Not an "Either-Or" Issue
The current facts have been presented in parts 1 & 2, and the bases for conclusion should be self-evident. Let me clarify that HIIT and linear high-intensity cardio are not the best and only ways to go. Many folks have perfectly legitimate orthopaedic, cardiac, and even psychological reasons to avoid them. Not only that, I sincerely believe that both low and high-intensity cardio have unique benefits unto themselves. Optimally, both types should be done, since each has specifically different effects. Saying that one is bottom-line superior to the other for improvement in body composition is as false as blanketly saying 5 reps per set is superior to 15. On the contrary, there is well-established benefit in periodising training variables, or as they say in the trenches, "mixing it up".
Too Much of the Same?
I've heard it mentioned that high-intensity cardio shouldn't be done concurrently with high-intensity weight training due to excessive stress on the central nervous system. Perfect excuse. My primary response is, there's no solid proof of that danger. Certainly there's no evidence of it in my observations as a professional in the field, working with bodybuilders, and all types of other competitive athletes such as gymnasts, sprinters, boxers, etc (you know, athletes whose incredible physiques have nothing to do with weights + high intensity cardio). It's true that some folks regard a precociously low carb intake as a legit reason to keep intensity low. However, if your nutritional program doesn't adequately support productive training, then you've designed it ass-backwards, painting yourself into a corner of compromised adaptation.
Options can be broken down in the following ways: If you're pressed for time, and you can do HIIT without any delayed onset muscle soreness overlap (by virtue of doing a low frequency of HIIT), and you can tolerate it joint-wise & heart-wise, and you hate spending time doing cardio to begin with, then do HIIT. On the other hand, if you have the time to allot for low-intensity steady state (LISS), and you do a particularly high volume & magnitude of resistance training which raises potential recovery conflicts posed by a high frequency of HIIT, then do LISS. If you're somewhere in between the aforementioned 2 camps and you don't have a specific preference or tolerance limit, do both types on either a cyclical, rotational, or even combined basis. Also, it can't be overstated that unless you undergo a very gradual progression towards the the musculoskeletal tolerance for something like sprinting, you can get hurt pretty bad & there goes your productive training for several weeks.
Fasted = Suboptimal
Fasted cardio is not optimal for reasons spanning beyond its questionable track record in research. There's unavoidable positive metabolic synergy in fed (read: properly fueled) training, regardless of sport. This effect increases with intensity of training; even in untrained subjects, whatever fat oxidation is suppressed during training is compensated for in the recovery period by multiple mechanisms, many of which are not yet identified.
Athletes are known for their gravitation towards self-sacrifice, but some rely on hearsay, while others rely on science. Did you know that way back in the 60's, it wasn't uncommon for coaches to tell athletes in various sports to avoid drinking water before and during training? No comment needed. Good thing researchers questioned it, and enough data surfaced to validate claims of the sceptics. Sometimes counterproductive dogma indeed dies, thank goodness. However, the myths addressed here are admittedly more subtle than the water example. Even on suboptimal protocols, athletes all over the world still inch along, although not at optimal rates, and not necessarily to optimal levels.
I see the bottom line like this.. Do the type you have a personal preference for, and also respect your physical limits. HIIT is quicker but riskier. LISS is safer but takes twice as long to accomplish the same thing. Again, do what you prefer & can tolerate, but do NOT make the mistake of assuming that LISS burns more fat. That's misunderstanding the physiology of the matter.
I'll end off by challenging you to diligently review the facts before blindly latching onto the myths.
This article was written by Alan Aragon who has over 13 years experience as a lecturer in the fitness industry. Check out his website at http://www.alanaragon.com
- Don't forget to bookmark Myths Under the Microscope - Final Discussion