Lactate Threshold
Lactate threshold is the exercise intensity where lactate accumulates faster than it can be cleared. Learn about LT1, LT2, and how lactate threshold relates to FTP and endurance performance.
Quick Answer
Lactate Threshold — is the exercise intensity at which lactate production exceeds the body's ability to clear it, causing rapid fatigue. There are two thresholds: LT1 (aerobic threshold) and LT2 (anaerobic threshold), with LT2 closely corresponding to FTP.
What is Lactate Threshold?
Lactate threshold refers to the point during exercise when lactate accumulates in the blood faster than it can be removed. Your muscles constantly produce lactate, but at higher intensities, production outpaces clearance.
There are actually two distinct thresholds:
| Threshold | Other Names | % of Max HR | What Happens |
|---|---|---|---|
| LT1 | Aerobic threshold, VT1 | 75-80% | Lactate begins rising above baseline |
| LT2 | Anaerobic threshold, MLSS, VT2 | 85-92% | Lactate rises exponentially |
FTP closely corresponds to LT2—the intensity you can sustain for approximately one hour.
LT1 vs LT2 Explained
LT1 (Aerobic Threshold)
- Occurs around 2 mmol/L blood lactate
- Top of Zone 2 training
- Can sustain for hours with proper fueling
- Conversation still possible
- Uses primarily fat as fuel
LT2 (Anaerobic Threshold)
- Occurs around 4 mmol/L blood lactate (varies individually)
- Corresponds to FTP
- Maximum sustainable effort (~60 minutes)
- Limited speech possible
- Relies heavily on carbohydrate fuel
The zone between LT1 and LT2 is where tempo and sweet spot training occurs.
Why Lactate Threshold Matters
| Factor | How LT Affects Performance |
|---|---|
| Race pace | LT2 sets your ~1 hour sustainable power/pace |
| Training zones | All training zones relate to lactate thresholds |
| Fatigue onset | Above LT2, fatigue accumulates rapidly |
| Recovery | Efforts below LT1 promote active recovery |
Improving lactate threshold allows you to ride or run faster before fatigue sets in.
How to Test Lactate Threshold
Lab Testing (Gold Standard)
Blood lactate is measured during progressive exercise:
- Exercise intensity increases every 3-5 minutes
- Finger-prick blood sample at each stage
- Lactate concentration plotted against intensity
- LT1 and LT2 identified from curve
Field Estimates
You can estimate lactate threshold without lab testing:
30-Minute Test (Cycling):
LT2 power ≈ Average power for 30 minutes at max sustainable effort
Heart Rate at Threshold:
- LT2 typically occurs at 85-92% of max HR
- Individual variation is significant
Use our FTP Calculator to estimate your threshold power.
Lactate Threshold vs FTP
| Metric | Definition | Relationship |
|---|---|---|
| Lactate Threshold (LT2) | Physiological marker (blood lactate) | The underlying physiology |
| FTP | Functional metric (power output) | The practical measurement |
FTP is essentially the power output at your lactate threshold—they're measuring the same thing from different angles. However:
- LT2 is more precise (requires blood testing)
- FTP is more practical (just ride hard for 20-60 min)
- Both improve with threshold training
Training to Improve Lactate Threshold
Key Adaptations
Training raises lactate threshold through:
| Adaptation | Result |
|---|---|
| More mitochondria | Better lactate processing |
| Increased capillary density | Better oxygen delivery |
| Enhanced lactate transport | Faster clearance |
| Improved fat oxidation | Spares glycogen longer |
Best Training Methods
| Method | % of LT2/FTP | Duration | Frequency |
|---|---|---|---|
| Zone 2 endurance | 70-75% | 2-4 hours | 2-3x/week |
| Sweet spot | 88-94% | 20-60 min | 2x/week |
| Threshold intervals | 95-105% | 8-20 min | 1x/week |
The 80/20 principle applies: ~80% easy (Zone 2) and ~20% hard work.
Read our guide on How to Improve FTP for specific workouts.
Lactate Threshold Heart Rate
For heart rate-based training, LT2 typically occurs at:
| Population | LT2 as % of Max HR |
|---|---|
| Untrained | 80-85% |
| Trained | 85-90% |
| Elite | 88-92% |
Individual variation is significant—some athletes have LT2 at 82% while others are at 91%.
Common Misconceptions
"Lactate causes fatigue"
False. Lactate itself isn't the problem—it's actually a fuel source. The hydrogen ions produced alongside lactate cause the burning sensation and interfere with muscle contraction.
"Train at threshold to improve threshold"
Partially true. While threshold work helps, high-volume Zone 2 training below LT1 is equally important for building the aerobic base that supports threshold improvements.
"Higher lactate threshold is always better"
Context matters. Threshold matters most for sustained efforts (time trials, triathlon). For sports with variable intensity (road racing, criteriums), VO2 Max and repeatability matter more.
Common Questions
How long can I sustain effort at LT2?
Approximately 45-75 minutes at LT2/FTP. This varies by:
- Individual physiology
- Pacing (starting too hard shortens duration)
- Fueling and hydration
- Environmental conditions
Does lactate threshold change with age?
Yes—lactate threshold naturally declines with age, similar to VO2 Max. However, training significantly slows this decline. A well-trained 50-year-old often has higher threshold than an untrained 25-year-old.
Should I train above or below lactate threshold?
Both, but mostly below. The 80/20 rule suggests:
Can I improve my lactate threshold quickly?
Initial improvements come faster (weeks), but significant gains require months of consistent training. Expect 5-10% improvement in lactate threshold power over 8-12 weeks of structured training.