When we exercise, we stress the body’s physiological systems in order to cause a signal for positive change, for adaptation to the training. To measure positive changes, we can use data that are extrinsic to the body. For example, how fast we can move across a timed segment, keeping up or making an attack in our group rides, how fast we complete our usual route or how fast we can climb that nemesis of a hill that you have struggled with. We also use data that is intrinsic, or inside of the body to track and measure progress.
Examples of intrinsic measures:
Rating of perceived exertion (RPE) - How hard an effort may is/was
Heart rate - A measure of how your heart responds to the strain of exercise. It increases with exercise as it forces blood to the working muscles.
Power - Measured in watts and the focus on this article.
Over the past 20 years, measuring how much power we can apply each pedal stroke has proved to be a reliable measure to track progress of the rider. This is measured by a device on the pedal, the drivetrain of your bike or the rear wheel where the chain puts pressure on the gear cogs. It measures the force the rider pushes into the pedal multiplied by how fast the rider can turn the pedals. This is far more effective than using heart rate alone, for various reasons. Heart rate takes time to ramp up to an effort level, it has a ceiling to how high it can go often called (HR Max), and it is highly variable to the effort you can put out on the bike. Some days you can put out an effort and your heart rate is low and steady, some days you can put out the same effort and your HR is sky high. Heart rate is highly variable based on sleep, hydration, stress, fatigue, and temperature. Power, on the other hand, is consistent, it is directly related to the force applied and how fast you can move your legs.
Functional Threshold Power (FTP) was coined by Dr. Andrew Coggan and Hunter Allen and is the most known out of all of the metrics that you may hear. By definition, it is the amount of power you can hold in a relatively steady state for about an hour. The goal was to correlate it to a physiological response of your aerobic energy system and the ability for the body to produce and clear a substance called lactate at a steady rate.
Lactate is a byproduct of energy utilization of the body and in the presence of oxygen, can be converted to energy. When oxygen is not present, it can accumulate in the blood, when this occurs, you will not be able to sustain this activity for much longer as you will eventually fatigue and eventually stop. The goal is to find the power level that you can produce this substance and clear it at a rate that it is produced. This is about where your FTP would theoretically be.
Why is this important?
It is important because FTP is the one of most reliable determinants of performance success on the bike. The higher your FTP is, the faster you can ride without getting tired, the better chance you can stay with that group and set yourself up to win a race or set a personal best on your favorite course. It is important to get a relatively accurate number of what you can ACTUALLY do here. It is difficult to accept a lower number, and often most numbers are much too high. Many people, including myself, have had to eat a bit of humble pie and accept that this is only a snapshot in time, and a place from which to build and set effective and accurate training levels. If your number is too high, you are not training efficiently and effectively and will most likely burn up for going too hard all of the time.
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