This challenging track session teaches you to recover while running fast. 

Need a challenging workout you can do year-round, regardless of your specific training focus?

Look no further than 400s on the track—but with a slight twist. Rather than busting out a handful of one-lappers as fast as you can with a long, hand-on-knees recovery between repeats, alternate running 400m at your 5K-10K pace with a 400m “recovery” lap 10 seconds slower than the one you just completed. The catch? These aren’t really 400m repeats—it’s a continuous workout. No stopping!

So how long should you go? Until you can no longer maintain the target paces, explains Nate Jenkins, an elite runner and coach based in Andover, Mass.

Jenkins, seventh-place finisher at the 2008 U.S. Olympic Trials Marathon who represented the U.S. at the 2009 world championships, says, “This is a workout you could do every week of the year and have it be the right workout at the right time. You get some specific work but the faster rests prevent it from becoming so anaerobic that it is dangerous in the base phase.”

Here’s how you do it: 

If your current 10K race pace is 8 minutes per mile, that breaks down to 2:00 per 400m. For this workout, alternate running one lap at 2:00 with a “recovery” lap at 2:10 (8:40/mi pace) until you can no longer maintain those paces. Alternating 400s, a similar workout to Deek’s Quarters, takes a lot of discipline in order to execute properly and stay on pace. It’s a great benchmark workout—one that you can repeat every few weeks as a means of tracking your progress. As your fitness level improves over the course of a training cycle, try running your faster laps closer to 5K pace, which means your “recovery” laps will also speed up a bit. If you can run more laps at the same pace than the last time you completed the workout, it’s a sure sign that your fitness is improving.

RELATED: Deek’s Quarters

“This is a great threshold workout,” Jenkins says. “It also really forces you to relax at quick speeds. Too often we hammer workouts and extend rests to hit times and that is counter-productive because there are no rests on race day. This forces you to recover while running pretty quickly and to relax while running race pace because if you aren’t relaxed at pace you won’t be able to recover during the quick 400m rest.”