High-Intensity Intervals

There’s a good chance you came across the following headline, or another one like it, a couple of weeks back: “Too Much High-Intensity Exercise May Be Bad for Your Health.” These click-baiting newsflashes referred to a new study out of Sweden’s famed Karolinska Institute that looked at the molecular and metabolic effects of a HIIT program in previously casual adult exercisers. Eleven unlucky volunteers were subjected to an utterly brutal regimen that ramped up to five HIIT sessions per week within three weeks, each session comprising a mix of four- and eight-minute intervals performed at maximum intensity. The consequences of this diabolic torture program included severely compromised mitochondrial function and erratic blood sugar levels.

My first thought on reading the above-referenced headlines was duh. In more than 20 years of serious endurance training I never attempted anything approaching the savagery of what those poor, unsuspecting guinea pigs underwent in a state of woeful unpreparedness. I know with 100 percent certainty that the same routine would have utterly steamrolled me even if I’d gone into it at my absolute lifetime peak of fitness. Hilariously, though, the negative effects seen in this study’s subjects were referred to in one article as “unexpected.” Is the popular media really that clueless? I guess so!

Coincidentally, these shockingly predictable fresh findings from the Karolinska Institute came fast on the heels of a highly complementary recent study by scientists at the University of Guelph. For this experiment, 23 overweight, sedentary men were separated into groups, one of which did three HIIT workouts per week on stationary bikes while the other did five longer, low-intensity workouts. Versions of this format had been used in many prior studies, but what was different this time was that the two exercise programs were not matched for total workload (i.e., total energy expenditure).

The purported rationale for matching workloads in past research was fairness. The scientists conducting these experiments wanted to see whether low-intensity or high-intensity exercise was more “effective,” and in their minds this required that total energy expenditure be held equal. In my mind, however, the format unfairly disadvantaged low-intensity exercise, for the thing about HIIT is that a little goes a long way, so of course it’s going to seem more effective if a little HIIT is compared against a little low-intensity exercise, which only has a chance to really shine in large amounts, which (unlike large amounts of high intensity) are well tolerated by the human body.

Anyway, in the new Guelph study, common sense prevailed at long last, and the low-intensity and high-intensity programs were balanced in a more realistic way. And wouldn’t you know, the low-intensity program kicked the HIIT program’s ass in terms of health benefits, yielding bigger improvements in body composition, lipid metabolism, blood pressure, and blood sugar regulation.

I’m now waiting for it to finally cross the minds of exercise scientists to investigate the health effects of mixing together workouts of different intensities as we endurance athletes do. Up to this point, researchers interested in the health effects of aerobic exercise have focused entirely on trying to figure out which intensity is “best,” but to me that’s a little like trying to determine which of a baseball pitcher’s five pitches is his best pitch with a view toward having him throw only that pitch going forward. What would happen in this scenario, of course, is that hitters would know exactly what was coming their way every time the pitcher wound up, and all of a sudden his best pitch wouldn’t be so effective anymore!

Okay, that’s a poor analogy, but you get my point. Sometimes things work better in combination than they do in isolation. And we already know this is true of exercise intensities when they are assessed according to their effects on fitness. Specifically, we know that an exercise program comprising an 80/20 balance of low intensity and moderate/high intensity yields greater gains in endurance fitness and performance than a program consisting entirely (or even mostly) of work at either low intensity or moderate/high intensity.

Would an 80/20 program also yield greater health benefits than the alternatives? It seems likely to me that it would. It’s been shown, for example, that 80/20 training yields greater improvements in aerobic capacity than does any other way of balancing intensities, and we know that aerobic capacity is a strong predictor of health in old age and longevity.

What are the chances, though, that 80/20’s factual superiority will result in its popularization beyond the endurance community? Rather slim, I would imagine. One of the reasons HIIT became so popular is that interval sessions are sexier than slow-and-steady aerobic workouts. Can you picture a bunch of folks gathering for a group fitness class where the instructor pedals nice and easy for 80 minutes straight and invites everyone else to do the same? Yeah, me neither. But one can dream.

There are lots of running-related techniques and methods that are widely known to be effective but that achieve their effects in different ways than most runners believe or assume. For example, drinking water and consuming carbohydrate during endurance exercise are known to enhance performance and are believed to achieve this effect by limiting dehydration and supplying energy to the muscles, respectively, but in fact drinking water enhances endurance performance by reducing the sensation of thirst and consuming carbohydrate does so by acting directly on the brain in a manner that reduces perceived effort. Actually, I lied: these two measures enhance endurance performance in all of the above ways, water by limiting dehydration and reducing thirst and carbohydrate by supplying energy and reducing perceived effort, but you get my point.

Here are three more interesting examples of techniques and methods that don’t work entirely the way most runners think they do.

3 interesting running techniques

High Intensity

Science has supplied iron-clad proof that high-intensity exercise is an essential ingredient of any program intended to optimize endurance running performance. Although high-intensity work should account for only a small fraction of a runner’s total training time, it is impossible to achieve the same level of competitive performance without it.

Why? Most runners believe or assume that high-intensity exercise complements low-intensity exercise via purely physical mechanisms, such as increasing aerobic capacity and lactate tolerance. And it does. But research suggests that the most important difference between high intensity and low intensity may be psychological.

In a 2017 study, British scientists divided 20 healthy volunteers into two groups. For six weeks, one group engaged in an exercise program consisting entirely of high-intensity interval workouts (HIIT) while the other group did an equal volume of exercise exclusively at low intensity. Testing performed both before and after this six-week intervention revealed that although the two exercise programs resulted in roughly equal changes in aerobic fitness markers, members of the high-intensity group exhibited significantly greater improvement in a time-to-exhaustion test and, separately, in a test of pain tolerance.

The researchers concluded, “The repeated exposure to a high-intensity training stimulus increases muscle pain tolerance, which is independent of the improvements in aerobic fitness induced by endurance training, and may contribute to the increase in high-intensity exercise tolerance following HIIT.”

Depletion Workouts

A depletion workout is a workout undertaken without any carbohydrate intake either before or during. For example, you might run 16 miles first thing in the morning on no breakfast and consuming only water as you go. Most runners who are familiar with this practice believe its intent is to enhance the fat-burning capacity of the muscles.

Again, this is true but not the whole story. Although studies have shown that depletion workouts enhance the fat-burning capacity of the muscles, this effect has not been linked to any performance benefit. But other research has demonstrated that the specific stress imposed by training in a low-glycogen state upregulates certain genes involved in mitochondrial biogenesis, and this adaptation does increase endurance performance. In plan English, depletion workouts add horsepower to the body’s aerobic engine. That’s why high-intensity interval sessions, in which glycogen and glucose supply almost all of working muscles’ energy—even when they are done in a carb-restricted state—work just as well as long endurance sessions as depletion workouts.

Plyometrics

Plyometrics is a form of training that consists of various jumping exercises such as hopping up into a box on one foot. It tests an athlete’s ability to produce power, or rapid application of force, and for this reason it is widely believed that the purpose of doing plyometrics as a runner is to increase stride power.

This is true for sprinters but not so much for long-distance runners. In distance runners, plyometrics training has been shown to enhance stride stiffness and thereby increase running economy. The type of stiffness I am referring to is the type that physicists talk about in relation to springs. The human body functions as a sort of spring during running, and just as a pogo stick with a stiff spring will bounce higher than a pogo stick with a loose spring, a runner with greater leg stiffness is able to capture more of the “free energy” that rebounds from the ground into the foot after impact and use it to propel forward motion.

Certain plyometrics exercises, including the drop jump, which entails stepping off a box and landing on the floor below, increase legs stiffness without increasing leg power. The fact that they, too, enhance running economy shows that, for distance runners, plyometrics really is about enhancing stiffness, not power.

Most runners target a single intensity in all of their workouts. Either it’s an easy run or long run at a slow and steady pace or a tempo run with an effort at lactate threshold intensity sandwiched between a warm-up and a cool-down or an interval session featuring a set of a certain number of repetitions of uniform length or duration all done at the same high intensity or—you get the idea. But there is something to be said for doing the occasional workout that includes a range of different intensities.

First of all, multi-pace workouts are a literal change of pace, and as such they’re an effective way to keep your training fun and interesting. Multi-pace workouts are also a good way to get appropriate doses of different intensities. For example, if you’re at a point in your training where you can benefit from a little work at VO2max intensity—but only a little—why set aside an entire workout for it when you can incorporate that work into a session focused on an intensity you need more of—say, lactate threshold intensity?

Yet another benefit of multi-pace workouts is that they help teach effective pacing. Can you shift accurately from half-marathon pace to 10K pace to 5K pace by feel? Most runners can’t, but runners who do workouts that include efforts at all three of these paces can. Finally, multi-pace workouts that put the fastest work at the end develop the capacity to dig deep and finish strong in races.

Here are three multi-pace workouts to try:

3 Multi-pace workouts to try

Intervals + Time Trial

This type of workout serves most of the purposes mentioned above. The interval segment provides the primary training stimulus and it should target a high aerobic intensity close to the lactate threshold. The closing time trial should be fairly short in order to serve the purpose of providing a modest exposure to VO2max and to get you suffering a bit. As a whole, an Intervals + Time Trial workout is very taxing and you shouldn’t attempt them very often. The specific session described below is one I did with NAZ Elite during my time in Flagstaff.

1-3 miles of easy jogging

Drills and strides

7 x 1 km @ lactate threshold pace with 1:00 standing recoveries (2:00 after the last rep)

1500-meter time trial

1-3 miles of easy jogging

30-20-10 Run

A few years ago, a team of Danish researchers led by Jens Bangsbo set out to see if they could come up with a high-intensity interval workout that was more enjoyable than standard formats without being less effective. They tested a variety of designs before settling on one that fulfilled their hopes: the 30-20-10 Run. After learning about it, I gave it a try, made a couple of tweaks, and started incorporating the workout into the training plans I create for my clients. I like to schedule 30-20-10 runs during recovery weeks and during the final weeks of preparation for longer races as a way to expose athletes to a range of intensities without making them go to the well. This workout is also a great way to teach better pacing. Here’s the basic format:

1-3 miles of easy jogging

5 x 1:00 with the 30 seconds at marathon pace, the next 20 seconds at lactate threshold pace (i.e., the fastest pace you could hold for one hour), and the last 10 seconds at a relaxed sprint. No recovery—just cycle right into the next interval until you’ve completed all five.

Complete three cycles of five 30-20-10 intervals with 5 minutes of jogging after each.

1-3 miles of easy jogging

Tempo + Sprints

As a long-distance runner, you should sprint, but not a lot. Because any sprinting you do in a race is likely (one hopes) to occur at the very end of a race when you’re tired, it makes sense to sprint on tired legs in training. In the Tempo + Sprints workout, you will do just that.

1-3 miles of easy jogging

Drills and strides

20:00 at lactate threshold pace

2:00 standing recovery

8 x 200-meter relaxed sprints with recovery by feel (i.e., go again when you’re ready)

1-3 miles of easy jogging

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