I’ve decided that when I see someone giving running advice that includes use of the term HIIT, it’s the equivalent of people referring to the city featuring the Golden Gate Bridge as “Frisco” or equating eating a heaping plate of fettucine alfredo the night before a leisurely bike ride as “crabo-loading,” Basically, it’s a signal that someone knows enough to give advice that might be mostly on target, but invites careful scrutiny.
HIIT stands for “high-intensity interval training.” Maybe I’m being picky, but experienced runners don’t call it that. They say “speedwork” or “intervals.” And maybe I’m a douchebag, but when I see the term, I’m reminded of a legion of neophytes talking endlessly about how tha marathon doesn’t start until the last 10K and telling each other calf pain on a downhill 23 miles into a marathon in someone who’s been training for all of six months is surely a sign of potassium deficiency.
So when a friend and experienced marathoner showed me an article in the fitness section of the Orlando Sentinel yesterday (don’t ask me why it’s been online for a month) and asked me if I agreed with the writer’s assertions in the following passage:
Intervals can be run outside, of course. But one benefit of a treadmill is that it makes it easy to track the speed changes inherent in HIIT. Already I’ve learned a few things by taking up interval training.
In my last article, I showed how the vast majority of calories burned due to exercise come off during the actual workout and that the caloric “after-burn” due to HIIT is quite minimal. So if fat loss is your goal, then you want to maximize your aerobic “work.”
This is interesting because my personal experience is that I can’t do as much work engaging in HIIT compared with running at a steady pace.
If I’m not trying to do anything fancy, I can sustain a 7 1/2 mile per hour pace for about two hours. By comparison, when I do interval training at the oft-recommended 1-to-1 work-to-rest ratio, I can cycle back and forth between running at a 10-mph pace for one minute, followed by two minutes at 5 mph, for an hour at most. That’s followed by whining.
Let’s do the math. Running at 7 1/2 mph equals — duh! — 7 1/2 miles run in an hour. Conversely, the above HIIT ratio works out to 20 minutes run at a 10 mph pace (that’s 31/3 miles) and 40 minutes at a 5 mph pace (that’s another 31/3 miles) for a total of 62/3 miles run in an hour. Less work is done and fewer calories are burned. And that’s not even taking into account the fact that I can run for an additional hour when I’m going at a steady pace.
As much as I’d like to burn off the beer that has taken up residence in my love handles, I’m willing to stick with HIIT twice a week in order to achieve the aforementioned personal best time for a 10K. The question is: Will it improve my chances of achieving this goal?
First of all, let me say that I’m glad that it’s acceptable to run intervals outside, despite the foreboding winters in Central Florida. (Okay, the guy lives in Calgary and this is apparently a syndicated column, but it’s still funny.)
Then there’s the “oft-recommended 1-to-1 work-to-rest ratio” her cites with respect to interval training. In reality, most coaches recommend something like a 50 to 75 percent rest-to-work ratio, maybe 90 percent for really short, intense (e.g., mile race pace or close) repetitions. But that is a time ratio, not a distance one. I do know runners who take a full 400 jog between 400-meter reps at 5K race pace or faster, and I explain to them that not only is this too much rest to ensure a modicum of race-specific conditions, but also using a distance-based recovery tends to see even disciplined runners jogging the rest interval more and more slowly as the workout progresses, which is no good. Using time as a metric allows for standardization.
Finally, leaving aside the fact that runners interested primarily in getting faster aren’t concerned with every run maximizing caloric expenditure, the writer oversimplifies the situation he describes, claiming that covering 7 1/2 miles necessarily burns more calories than covering 6 2/3 miles because it involves more work. What he’s ignoring is that in interval training, a runner is cranking along at about 95 percent of heart-rate max by the end of his reps and that slowing his speed by 50 percent at the start of the recovery portion (which is a pain in the ass on a treadmill, by the way) does not entail an immediate transition to a heart rate commensurate with running steadily at that recovery pace. That is, if this guy is running for a minute at 6:00 pace and two minutes at 12:00 pace, for an hour, he’s spending a great deal of those 40 “slow” minutes in a metabolic zone corresponding to a much greater intensity level.
Put in terms of a car engine, if you drive for an hour at a steady speed of 75 miles an hour, you’ll burn about two gallons of gas and cover 75 miles, whereas if you alternate hammering along at 100 mph for two minutes with slowing to 50 mph for four minutes for the same one-hour period, you’ll cover only 66 2/3 miles, but will assuredly burn more gasoline in the latter case. The analogy is far from perfect, but the key is that running unevenly is inefficient and hence more costly in terms of energy. That’s what you want in an interval workout, of course, or at least require as a by-product of spending a lot of the run at race pace without the same stress as an actual race.
Anyway, the article is a decent overview for newer runners who are intent on both getting faster and losing weight, but is misleading in non-negligible ways (and I get to decide what’s negligible, which is why I’m so fond of the formal term “non-negligible.” It gives me the same escape-hatch as that time-honored use of “recently” in journalism).