Heart Rate Variability (HRV) and Recovery
Our heart rate refers to the number of heartbeats every minute, but the number itself does not describe the rhythm of these beats. Heart beats are inconsistent and the small degrees of variability between each beat is completely normal. Heart rate variability (HRV) reflects the average time difference in milliseconds between consecutive heart beats.
It is regulated by our autonomic nervous system (ANS) and the balance between its two divisions, the parasympathetic nervous system (rest and recovery) and sympathetic nervous system (stress and exertion).
Tracking HRV
There are several different means to track HRV, from wearing watches (Garmin, Whoop) and rings (Oura) to downloading an app on our phone (HR4) and connecting it to a chest strap. Normative data is very broad and highly individualized, but we tend to see a trend of decreasing HRV as we age. That being said, Kiss et al found that this trend is negated when individuals stay highly active. Everyone’s “normal” is specific to them (1).
HRV and Injuries
As mentioned above, our HRV is controlled by our ANS which is also involved in regulating tissue repair. When we see a disruption in our typical HRV, it may reflect changes to the ANS and our body’s ability to recover. While it is difficult to predict an ankle sprain from a misstep or a hard collision on the field, tissue changes during periods of overloading often occur before we identify symptoms or pain. HRV appears to be an objective, non-invasive biomarker of our ANS health that may help us to predict and mitigate overuse injuries (2).
When wearing tracking devices, it takes a period of time for the technology to learn your average HRV and related trends. We can use these metrics and trends to try to predict and prevent injury. Williams et al followed crossfit athletes over 16 weeks and tracked their acute to chronic workload ratios (ACWR) and their HRV. They found that athletes who had higher ACWRs (periods of overtraining) were “very likely” to report an overuse injury the subsequent week if they concurrently had a reduced HRV (3).
When your HRV dips below your typical range, it may indicate something in your system is off. This can cue us to pay more attention to our training program and recovery methods and make adjustments to help us stay healthy and perform at our best. HRV monitoring is thus an important tool to inform our decision making and individualize our programming.
How to Restore HRV
HRV reflects our readiness to train and performance can begin to decline if recovery is neglected (4). Outside of appropriate programming, our best recovery tool is adequate sleep. Milewski et al followed over a hundred student-athletes and found a significant correlation between sleep deprivation and increased risk of injury, up to around four times the risk of reducing sleep time from 9 hours to 6! (5) Sleep plays an important role in injuries, pain, and recovery and you can read more about it here.
Diet is another factor shown to help in HRV recovery, such as eating adequate protein and leafy greens while consuming less fast food, alcohol, sweets, and red meat (6, 7). See a registered dietician for more specific information pertaining to diet and performance.
Zooming Out
HRV is a useful tool indicative of our heart health, fitness, and ability to recover. We can use it as a tool to prevent overuse injuries and we can best support our HRV (and by extension, ourselves) through improving our overall fitness, eating a healthy diet, and getting consistent sleep. It is not a number to obsess over and beat ourselves up about, but rather another useful tool for us to feel strong and perform at our best. Happy training!
Left: Ben on Waterworks with the Garmin Forerunner 165 Music
Right: Aly finishing the Missoula Marathon with Garmin Forerunner 745 and Whoop
Written by Benjamin Blakely PT, DPT, CSCS
References:
Kiss, O., Sydó, N., Vargha, P., Vágó, H., Czimbalmos, C., Édes, E., … & Merkely, B. (2016). Detailed heart rate variability analysis in athletes. Clinical Autonomic Research, 26(4), 245-252. https://doi.org/10.1007/s10286-016-0360-z
Gisselman AS, Baxter GD, Wright A, Hegedus E, Tumilty S. Musculoskeletal overuse injuries and heart rate variability: Is there a link?. Med Hypotheses. 2016;87:1-7. doi:10.1016/j.mehy.2015.12.003
Williams S, Booton T, Watson M, Rowland D, Altini M. Heart Rate Variability is a Moderating Factor in the Workload-Injury Relationship of Competitive CrossFit™ Athletes. J Sports Sci Med. 2017;16(4):443-449. Published 2017 Dec 1.
Dong, J. (2016). The role of heart rate variability in sports physiology. Experimental and Therapeutic Medicine, 11(5), 1531-1536. https://doi.org/10.3892/etm.2016.3104
Milewski MD, Skaggs DL, Bishop GA, et al. Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. J Pediatr Orthop. 2014;34(2):129-133. doi:10.1097/BPO.0000000000000151
Park SK, Tucker KL, O'Neill MS, et al. Fruit, vegetable, and fish consumption and heart rate variability: the Veterans Administration Normative Aging Study. Am J Clin Nutr. 2009;89(3):778-786. doi:10.3945/ajcn.2008.26849
Murray, O. and Vick, R. (2016), The Correlation between Heart Rate Variability and Diet. The FASEB Journal, 30:754.2.https://doi.org/10.1096/fasebj.30.1_supplement.754.2