Hi there,
I am currently reading your HIIT science book and I recommend you talk about this topic on the podcast as it is generally believed that active recovery is better. “Maximizing work capacity during subsequent intervals. Since active recovery can lower muscle oxygenation (15, 22), impair PCr resynthesis (O2 competition), and trigger anaerobic system engagement during the fol- lowing effort (50), it may be recommended to use passive recovery typically to allow the maintenance of work quality, and in turn, a longer Tlim (i.e., figure 4.7a) (Laursen & Buchheit, 2019).”
Have a great day!