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In-Your-Face Fitness: Giving interval training a shot

It may not live up to the hype in terms of fat burning, but it's worth trying in pursuit of a faster 10K time.

March 14, 2011|By James S. Fell, Special to the Los Angeles Times
  • Treadmills can keep track as you step up interval training.
Treadmills can keep track as you step up interval training. (Christian Gooden / St. Louis…)

It gets cold where I live. But even when the forecast is for "hideous below zero" — as some Canadians are fond of saying — I'd still rather go outside than run on a treadmill.

That should give you an idea of how much I dislike this particular piece of workout equipment. Nevertheless, in the past week I've found myself doing the hamster imitation because I find treadmills good for one thing: high-intensity interval training, or HIIT for short.

In my last column, I busted the myth that HIIT burns a lot more calories than regular aerobic exercise done at a steady pace. Ironically, while researching that column I began doing HIIT for the first time in many years.

It wasn't to burn extra calories. The reason I'm using HIIT is that I'm training for a personal best in a 10K race. I'd like to finish in less than 40 minutes and cross that off my fitness bucket list. I'm in my 40s already, so I figure it's now or never.

As I explained last time, one of the things intervals are actually good for is making you faster at endurance racing. And because I've started running intervals — one minute at high speed, followed by two minutes at a more relaxed pace — I'm using a treadmill.

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 71/2 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 71/2 mph equals — duh! — 71/2 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?

To get the facts, I got in touch with James Fell, a senior lecturer who coordinates the Exercise Science Program at the University of Tasmania. And yes, I did find him by Googling myself. Don't pretend like you've never done it.

Fell (the one in Tasmania) has authored a number of published studies on interval training and athletic performance. Via e-mail, he explained that "high-intensity interval training DOES improve endurance performance. There are many studies to confirm this ranging from the relatively untrained up to highly trained athletes." Fell also told me that the Scandinavians invented the concept in the 1930s with fartlek training but that today the approach is much more scientific.

Fell sent me graphs showing that intense exercise in short bursts followed by suitable recovery periods (i.e. in "intervals") allows for greater total work to be completed compared with going at top speed until you're wiped. This larger volume of work allows for a greater training stimulus.

The effects of interval training on athletes, Fell reports, are "increases in the lactate threshold, maximal oxygen consumption and maximal aerobic speed or power. At the cellular level there are changes in mitochondrial number and function, enzyme activity, energy stores in the muscle cells" and a bunch of other stuff that all boils down to being able to kick a lot more butt on race day.

How much more? Fell co-authored a 2009 study in the International Journal of Sport Physiology and Performance that analyzed 10 well-trained male and female rowers. Half practiced HIIT for four weeks and half did traditional training. At the end of the experiment, the athletes in the HIIT group improved their 2,000-meter race time by 8.2 seconds, compared with a 2.3-second improvement for those in the control group. That extra 5.9-second improvement in a competitive race that lasts around seven minutes can be the difference between first place and the middle of the pack.

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