For many, this is the season they rest or maybe you're thinking about racing next year.  If you're coming off a long rest or starting here are the "Cardinal Rule of Training" excerpt from Joe Friel.  Although this excerpt is about cycling, the principles apply to fitness in general.  This excerpt from Cycling Past 50 is reprinted with permission by Human Kinetics.

"Since 1971, I’ve trained and coached athletes in a variety of sports with abilities ranging from beginner to professional. Some became national- and world-class competitors; others achieved less impressive, but no less important, personal goals. All improved their physical abilities in some way.

I don’t know who learned more - me or them. My lessons came from observing how small changes in training brought big results. Some riders obviously had a lot of potential when they came to me. They were highly motivated and did challenging workouts, but for some reason they weren’t getting all they could from training. At first this was perplexing. How could athletes with such great potential achieve so little? After years of reviewing hundreds of training logs, I began to see patterns and understand why a person with latent ability was not coming close to attaining it. He or she was breaking one of what I call the Cardinal Rules of Training.

No matter what you want from riding, there are three rules you must obey. Breaking any of these means, at best, limited improvement, and, at worst, overtraining and loss of fitness. The Cardinal Rules of Training are as follows:

• Rule 1. Ride consistently.
• Rule 2. Ride moderately.
• Rule 3. Rest frequently.

These may seem overly simple. Sometimes, however, the most important things in life are the simplest. Such is the case with training.

Rule 1 is based on the premise that nothing does more to limit or reduce fitness than missed rides. The human body thrives on regular patterns of living. When cycling routinely and uniformly progressing for weeks, months, and years, fitness steadily improves. Interruptions from injury, burnout, illness, and overtraining cause setbacks. Each setback means a substantial loss of cycling fitness and time reestablishing a level previously attained. Inconsistent riding is like pushing a boulder up a hill only to see it roll back down before reaching the top - frustrating.

Riders who violate the first rule of training are usually frustrated. The solution to their problem is simple: Train consistently. "Okay," they say, "but how do I do that?" Good question, and that leads to the other Cardinal Rules. The second Rule, ride moderately, is the first step in becoming more consistent. This one usually scares highly motivated, hard-charging cyclists. They can see themselves noodling around the block in slow motion and not even working up a sweat. However, that’s not what moderate means.

Moderate riding is that level of training to which your body is already adapted, plus about 10 percent. For example, if the longest recent ride is 40 miles, then a reasonable increase is to 45 miles next week. That’s moderate. A 60-mile ride would not be moderate and could lead to something bad, such as an injury or overtraining that forces several days off the bike and a lapse in consistency. Another moderate change is steadily progressing from riding flat terrain to rolling hills, to riding longer hills, to riding steep and long hills. Going from riding on the flats to steep, long hills is not moderate.

Consistent riding also requires frequent resting. That means planning rest at the right times, such as after challenging rides or hard weeks. Chapter 7 discusses this misunderstood concept in greater detail. Rest taken in adequate doses and at appropriate times produces consistent training and increased fitness.

Even though the Cardinal Rules of Training are basic, if you follow them, fitness will improve regardless of what else you do on the bike. They are deceptively simple to read about; incorporating them into training is a different matter. At first, it may be difficult to ride moderately and rest frequently. Keep working at it. Old habits are hard to break. When you initially train this way, it’s better to err on the side of being conservative with moderation and rest if you’re a rider who has frequent breakdowns and missed workouts. With experience you’ll become better at determining what is right for you.

Although what we have discussed so far came strictly from experience, the following basic components of training come mostly from science.

F.I.T. for Riding
Even though moderation is necessary, it’s obvious that a portion of your riding must be somewhat stressful to cause a positive change in fitness. Moderate stress comes from carefully manipulating three workout variables:

• Frequency - how often to ride
• Intensity - how hard to ride
• Time - how long to ride

Frequency
The first question to ask at the start of a week is, "How often should I ride?" Training to race, for example, in the United States Cycling Federation’s national age-group championship, requires a different response to this question than if the goal is general health and fitness. The higher the goal for ultimate performance, the more often you need to ride.

Potential is an elusive concept: an ability that is possible but not yet realized. None of us ever knows how close we are to our potential. We do know, however, that getting there demands many sacrifices, one of which involves being on a bike several times a week instead of sitting in front of a TV nibbling on potato chips. When it comes to frequency, there are suggested minimums and maximums, depending on goals. If your reasons for riding are strictly health and basic fitness, the minimum number of rides each week is three. This assumes you ride only and don’t cross train. Because training in other aerobic sports has a cardiovascular benefit, you could get away with riding less frequently and still improve the most basic elements of health and fitness.

Other than achieving high levels of fitness, another frequency issue is how to get in shape the fastest. When first starting to train on a bike, five or six rides each week will cause the most rapid change in fitness. Scientific research shows an increase in aerobic capacity, one measure of fitness, of about 43 percent for novices training this frequently. Three to four rides each week bring a 20- to 25-percent improvement.

If you already have a high aerobic capacity from many weeks of consistent training, all you need to maintain it is four rides a week. High-performance racers, however, usually ride five to seven times a week.

Intensity
Regardless of training frequency and time, the single most critical training variable is how hard and fast you ride. There are several ways of measuring intensity. The one you’re most likely to have available is heart rate. The greatest changes in aerobic capacity come from training at high heart rates, in excess of 90 percent of maximum. Although the highly motivated athlete often seeks such benefits, frequent training over 90 percent of maximum heart rate obviously violates the Cardinal Rule of moderation and will eventually lead to inconsistency and loss of fitness.

The key to cycling intensity is knowing when to ride at higher heart rates and when to slow down. So, 90 percent plus is the high side, but what about the low end? Riding less than 50 percent of maximum heart rate has little or no impact on aerobic fitness. Such low-effort riding is of little physiological value except, perhaps, for recovery.

Getting intensity right is the trickiest aspect of training. Later, this chapter will teach you how to use a heart rate monitor, and chapters 5 and 6 will pull all pieces of the training puzzle together with suggested routines based on riding goals.

Time
The duration of your rides is the second most effective variable in improving fitness. In fact, there’s good reason to believe that longer, slower workouts are equivalent to shorter, faster training sessions in improving aerobic capacity. Because lower intensity workouts are easier on the body, most athletes and coaches recommend building a base of endurance with long, steady rides before starting to do high-intensity workouts, such as intervals, later in the training year.

The length of your rides depends on what you’re used to. In your first five years of cycling, you should be able to increase riding mileage or time by about 10 percent over the previous year’s volume. However, if you’ve ridden for several years, there’s a limit to how many miles you need to improve. Through experience, you may have already discovered that limit - due primarily to an inability to recover and go again."

In the Massachusetts Institute of Technology's Chemistry of Sports course, they "... will be focusing on three sports, swimming, cycling and running. There will be two components to the seminar, a classroom and a laboratory. The classroom component will introduce the students to the chemistry of their own biological system. Since we are looking at swimming, running and cycling as our sample sports, we will apply the classroom knowledge to complete a triathlon.

This is an excellent excerpt reprinted from Burke's book with permission with permission from Human Kinetics, High-Tech Cycling-2nd Edition.

"Human physiology is affected in different ways at high altitude. In general, the various systems of the human body—pulmonary, cardiovascular, endocrine, skeletal muscles—respond and adjust in an effort to provide enough oxygen to survive in the hypoxic environment of high altitude. Some of these life-supporting physiological responses may also enhance athletic performance, particularly in endurance sports.

Hematological
The scientific rationale for using altitude training for the enhancement of aerobic performance is based on the body’s response to changes in the partial pressure of inspired oxygen (PIO2) and the partial pressure of oxygen in the arterial blood (PaO2). PIO2 at sea level is equal to 149 mmHg. At Mexico City (2300 m, 7544 ft), PIO2 drops to approximately 123 mmHg. At the summit of Mt. Everest (8852 m, 29,035 ft), PIO2 is approximately 50 mmHg or only about 30% of sea level PIO2.

What is the lactate curve? Why do I need to know the lactate curve? How does it fit into my triathlon training? When should it fit in my triathlon training? How does it affect my triathlon racing? What does the lactate curve mean to endurance athletes?

Peter Jannsen answers many of these questions in his book, "Lactate Threshold Training." An excerpt follows that will likely wet your appetite to learn more about how it can help your racing.

"The lactate content of the blood is a parameter of great importance. This content is measured in millimoles of lactate per liter of blood. Healthy persons at rest have values roughly between 1 and 2 millimoles per liter, and strenuous exercise increases this value. Even slight increases in lactate content (6 to 8 millimoles per liter) may impair an athlete’s coordination. Regularly high lactate values impair aerobic endurance capacity.

THE LACTATE CURVE
For this reason, athletes should be prudent with the number of intensive workloads they undergo in a certain period of time. The workload intensities needed for various workouts can be determined by means of the lactate curve. Graph 89 shows the relationship between lactate content of the blood and the intensity of exercise. Intensity is expressed as running pace in meters per second.

To obtain a lactate curve, the athlete should run the same distance a number of times, each time at a higher pace. After every run, determine the lactate concentration in the blood. Every distance should be run at an even pace, and the running pace should be increased in small steps. The length of the run should be such that the athlete needs at least 5 minutes to cover the distance. When well-trained athletes run slowly, they have low lactate values; their energy supplies are fully aerobic. When the pace is increased, the curve begins to rise; the working muscles do produce lactate, but the quantities are so small that, for the most part, they can be neutralized by the body. It is a widespread belief that this is the case between 2 and 4 millimoles per liter. Therefore, this area is called the aerobic-anaerobic transition zone.

Each athlete can maintain a certain running pace for a long period of time without lactate accumulation in the body. If the pace is increased to a certain point, ongoing acidosis will occur, depending on the degree and duration of the increase, and at a certain moment this acidosis will force the athlete to stop. The lactate content that is measured at this borderline pace is also called the anaerobic threshold. The anaerobic threshold value is around a lactate content of 4 millimoles per liter. Exercise surpassing the anaerobic threshold will inevitably increase lactate content within the body.

Thus, exercise up to this level of the aerobic threshold is fully aerobic. Lactate content at the aerobic threshold is about 2 millimoles per liter. Exercise within the aerobic-anaerobic transition zone is more intensive, and energy supply is both aerobic and anaerobic. Production and neutralization of lactate are balanced. This zone is between 2 and 4 millimoles per liter.

The anaerobic threshold occurs when exercise at a high intensity results in an accumulation of lactate in the blood. Therefore, this type of exercise can be maintained for a limited period of time. But at an intensity just below the anaerobic threshold, this lactate content can be kept at a steady-state level, and this type of exercise may be maintained for a longer period of time, about 1 to 1.5 hours.

Lactate content at the anaerobic threshold is for many athletes about 4 millimoles per liter, but there are wide individual variations among athletes. Anaerobic threshold can be as low as 2 to 3 millimoles per liter or as high as 6 to 8 millimoles per liter. By drawing a lactate curve for every athlete, the anaerobic threshold can be found and subsequently used to set training intensities. The best way to find the anaerobic threshold is to determine maximal lactate steady state (MLSS), which is discussed elsewhere in the book.

Endurance capacity can best be trained by endurance workouts around the level of the anaerobic threshold, that is, workouts with lactate values of 2 to 6 millimoles per liter. These values may be determined according to the athlete’s test results. Very well-trained people mostly train their endurance capacity at somewhat lower values, between 2 and 3 millimoles per liter. Less well-trained persons often cannot help but peak to higher levels. They then surpass their anaerobic threshold and make their workouts less effective. Though they often feel satisfied with a strenuous workout, this type of workout does more damage than good.

The threshold pace is the speed that corresponds with the anaerobic threshold. Above the anaerobic threshold this speed can be maintained for a short period of time, but below the threshold it can be maintained 1 to 1.5 hours. The threshold pace, the running or cycling speed at the heart rate deflection point (HRdefl), is also called the V4 pace, as discussed in chapter 3. However, the term V4 is somewhat misleading, because many athletes have an anaerobic threshold over or under 4 millimoles per liters. For example, an athlete with an anaerobic threshold of 6 millimoles per liter could be said to have a threshold pace of V6.

Sport-specific performance capacity could be defined as the speed that is reached at a lactate content of 4 millimoles per liter, or V4. V4 is an important indicator of the athlete’s capacities. Any improvement of V4 pace will also improve performance capacity. Regular V4 tests indicate the athlete’s condition, so athletes can be monitored in their development and can be mutually compared. But remember that V4 is not the threshold pace for everybody, because many athletes have an anaerobic threshold under or over 4 millimoles per liter. Therefore, it might be better to test MLSS than V4.

Recovery workouts should not be intensive, and lactate content should remain less than 2 millimoles per liter. Intensive interval workouts give high lactate values, far surpassing 4 millimoles per liter. The effect of training will be that the lactate curve shifts to the right, as shown in graph 90.

Therefore, training intensities should be readjusted from time to time, and a new test procedure with blood sampling will be necessary. Not every athlete has access to blood testing, but other methods can supply the same or at least the most important information. All these other methods of finding the anaerobic threshold are discussed elsewhere in this book."