Heart rate variability is where the amount of time between your heartbeats fluctuates slightly. These fluctuations are undetectable without specialised devices, like the WHOOP band. HRV can indicate current or future health problems, including heart conditions and mental health issues.
Your heart’s variability reflects how adaptable your body can be, so – generally – low heart rate variability is considered a sign of current or future health problems because it shows your body is less resilient and struggles to handle changing situations.