This post is much different from the one I wrote earlier today. Ie...it has a point! It began as a response to a blog called 'Healthy Habits' (which BTW is a terrific, informative and accessible health and fitness blog) and more specifically to an entry/post called "HIIT Kicks Cardio's Butt." See the link here: http://www.healthhabits.ca/2010/03/16/hiit-kicks-cardios-butt/ It has since turned into a much lengthier and complete reaction to not only the blog post, but HIIT in general which I have been following with great interest for some time.
For those who don't know, HIIT stands for high-intensity interval training and is a hugely popular and more recent 'trend' within the exercise physiology and training circles. Essentially, it suggests (and good research has been done to back it up!) that rather than long duration continuous aerobic exercise (which is currently recommended); individuals should perform between 6-12 short intervals lasting 30-60 seconds of extremely high-intensity exercise ("all-out" running/sprinting, or on a bike) with short (60-90sec) bouts of rest/recovery in between. This extremely time-efficient method of exercise has been shown to be just as effective, if not more effective, at improving performance, metabolic functioning, biochemical and physiological adaptations to exercise and may even expediate weight loss. So just imagine that instead of doing 5 days a week of 60min or more of running or cycling, you can do a workout of less than 30min (including warm-up and cool-down), only 3 times a weeks, equating to as little as 1.5hrs a week...and get the exact same results. Sounds too good to be true doesn't it?!
That's probably because it is!
First things first. I am a huge fan of HIIT and honeslty believe that based on the research and even anecdotal accounts, that it does indeed "work." However the caveat is that it only works if one is willing to push themselves past a high level of pain and discomfort and do the workout at a high enough intensity. For those new to exercise, that might not seem like much but it can be extremely discomforting and perhaps even dangerous! But hey, for those wishing to get fit fast, and don't mind pushing themselves to the limit, it will probably get you results. Thus I will agree that HIIT is practical in the sense that it saves times! Maybe even a lot of time. I mean who can afford running an hour or more 5 days a week (besides those of us who are committed and actually enjoy what we are doing!). However, a lot of HIIT proponents will also say that this is the solution to our current sedentary lifestyles and high rates of inactivity. Anybody can do it right? Wrong! HIIT in NOT practical in the sense that anyone and everyone can get up and do it! Most people have such a low level of fitness that telling them to sprint: run, bike, swim, whatever! all-out, even once, is probably not going to turn out well. It takes time and practice to learn proper form which most people will not have and this could easily result in injury. How did we go from telling people to walk briskly for 20min a day to now saying that they should sprint multiple times? Certainly people like being told that they can get by, by doing less, but in this case, less equals time not effort. You're going to need to give a lot more effort than you ever thought possible (and which may in fact be IMpossible). It's also not practical in the sense that not everyone has equal access to a stationary bike, a track or fancy gadgets which can tell them the proper intensity/HR/power (okay, this is a pretty weak argument but I've heard it before and for some it could be relevant). The point I'm making is that HIIT is not as practical than it's touted to be and certainly not for everyone.
Next, suggesting that improved athletic performance will result from HIIT does not seem convincing to me. What exactly does this mean? To me, performance is highly specific to the sport/activity one is doing. You want to do the 100m? HIIT is probably pretty effective for that; maybe other shorter track running as well. Training for a marathon, a half or even a 10k (and whatever the cycling equivalents of these are) on the other hand is probably not ideal for a HIIT style workout and may even be a big (little) waste of time. Show me a study where marathon runners trained using HIIT do better than matched controls doing traditional high mileage and you'll have me convinced. There's a reason that ALL the elite endurance athletes do long endurance training...and that's because we know it works. Intervals, even very hard ones, have also been around for a long time (ie HIIT is not really that new) and it has it's place in training. But it's never been able to replace traditional endurance training as the single most effective staple of training for endurance sport...and perhaps it never will! As far as metabolic and physiological adaptations are concerned, I admit that the research has shown that HIIT can mimic the changes common in traditional endurance training. But the research has also used small sample sizes, short follow-up periods and often trained (or at least marginally healthy) participants. Will one get fit(ter) doing HIIT? Absolutely. Will one save time? Most likely. Will one enjoy it and continue to do it? Umm, maybe!? Thus my final point.
Finally and perhaps most importantly: I love to run and I loving running long. Telling me to run for only 20min is not what I want to hear and I just won't do it (I'll do more)! Endurance exercise is, for many, a way to spend time away from the world, alone, or perhaps with friends and family. What exactly are we trying to acheive here? Do we want everyone to be fit to run a 400m as fast as possible? Who wants to do that? Probably not many people! A lot of people say that doing HIIT is more enjoyable and fun than traditional endurance exercise. I won't argue with them. But I've done it, and it isn't! It hurts, it's painful and hugely discomforting! My bet is that most people will agree with me. I've already admitted that it probably does work quite effectively and incorporating it into your exercise/training program probably isn't a bad idea at all. However, I doubt it is going to become the new way to train nor will it solve our problems of inactivity and poor fitness. Why not let people decide for themselves which mode of exercise is best suited to them and which is most enjoyable. That produces adherence and compliance. Not hyped and exaggerated promises of total fitness with little time or effort. HIIT might work for some people, but let's not get carried away and suggest it's for everyone. Why must we always pit one form of exercise or one training program against the other? Exercise is effective when it is done by a large number of people; it is done safely; it is enjoyable; it is maintained over time; and it gets the results that the individuals desire (not the results we desire for them!) You do your 30min, 3x per week on a stationary bike or treadmill. I'll do my 60, 90 or even 120min runs everyday and anywhere I wish!
Gibala MJ, McGee SL. 2008. Metabolic Adaptations to Short-term High-Intensity Interval Training: A Little Pain for a Lot of Gain? Exerc. Sport Sci. Rev. 36(2): 58-63.
Little JP, Safdar AS, Wilkin GP, Tarnpolsky MA, Gibala MJ. 2010. A practical model of low-volume high-intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms. Journal of Physiology 588: 1011-1022.