This is from the author of Delavier's Stretching Anatomy. It's published with permission of Human Kinetics.

Athletes spend hours training to hone their skills, but few consider stretching a vital component to their athletic performance. According to popular author Frédéric Delavier, stretching has the ability to increase performance levels and should be included in every athlete's training regimen. In his upcoming book, Delavier's Stretching Anatomy (Human Kinetics, October 2011), Delavier discusses the top five reasons every athlete should stretch.

Maintain or increase range of motion. Repetitive athletic movements can reduce range of motion by tightening the muscles and tendons. "A certain tension is required, especially in strength sports, but too much tension and a decreased range of motion can ultimately lead to injury and reduced performance," Delavier explains. "Stretching regularly can prevent this problem." In certain fields, like swimming or gymnastics, stretching must be done regularly to increase the range of motion in a joint when that range is synonymous with increased performance.

Increase muscle tone. Stretching is a powerful signal to strengthen muscles. "Using the muscle's passive resistance strength, stretching accelerates the speed at which the proteins that compose the muscle fibers are synthesized," says Delavier. "Your body gains muscle tone, strength, and resilience this way."

Warm up before working out. Stretching warms up the muscles, tendons, and joints, which prepares the body for physical exertion.

Relieve stress. "Thanks to its euphoric oxygenating effects, stretching minimizes stress that can paralyze muscles, which is especially beneficial before a competition," Delavier says.

Relax, recuperate, and prevent injuries. Most muscular efforts compress various joints as well as the spine. "Stretching decompresses your back as well as your joints," Delavier says. "This prevents injuries while accelerating recovery of the joints, tendons, and muscles."

Although flexibility is important for an athlete, Delavier advises finding a balance between muscle tension and flexibility. The muscle must be flexible enough to have a slightly greater range of motion to prevent injuries and aid movement, but not so flexible as to diminish performance by becoming like a rag doll whose joints move around easily. "Stretching has the ability to increase or diminish performance levels," Delavier adds. "So we must be careful to use stretching properly." Delavier's Stretching Anatomy offers stretches for releasing tension, increasing flexibility, and creating an overall sense of well-being.

'Tis the season for setting goals and resolutions. In that regards, here's an excerpt from Energy Every Day written in conjuction with the Human Performance Institute. It's published with here permission of Human Kinetics.

"It is important to take a step...

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.