Recovery: trust your gut feeling

How do you determine the duration of the recovery periods during an interval training? On your gut feeling according to recently published research findings published in Psychophysiology.

During the research three groups were asked to do a 5 times 1000 interval at 90% effort. Recovery was done by:

recover for teh same duration as the duration of the interval, the work to rest ration (WR)

recover untill the heartrate is below 130 BPM

recover on your feeling

Result: With the heartrate methode the later interval went slower. Based on feeling or the WR method there was no decline in the duration of the intervals. Howerver the recovery periods were shorter with the gut felling method.
I wonder how far the heartrate sank with the recovery periods but the this is not mentioned in the abstractof the report:(