In the early 1980s, a Swedish exercise physiologist named Bertil Sjödin demonstrated that it was possible to get a large training boost by doing do weekly 20-minute runs at a pace he called VOBLA, or the speed at which there is an “onset of blood lactate accumulation.” A few coaches had been doing similar training runs for years—University of Oregon coach Bill Bowerman was doing them in the 1960s—but it wasn’t until Sjödin published his work in 1982 that the modern tempo run was born…and it has been a staple of training ever since.

But that doesn’t mean there aren’t ways to improve on it.

Dancing Around a Pace

As a coach of runners from beginners to Olympic Trials qualifiers, I like to give athletes a workout I call “long alternations.”

The idea is simple. Classic tempo runs are steady paced—generally at Sjödin’s VOBLA pace—which, for those who don’t have easy access to blood lactate tests, is about the pace you’d run in a race lasting an hour. It’s also often called “threshold” pace.

Alternations, as the term implies, “alternate” paces from slightly faster than VOBLA to slightly slower. For example, if your normal tempo-run pace is 6:30s, you might alternate between 6:20 pace and 6:40. Or 6:15 and 6:45. The exact paces aren’t critical; what matters is that you shift back and forth between faster than VOBLA, and slower than it.

group training on track
photo: Getty images

Improving the Shuttle

The theory is that at or above VOBLA, your blood levels of lactate start to rise. So, you run that pace or faster until you’ve accumulated a bit of lactate. Then, you slow down, while still running fairly briskly. This encourages your body to learn to use the accumulated lactate via a mechanism known as the lactate shuttle.

The physiology is complex, but in a nutshell, what’s going on is that lactate is produced in the first, high-energy step of burning glucose—a process that does not require oxygen. The resulting lactate, however, requires oxygen to burn—oxygen that is in increasingly short supply in hard-working leg muscles.

To deal with this, the body allows lactate to escape into the bloodstream, where it is transported—or “shuttled”—to better-oxygenated tissues such as the heart, brain, and arms, thereby sparing glucose for the legs. Some also goes to the liver, which can use its oxygen supply to build lactate into fresh glucose.

What this mean is that the more efficient the lactate shuttle, the stronger your overall aerobic engine.

Alternating Options

It is possible to use this approach to break tempo runs into smaller segments punctuated by briskly-paced pseudo-recoveries.

One option is to run 700s on 100m (brisk) recoveries. It’s a fun workout, partly because most people never run 700s, so it’s guaranteed to be different.

The idea is to run 700m at threshold pace or slightly faster (not a lot faster, because you don’t have a lot of recovery), then run the 100m “float” at enough slower than threshold that you’re ready to jump into the next 700 when you get to it. How much slower is up to you—your floats will get faster as you both learn the workout and get in better shape. But as a general rule, you should be looking to do them at marathon pace, or a little slower.

That’s one option.

You can also do 600/200s, where the first 600 is slightly faster than you’d do the 700s, because you now have a 200m float in which to recover. Or, you can do 600/400s, 800/800s, 1000/1000s, or pretty much anything else you can invent. The key is to make sure the float/recoveries are brisk, but not so brisk that they are faster than threshold pace.

group doing track intervals
photo: Getty images

Tailored Training

How much of this you do in a workout depends on what you’re training for, and your weekly training volume.

People training for shorter races (10K and under) might want to break these into sets adding up to 2K to 4K of volume per set, with an easy 400–800m recovery jog between sets. E.g., 600/200/600/200/600/200 would be one 2400m set. Marathoners and half-marathoners will probably prefer longer versions, such as 600/400 or 800/800, all done as a single extended set.

Total volume will depend a bit on which option you choose; 700/100s are, obviously, more taxing per mile than 600/400s, but as a rule of thumb, I’d start with 20 minutes (the duration of a conventional tempo run), building to a maximum of no more than four miles or one mile more than 10 percent of your weekly volume, whichever is larger. Note: runners training for races 10K or shorter may not need to go this high, maybe topping out at 8000 meters.

And remember: the goal is to substitute for a tempo run, not a time trial or a race. That means it’s very important to keep the pace under control, especially in the first few alternations. If it doesn’t feel easy at first, you are probably going too fast.

Also, don’t expect too much, too soon. Like any new workout, this not only has a learning curve, but requires a few weeks for your body to start adapting—which, of course, is exactly the point.

Richard A. Lovett coaches Portland, Oregon’s, 220-member Team Red Lizard running club, an all-comers group whose members range from road-racers seeking PRs to national age-group champions and Olympic Team Marathon Trials contenders.  He is the author of two books about training and dozens of magazine articles.