Functional Threshold Power Test
“The purpose of this initial test is to do a ride where you can average the highest watts possible for a substantial period of time. Be sure to do the same warm-up, and to use the same intensity in your warm-up, each time you do the test. The warm-up and recovery intervals throughout the test should be at about 65 percent of your functional threshold power, which would be Endurance pace. After the three fast pedaling intervals, the true warm-up begins.
When you begin the 5-minute all-out effort, punch it and hold it! Start at a high pace, but not so high that you die at the end. You should have a little in reserve to kick it to the finish line in the last minute. The goal of this first part is twofold: first, to “open” up the legs for the rest of the effort, and second, to capture your ability to produce watts in what is called VO2max power, or Level 5 (discussed later in this chapter). Your next effort is more likely to be truly representative of your FTP.
For the 20-minute time trial, ride on a road that is fairly flat, allowing a strong, steady effort for the entire 20 minutes. Do not start out too hard! Get up to speed and then try to hold that speed. If you have never done one of these efforts before, try this on a steady climb or into a slight headwind, where you are forced to ride at a maximum effort for the entire 20 minutes. Your goal is to produce the highest average wattage over the entire period. If you suddenly run out of energy, you will not be able to produce your true maximal steady-state power. It is always better to be a little under what you believe to be your FTP for the first 2 minutes, build speed, and then ride at your maximum level in the last 3 minutes.
Finish the ride at an easy pace.
Once this test is over and you have downloaded the data, you will need to figure out what your average power was for the entire 20-minute effort. Then you will take this number and subtract 5 percent from it. The number that results will be your functional threshold wattage value. (Hold on to this number, as we will come back to it later in this chapter.) So, for example, if you average 305 watts for the 20-minute time trial, you would calculate that 305 × 0.05 = 15.25, and 305 – 15.25 = 290. Thus, your functional threshold power is 290 watts.
The reason for subtracting 5 percent of the watts from your 20-minute test is that FTP is defined as the highest average wattage or power that you can maintain for 60 minutes. Because some athletes have a hard time focusing for 60 minutes on a maximal effort, and those who can learn very quickly that a 60-minute time trial is not that much fun, we have found that 20 minutes is more realistic in terms of getting athletes to do more regular and higher-quality tests. Since 20 minutes is a shorter time period, it incorporates more of the athlete’s anaerobic capacity, however, and this skews the wattage data by about 5 percent over a 60-minute effort. By subtracting that 5 percent, you will come up with a wattage number that would be very close to your 60-minute power measure.
One goal of any training program is to increase power at threshold (FTP), and how often threshold power changes significantly depends in part on an individual’s training history and habits. For example, someone who is just beginning to cycle or returning to cycling after a long break may see large and rapid changes in threshold power at first, whereas an experienced rider who has been training for many years, or an athlete who maintains a high level of conditioning year-round, will probably experience much less variation. In general, assessing FTP four to six times a year (e.g., in the middle of winter training, near the start of serious outdoor training as a baseline, partway through the pre-competition period to track improvement, a couple of times during the season to determine peak fitness, and finally, after your peak fitness is over for the season, to determine how far you have “fallen”) is probably sufficient.”
“The ultimate reason for having a power meter is to reach your goals and achieve your potential in cycling. Surely, the scientist in all of us wants to experiment with new toys and gear, but that same scientist recognizes that, as cyclists or multisport athletes, using a power meter is quite possibly one of the best ways to get to know ourselves at an even deeper level.”
“What Is Functional Threshold Power (FTP)?
The term “threshold” has become synonymous with the word “confusion” in the minds of many athletes. There are many different words for essentially the same concept: anaerobic threshold (AT), lactate threshold (LT), maximal lactate steady state (MLSS), onset of blood lactate (OBLA), and just plain old “threshold.” It seems that there are just as many possible quantitative definitions, with different versions of the concept based on heart rate (HR), blood lactate, wattage, and so on. As a result, even in many scientific articles the authors have to present their own definition to clarify what they are talking about.
For more than thirty years, exercise physiologists have known that the exercise intensity at which lactate begins to accumulate in a person’s blood—that is, his or her LT—is a powerful predictor of that person’s endurance performance ability. This is because although an individual’s cardiovascular fitness—that is, his or her maximal oxygen uptake (VO2max)—sets the upper limit to his or her rate of aerobic energy production, it is the individual’s metabolic fitness—that is, LT—that determines the percentage or fraction of this VO2max that he or she can utilize for any given period of time.
“The physiological factors determining LT are complex, but essentially blood lactate levels serve as an indirect marker for biochemical events within exercising muscle. More specifically, a person’s LT reflects the ability of his or her muscles to match energy supply to energy demand, which in turn determines the fuel “mix” (i.e., carbohydrate versus fat) used and the development of muscle fatigue. Consequently, LT is the single most important physiological determinant of performance in events ranging from something as short as a 3 km pursuit to a stage race lasting as long as three weeks. This is especially true when LT is expressed in terms of power output, which also takes cycling efficiency into account. Because the effort that is experienced by an athlete when exercising at any given intensity is dependent upon his or her power output relative to power at LT, this parameter provides a physiologically sound basis around which to design any power-meter-based training program.
However, few athletes have ready access to lactate testing on a regular basis. What’s more, even those who do are still generally dependent on the person performing the test to first design an appropriate protocol, and then to correctly interpret[…]”
“Almost all current power meters report the amount of work you have performed in joules in addition to measuring and recording your power in watts. Joules (J) and kilojoules (kJ) are therefore a measure of energy expenditure, or work performed. Here in the United States, however, this is usually measured in kilocalories, or Calories (1 kilocalorie, or large Calorie [with a capital “C”], is equal to 1,000 small calories [lowercase]).
By definition, there are 4.184 kJ per Calorie, so at first glance it would seem that to determine your energy expenditure using power-meter data, you would simply divide your total work in kJ by 4.184. However, this is not correct because power meters measure external work production, not the amount of energy needed to perform that work. Most of the energy expended during cycling is actually converted into “waste” heat that must be dissipated to the environment, with only a portion available to actually turn the pedals. The relationship between work performed and energy expended depends upon your thermodynamic efficiency (i.e., your ability to process food and convert it into energy) when cycling, which, for most trained cyclists, is on the order of 20–25 percent.
Thus, to estimate your energy expenditure (in Calories, or kilocalories) from the amount of work performed, using a power meter, you would need to first divide your total work in kilojoules by 4.184, but then multiply this result by either 4 (if efficiency is at 25 percent) or 5 (if efficiency is at 20 percent). These conversion factors tend to simply cancel one another out, such that you can also take the value for the total work performed in kJ as an estimate of your energy expenditure in kilocalories (or Calories). Although the exact relationship between kJ and kcal is not one to one, it probably is not worth worrying about any error this assumption creates, since an individual’s efficiency can only be readily determined in a laboratory setting, and can vary depending upon the intensity and duration of training, environmental conditions, and other factors.”
“Enhance Indoor Training
With a power meter, you can use your indoor trainer to the fullest extent. One of the first things you will learn about using a power meter on the road is that your wattage will have a high degree of variability. Your wattage fluctuates on a moment-by-moment basis depending on the conditions, and sometimes this is not the best way to train. On an indoor trainer, without the outside influences of wind, hills, dogs, and so on, you can focus your intervals in exact wattage zones for optimal improvement.
In addition, indoor training gains new meaning when you can compare your intensity with on-road efforts. Indoor training also becomes more interesting, as now you have a new goal and focus to your workout. With the advent of the latest computerized indoor trainers, a cyclist with a power meter can even go out and ride a particular racecourse, come back, and download these data into the trainer to re-create this exact ride indoors. Power-meter data from indoor training sessions are also “cleaner” than from on-road efforts, as the massive wattage fluctuations caused by changes in terrain, riding with others, and justthe variable nature of pedaling frequency are gone from the power file, making it easier to analyze the periods of effort.”
“Heart rate monitoring alone does not tell you how much you are improving on your bicycle; it just tells you how fast your heart is pumping. Your heart rate may be affected by factors that have little to do with actual performance, however, and using only a heart monitor could easily trick you into believing a false conclusion about your fitness, mislead you about your performance, or even undermine your confidence.
Your heart rate is influenced by your level of hydration, by the air temperature, by your core temperature, by how well you slept the night before, by the level of stress in your life, and other factors. The rate at which your heart can pump depends on so many factors that sometimes you really are better off not knowing your heart rate when training or competing, and going on your “perceived exertion” instead. Although heart rate monitors can be valid and useful tools—athletes have been training with them now for more than twenty years, and certainly this has improved the level of fitness of many athletes—heart rate is just one small piece of the puzzle. How fast your heart is pumping is a response to a[…]”
Excerpt From: Hunter Allen & Andy Coggan PhD. “Training and Racing with a Power Meter, 2nd Ed.” iBooks.