Ask any coach about the most important speed workout on a half or full marathon training plan, and they’ll probably tell you it’s a threshold run. These sessions help you run faster for longer, raising your lactate threshold ceiling, or the most intense effort you can sustain while still clearing lactate, which eventually slows you down. These workouts also improve your overall endurance, explains Brian Rosetti, certified run coach and founder of V.O2.
Executing threshold efforts requires running at a comfortably uncomfortable pace, which can feel pretty difficult to hold for a long period of time. That’s why Rosetti recommends cruise intervals as the smartest place to start.
HOW TO FIND YOUR THRESHOLD PACE
A cruise interval workout, originally introduced to the running community by legendary run coach Jack Daniels in the 1980s, essentially requires running a series of intervals at your threshold pace with short rests in between.
Rosetti considers cruise intervals the “bread and butter” of his coaching method, because they’re a great way to rack up more threshold volume in your training thanks to the short breaks.
“This type of training is really important whether you’re an 800-meter runner right up to a marathon,” Rosetti says.
Your race distance and weekly mileage will determine how often you do cruise intervals throughout your training plan. If you’re working toward a half marathon or a marathon, for example, you might do more threshold sessions than if you’re training for a 5K, Rosetti says. But no matter the distance you’re eying, cruise intervals will get you to faster finishes. Here’s how to do them.
Related StoryThe Threshold Interval Workout Every Runner Needs
Why it works: This workout allows you to fit more threshold work in than if you were to go out for a 20-minute effort because the rests in between allow you to recover before the next interval, Rosetti says. It also makes you more likely to sit right at your threshold pace for those intervals.
These 1K repeats are particularly helpful because longer reps, like mile repeats, might be too challenging if you’re just starting out, he adds. (Once you’ve had a few weeks of experience with cruise intervals, you can progress to mile and then two-mile repeats.)
How to do it:
1-2 miles of easy running to warm up, followed by 4-5 strides.3-4 x 1,000 meters at threshold pace (88 to 92 percent of your maximum heart rate), with 1-minute jogging or walking recovery between each1-2 miles of easy running to cool downRelated StoryHow to Master Cruise Intervals1. Go to Flat Land
Cruise intervals aren’t the ideal workout for hilly terrain; they’re best performed on flat land, whether that’s the track, a flat stretch of road, or the treadmill, Rosetti says. “You really want to focus on doing [cruise intervals] at a place where you can control the pace and the effort,” he explains.
2. Follow the 10 Percent Rule
A good rule of thumb to follow with cruise intervals is to make sure the amount of threshold work you do doesn’t exceed about 10 percent of your weekly mileage. For a runner at 20 miles per week, that would look like three to four 1,000-meter repeats.
3. Don’t Push Too Hard
The key with threshold pace is learning how to stay in the “comfortably hard” state, focusing on how you feel during that effort, and being patient with yourself as you do more thresholds over time, Rosetti says. “It’s important to understand what [threshold pace] feels like, so you really want to master that feeling,” he says, encouraging runners to hit their threshold pace without relying on a watch.
You’ll know you’re at the right pace if you can say a few words out loud to a running buddy, but you definitely don’t want to keep chatting. You should feel physically relaxed, as if you’re tempted to slow down or speed up a little (but don’t), and you shouldn’t feel any heaviness or tightness in your legs. “If you feel like the backs of your legs are getting heavy, that probably means the lactate is accumulating faster than you’re clearing it, so you have to back off a little bit,” Rosetti adds.
Another thing to keep in mind: A “good workout” isn’t necessarily the one that makes you sore or depleted, but one where you stick to your pace consistently, without overdoing it, Rosetti explains.
Kristine Kearns, a writer and avid runner, joined Runner’s World and Bicycling in July 2024. She previously coached high school girls cross country and currently competes in seasonal races, with more than six years of distance training and an affinity for weightlifting. You can find her wearing purple, baking cupcakes, and visiting her local farmers market.