end up in a non-functional overreach or overtraining situation. Explain to the patient that measuring HRV gives us a direct measurement of how their autonomic nervous system and physiology is responding to training. High HRV is good, low HRV is bad. If your HRV is low, you are not adapting well to the training load you are under. Period.
Obviously this is a very simplified explanation of HRV. The purpose of this blog post is not to go into a deep exploration of HRV, but I strongly encourage each of you reading this to start looking into the role of measuring HRV not only for athletes but for general population as well.
To sum this post up, here is a brief explanation of what I have been doing with my athlete patients. The first thing I have them do is get the HRV4training app and begin tracking their HRV and emailing the readings to me on a weekly basis so I can assess their weekly trends. When the patients come to the office I talk with them about what type of training load they are under, as well as how they seem to be responding (are they improving performance, do they feel beat down, etc). Last, we examine how they do the day after they are adjusted and what changes they are noticing after getting adjusted in the office. I am seeing some excellent changes in HRV readings and subjective measures following Chiropractic adjustments, however it is way to early and too small of a sample size to begin to draw any inferences from it.
I encourage any DC with a large athlete population in their practice to begin utilizing simple measures to track HRV. Keep in mind that consistency is the most important factor!
1) Buchheit, Martin. "Monitoring training status with HR measures: do all roads lead to Rome?." Frontiers in physiology 5 (2014): 73.
2) Morales, José, et al. "Use of heart rate variability in monitoring stress and recovery in judo athletes." The Journal of Strength & Conditioning Research 28.7 (2014): 1896-1905.
3) Flatt, Andrew A., and Michael R. Esco. "Evaluating individual training adaptation with Smartphone-derived heart rate variability in a collegiate female soccer team." The Journal of Strength & Conditioning Research 30.2 (2016): 378-385.
4) Le Meur, Yann, et al. "Evidence of parasympathetic hyperactivity in functionally overreached athletes." Med Sci Sports Exerc 45.11 (2013): 2061-71.
5) Plews, Daniel J., et al. "Comparison of Heart Rate Variability Recording With Smart Phone Photoplethysmographic, Polar H7 Chest Strap and Electrocardiogram Methods." International Journal of Sports Physiology and Performance (2017): 1-17.
6) Bolkhovsky, Jeffrey B., Christopher G. Scully, and Ki H. Chon. "Statistical analysis of heart rate and heart rate variability monitoring through the use of smart phone cameras." Engineering in Medicine and Biology Society (EMBC), 2012 Annual International Conference of the IEEE. IEEE, 2012.
7) Jonathan, E., and Martin Leahy. "Investigating a smartphone imaging unit for photoplethysmography." Physiological measurement 31.11 (2010): N79.