Unlocking Performance: Joe Friel’s Lactate Threshold Test and How to Use It
If you’re serious about training smarter, not harder, then understanding your lactate threshold (LT) is key. Joe Friel, renowned endurance coach and author of The Triathlete’s Training Bible, has long advocated for using LT as a benchmark for structured training. His simple yet effective field test allows athletes to determine their threshold without invasive or lab testing. Here’s how it works and how you can use it to level up your performance.
What is Lactate Threshold (LT)?
Lactate threshold refers to the highest intensity you can sustain before lactate accumulation outpaces your body’s ability to clear it. Go beyond this point, and you’ll start to fatigue much faster. Knowing your LT helps structure training zones for better endurance, pacing, and race-day execution.
Joe Friel’s Lactate Threshold Field Test
Joe Friel’s test is a simple 30-minute time trial designed to estimate your functional threshold pace, power, or heart rate. Here’s how to do it:
- Warm-up: 15-20 minutes of easy running or cycling with some strides.
- Time Trial:
- Run or cycle at the hardest (near max) sustainable effort for 30 minutes.
- After the first 10 minutes, take a lap on your watch or cycling computer for the remaining 20 minutes.
3. Calculate Your LT: The average HR, pace, and power for the last 20 minutes approximates your lactate threshold intensities.
Note: It is recommended that you use a chest heart rate monitor for the most accurate HR data.
How to Use Your Lactate Threshold to Train Smarter
Once you have your LT heart rate, you can structure your training into effective zones:
Heart Rate Training Zones (Based on LT from Friel’s Method)
| Zone | Heart Rate % of LTHR | Description |
| Zone 1 (Recovery) | ≤ 75% | Easy effort for recovery runs and warm-ups. Helps build aerobic base with minimal fatigue. |
| Zone 2 (Endurance) | 76-87% | Aerobic endurance training, ideal for long runs/rides. Builds efficiency and fat-burning capacity. |
| Zone 3 (Tempo) | 88-94% | Moderate intensity for sustained efforts. Improves aerobic threshold but should be used strategically. |
| Zone 4 (Threshold) | 95-100% | Hard but sustainable intensity, close to race pace for events like the half marathon. Key for improving lactate clearance. |
| Zone 5 (VO2 Max) | 101-105% | High-intensity effort, pushing max aerobic capacity. Used for short intervals to develop top-end speed and power. |
Practical Applications for Your Training
- Dial in your race pace: Use LT data to pace effectively during endurance events.
- Improve efficiency: Train at or just below LT to push your endurance limits.
- Customise hydration and fueling: LT testing helps determine how much energy your body burns at different intensities—critical for dialing in fueling strategies.
- Track progress: Repeat the test every 6-8 weeks to monitor improvements.
Ready to Train Smarter?
Joe Friel’s lactate threshold test is one of the best DIY performance tests available. By incorporating it into your routine, you can optimise pacing, endurance, and training efficiency.
Looking for the right fuel to support your high-performance training? Pulse Nutrition’s Endurance Fuel is designed to sustain energy and hydration at the intensities where it matters most. Fuel your why.
Try the test, adjust your training, and let us know how it goes! 🚀
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