Lactate threshold (LT)

What it is

As effort rises, blood lactate stays near resting levels at first, then starts to climb, then rises steeply. Sport scientists describe two key points:

• First threshold (LT1): where lactate first rises above baseline. Easy aerobic training sits around or below this.
• Second threshold (LT2): roughly the highest effort at which lactate production and clearance stay in balance (the maximal lactate steady state). This is what most athletes mean by “threshold”.

A 2009 review found 25 different lactate threshold concepts in the literature, which is part of why labs and apps don’t always agree.

Why it matters for training decisions

Threshold measures relate closely to endurance performance, especially in running. They’re also a good anchor for training zones, because they reflect your current fitness rather than a population formula.

How it’s measured, and the limits

A lab test measures blood lactate during a step test. Field tests estimate threshold heart rate, pace or power from a sustained hard effort, and some watches and platforms estimate it from your training data. Results depend on the protocol, so stick with one method when retesting, and test when you’re fresh.

How P247 uses it

If you know your threshold heart rate, P247 can build your heart rate zones from it once you turn zones on. You can also copy in, by hand, threshold-based zones you already use in another app.

This glossary is general information to help you understand your training data. It isn't medical advice, diagnosis or treatment. For injury, illness, medication, blood test results or any health concern, speak to a qualified health professional.

← Back to the glossary