Why Critical Velocity Training (B Pace) Should Be Part of Your Running Plan
When it comes to running faster, longer, and stronger, critical velocity (CV) training is like the Swiss Army knife of workout strategies—versatile, effective, and deceptively simple. But what exactly is critical velocity, why do the coaches at PGC1 love it, and how can it take your performance to the next level? Let’s dive in.
What is Critical Velocity or ‘B- Pace’?

Critical velocity is the fastest pace you can sustain for approximately 30-40 minutes of running without your performance dropping off a cliff. Think of it as the sweet spot between easy running and all-out effort—a challenging but controlled pace that improves your engine without leaving you gasping for air or hobbling for days.
In more scientific terms, CV is roughly 88-92% of your VO₂ max and sits just above your lactate threshold (LT2). This is the point where your body is starting to accumulate lactate a little bit faster than it can clear it. To be really technical we would expect most athletes to be around 4-6 mmol of blood lactate here. The intensity is hard but manageable. This helps us improve your maximal aerobic capacity as we are running with increased intensity without adding too much fatigue.
Why Do Running Coaches Use Critical Velocity Training?
Here’s the magic of B Pace training: it targets multiple physiological systems that underpin endurance performance. Coaches use it because:
It Boosts Aerobic EfficiencyRunning at CV teaches your body to use oxygen more efficiently, improving your ability to sustain effort over time. It’s like upgrading the fuel economy of your car—you’ll go further on the same energy.
It Increases Lactate ClearanceTraining at this pace enhances your body’s ability to shuttle lactate out of your muscles and back into usable energy. This means you can hold a faster pace before fatigue sets in.
It’s High Reward, Low RiskUnlike all-out interval sessions, such a VO2 max effort, B Pace training is intense enough to stimulate adaptation but controlled enough to reduce the risk of overtraining or injury. It’s the Goldilocks zone of running intensities.
It’s VersatileWhether you’re training for a 5K or a marathon, B Pace workouts fit seamlessly into most training plans. They’re an excellent bridge between your easy runs and top-end speed work.

What Does a B Pace Workout Look Like?
B Pace workouts typically consist of intervals at your critical velocity pace, with short rest periods to ensure you’re staying aerobic. As a running coaching team we can manipluate different parts of the session to give more stimulus. Here are a few examples:
Classic B Pace Intervals: Anything up to around 5 mins of running in one go with a third of the rep time as a jog recovery maximum volume around 30 mins.
B Pace Fartlek: 10 x 2 minutes at CV pace, 1-minute float (run slightly faster than an easy jog).
Blended Threshold and B Pace Workout: A staple on the PGC1-Coaching training plan here we blend threshold work with B pace work to help aid your ability to remove lactate from the muscle and simulate race performance.
These sessions are hard enough to leave you feeling accomplished but not so brutal that you’re wrecked for days.
What Are the Benefits to Performance?
The results of B Pace training speak for themselves. Runners who incorporate it into their training often experience:
Improved Stamina: You’ll find it easier to hold race pace for longer periods without falling off the pace.
Better Race-Day Performance: Because B pace is close to your lactate threshold, it directly translates to faster times in events from 5K to marathon.
Enhanced Recovery: B paced training doesn’t beat up your legs like all-out intervals, so you’ll recover quicker and stay consistent in your training.
Just be careful though: It’s very easy to slip out of B Pace and into VO2 effort and faster. When doing B pace respect the intensity and don’t try and push too hard within this zone!

The Fun Factor
Let’s face it—running can sometimes feel like a grind. B Pace training adds variety and purpose to your plan, breaking the monotony of easy miles while still feeling productive. As a running coach is is great setting athletes sessions that we know they will respond well to physiologically which has good scientific backed logic and they will enjoy too (mostly!). There’s a special kind of satisfaction in nailing a B Pace session, knowing you’re working smart and hard.
In a Nutshell
Critical velocity training is the secret sauce of endurance training: challenging enough to spark adaptation, gentle enough to keep you healthy, and versatile enough to fit any goal. This is why as coaches we incorporate B Pace sessions into your training plan, so that you’ll build strength, stamina, and speed in a sustainable way.
About the Author: Joshua Schofield
Joshua Schofield is the Head Coach at PGC1-Coaching, where he combines his passion for endurance sports with science-backed training methods to help runners of all abilities achieve their goals. Known for his engaging and informative writing style, Joshua is dedicated to breaking down complex training concepts into actionable advice. When he’s not coaching or writing, you’ll likely find him testing out the latest training theories on the trails or cheering on his athletes at races across the UK.
Great blog, very interesting to read about the use of science behind the plans!