What Is Lactate Threshold?

Lactate threshold (LT) is the exercise intensity at which lactate begins to accumulate in your blood faster than your body can clear it. It's one of the most important physiological markers for distance running performance.

Why Threshold Matters

Your threshold pace represents the fastest pace you can sustain for an extended period (roughly 45-60 minutes for trained runners). Improving your threshold directly improves your:

• Half marathon pace (run just below threshold)
• Marathon pace (significantly below threshold)
• 5K/10K performance (threshold determines sustainable speed)
• Recovery between hard efforts (better lactate clearance)

Understanding Threshold Training

Threshold Pace Characteristics

When running at threshold:

• Breathing is heavy but controlled
• You can speak in short phrases, not full sentences
• Effort feels "comfortably hard"
• You could sustain this for 45-60 minutes in a race
• Heart rate is typically 85-90% of maximum

How Threshold Relates to Race Paces

Pace Type	Relative to Threshold
Easy pace	60-75 sec/mile slower
Marathon pace	15-25 sec/mile slower
Half marathon pace	5-15 sec/mile slower
Threshold pace	Baseline
10K pace	10-15 sec/mile faster
5K pace	20-30 sec/mile faster

Threshold Workout Types

Classic Tempo Run

A continuous run at threshold pace:

• Duration: 20-40 minutes
• Intensity: Threshold pace
• Structure: Warm-up → Tempo → Cool-down

Example: 15 min easy, 25 min at threshold, 10 min easy

Benefits:

• Teaches sustained effort
• Builds mental toughness
• Simulates race-like fatigue

Cruise Intervals

Threshold pace broken into segments with short recovery:

• Work intervals: 5-15 minutes each
• Recovery: 1-2 minutes easy jogging
• Total threshold time: 20-40 minutes

Example: 4 × 8 min at threshold, 90 sec recovery

Benefits:

• Accumulates more time at threshold
• Easier to maintain pace quality
• Good for building toward longer tempos

Threshold + Race Pace

Combines threshold running with race-specific pace:

• Alternating segments of threshold and goal race pace
• Good for half marathon and marathon preparation

Example: 3 × (8 min threshold + 5 min half marathon pace)

The Science of Threshold Training

Physiological Adaptations

Training at threshold pace causes specific adaptations:

Increased lactate clearance: Your muscles and liver get better at processing lactate, turning it back into usable fuel.

Higher threshold point: The pace at which lactate accumulation begins shifts faster—you can run harder before hitting the wall.

Improved fat oxidation: Better fat burning at higher intensities spares glycogen for when you need it.

Capillary density: More blood vessels in muscles improve oxygen delivery and waste removal.

Why 85-90% Effort?

Threshold training works because it stresses the lactate system without overwhelming it. Running harder (like VO2max intervals) trains different systems. Running easier doesn't sufficiently stress the threshold.

The goal is maximum time at threshold intensity—which means sustainable pace, not all-out effort.

Using Your Threshold Pace

Weekly Threshold Training

For most runners, one threshold session per week is sufficient:

Base building phase:

• 20-25 min tempo or cruise intervals
• Focus on consistency, not maximizing

Build phase:

• 25-35 min tempo or longer cruise intervals
• Can add marathon pace segments

Peak phase:

• Maintain threshold fitness
• May reduce volume slightly, maintain intensity

Combining with Other Training

Threshold training fits well with:

• Easy runs (recovery between threshold sessions)
• Long runs (aerobic base complements threshold work)
• VO2max intervals (different energy system, different day)

Avoid doing threshold work:

• The day before or after VO2max intervals
• When significantly fatigued from recent racing
• During recovery weeks (reduce to maintenance level)

Common Threshold Training Mistakes

Running Too Fast

The most common error. Threshold should feel controlled, not desperate. If you're struggling to complete the workout, you're probably running too fast.

Signs you're too fast:

• Can't complete planned duration
• Gasping for breath
• Pace drops significantly late in workout
• Need excessive recovery afterward

Running Too Slow

Less common but still problematic. Easy-moderate effort doesn't stress the threshold system enough to drive adaptation.

Signs you're too slow:

• Workout feels easy throughout
• Could easily run faster
• Heart rate stays below 80% max
• No real fatigue at finish

Too Much Volume

More threshold running isn't always better. Beyond a certain point, you're just accumulating fatigue without additional adaptation.

Guidelines:

• 10-15% of weekly mileage at threshold (maximum)
• One threshold session per week is usually optimal
• Quality matters more than quantity

Not Enough Recovery

Threshold training is demanding. Insufficient recovery leads to diminishing returns and injury risk.

Recovery guidelines:

• Easy day before and after threshold sessions
• At least 48 hours between quality sessions
• Cutback weeks to absorb training

Threshold vs. Tempo: Clarifying Terms

These terms are often used interchangeably, but technically:

Threshold pace: A specific physiological intensity—the pace at which lactate begins accumulating.

Tempo run: A training session at sustained moderate-hard effort—typically at or near threshold pace.

A tempo run is usually run at threshold pace, but the terms describe different things (intensity vs. workout type).

Testing Your Threshold

Race-Based Estimation

Your recent race times provide good threshold estimates (this calculator uses this method).

Field Test

A 30-minute time trial gives a direct threshold measurement:

1. Warm up thoroughly
2. Run as fast as you can sustain for 30 minutes
3. Your average pace ≈ threshold pace

Note: This is demanding and should replace a hard workout, not be added to one.

Lab Testing

Lactate testing in a sports lab provides the most accurate threshold measurement, but isn't necessary for most runners.

Threshold Pace Through the Season

During Base Building

• Limited threshold work (strides, short fartlek)
• Focus on aerobic development first
• Threshold will improve from general fitness

During Race Preparation

• Weekly threshold sessions
• Progressive increase in duration
• Race-specific combinations

During Taper

• Maintain some threshold work for sharpness
• Reduce volume significantly
• Last threshold workout 7-10 days before race

During Recovery

• No structured threshold work
• Easy running only
• Let the body absorb training stress

Use the Training Load Calculator to monitor your overall training stress as you incorporate threshold work.