Training Aerobic Threshold Pace: Why It’s a Double-Edged Sword

Aerobic Threshold training—sometimes referred to as "steady state" or "Lactate Threshold 1 (LT1)"—has become a buzzword in endurance training circles. On the PGC1 Pace chart we define it as ‘D-Pace’ for Discipline because it requires discipline to hold the effort and discipline as to when we should use it. It’s not quite easy running, but it’s not flat-out either. It’s that pace where you feel like you’re working, but you feel relatively strong in doing so. 

It’s also where things can start to go wrong—if it’s overused or misunderstood.

Let’s break it down.

What is The Aerobic Threshold, Really?

LT1 marks the point where blood lactate levels begin to rise above baseline but are still manageable and mostly being cleared. The zone is still heavily aerobic which is why typically it sits around marathon pace or effort for most people. Within training zone setups this sits below LT2 or Threshold work. I would see this as being the middle zone as outline below: 

Zone	Description
Easy, E Pace or Aerobic	Internal aerobic hypertrophy, simply put just volume at a low intensity where we increase your aerobic efficiency.
LT1, D Pace or Steady State	Typically around Marathon Effort for most people it’s where lactate starts to rise but we are able to get rid of it faster than it appears.
LT2, C Pace, Threshold or Tempo	Typically around the pace you can sustain for 60 mins and around the 4mmol blood lactate marker. Above this threshold value the body produces lactate faster than it can get rid of it.
Critical Velocity or B Pace	Critical Velocity sits between all out effort and threshold, here we can run hard and get anaerobic benefits of training without going all in.
VO2 Max or A Pace	VO2 max refers to the maximal amount of oxygen our lungs can inhale and utilise at any one moment. This is your maximal aerobic capacity, work here is tough and painful!
Anaerobic Pace Zones	We don’t do too much work here as it’s not massively trainable or specific but it’s running very hard!

It feels like you're doing something productive—and you are mostly doing something productive but potentially not too specific. And that’s exactly why it’s dangerous.

The Benefits of Aerobic Threshold Work

• Aerobic Development: LT1 work sits right in the sweet spot for building mitochondrial density, fat oxidation, and overall aerobic capacity.

• Efficiency Gains: Training at this intensity teaches your body to become more efficient at clearing and utilising lactate, which is a huge plus for endurance performance.

• Sustainable Focused Work: Unlike threshold or VO₂max sessions, LT1 efforts can be sustained for longer durations, offering extended stimulus without needing as much recovery—in theory.

But Here’s the Catch…

The Aerobic Threshold is very close to the pace most of us race at—whether you're targeting a half marathon, Olympic triathlon, or marathon. It’s fast enough to feel race-specific but not quite hard enough to trigger a big red flag from your central nervous system.

That’s why many athletes accidentally drift into LT1 pace during easy runs—and that’s where the fatigue starts to creep in.

• It’s Too Hard to Be Easy: If you're doing lots of volume and letting your easy runs creep into LT1, you’re not truly recovering.

• It’s Too Easy to Be Hard: If you rely too heavily on LT1 work for your “quality” sessions, you might not be getting enough top-end stimulus to shift your lactate threshold or VO₂max.

  
  

 Why This Matters for Your Goal Race

Most endurance events (especially half marathons and marathons) are run around or just above LT1. That means the pace is very specific—and very fatiguing when overused in training. Because it mimics race pace so closely, your body accumulates subtle fatigue if you do too much of it, which can blunt your freshness and reduce race-day sharpness.

In other words, LT1 training is like a scalpel: incredibly powerful when used precisely, but risky if used carelessly. 

Our Take at PGC1

We love LT1 work—when it’s strategic. We program it carefully to build aerobic strength, to simulate segments of race pace, or to add intensity during high-volume phases. But we’re just as mindful about not letting it creep into easy runs or dominate the training week.

Because more isn’t always better.

The Bottom Line

LT1 is a valuable tool—but it’s not a magic pace. Know when you’re using it, and why. If you’re unsure whether you’re training in the right zones, your coach can help fine-tune your approach.

Train smart. Race strong.

This blog was written for the PGC1-Coaching website by Joshua Schofield. Josh is the Head Coach and Founder of PGC1-Coaching. With a background as a sport and exercise scientist and former international athlete; Josh has developed a deep understanding of sports science and endurance coaching. Josh leads the PGC1 team with a passion for helping athletes of all abilities reach their potential. His coaching philosophy blends evidence-based training with a personalised, athlete-first approach.