Looking at the training logs of elite American distance runners, you might notice two letters popping up once a week or so: CV. That stands for critical velocity, which has become an increasingly popular training pace in the running community over the last few years.
So what is critical velocity, and how can you use it to improve your own running? Runner’s World talked to Tom Schwartz, PhD—commonly known as Tinman—to learn more about the training pace. Schwartz has three decades of experience coaching elite athletes to U.S. titles and world championships appearances and researching kinesiology and exercise science to earn a masters and doctorate degree.
What actually is critical velocity pace?
CV pace, says Schwartz, is roughly equivalent to half-hour race pace. Some elite runners and coaches might casually refer to it as 10K pace, based on the 30-minute barrier many NCAA and post-collegiate athletes aim to break. But Schwartz says that’s an incorrect association, because most runners can’t run a 10K in a half hour.
There are a couple ways to find your CV pace. The simplest way is to use Schwartz’s online calculator. Type in a recent 5K or other race time (as long as it's between seven and 60 minutes), and it’ll spit out your CV pace. If you want to calculate it on your own, you’ll need to know your VO2 max, which is a measurement of the amount of oxygen your body uses to aerobically exercise as hard as possible.
You can figure out your VO2 max by going to a sports medicine clinic to perform a treadmill test, during which you wear a mask to measure oxygen consumption as the treadmill speed and incline increase gradually. You can also do the Cooper Test, during which you run as many laps as possible on a track in 12 minutes. Your resulting number of laps predicts VO2 max. Once you know your VO2 max, calculate 90 percent of it. That’s your approximate CV pace.
Why and how does CV work?
There are different types of muscle fibers in the human body, commonly referred to as slow-twitch (type-1) and fast-twitch (type-2).
“[Type-1 muscle fibers] don’t have a lot of power but they have a lot of natural endurance,” Schwartz says. “They’re the kinds of muscle fibers that we use for postural maintenance, being upright… easy continuous long distance running, cycling, swimming, and so on.”
So, you can get pretty good at running by sticking to easy distance runs. You’ll work on aerobic fitness—about 60 to 75 percent of your VO2 max—as well as your type-1 muscle fibers. But if you want to see bigger improvements, you have to improve type-2 muscle fibers.
Type-2 muscle fibers are broken down into 2a and 2x. Type-2x muscle fibers activate when sprinting or performing very explosive, powerful movements. Type-2a muscle fibers activate when running intermediate paces between aerobic running and sprinting.
For a long time, lactate threshold pace, also known as anaerobic threshold, was considered the holy grail for endurance training. The more often you work at that pace—which is 80 to 83 percent of VO2 max for most avid runners, according to Schwartz—the higher your lactate threshold becomes over time, thereby improving your ability to sustain a fast pace without having to slow.
Schwartz wasn’t convinced: “The question I always had is: is running at lactate threshold the best way to improve the lactate threshold pace?” His answer? Critical velocity—90 percent of your VO2 max—is better.
By training at CV pace, he says, you become fatigue-resistant. Your heart pumps more blood, red blood cell count increases, many capillaries develop and surround your type-2a muscle fibers, and you create more mitochondria, which process oxygen.
“Your fast intermediate muscle fibers are so good now at using the available oxygen and not generating fatigue that you can go faster longer,” Schwartz says.
How can you incorporate CV pace into your training?
For most people, Schwartz recommends running repetitions of roughly three to four minutes at CV pace. For 30-minute 10K runners, that would mean reps of 1,000 to 1,200 meters. For a 30-minute 5K runner, that would mean less distance, roughly 500 to 600 meters. Complete beginners should aim for two-minute reps. You can run fartlek-style by alternating “on” portions at CV with “off” portions at an easy jog, or run them on the track as an interval workout.
As for recovery, it depends if you’re running by time or distance. If running by time, Schwartz says to take one-third of the rep time as rest. If you’re running by distance, take 20 percent of the distance as rest. For example, if you’re running 3-minute reps, take a one-minute jog between. If you’re running 1,000-meter reps, jog 200 meters.
Schwartz says that those new to CV pace should start with no more than four CV-paced reps once a week. As you get better, there are a few ways you can make the workouts more challenging. You can increase the number of reps, increase the distance of reps, or decrease the amount of rest. When you get used to the pace, you can play around with workouts a little more. Maybe you include the pace in a mixed-zone workout (a workout with reps of varying distances and speeds) or tack on some CV-paced reps at the end of a tempo run.
Finally, Schwartz warns not to neglect CV pace in favor of speed work as you get closer to race day: “High-intensity training is very much like salting your food. Add a little salt to your burger, and it tastes great. But you put more than a little salt, it starts to become unpalatable and you gotta throw it away.” He recommends never dropping below 50 percent of your typical CV pace volume; otherwise, you’ll start to lose that fitness.
Critical velocity workouts to try
Remember to prepare for every workout with a proper warmup.
If you can race 5K or less in 30 minutes
Shorter reps are your friend. As you improve, add more reps. Once you feel comfortable, you can add more time or distance.
- 3 or 4 repetitions of 2 minutes at CV pace, 40-second easy jog recovery.
- 3 or 4 repetitions of 400 meters at CV pace, 100-meter easy jog recovery.
If you can race 5K to 8K in 30 minutes
You should feel like you can run CV pace for three to four minutes at this point. From here, try to improve how far you can go.
- 6 repetitions of 3 to 4 minutes at CV pace, 1-minute to 80-second easy jog recovery.
- 6 repetitions of 800 meters at CV pace, 160-meter easy jog recovery (can be 200 meters for simplicity).
If you can race 8K to 10K in 30 minutes:
You’re close to an elite level. To continue improving, add more reps or lengthen the distance of each one.
- 6 to 8 repetitions of 4 minutes at CV pace, 80-second easy jog recovery.
- 6 to 8 repetitions of 1,000 meters at CV pace, 200-meter easy jog recovery.