Glossary: Lactate threshold vs FTP

Definitions

• Lactate threshold (LT): the exercise intensity at which blood lactate accumulation begins to exceed clearance. Measured in a lab via blood draws across a ramped test.
• Functional Threshold Power (FTP): the highest average power sustainable for approximately one hour. Field-tested, not lab-tested.

Relationship

For most athletes, FTP and the power at LT are very close (within 5 to 10 W of each other), but they are not the same thing:

• LT is a physiological event (lactate kinetics).
• FTP is a performance ceiling (sustained power).

A well-trained athlete can hold a small range above LT for short periods, so FTP can sit just above LT, not exactly at it.

Which one the Hub uses

The Hub anchors training zones to:

• CP (Critical Power) for the dashboard bike zones (see Glossary: zones).
• FTP for activity time-in-zone calculations.
• Run threshold pace for run zones (analogous to FTP).
• CSS for swim zones (the swim equivalent).

LT itself is not a stored Hub metric type. If you have a lab LT value, log it as FTP if it matches your sustained hour power, or as a CoachNote with the lab context.

How to test each

• FTP test: 20 minutes all-out, take 95 percent. Or a ramp test. Or the CP test (3 + 12).
• LT test: lab visit with blood draws every 3 to 4 minutes during a graded ride.

Most athletes never have a lab LT measured. The FTP / 20-min test is the practical substitute and is close enough for training prescription.

When the distinction matters

• You have both LT and FTP and they disagree by more than 15 W. Then the LT data point is useful for placing zone boundaries; FTP alone may not be enough.
• You are doing structured lactate-test-based training. Most age-groupers do not, and this is fine.

See also: Glossary: FTP, CSS, threshold pace, Critical Power Test.