How to Determine Lactate Threshold (LT) Without a Power Meter for Cyclists

Question:  I want to improve my power at lactate threshold (LT) so I can excel in time trials and on long climbs. But I don’t know how hard to ride during LT training. Lab tests are expensive, I’m told that heart rate is unreliable, and I don’t have a power meter. Is there a simple method for nailing LT intensity without all the black magic? — Barry S.

Coach Fred Matheny Replies: LT can be gauged by wattage, lactate accumulation, heart rate or perceived exertion. The first requires a relatively expensive power meter as well as a lab test to find your wattage at LT for training purposes. Measuring lactate means periodic blood draws — not too practical while you’re riding the road! And heart rate can vary for a given power output due to hydration status, environmental conditions and other factors.

Then there’s the rating of perceived exertion (RPE). In other words, how hard you feel like you’re riding.

In the old days, we trained with RPE. Before heart monitors there was no other way. The good news is that research shows RPE is an effective way to determine intensity.

Allen Lim did ground-breaking research on cycling power while working on his Ph.D. in exercise physiology at the University of Colorado. While he was still studying, in an e-mail to me he wrote:

“Training prescriptions don’t need to be overly complicated. If athletes are in tune with themselves and quite experienced at perceiving effort, then what they perceive as hard can be used consistently as a reference point for training-induced adaptations and for determining training pace.”

So, if your workout calls for a 20-minute effort at close to your LT, it’s fine to forget the technology and simply ride at an intensity that feels hard. You’ll be close to your lab-determined ideal intensity.

How hard is hard? Think of effort on a scale of 1 (lying on the couch) to 10 (riding flat-out and suffering). On this simplified RPE scale, LT intensity is between 8 and 9. This is the point at which breathing is at the breakpoint between hard but steady and labored with gasping.

Another way to find it: Increase intensity until you begin to gasp, then back off a notch.