Sunday, March 14, 2010

Physiological Fitness - Lactate Threshold

I apologize for the recent gap in posts. I'm preparing to go to Majorca for a camp next week and so have been up to my ears in work that needed to be done first. This post is a continution of the topic I started last week - the three determiners of physiological fitness. The last post discussed aerobic capacity. This one has to do with lactate threshold.

While aerobic capacity gets a lot of ink in endurance-sport magazines, for the competitive athlete the lactate threshold is what the bulk of the hard training should focus on. Your aerobic capacity isn’t going change a lot if you’ve been training and racing seriously for three or more years. But you may be able to bump your lactate threshold up a lot.

So what is lactate threshold? We need to start with a little biochemistry to understand this measure of intensity.

As your body uses carbohydrate to create energy it creates a by-product inside the working muscle cells called lactic acid. As the intensity of a workout increases this liquid begins to seep out of the muscle cell into the surrounding space and blood stream. In so doing it changes its composition by giving off hydrogen ions. It’s now called lactate. Despite its “bad boy” reputation, lactate is actually a beneficial substance for the body during exercise as it is used to create more energy so that exercise may continue. It’s the hydrogen that is the real bogey man. This is what causes the burning sensation in your muscles and the heavy breathing at high effort levels. Measuring lactate levels in the blood is a convenient way of estimating how much hydrogen is in the body. The more intense the workout, the greater the amount of lactate released into the blood — and the more hydrogen ions interfering with muscle contractions. (By the way, neither lactate or hydrogen ions cause the muscle soreness you may experience the day after a hard workout. That's another of the myths that refuses to die in sport. Some day I will do a post just on such old saws.)

Lactate threshold is sometimes referred to as anaerobic threshold. While sports scientists may argue about the differences between these two terms, for athletes there is little reason for concern. Both are essentially the high intensity at which you begin to “red line.” On a perceived exertion scale of 1 (low) to 10 (high) you redline at about 7 or 8. Whatever your heart rate, power or pace is at this moment is your lactate threshold intensity. The higher this is as a percentage of your aerobic capacity the faster you will race, especially in steady-state events such as triathlons or endurance running races. It’s common with fit athletes for their lactate thresholds to fall in the range of 80 to 85 percent of their aerobic capacities.

Most well-conditioned athletes can sustain this level of intensity for about an hour. Because of this there is a new term created by Hunter Allen and Dr. Andrew Coggan, the authors of Training and Racing With a Power Meter, to describe this intensity – functional threshold. This is the average bike power (functional threshold power – FTPw) or running pace (functional threshold pace – FTPa) you can maintain for one hour. Simple.

If you are using heart rate to determine your training zones, your lactate threshold heart rate (LTHR) is your average heart rate for a one-hour race effort. This is unique to the sport, so your rowing, cross-country skiing, swimming, cycling and running LTHRs are likely to be different. And therefore your heart rate zones will also be unique to each sport.

The body has two ways of improving your lactate threshold as a result of training. It can come to better tolerate the acid and it can also become more effective at removing the acid. As with all aspects of fitness, the way to train your body to tolerate and remove hydrogen ions is by training at your lactate threshold. This, then, is the best marker of training intensity. That’s why I base heart rate zones on it rather than on maximum heart rate.

I hope to get something posted on the last topic - economy - soon but expect this may be at least a week or more. We'll see.

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Thursday, September 3, 2009

Functional Threshold

Someone asked on my Twitter feed today what ‘FTP’ is. I had recently mentioned it in a tweet. Since I use that term a lot it’s probably a good idea to define it. A little background first…

Anaerobic threshold. Lactate threshold. Ventilatory threshold. These are terms used to describe points in the intensity spectrum when the athlete is on the verge of or is already accumulating lactate and hydrogen ions in the body’s fluids. This means that the body is rapidly becoming acidic. Scientists attempt to define the above terms very precisely and see each as having unique conditions. Despite their best efforts even they fail to be in complete agreement on what each means.

As athletes we seldom get involved in such discussions. We tend to see these terms as interchangeable and meaning roughly the same thing – you are “redlining.” And for all intents and purposes, that is reasonable since these thresholds occur at roughly the same point and are seldom exactly the same from one day to the next due to variations in fitness and fatigue.

Magazines and books written for the athletic market use these terms when talking about training for endurance sports, also often interchangeably. So we have come to accept and generally understand what they mean, especially 'anaerobic' and 'lactate' threshold. They are less clear on 'ventilatory' threshold since this term is used much less frequently than the other two. In fact, you can simply use the word 'threshold' when speaking with other athletes and they will usually take that to mean a high effort with an RPE of about 7 or 8 on a 10 scale.

Now there is a new term being used to describe this level of intensity – 'functional' threshold. This is largely due to the work of Andrew Coggan, PhD, and Hunter Allen and their book, Training and Racing with a Power Meter (VeloPress, 2006). I like this term for field work because it removes all of the mystery associated with scientific concepts such as hydrogen build up, lactic acid, lactate, aerobic, anaerobic, RER, ventilatory rates, and the like. Very few really understand these terms. Functional threshold solves this problem by defining redlining based on actual output in a field test or race.

Functional threshold power or pace (FTP) is the highest mean average power or pace you can maintain for one hour. That’s quite precise, clear and logical. It even fits nicely with what we know about AT, LT, and VT. When you are in good shape these various measures of intensity can be maintained for about an hour. So rather than trying to describe this phenomenon with biological conditions, we simply define it based on a common output denominator.

Once you know FTP your training zones may be established based on power or pace. WKO+ software does this for you. All you do is plug in your FT power (cycling) or pace (running) and the zones are automatically calculated. Then workout intensity is determined based on pace or power zones. WKO+ will also determine heart rate zones using the system described in my books. Just enter your average heart rate for a one-hour race effort. Of course, this software goes well beyond simply setting zones. It also allows you to see a visual representation of the pace- or power-based workout and graph the workout/race data into several different charts for analysis.

All of this analysis data is based on FTP so it must be kept updated with periodic testing to make sure you have it right. Over the course of a season FTP will change a lot if your training is affective. And it is one of the best indicators of how your fitness and race readiness are progressing. While heart rate remains rather steady throughout the season, power and pace change considerably. That’s obvious since becoming more fit provides several benefits including being faster and more powerful. Training is all about accomplishing these goals. That’s why I keep a close watch on FTP for the athletes I coach and highly recommend that self-coached athletes do the same.

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