1st QUESTION: What is the main mechanism on which HIIT is based?

2nd QUESTION: What percentage of maximum heart rate is mentioned as anaerobic threshold?

It is completely safe for everyone
It is recommended to avoid all types of machines
People with joint or heart problems should approach with extreme caution and prefer low-impact machines
Ignoring weekly recovery times is inconsequential

Deep joint warm-up is not necessary
It is imperative to perform a deep joint warm-up and to respect recovery times to avoid overtraining
No risk of overtraining
Only the increase of sessions reduces the wear and tear of the central nervous system