Heart rate variability (HRV) is a key metric discussed in the podcast episodes, as it is an important indicator of autonomic nervous system balance and overall health and recovery status.

In episode "Screen apnea": How our use of tech affects our breathing, HRV monitoring is mentioned as a tool for assessing breathing quality and stress levels related to the phenomenon of 'screen apnea'.

The importance of HRV is further explored in episode Unlocking Your Body's Potential with WHOOP CEO Will Ahmed, where the host dives deep into the science behind HRV, its relationship to sleep and recovery, and how wearable technologies like WHOOP can be used to track and optimize these metrics.

Understanding and managing HRV is crucial for optimizing overall health, performance, and longevity, as discussed across these podcast episodes.