The Limits of HIT Training

In recent years, we’ve been inundated with articles, promotions, and studies in praise of high intensity training (HIT), sometimes called HIIT (High Intensity Interval Training). The stories came from many varied sources, including CrossFit, something called Tabata training, and the McMaster University laboratory of exercise scientist Martin Gibala.

The message was always highly alluring, almost magical: “You can get fitter by doing less.” These HIT efforts often required just 6 to 8 all-out sprints of 20 to 30 seconds each several times a week to achieve their results. It seemed like the weight-loss equivalent of “Eat more, weigh less.”

Now, it seems the tide is turning. It’s about time. At this point, we ought to be able to evaluate HIT more broadly. I’m actually a fan, but I also believe in perspective and balance. That’s what we need to understand HIT, and use it effectively.

A few years back, HIT seemed like a secret sauce. Gibala even wrote a book titled The One-Minute Workout: Science Shows a Way to Get Fit That’s Smarter, Faster, Shorter. Similar words appeared in hundreds of articles. HIT was like a winning lottery ticket.

However, last week the New York Times reported on the other side of the miracle. A Swedish research team found that subjects did quite well on two HIT workouts a week. So they pushed their subjects a little harder, and then a little harder again. Result: The poor souls “developed sudden and severe declines in the function of their mitochondria, which are the energy powerhouses inside of cells, along with incipient signs of blood sugar dysfunction.”

One of the researchers commented that “HIIT exercise should not be excessive if increased health is a desired outcome.” No kidding. It’s hard to get fitter and faster if your general health is under attack. That’s simply not a sane path to pursue.

Embarrass Your Body, Don’t Punish It

University of Houston distance coach Steve Magness appreciates the science of running so much that he has written a book with that exact title. He also knows where to draw the line. In a recent column from The Growth Equation, Magness used a verb I haven’t encountered before in training discussions. He wrote that our training should “embarrass” our bodies from time to time. I like it.

He meant that we have to inject unexpected surprises into our training. No, we don’t have to push to the point of collapse. We don’t have to leave ourselves wobbling like a tower of jello — even though that sounds exciting on social media. “Going until you have nothing left is appealing,” Magness noted. “It sells the notion of the grind, of going to the well, pushing through barriers and being a badass.”

But it’s probably not smart training. Magness has another useful word for that: “signal.”

He writes: “We need a signal that says we aren’t quite strong enough or don’t quite have the fitness required to perform a given task. This signal tells our muscles to grow a little stronger or process a bit more oxygen.”

Eliud Kipchoge provides a similar message in his own unique way. To me, the most amazing thing about Kipchoge isn’t that he can run a 1:59 marathon, but that he can do so without an all-or-nothing approach to his training. He’s the ultimate poster boy for consistency and control.

When Wired magazine writer Ed Caesar visited Kipchoge’s training camp several years ago, he was impressed to learn that Kipchoge doesn’t rely on world-record workouts to produce world-record races. “He estimates that he seldom pushes himself past 80 percent  — 90 percent, tops — of his maximum effort,” Caesar wrote.  Kipchoge’s coach, Patrick Sang, kept saying that the training was based on “slowly by slowly.”

Kipchoge’s manager confirmed this philosophy. He told Caesar that “Kipchoge never killed himself in training.” The goal was “never 100 percent in any session.”

That’s what I call a healthy perspective. But it doesn’t mean that HIT workouts can’t be productive. It can. You just have to use it judiciously, with guidelines like the following.

Guidelines for Successful HIT Training

1) For runners, HIT workouts do not a training program make. The workout is simply a tool, like a tempo run, a foam roller, or a high-carb meal. The goal is to use HIT workouts when they make sense. They are not the full monty.

2) Several well-placed HIT workouts can help when you are peaking for an important race. But remember: Too many can quickly push you over the top, and down the other side like the subjects in that NYT story.

3) Accept the lower volume of short HIT workouts. Don’t try to “make up for” a few low-mileage, high-intensity days by piling on miles the other days. That might look good in your training log, but will likely bite you in the big race.

4) Use HIT workouts as part of a polarized approach to peaking. Go short and hard on some days, easy and moderate on others.

5) Understand that HIT workouts will likely increase your injury risk. Do plenty of pre-covery and recovery. You can rush through a short workout, but you can’t put your whole life on speed dial.

6) Stop at two (at most). If you’re following a well-balanced training program for runners — and I hope you are — don’t even think about more than two HIT sessions in a week. Honestly, one is probably the right number.

7) Don’t get stuck on the idea that HIT training must push you to the brink. You don’t have to do the intervals at 100 percent effort. You can do excellent HIT workouts at 90 to 95 percent of max.

8) Consider HIT workouts if your calendar is jammed full for several weeks and you won’t have time to maintain your normal schedule. A few HIT sessions can keep you fit even if you can’t do your other workouts. But this is a short-term, “fill in the gaps” approach. You can’t make it last for long.

9) If you like experimenting, try several HIT workouts as part of a “shock and awe” cycle in your training program. Here’s a cycling study that produced good results. Make sure your next week has plenty of moderate running.