The Paleo Diet for Athletes (18 page)

WHAT IS FITNESS?

Athletes talk about fitness a lot. So what is it? Endurance athletes usually discuss fitness in terms of performance. Runners talk about their 10-km pace or a recent marathon time. Cyclists lay claim to high-power
outputs. While these are actually quite good ways to define fitness, they don’t tell us anything about the mechanisms responsible for it—which may provide clues regarding how to go about improving it. That, of course, is the ultimate goal of athletic training.

Exercise physiologists are a bit more precise when it comes to “fitness.” For decades they have proposed that there are only three things you can do to become more fit for endurance sports. You can increase your aerobic capacity, elevate your anaerobic threshold, and become more economical. That’s it. Nothing else. All of your training comes down to these three elements. And they are what ultimately produce your fast 10-km run and high-power output. So what are they, what can you do in training to improve them, and how are they affected by what you eat?

Aerobic Capacity

You probably know this as “max VO
₂
.” It’s a measure of how much oxygen your body uses when working at a maximal aerobic effort. Physiologists define it as the maximal volume of oxygen consumed in milliliters per kilogram of body weight per minute (the formula is ml O2/kg/ minute). The higher your max VO
₂
, the more likely you are to perform at a high level in endurance events.

Your aerobic capacity is unique to each sport. If you have a high max VO
₂
for swimming it won’t necessarily be high for cycling or running.

To raise your max VO
₂
, do highly intense intervals. This workout would be something along the lines of 3-minute intervals at an intensity you could hold for only about 5 or 6 minutes. Do four to six of these intervals in a session with 3 minutes of recovery between them at least once each week. Doing one to three of these sessions weekly in the last 12 weeks before a priority A race has been shown in the research to produce significant gains in aerobic capacity.

Aerobic capacity is also raised by losing excess body weight. In the formula above, oxygen consumed is divided by body weight, so as body weight goes down, max VO
₂
rises. This is undoubtedly obvious to you.
At those rare times when your body weight has increased, riding your bike up a hill or running became a bit harder. Your aerobic capacity had decreased. Later in the chapter we’ll get into this issue of body weight and performance along with the related benefits of eating the Paleo Diet.

Anaerobic Threshold (AT)

You may know this as “lactate threshold” or even “ventilatory threshold.” Sport scientists differentiate among these three thresholds, but for the average athlete the differences are not critical to training or performance. Basically, this is the highest intensity you can maintain for about an hour. Another way of thinking of AT is that it’s the intensity at which you begin to “redline.” When you cross this threshold as you speed up, you sense the effort becoming
hard.
On a perceived-effort scale of 1 to 10, with 10 being
very, very hard,
AT occurs at about 7.

A high AT is very important for endurance performance. Among athletes with similar aerobic capacities, AT plays a major role in determining the outcome of a race. Many studies have shown it to be the better predictor. In other words, you really can’t predict who will win an endurance race based only on aerobic capacity (max VO
₂
). But we know that people with a high max VO
₂
will cross the finish line first. That person is likely to have the highest AT among those with high aerobic capacities.

In the lab, AT is measured as a percentage of aerobic capacity. During a high-intensity workout or race, a highly fit athlete will experience AT at about 85 percent of max VO
₂
. Less fit athletes will have lower ATs at around 75 to 80 percent. The higher the AT as a percentage of max VO
₂
, the faster the athlete will be.

In workouts AT can be gauged using heart rate, pace, or power. This can be done using a heart rate monitor, a runner’s GPS device for pace, or a bike power meter. Your average heart rate, pace, or power for an all-out 30-minute effort is a good predictor of your AT intensity.

To improve AT do long intervals at your AT pace, power, or heart rate with short recoveries between them. The high-intensity interval
duration could be 5 to 20 minutes long with 20 to 60 minutes of accumulated AT time within a session. For example, a common AT workout may be 5-minute intervals at AT pace, power, or heart rate five times (5 x 5 min @ AT). This workout could be 300-meter swim intervals, 2-mile bike intervals, or 1,200-meter run intervals. The recovery time between intervals is about one-fourth the duration of the work interval. So for 5-minute intervals the easy recoveries would be 75 seconds.

As your AT rises with increasing fitness you will go faster at your AT heart rate or have a lower heart rate at your AT pace or power. You’re becoming more fit. When this change occurs, it’s time to retest your AT.

Training and racing at your AT or slightly below it, as in races lasting about an hour or longer, can be improved by becoming better at burning fat for fuel. We’ll take a closer look at what that means in relation to your diet later in this chapter.

Economy

Sport scientists understand less about economy than about aerobic capacity and anaerobic threshold. Yet it may be the most important of the three when it comes to performance in long endurance events.

I’m certain you understand the concept. Your automobile has an economy rating—how many miles it gets per gallon of gas. Your body also has an economy rating—how far it can go on a given amount of energy (or oxygen, which is an indirect indicator of energy use). While your car runs on gasoline, for humans the primary fuels are fat and glycogen (stored carbohydrate). Highly economical endurance athletes use their stored energy sparingly.

Many variables affect economy. Some of these are the result of genetics—the physical characteristics your parents gave you. For example, good swimmers tend to have long arms and big hands. Most of the best cyclists have long femur (thigh) bones relative to the lengths of their legs. Economical runners tend to have long tibias (shin bones). In general, the best endurance athletes have more of the slow-twitch muscles than do power-sport athletes, who inherited lots of fast-twitch muscles. The list
of such genetic traits common to the best endurance athletes by sport is quite long.

Economy isn’t just the result of the athlete’s physiological makeup, however. It is also improved by using lightweight, aerodynamic, and hydrodynamic equipment (shoes, bikes, skis, swimsuits), having well-honed skills, and improving sport-specific strength.

In terms of your diet, the most important component of economy is your body’s fuel preference. A body that prefers to use fat for fuel, as opposed to carbohydrate, is economical. Even the skinniest athlete has enough fat stored away to exercise for hour after hour. But our bodies store relatively little carbohydrate. Training the body to burn fat while sparing carbohydrate improves economy.

FAT BURNERS AND CARB BURNERS

Are you a fat burner or a carbohydrate burner? Most athletes don’t know, yet this is valuable information, especially if you compete in endurance events lasting longer than about 2 hours. The longer your event, the more critical this concept is to performance.

A limiting factor for such events is carbohydrate intake. If you don’t take in enough sugar (the common form of carbohydrate found in sports drinks, bars, gels, and other sport nutrition products) during the event, you are likely to run low, which ultimately means your name in the results will be followed by the letters DNF (did not finish). On the other hand, take in too much sugar and your gut can’t process it—possibly resulting in bloating and nausea.

To further complicate the matter, there is a considerable amount of individual variation when it comes to using carbohydrate during such events. Some people’s bodies burn more carbohydrate as a percentage of total calories used. They are “sugar burners” and need to be very concerned with carbohydrate intake. The “fat burner” has a body that prefers to use fat for fuel and so spares stored carbs. This person is metabolically
ready for long endurance. That may be the result of fortunate genetics, effective training, wise nutrition, or some combination of these variables.

How do you know if you’re a sugar burner or a fat burner? And how do you determine if you are taking in the right amount of carbohydrate? The answers are found in your respiratory equivalency ratio (RER), sometimes also called the respiratory quotient (RQ). They aren’t exactly measures of the same factor, but are close. Once you know your RER, you have a better idea of your fat- versus sugar-burning preference and what your carb-intake needs are during exercise. If you find you’re a sugar burner, it is possible to change your body so that it relies more heavily upon fat. More on this later.

RER is determined by doing a metabolic assessment or max VO
₂
test. Until recently you had to go to a medical clinic or university lab to have such a test done, but now there are boutique testing centers popping up around the country in health clubs, bike shops, and running and triathlon stores. A few coaches even offer this service. You can probably find a test facility somewhere near where you live. The test generally costs between $150 and $250.

RER testing is most common for cycling and running. There are a few facilities that can test rowers, Nordic skiers, and swimmers. If you’re a triathlete and can afford only one test, I’d suggest doing it on the bike, as your nutrition here generally has a greater impact on your race performance than when you are swimming or running, since half of the race is on the bike.

The typical test protocol is simple. It starts you out at a very easy effort and increases the intensity every few minutes until you fatigue and can no longer continue. In order to get good data, you need to treat the test like a race by resting for a couple of days before. Doing this test with accumulated fatigue from several days of hard training will muddle the results and what you learn from them.

There will be several pieces of information resulting from such a test. One is the all-important RER. As the intensity of the test increases, you will gradually burn more carbohydrate (stored as glycogen) for fuel. The RER closely estimates how much of the energy came from carbs and how much from fat.
Table 6.1
may be used to determine your percent of energy burned from these two nutrients throughout the test.

TABLE 6.1

Carbohydrate and Fat Utilization as a Percentage of Total Calories Relative to Respiratory Equivalency Ratio (RER)