Guys,

I'm currently doing a 1:3 protocol on HIIT. What I notice is that when I use this protocol, I find it difficult to reach 95% of my MaxHR. I also am not able to lower my HR to 60-65% during my rest interval (1m 30s). However, I notice that when I rest a little longer like 3:00, I can easily get to 95% of my heart rate.

My question is, is it more practical for me to wait long enough so that my HR lowers down to 60-65% or is it more important to stick to my rest interval as stated above? Is it still HIIT if I bump up my protocol to 1:4 or even 1:6?

Hope you guys can help me out on this. Cant seem to find my zone. Cheers!

Part of the reasoning for the recommendation of HIIT is that it shortens cardio workouts and maximizes overall caloric expenditure by maintaining a high intensity for a large portion of the overall exercise. In general terms, anything over 75% of max HR can usually be considered high intensity (even lower than that in unfit individuals from a perceived exertion standpoint). That being said, I've not seen enough research that specifically compares different HIIT regiments to be able to soundly say that one HIIT regiment is more correct or effective than another.

However, at such a high intensity (95%) your body will be utilizing far more carbohydrates than fats, and you face an increased chance that you are impeding overall fat metabolism because you are operating past aerobic capacity and so close to exhaustion. Because of this, and because of the fact that you are so close to anaerobic limits, in terms of ratios of overall caloric expenditure, you are probably burning more calories overall exercising at a 1:2 or 1:3 ratio and a lower max intensity and high minimum intensity than you are at a 1:4 or 1:6 ratio at high max intensity and lower min intensity over the same amount of time. This is because of the fact that as you breach the 90% range, caloric expenditure as a function of intensity actually begins to plateau because your body is nearer to overall capacity and because of the negative impact on fat utilization. The negative impact on fat utilization stems from increased limits placed upon aerobic oxydation due to the fact that energy from anaerobic oxydation of carbs that is used to provide the required "start-up" energy needed for aerobic oxydation of fats is instead being utilized for motor production.

So in essence, you're may not be burning as many calories overall at a 1:4 95%, 65% than you are with a 1:2 85%, 75%, and significantly impacting the utilization of fats, and as a result, the amount of fat burned during exercise.

Wow illiniphase4, thanks for that thorough explanation! That's very educating. I've always had the impression that the closer you get your maxHR, the better it is for overall fat loss. I thought when they say that "going all out" means trying to hit 95%. I'll try to adopt a "lower max intensity and high minimum intensity" on my next session. Thanks again for the information!

There is no ' hard and fast rule ' that says your work interval has to hit 95% of my MaxHR or that your rest interval must drop to 60-65%........you just have to play it by ear and do what seems most comfortable for you.

So, if you find that resting a bit longer gets you the intensity of work interval you want, then go for it.

I'd just find a rest interval that allows you give 100%+ - at the duration / intensity you want - on all your work intervals. So, if a given HIIT session involves a total of 7 - 10 work intervals for example, you want to be rested enough so you can give 100%+ on each one.

Thanks for the input Wrangell! I'll be keeping that in mind. I'll just have to find which one fits me more. Thanks!