(Here) is a link to more details on a recent post from ithlete which they asked me to publicise. I’ve also included the summary below in case you are pressed for time.
Relatively untrained runners had their HRV monitored and the type of recommended session varied according to each individual’s HRV at the time.
ithlete is a very low cost ‘waking HRV’ app. It requires a smartphone and chest HRM.
This study puts HIIT for recreational runners into action, using HRV to select the days when the participants bodies were best equipped to both tolerate and benefit from high intensity intervals. The HRV guided group ended up doing significantly more HIIT sessions than the control group, but any prescribed training plan would have to err on the side of caution when prescribing a number of HIIT sessions per week, especially in the case of less experienced / novice runners in order to avoid injury and potential overtraining.
What is most notable about this study is that every participant using HRV guidance improved more than their ranked equivalent in the control group.
The relatively simple protocol also makes this technique highly applicable even to self-coached runners, armed only with a smartphone and preferably a running watch capable of showing pace, based on either stride length or GPS.