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 thing: 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 definitions, with different versions of the concept based on heart rate, 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 functional lactate threshold (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 functional lactate threshold 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, functional lactate threshold—especially when expressed in terms of power output, which also takes into account cycling efficiency—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. Just as important, 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. Functional threshold power is the highest power that a rider can maintain in a quasi–steady state without fatiguing for approximately one hour. When power exceeds FTP, fatigue will occur much sooner, whereas power just below FTP can be maintained considerably longer.
Determining Functional Threshold Power
So, how do you go about determining your functional threshold power? One way is via laboratory testing with invasive blood sampling, but few people have access to such testing on a regular basis. In addition, power at LT as determined in this manner is often significantly below what athletes and coaches tend to think of as a “threshold.” A more convenient and possibly more accurate way of determining your FTP is to simply rely on data collected using your power meter in the field. There are a number of different ways to do this, each of which has its advantages and disadvantages, but all of which provide very similar estimates of threshold power.
I believe that the best way to begin is to just go out and do a ride specifically designed to find your threshold, such as the one described below. This is without a doubt the first big step in your new adventure in training with power.
The Threshold Test
The purpose of this initial test is to do a ride where you can average the highest watts that you can for a substantial period of time. When you get to the effort, make sure to pace yourself so that you do not tire prematurely. Start out with a 20-minute warm-up, which is just riding along at a moderate pace, or at about 65 percent of your max heart rate (HR), or what would be called your endurance pace. Again, be sure to do the same warm-up, and to use the same intensity in your warm-up, each time you do the test. Then do three fast pedaling efforts at 100 rpm for 1 minute each, with 1 minute of easy recovery pedaling between each, in order to further prepare the muscles for the effort. After these, ride easy for 5 minutes at 65 percent of max HR. Then the true test begins:
- 5 minutes all out. Punch it and hold it! Make sure that you 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). Doing this initial 5-minute effort also helps to dispense with the initial “freshness” that always exists at the beginning of a ride. Then, when you do your next effort, you will be able to produce power that is more likely to be truly representative of your FTP.
- 10 minutes easy at endurance pace. Ride at 65 percent of max HR.
- 20-minute time trial. Try to do this on a road that is fairly flat and allows you to put out a strong, steady effort for the entire 20 minutes. Do not start out too hard! That’s a common mistake, so make sure that you get up to speed and then try to hold that speed as best you can. If you have never done one of these efforts before, we would suggest trying this on a steady climb or into a slight headwind, where you are forced to do it at a maximum effort for the entire 20 minutes.
- 10–15 minutes at endurance pace. Again, pedal easy at 65 percent of max HR.
- 10–15 minute cooldown. Finish the ride at an easy pace.
Your goal in the main portion of the test, the 20-minute segment, is to produce the highest average watts over the entire period. It’s not a good test if you go out too hard and suddenly run out of energy, because you will not be able to produce your true maximal steady-state power. It is always better to start out in the first 2 minutes a little under what you believe to be your FTP, build up along the way, and then ride at your maximum level in the last 3 minutes.
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. So, for example, if you average 300 watts for the 20-minute time trial, you would calculate that 300 x 0.05= 15, and 300 – 15 = 285. Thus, your functional threshold power is 285 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 most 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.
Now that you know your FTP, you can determine your Power Training Levels…. and that’s the topic for my next article…
PS: Check out my twitter feed @hunterpeaks for power training tips and to keep up with my latest adventures.
Hunter Allen is a USA Cycling Level 1 coach and former Professional Cyclist. He is the co-author of “Training and Racing with a Power Meter”, co-developer of TrainingPeaks WKO+ Software, and is the CEO and Founder of thePeaks Coaching Group. He has coached over 500 athletes ranging from professionals to fitness enthusiasts, and has helped many athletes achieve dreams and goals that they didn’t think were possible. He specializes in coaching cyclists with wattage meters and is on the forefront coaching with cycling’s newest tool.
Hunter has online training programs available here (including some great winter training plans)
Contact Hunter directly at www.PeaksCoachingGroup.com
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