When I started at Victoria University, I was going to be a computer scientist, and when Julian Thayer went to Boston’s noted Berklee College of Music, he was going to be a jazz bassist. Both of us ended up in psychology, or in Thayer’s case psychophysiology, but he’s both rather more famous than me and an accomplished bass player.
Psychophysiology is the study of the intersection of psychological and physiological phenomena. In particular, Thayer is a world authority on heart rate variability. In Thayer’s words, “When you inhale, your heart rate increases, and when you exhale it decreases … and, contrary to what you might believe, your heartbeat is not regular. And the more variability, in some ways, the better.”
When you stand up, your heart rate variability goes down, to make sure blood gets to your brain, for example. The time between beats is not perfectly regular, and that is often a good thing.
So far, so technical, but this is seriously important. If you have lower heart rate variability, your chance of survival is lower, says Thayer, because your body is less able to adapt to what you need in the moment.
Why? Part of the answer comes down to balance between the two command centres of our body – the sympathetic and parasympathetic nervous systems. The specific part of the parasympathetic nervous system that supervises heart rate variability is the vagus nerve – the Route 66 of our bodies because it runs from our eyeballs to our bladders. If we perceive a threat, our sympathetic nervous system kicks in to fight, flee, or freeze (in the hope that the serial killer won’t see us). If there are no threats, our parasympathetic nervous system activates the bodily functions we need to feed and (ahem) breed.
Evolutionarily, we have developed to experience times of threat – cue sympathetic – interspersed with peace (parasympathetic). This means a good amount of heart rate variability.
Greater heart rate variability (or HRV, as the pros call it) is associated with stronger connections to the part of the brain that detects safety. If you’re constantly perceiving threat – as Thayer suggests is the case for many black men in the US – you’re spending more time in sympathetic nervous system overload, with lower HRV.
For black men, and anyone experiencing chronic stress, low HRV means your engine is running on high all the time and, like any machine, it’s gonna break down sooner or later.
Perhaps a better analogy is our Route 66 vagus nerve: if the highway gets too much use, it makes for a bumpier ride. Cue cardiovascular disease, which, Thayer has shown, follows from reduced HRV.
But it’s not just physical health that is associated with this variability. In a study, Thayer and colleagues showed that Norwegian Navy sailors with high HRV demonstrated faster and more accurate performance on a cognitive test. Importantly, this difference was greatest for tests involving executive function – our higher-level decision-making faculties, such as planning.
As far back as 2000, Thayer was the first person to show a link between HRV and the neural circuitry that is involved in executive function. In short, greater variability means better thinking and particularly decisions. And the positives extend to broader psychological characteristics, too – empathic responding, attachment, and social interaction, to name just a few.
If HRV is a marker for future health, what can we do to improve our HRV resilience? You can probably guess a few strategies. Look after our bodies, particularly through good nutrition, sleep and exercise. It’s also possible to improve HRV by focusing on our breathing. In the lab or in therapy, this might involve biofeedback – practising breathing in response to feedback about what your heart is doing.
Unsurprisingly, biofeedback has also shown benefits for stress and worry. For now, just concentrate on in and out, in and out.
