Monday, March 22, 2010

Physiological Fitness - Economy

It's been a long time since I lasted posted anything here. Putting on a camp in Majorca wih all of the travel and time zone changes has made things a bit challenging this past few days. And then a flu bug on top of all of that really did me in. But I'm much better today and managed to find time between camp activities to do some writing.

The last of the big three physiological fitness determiners is economy. Sport science understands less about this one than the other two, but it may be the most important. It has to do with how efficiently you use oxygen while exercising. Measuring oxygen used is just another way of measuring energy during exercise since in the human body how much oxygen you use also tells you how much energy you’re expending. Your economy is much like the economy rating for a car. – how many miles per gallon of gas. Only in the case of exercise it’s how many milliliters of oxygen per mile.

The longer the race is the less important aerobic capacity becomes and the more important economy is. This is because at the longer distances you exercise at a lower percentage of your aerobic capacity. So having a big VO2max won’t be of great benefit. But wasting even a little energy per stroke or stride due to poor economy will add up to a lot of wasted energy – and a slow performance – in a long race.

We know what can be done to boost your aerobic capacity. You can do lots of miles and mix in high-intensity intervals. Economy is a bit different. There are some things you have control over, but many you can do nothing about. For example, we know that for swimming being tall with long arms and legs and big feet improves economy. Unfortunately, you can’t change those. In the same way, for cycling having a long femur bone relative to your total leg length improves economy. For running being short and small are good for your economy. As an endurance athlete economy is improved by having a greater percentage of slow twitch muscle fibers. And there are other improvements to our physiology we would also make if we had control over them such as increasing the number of mitochondria we have (these are the little powerhouses in the muscle cell that produce energy). These are all things we have little or no control over.

So what things can you control to improve your racing efficiency and use fewer milliliters of oxygen per mile? The most common technique. You must realize that if you decide to go this route and make changes to your current technique that there will be a period of time during which you become less efficient. This will show up as a higher than normal heart rate at any given speed or power. And it may take weeks if not months to make the new technique your normal. At that point you should be faster at the same heart rates as before.

Others that are beneficial for the bike and run are reducing excess body weight and using lighter equipment. Then there are sport-specific efficiency improvers. The most notable is aerobars on the TT or tri bike along with other aerodynamic equipment such as wheels, helmet and bike frame. As a swimmer you can improve economy by improving the flexibility of your shoulders and feet, especially the ability to point your toes. Interestingly, the research shows that having less flexibility in the ankle joint makes for more economical running as this appears to improve the release of energy stored in your calf muscle with each footstrike.

Training components that improve economy are intensity and frequency. Training at a high speed or power has been shown to make athletes more economical at all speed and power outputs including the lower range. But it doesn’t work both ways. Going very slowly doesn’t pay off with greater economy at the high end of speed and power.

One of the best ways to improve your technique and therefore your efficiency is to do your sport frequently even if each session is very brief. For example, for a triathlete to become a more efficient swimmer with only two hours a week to devote to it, swim four times a week for 30 minutes each time. That will improve your efficiency sooner than doing two, one-hour swims each week.

Plyometric exercises have also been shown to improve economy in both runners and cyclists. This involves doing explosive jumping, bounding and hopping drills. For the run brief, powerful hill repeats are much like plyometrics.

There is still a great deal of debate about whether or not traditional strength training with weights improves economy. I believe it does as I have seen so many of the athletes I’ve coached over the years improve their performances remarkably after a winter of lifting weights – provided they did exercises which closely mimic the movements of the sport. Doing curls is unlikely to make you a better runner. But doing step ups may help.

In summarizing the three physiological fitness determiners remember that aerobic capacity is largely the result of your genetics as optimized by steady training over many years. And the longer your race is the less significant this is to performance, even though it wouldn’t hurt to have a high VO2max. Lactate threshold is highly trainable and you should see a steady improvement in your speed or power when you reach this threshold. Economy may be the best determiner of performance of the three. But, as mentioned, we don’t know a whole lot about it and much of what is known to be important is out of your control. The things you do have some measure of control over often take a long time to accomplish (e.g., changing your technique), are difficult to achieve (e.g., lower body weight) or are expensive (e.g., lighter bike).

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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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Sunday, March 7, 2010

Physiological Fitness - Aerobic Capacity

Exercise physiologists generally agree that there are only three things you can improve to become physiologically more fit for endurance sports performance: aerobic capacity, lactate threshold and economy. Ultimately, these are the reasons you train. So what are they and how do you improve them? I'll discuss aerobic capacity now and come back to lactate threshold and economy in a few days.

Also referred to as VO2 max, aerobic capacity is your ability to use oxygen to produce energy. The more oxygen your body can process the more energy you can produce and the greater your output (power or pace). It’s common to find that the fastest athletes in a race have the highest aerobic capacities of the entrants. The farther down the race results you go typically the lower the athletes’ aerobic capacities. But don’t take this to mean that knowing your VO2 max tells you how fast you will go or how well you will do compared with others in your race category. The two other physiological factors – lactate threshold and economy – also play a major role in race outcomes. One of these by itself does not constitute all of what it takes to race fast.

Aerobic capacity is literally at the heart of success in endurance sport. Improvements in aerobic capacity have largely to do with how much blood (which contains oxygen) the heart pumps out to the working muscles with every beat. This is called “stroke volume” and has a lot to do with how much aerobic capacity you have. A purpose of training is to improve your stroke volume. There are basically two ways to do this. The first is to focus on the volume of your training. The heart responds to lots of time spent at higher-than-resting intensity (above about 50 percent of VO2 max) by becoming more efficient and effective which ultimately means pumping more blood per beat.

The other way to improve aerobic capacity is by doing high-intensity intervals, especially those done at about the power or pace associated with your VO2 max. At that intensity your heart rate is approaching maximum, so these are very hard efforts. This method will produce a higher stroke volume sooner than by relying only on volume. Most experienced athletes employ both strategies.

There are other physiological contributors to aerobic capacity such as aerobic enzymes found in the muscles, blood vessel diameter and ability to dilate, blood volume and related hematocrit (red blood cells). Many athletes seem to believe their lungs are the deciding factor when it comes to aerobic capacity. Training produces insignificant changes in lung volume.

Body weight also has a lot to do with aerobic capacity. The formula for determining VO2 max is expressed in terms of milliliters of oxygen consumed per kilogram of body weight per minute. What this means is that as you lose body weight, especially fat as opposed to sport-specific muscle, your VO2 max increases. And most of us have experienced this at both ends of the weight spectrum. When we have gained weight it’s harder to run or ride a bike uphill. Conversely, when body weight has been low the effort of exercise is decreased at any given power or pace. This is clearly the affect of body weight on aerobic capacity.

Aerobic capacity is largely dependent on who your parents were. Research (Bouchard, 1986) has shown that identical twins have nearly identical aerobic capacities. While genetics probably sets the boundaries for the upper limit of your VO2 max, proper training can take you to near the upper limit. But also bear in mind that there are two other physiological factors that contribute to endurance performance. I'll come back to them soon (I hope).

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