Originally Posted by wj4
Can you set up an example of a H.I.I.T. routine? I think I understood the gist of your post, but I just want to be sure.
Anything that includes high levels of work followed by rest is HIIT in my eyes. So weight training with loads between 70 to 100% of 1RM for sets at or near failure followed by 30s to 5 minute rest periods in between sets is HIIT. The amount of rest and the load used will depend on what you're trying to do with your training. Some may disagree with this interpretation of HIIT which is fine, but ultimately you will still receive the benefit of EPOC if done properly as well as the bonus of recruitment of much of the muscle fiber continuum.
Someone already mentioned the Tabata protocol (20s of effort, 10 seconds rest, repeated 8 times for total of 4 minutes). This is a good way to tax the lactic acid energy system. However, due to the very short rest periods, you aren't able to use heavy loads. You can manipulate the Tabata to match your level of fitness (15s on, 15s off; 10s on, 20s off; decrease the number of rounds). It's not easy. Use multi-joint movements like the back squat, front squat, or pushups.
Sprint Interval Example with 1:3 work to rest ratio
60s on, 180s off repeat 1 times
45s on, 135s off repeat 2 times
30s on, 90s off repeat 3 times
20s on, 60s off repeat 3 times
15s on, 45s off repeat 4 times
Total work time = 7m 05s
The intent must be full effort on each sprint despite fatigue; I wouldn't do this on a treadmill. Ultimately, the program you make and the methods you use should match your training goal and should be progressed weekly for 2 to 5 weeks followed by a week of decreased volume (deloading) in preparation for your next training phase.