Answer: Functional Threshold Power, or FTP, is an estimated measure of your highest sustainable power and is used to anchor training levels. These training levels are associated with particular physiological responses and allow you to design workouts and training plans that address specific types of fitness.
FTP is a measure of your ability to maintain a high — but manageable — workload for a somewhat lengthy duration. From a physiological perspective, it’s the point at which your lactate production has risen, leveled off, and then closely matches your lactate removal and just barely keeps that flooding at bay. In other words, it’s that grey area between the power you can sustain for a very long duration, typically an hour, and the fleeting power you can only tolerate for a couple of minutes.
FTP is supposed to be analogous to a rider’s hour power, but for most it is not, and that’s okay. As long as you properly assess your FTP (here’s a resource for how to do that) to get the best possible estimate of your fitness, you can get faster.
More on the Science Behind FTP
On a deeper level, your FTP is a balancing act between energy demand and energy supply closely involving your aerobic and anaerobic energy delivery systems. When your aerobic energy system — the one that uses oxygen to metabolize key fuel sources — is able to meet the energy needs of your muscles, there’s less contribution from your anaerobic energy system.
But as you work harder and put out more power, oxygen uptake tops out even as your leg muscles require more energy. This increases the demand on your anaerobic system — the one that can metabolize fuel sources without oxygen and create energy a lot faster. But eventually, your anaerobic system can’t even keep up and your muscles accumulate lactate — they can’t clear it as quickly as it’s being generated. Your breathing ramps higher, your legs start to burn, and your time at this power output becomes very limited.
But just below this point, there’s a harmony between energy supply and demand and a ‘lactic balance’ is achieved. This metabolic steady state, often termed your lactate threshold, actually correlates really closely with your FTP. So much so, that the two terms are basically synonymous.
The Core Reason FTP is Important to Cyclists
Once you know your FTP, you’re able to customize every workout you do so that it’s optimized to your current fitness level. TrainerRoad does this automatically for you. The more precise your FTP is, or better said, the more precise your FTP estimate is, the more effective your training will be.
By using your FTP as the foundation upon which all of your workouts are built, it opens the doors for you to introduce a training stimulus that can bring about consistent and lasting increases. Structured training is that stimulus, and stimulus paired with adequate recovery is exactly what you need to get faster.
For more answers to your cycling training questions, listen to the Ask a Cycling Coach podcast presented by TrainerRoad. New episodes are released weekly.
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