Can Functional Threshold Power Replace Lactate Threshold Testing?

When it comes to endurance cycling, knowing your threshold is very important. If you're an athlete chasing performance, threshold data helps you train at the right intensity, avoid burnout, and track improvements over time.

For years, lactate threshold (LT) testing in the lab has been seen as the gold standard. It's precise, grounded in physiology, and gives insight into when the body starts to accumulate fatigue related byproducts. But it's not always practical or accessible. That’s where Functional Threshold Power (FTP) comes in. FTP as we know, is a simple, cost-effective way to estimate an athlete’s threshold using power output, without needing a lab. Most of us serious cyclists have power meters or use smart trainers nowadays which are an excellent training tool.

So the question is: can FTP actually replace lactate threshold testing? A 2022 study by Sitko and colleagues explored exactly that, and the findings are worth digging into.

In this study, 46 trained road cyclists completed two key tests. The first was a graded exercise test in the lab to determine several lactate threshold markers. The second was a 20-minute time trial to calculate FTP, defined as 95% of the average power from that effort. The researchers then compared FTP with seven common lactate threshold markers, including Dmax, modified Dmax, fixed lactate concentrations of 2 and 4 mmol/L, and a few points based on how much lactate had risen above baseline.

The results were interesting. FTP showed strong correlations with several lactate thresholds, especially Dmax, modified Dmax, and the 4 mmol/L point. Correlation coefficients ranged from 0.68 to 0.93, which is considered large to very large. That supports the idea that FTP can provide a fairly accurate estimate of some lactate thresholds.

However, significant differences were found between FTP and other thresholds, especially the 2 mmol/L point and the thresholds defined by smaller increases above baseline. This suggests that while FTP works well in some cases, it’s not a direct replacement for all lactate thresholds, especially when more detailed physiological insight is needed. So what does this mean for us as coaches and athletes?

For most cyclists and coaches, FTP is a very practical tool. It’s easy to run, repeatable, and provides useful information for training. If you’re programming workouts, tracking progress, or building broad training zones, FTP can be a great option. But if you’re working with elite athletes, aiming for high precision, or need detailed metabolic profiling, lactate testing still holds value.

In short, FTP isn’t a complete replacement for lactate testing, but it is a reliable and accessible estimate when used appropriately. Both tools have their place, and knowing when to use each one will help you make smarter decisions for performance and progression. If you get a chance to do a lactate test in a laboratory setting on your own cycling equipment or a setup that is very close, such as an SRM bike where you can try to match the position as accurately as possible, then I would highly recommend availing of this.

Thanks for reading,

Graham

OBN Performance

Reference:

• Sitko, Sebastian; Cirer-Sastre, Rafel; Corbi, Francisco; López-Laval, Isaac. Functional Threshold Power as an Alternative to Lactate Thresholds in Road Cycling. Journal of Strength and Conditioning Research 36(11):p 3179-3183, November 2022. | DOI: 10.1519/JSC.0000000000004070