I’ve been experimenting with HRV for some time now, trying to tie it into my triathlon training regimen and was going to figure all this science stuff out.
Over the past several years there have been a lot of studies and training using Heart Rate Variability (HRV) as a tool, and it’s becoming a kind of buzzword in the athletic world. HRV is the small variation in timing between heart beats….times in the millisecond range.
In a nutshell, the more variable the heart beat timing, the less stress and the more the autonomic nervous system is in control. And the more constant the timing between beats, the more stress and the more the sympathetic nervous system is controlling the heartbeat. Ultimate stress example….being chased by a tiger …that heart beat is locked in tight, really tight (besides being a million beats per minute)! Stressors can be physical, emotional, dietary, disease, and subsets of all of those mentioned.
The picture is an EKG of a heartbeat; the distance between the “R wave” peaks is shown in milliseconds. Here the variation is quite large; from 754 to 845 milliseconds. This is a relaxed patient, under no stress. The heart rate shown here is roughly 70 beats per minute if read by your heart rate monitor. It has to be a more accurate measuring system than the average wrist-worn monitor to pick out those timing differences.
So I got a new heart rate belt, one that will work with the smartphone app I chose for HRV (there are several available), and proceeded to measure my heart rate variability every morning, just after I woke up, to see how my previous day’s workout affected me, and whether I was working too hard or not working hard enough to warrant a day of recovery. Surprisingly, the results were not at all what I expected.
As a benchmark, I used my Training Peaks CTL (chronic training load) and Fatigue numbers to verify if the HRV numbers, before starting my daily workout, had any correlation with my previous day’s exercise stress. I thought it might help me to figure out whether or not I needed recovery that day [down time], for my body to heal itself. Surprise! The correlation was very slight. Only if I beat myself silly for a couple days would my HRV numbers really begin to show low variability numbers. Here are examples of my experiments, and what researchers have found, that show up as HRV-indicated stress, besides a grueling workout.
- Alcohol use: Effects can last as long as 4-5 days, slowing recovery and ability.
- Emotional stress: I’ve noticed this has a big effect. My body thinks I’m in danger.
- Beginning of a viral or bacteria infection: The body is gearing up and antibodies are working overtime. Sometimes I wasn’t even aware of the impending disease, and it didn’t show up as an increased load in Training Peaks. I thought I just felt a bit more worried than usual.
- Emotional intelligence: Yup, not surprised; having an awareness of being controlled by your emotions and also being aware of them in your daily life, seems to hasten recovery.
Turns out that my intuition and how I’m feeling are actually fairly good indicators of whether I really need more recovery. Looking at my results on Training Peaks for Fatigue seem to be fairly good indicators, besides having sore muscles or feeling somewhat down upon waking up, even after coffee!
The HRV indicators can get amazingly complicated, and researchers are looking at more components of the data, using many mathematical algorithms as well as analysis of low and high frequency components of the EKG wave. I admit this is the kind of stuff I love as a scientist, but as a triathlete and coach, where the rubber meets the road in today’s world, that depth of biophysics is outside of my daily metaphorical scrum.