SuppVersity - Nutrition and Exercise Science for Everyone: Making HIIT a Hit Part I/II: The Quest for the Opt...: This series  will not readdress  the "HIIT and/or LISS debate", but simply try to do what the title says: Help you to determine ...
Take home message: While it appears as if it would not make a difference 
whether you perform your HIIT workouts blocked or within your training week. The 
non-significant differences in figure 5 could suggest that endurance 
athletes intending to improve their already high VO2Max even further would be 
better off with the blocked training. Everybody else has the choice and I would 
pick the interspersed variety, whenever my schedule allows me to do this - my 
personal experience told me that this works better for me... apropos, take 
another look at figure 5 you see the narrow bars indicating the standard 
deviations? This goes to tell you that it is very likely that not just the 
personal preferences, but also the actual outcome will vary from trainee to 
trainee, which supports the notion that you will have to experiment to find what 
works best for you.
