A relatively new and oft-debated training tool for all types of athletes, HIIT has become an undefined conglomerate of running short, fast intervals with little rest. The name and defining parameters of HIIT are a bit ambiguous, which is one of the reasons HIIT is such a controversial and oft-negated topic among those who have previously followed more traditional running programs.
“I’ve approached a cross country team before and asked three of the runners what HIIT is and I got three different answers,” Daniels says. “Then I went to their coach and got another answer.”
Consensus among most of the coaches interviewed for this article was that the bouts of faster running involved in HIIT are roughly equivalent to the pace required for a sustained 1-1/2- to 2-mile race effort. That’s considerably faster and harder than most half-marathon and marathon programs prescribe.
Breaking that fast pace into short, intense intervals with little rest allows maximum training uptake without the debilitating effects a sustained effort at near race-pace would produce.
While some HIIT coaches prescribe lower-volume training plans, HIIT runners, by design, do less overall mileage during any given week because the duration of hard workouts result in only a fraction of the mileage compared to more traditional training programs.
“When you add in those quality workouts once or twice a week the mileage may not be more than a mile and a half or two miles; it’s a really compact intense work- out,” McLaurin says. “You really get a lot of benefit in that time, but it’s going to pull down your weekly mileage.”
That runs counterintuitive to traditional thinking, but there are studies to back it up. For example, a 2010 McMaster University study showed that doing intervals on a stationary bike at 95 percent of maximum heart rate produces the same physical benefits as conventional long-duration endurance training despite taking much less time. The study suggests HIIT stimulates many of the same cellular pathways that are responsible for the beneficial effects we associate with endurance training.
“We have shown that interval training does not have to be ‘all-out’ in order to be effective,” says Martin Gibala, Ph.D., who led the study. “Doing 10 one-minute sprints on a standard stationary bike with about one minute of rest in between, three times a week, works as well as many hours of conventional long-term biking less strenuously.”
Daniels says HIIT training should only be added to a training schedule after building a proper aerobic base from six to eight weeks of consistent running. Once that basic fitness is achieved, Daniels says his rule of thumb is to never allow the working mileage of HIIT to exceed the lesser of 8 percent of the runner’s weekly mileage or 10K. Whether those miles are broken up into one or two workouts is less important than the overall mileage.
For example, a well-seasoned runner who is running up to 80 miles a week should never run more than a 10K or 6.2 high-intensity miles a week since that amount is less than 8 percent of her weekly mileage. For a casual runner logging 20 miles a week, that would mean capping high-intensity mileage at 1.6 miles.
Workouts are personalized by ensuring the intervals are run at a perceived pace a runner can withstand for 10 to 12 minutes based on their individual fitness. For example, Runner A is a 3:10 marathoner and the fastest pace she can hold for 10 minutes is a 5:40 pace. Runner B is a 4:15 marathoner and the quickest pace he can hold for 10 minutes is a 7:40 pace.
“If you’re running an interval for two minutes and you don’t think you can go a minute longer, you’re going too fast,” Daniels says.
Vince Sherry, a Flagstaff, Ariz.-based head coach with the Run SMART Project agrees. “At no point do you want to be fading from your effort,” he says. “If anything you want your last interval to be the strongest.”
As with any hard workout, Daniels says HIIT days should always be bookended with rest or active recovery days. Scheduling HIIT to follow and precede easy days allows tired muscles to recuperate and ensures the workouts aren’t run on tired legs or are putting a runner in position to run with bad form and become more susceptible to injury.
One HIIT workout McLaurin has many of his athletes do is a modified version of a traditional fartlek workout. Named after four-time Australian Olympian and 2:08 marathoner Steve Moneghetti, the “Mona Farlek” is a version of HIIT that calls for random distances of short, fast work from 15 to 90 seconds, run at a runner’s near- max pace, followed by equal periods of recovery, which can be a slow jog or walk— whichever the runner needs to recover enough to complete the remainder of the workout with proper form.
As with traditional fartlek workouts, McLaurin says his version can be done anywhere—you don’t need a track, a common misconception of speed work—and it can be more productive than traditional track-based speed sessions for distance runners because it is centered around perception of effort rather than being tied to specific splits.