Lactate Threshold Test
The lactate threshold is the exercise intensity at which lactate, a secondary muscle fuel, begins to accumulate rapidly in the blood because it’s being produced faster than it’s being used. Exercise scientists argue constantly over the definition and meaning of the lactate threshold, but one thing is certain: It is a very powerful predictor of endurance performance.
In clinical environments, the lactate threshold is determined through a graded exercise test (a workout in which the intensity increases incrementally every few minutes) combined with blood draws. Typically, the intensity level at which the blood lactate concentration reaches 4 mmol/L is marked as the lactate threshold.
Troy Jacobson, a longtime triathlon coach and the creator of Spinervals, is among the top coaches who believe it’s possible for athletes to find their lactate threshold on their own with a functional test requiring no needle pricks. According to Jacobson, in trained athletes, lactate threshold intensity is roughly the highest intensity that can be sustained for 60 minutes. Since going all-out for 60 minutes is one killer workout, Jacobson instead uses a 20-minute max effort that is then adjusted to estimate the result of a 60-minute effort.
Hop on your indoor bike trainer and begin with a gentle warm-up of 10-15 minutes. To determine your lactate threshold power, you will need to use a trainer with a built-in power meter. If you want to know your lactate threshold heart rate, wear a heart rate monitor. After completing your warm-up, run or ride as fast as you can for 20 minutes. Be sure to pace yourself so that you aren’t forced to slow down before 20 minutes due to fatigue. Finally, cool down for at least five minutes.
Note your average power output and/or heart rate for the 20-minute max effort. Adjust these numbers downward by 5 percent to determine your lactate threshold numbers. For example, if your average heart rate in the test was 179 bpm, your lactate threshold heart rate is approximately (179 x 0.95 =) 170 bpm.
“This is a repeatable benchmark test that any conditioned athlete can perform every six to eight weeks to assess changes in fitness,” says Jacobson.