What is heart rate variability?

Heart rate variability, or HRV for short, describes the way your heart beat varies - both at rest, and during exercise. Contrary to popular belief, the healthy heart does not beat like a metronome, but is constantly changing the time between beats in a rhythmic way. These changes are driven by the nervous system, constantly trying to find the most efficient way for the body to operate. The fact that the nervous system makes itself visible through HRV makes the heart a wonderful barometer of how hard your body is trying to preserve its equilibrium.

HRV has been used in hospitals for many years, mostly to help very sick patients whose beats are very regular, with little HRV, and has also been used in high end systems to help elite athletes. The widespread availability of heart rate monitor chest straps and the computing power packed into an iPhone mean that competitive & recreational athletes can now benefit from the big improvements in training effectiveness that HRV monitoring brings.

Intensive, or high volume, exercise will stress & tire your body, and this stress is reflected as reduced HRV. Recovery, which is vital both for improved athletic performance and general good health will cause your daily HRV to rise, letting you know that you are both getting fitter and avoiding staleness & sickness.