As a coach, I spend a large proportion of my time discussing recovery to avoid over-training and maximize adaptation from harder workouts. Historically this has been a more subjective concept, since any individual’s idea of being well recovered depends on their day-to-day lifestyle. However, being able to objectively assess the effect of all the stressors during the day, not just how hard the runs are, is somewhat of a holy grail for optimum training.
What is Heart Rate Variability (HRV)?
HRV is the difference in timing between heartbeats. Your heart has an irregular rhythm that causes the timing between each beat to change, and HRV is a statistical measurement of that heart rate irregularity. Originally used as a predictor of survival after acute medical emergencies, this is an area that’s attracting a lot of medical study regarding relationships to health and wellness. HRV has been shown in studies to positively correlate with athletic performance and training adaptation, and to negatively correlate with the risk of overtraining and injuries. Additionally, HRV is lower in individuals suffering from acute anxiety, stress or PTSD.
What Does Heart Rate Variability (HRV) Measure?
Our heart rate has irregularity because of our Autonomic Nervous System, which is the part of the nervous system responsible for the control of bodily functions not consciously directed, also including breathing and digestive processes. This system has two competing divisions, the sympathetic (this can be thought of as the “fight or flight” division, responsible for activation) and the parasympathetic (this can be thought of as the “rest and digest” division, responsible for deactivation).
Within your body are constant stimuli forcing these two divisions to interact with each other. “On” switches correlate to your sympathetic branch, and “off” switches correlate to your parasympathetic branch. Your body is exposed to various situations all the time that require these switches to be turned on and off, such as changes in the intensity of movement. The faster they can be switched, the better your body can adapt quickly to changes. This means that the more rapidly the on-off switches work, the more energy can be tapped into for an activity, resulting in faster reactions, faster running and more endurance.
What Does High and Low HRV Mean in Ultra Running?
High HRV means you’re getting both strong “on” and “off” outputs and your body is highly responsive to your environment. It can quickly shift energy to easily match its surroundings. Low HRV means that either your sympathetic or parasympathetic system is holding back the other, meaning your ability to respond to the inhibited branch’s inputs is reduced. However, everyone’s absolute HRV is different and it is changing in your individual HRV that corresponds to better or worse levels of recovery. There is no optimal number we all should be striving for.
How Does Heart Rate Variability Help with Ultra Marathon Training?
For all athletes, relative HRV changes indicate an athlete’s ability to tolerate and respond to a given exercise stimulus. Training factors that affect HRV the most are volume, intensity, novelty, complexity and the degree of Central Nervous System stimulation. In addition, HRV is affected by the time of day when training or other stressors occur.
How Do I Use HRV to Recover from an Ultra Run?
Recovery can be optimized by monitoring HRV following workouts, especially if this can be summarized to allow for the overall stresses on the body over an entire day, including the quality of recovery through sleep. HRV allows a more precise way of tracking changes in recovery levels, which is crucial for preventing extreme accumulation of physical fatigue during training. The more power, speed and strength in a training run, the bigger the strain on the body, requiring better or more recovery.
Note that reactions to training are highly dependent on an individual’s training history, demographic info and current training load. Often recreational athletes try to train as if they were professional athletes but it takes a long time to build tolerance to higher workloads in training. To train like a pro, you need to be able to recover like a pro, and HRV is an effective way to measure your recovery.
Dong, Jin-Guo. “The role of heart rate variability in sports physiology.” Experimental and Therapeutic Medicine 11, no. 5 (2016): 1531-536. doi:10.3892/etm.2016.3104.