3 Next-Level Running Interval Workouts

Throughout the long history of the sport of running, training innovations have come primarily from athletes and coaches, not scientists. With few exceptions, it’s been the folks in the trenches who figure out what works, leaving scientists to figure out why it works afterward—an important, but secondary, role. German track coach Woldemar Gerschler, for example, is credited with pioneering modern interval training methods in the 1930s, while Arthur Lydiard, a New Zealand shoe factory worker turned running coach in the 1950s, developed the high-volume, mostly low-intensity approach to training that remains a best practice today.

Things are beginning to change, however. Training methods have advanced to the point where it’s becoming harder and harder to find new ways to make runners fitter and faster. Increasingly, it has fallen on scientists to come up with ways to tweak existing methods to make them more effective. As a coach myself, I am wary of putting too much stock in any single study that appears to identify a new and improved workout format.

Oftentimes scientific experiments are just too far removed from the real world for any broad conclusions to be drawn from them. But when a particular study of this kind involves real, elite athletes and relevant outcome measures such as time-trial performance, I pay a little more attention. And when a novel workout that passes initial scientific mutter begins to be prescribed by elite-level coaches operating in the real world, I am willing to give it a try, first on myself (usually) and then on athletes I coach. Finally, if the workout yields good results for me and my clients—well, then I tell you about it.

The following three interval workouts were all created by scientists and have passed through these crucial validation steps. None of them are easy, but each is fun in its own way and all are likely to make you fitter.

Variable-Speed Intervals

Traditionally, work intervals in any type of high-intensity interval workout are done at a fixed intensity. For example, you might do five times 4 minutes at critical velocity (the fastest pace you could sustain for about 30 minutes) with 2-minute jogging recoveries. Recently, though, scientists at the University of Kent and Inland Norway University got the idea to create and test a workout that featured work intervals of variable intensity.

Specifically, they sought to come up with a design that would enable athletes to spend more time at or very near 100% of VO₂max (i.e., consuming oxygen close to their bodies’ maximum rate) without becoming exhausted.

Tests of this kind are easiest to do with cyclists riding stationary bikes, so the designers of this study came up with a cycling-specific workout based on a traditional VO₂max interval session consisting of six 5-minute intervals ridden at 85% of maximum aerobic power (or MAP, which is the highest power output an individual cyclist achieves in a ride to failure at increasing power levels) separated by 2.5-minute active recoveries. The wrinkle they added was the insertion of three 30-second surges at 100% of MAP within each 5-minute interval, with the baseline effort lowered slightly to 77% of MAP to make the intervals feasible as a whole.

Fourteen trained cyclists completed both the traditional and modified versions of the workout on separate occasions. On average, the cyclists spent 6 minutes and 50 seconds of cumulative time above 90% of VO₂max during the modified workout compared to just 4 minutes and 46 seconds above 90% of VO₂max during the traditional workout. After each session, the cyclists were asked to rate how difficult it was, and despite the discrepancy in physical demands, the two versions were judged about equal—6.0 vs. 6.6 on a 1-10 scale of perceived effort. These findings, which were reported in the International Journal of Sports Physiology and Performance, indicate that the variable-intensity interval workout is more beneficial without being harder.

To adapt this new workout format for running, it’s necessary to translate power into pace. The running equivalent of maximum aerobic power is maximum aerobic speed (MAS), which, for most runners is a speed that can be sustained for about 6 minutes, or a little slower than one-mile race pace for fast runners and a little faster than one-mile race pace for everyone else. This is the pace at which you will complete the 30-second surges within the 5-minute intervals. Your baseline pace for the intervals will be somewhat slower. In the testing I’ve done with my clients and on myself, I’ve found that lactate threshold pace (or LTP, sustainable for 60 minutes, or between 10K and half-marathon pace for most runners) is a good target.

The first time you try the variable-intensity intervals workout, treat it as an experiment. Don’t overthink the numbers. Just aim for the prescribed targets and adjust your effort as you go so that, when you finish, you rate the workout as a 6-7 out of 10 overall effort. It’s likely your pacing is less than perfect the first time. That’s okay; just apply what you’ve learned the next time.

Introductory Version

Warm-Up

• 5:00 jog
• 4 x 15-second strides (relaxed sprints followed by 30 seconds of rest)

Interval Set

• 3 x 30 seconds @ MAS/70 seconds @ LTP
• 2:30 jog
• Repeat 4x total

Cooldown

• 5:00 jog

Advanced Version

Warm-Up

• 10:00 jog
• 4 x 15-second strides (relaxed sprints followed by 30 seconds of rest)

Interval Set

• 3 x 30 seconds @ MAS/70 seconds @ LTP
• 2:30 jog
• Repeat 6x total

Cooldown

• 10:00 jog

30-15 Intervals

One of the oldest traditions in workout design is that of making the intensity and the duration of intervals inversely proportional. In plain English: the lower the intensity, the longer the intervals. This tradition makes sense, because very high intensities can’t be sustained for long periods of time, while short intervals at somewhat lower intensities aren’t taxing enough to be of much benefit unless the recovery periods between intervals are even shorter.

Well, guess what: A research team including some of the same scientists who came up with the variable-speed intervals workout I just described have also developed and tested a workout made up of shorter-than-traditional intervals separated by really short recoveries, with the same purpose in mind. And it turns out that, too, delivers better results than the traditional format it derives from.

The 30-15 workout, as I call it, consists of large numbers of 30-second intervals punctuated by 15-second active recoveries. The specific format that Bent Rønnestad and colleagues at Inland Norway University tested on elite cyclists comprised three sets of thirteen 30-15 intervals with 3 minutes of easy pedaling between sets. This format was compared against a traditional format similar to the one used in the variable-intensity workout study: 4 x 5:00 @ 85% MAP/2:30 active recovery. In this case, though, one group of cyclists did the traditional workout three times per week for three weeks with supplemental low-intensity riding while a second group did the same thing, except with 30-15 workouts taking the place of the traditional interval workouts.

All of the cyclists completed performance tests before and after this three-week intervention. On average, members of the 30-15 group experienced a 4.7 increase in power output in a 20-minute time trial, whereas performance actually decreased slightly in the other group. Rønnestad’s team attributed these disparate outcomes to differences in mean power output and cumulative time spent above 90% of VO₂max between the two workouts. Again, though, the subjects rated the two sessions as about equal in difficulty.

The 30-second intervals were completed at 94% of MAP, which equates to a running pace that can be sustained for about 15 minutes, or a little faster than 5K race pace for most runners. In my experience, 30-15 intervals are even trickier to pace than variable-intensity intervals. They’re also just plain harder. For these reasons, I recommend that runners of all levels start with the introductory version of the session, aiming for a 7-8 effort overall. Once you’ve gotten a feel for the format, consider advancing to the advanced version, which should be an 8-9 effort as a whole.

Introductory Version

Warm-Up

• 5:00 jog
• 4 x 15-second strides (relaxed sprints followed by 30 seconds of rest)

Interval Set

• 13 x (30 seconds @ fast*/15 seconds easy) *Fastest speed you could sustain for 15:00
• 3:00 easy
• Repeat 2x total

Cooldown

• 5:00 jog

Advanced Version

Warm-Up

• 10:00 jog
• 4 x 15-second strides (relaxed sprints followed by 30 seconds of rest)

Interval Set

• 13 x (30 seconds @ fast/15 seconds easy)
• 3:00 easy
• Repeat 3x total

Cooldown

• 10:00 jog

Depletion Intervals

Chances are you’re familiar with the practice of intentionally withholding carbohydrate before and during selected runs, commonly referred to as depletion runs. If you’ve tried this method, you’ve probably done it in the context of long runs with the hope that it will increase the capacity of your muscles to use fat as fuel. But research has shown that the biggest benefit of training in a carbohydrate-restricted state is actually an increase in aerobic capacity (VO₂max), and that high-intensity interval workouts may work best for this purpose.

For the past year or so, I’ve practiced and prescribed a protocol that I learned about in a study led by Laurie-Anne Marquette of the French National Institute of Sport and published in Medicine & Science in Sports & Exercise in 2016. It’s rather involved, encompassing two separate training sessions and a nutrition component, but it’s not as onerous as it may appear at first blush and my athletes and I have found it to be quite doable.

Marquette’s team used triathletes as subjects, all of whom were placed on a moderate carbohydrate diet supplying with 6 grams of carbs per kg of individual body weight per day. Four days each week for three weeks, all of the subjects completed a high-intensity interval workout in the afternoon followed by an easy, low-intensity exercise session on an empty stomach upon waking up the next morning.

Half of the subjects ate a low-carb dinner after the interval workouts, whereas the other half ate a normal moderate-carb dinner. Total daily carb intake remained the same for both groups on these days; only the timing was different. The intended effect of combining a high-intensity interval workout with a low-carb dinner and an overnight fast was to set the subjects up to perform the morning training session with very low carbohydrate stores.

The benefits of so doing were significant. Testing revealed that members of the group that trained routinely in a carbohydrate-depleted state experienced greater improvements in cycling economy, high-intensity cycling performance, and 10K run time. But do you really need to put yourself through this regimen four times every week to see benefits? Personally, I don’t think any endurance athlete should do four high-intensity interval workouts every week. In my view, it’s sufficient to complete the following running-specific version of the depletion intervals protocol once a week, and there’s no reason you can’t vary the workout format to fit your current fitness needs.

Step 1: Afternoon Interval Workout

• 5:00-10:00 jog
• 4 x 15-second strides
• 6 x 5:00 @ 10K race pace/1:00 rest
• 5:00-10:00 jog

Step 2: Low-Carb Dinner

Eat normal portions, but avoid high-carb foods such as grains and potatoes. I usually go for broiled salmon and steamed vegetables with olive oil, supplemented by an evening snack of nuts, if necessary.

Step 3: Morning Easy Run

• 40:00-60:00 jog on empty stomach after waking up