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(How Do Your Muscles Work continued)

Thousands of thin spaghetti-like fibers make up muscle tissue. These fibers receive messages from the brain, causing the fibers to contract. The main muscles at work in cycling are the quadriceps and hamstrings in the upper leg, and the gastrocnemius and soleus in the calf. These muscles contract in a sequence that creates the pedaling action.

Muscle Animation
The quadriceps and hamstrings do most of the work when you ride a bicycle.

Anaerobic vs Aerobic

It's one thing to have the brain send a message to the muscles, but what fuels the muscles during the thousands of contractions that occur during extended cycling? You've probably heard the terms aerobic and anaerobic. These terms describe two ways in which your muscles get energy.

In aerobic exercise, muscles draw on oxygen as well as the glucose and fatty acids carried in by the blood to produce adenosine triphosphate or ATP. ATP is the energy source that enables muscles to contract. The ability to keep exercising aerobically depends on the delivery of oxygen and fuel molecules (glucose and fatty acids) to your muscles. And that depends on circulation and respiration, provided by your heart and your lungs.

When exercising anaerobically, muscles are drawing on stores of glycogen (which is formed from glucose) and converting them to ATP. During this type of high-intensity exercise the muscles are producing energy without oxygen--the cardiovascular system is unable to keep up the demand. There is a price to pay for excercising anaerobically, as a waste product called lactic acid builds up. This is what causes the burning sensation in muscles and causes them to fatigue more rapidly.

In competition, riders are very aware of their own physical limits and try to use their more limited anaerobic capacity strategically. Ruthie Matthes explained, "One of the toughest things about mountain bike racing is that from the gun we do a sprint. The first person to get to the single track or to make a jump on the field has an advantage so right from the start we go into the anaerobic zone. And that can be very tough. We need to train our bodies to adjust for that."

Two Champions

A Tale of Two Champions

The training of bike racers has undergone many changes in the past hundred years, as scientific and medical understanding of human athletic performance has improved.

Major Taylor, one of the first African- American bicycle racers, was, during the 1890s and 1900s, the fastest cyclist in the world. Absent from most history books, he was also the highest paid athlete of his era. Known as "the Ebony Streak," he would prepare for his races with long miles on the road, and moderate weight-lifting for general fitness, followed by sprint work on the track, to build the power needed to win. However, much of Taylor's training had to be guided by his own experience, as little scientific data existed on the nature of performance.

Miguel Indurain, the recently retired Basque rider who won five consecutive Tours de France from 1991-1995, was a champion who trained according to advanced knowledge of physiology. Called "the Extra-terrestrial" by his opponents for his overwhelming power and his emotionless demeanor while racing, Indurain's training was designed by doctors and physiologists, and his performance was constantly monitored, using heart-rate monitors, power-output strain gauges, blood tests, and physical exams. Through careful planning, Indurain was able to reach peak fitness for the Tour each year.

Ruthie Matthes
Ruthie Matthes

Slow & Fast Twitch Fibers

Every muscle is made up of two types of fibers. Fast-twitch fibers move 2 to 3 times faster than slow-twitch fibers, but they tire more easily. Fast-twitch fibers, logically, are used for sprinting and quick ascents. Inversely, slow-twitch fibers are used for long rides of moderate intensity.

Most people have half slow-twitch and half fast-twitch fibers in their muscles. However, genetics again plays a role. Some long-distance runners have as much as 80 percent slow twitch fibers, while sprinters tend to have more fast-twitch fibers.

The Drive to Cycle

While genetics can certainly play a role in deciding whether a cyclist will be a champion or not, the drive to win and compete also has to be present. Long hours of training and intensive competition require the cyclist to be extremely determined. In addition, competitve cycling requires adherence to details and to finely tuned techniques.


People who commute by bicycle or ride recreationally may not have the extreme determination that a pro cyclist has, but nevertheless cycling provides challenges and rewards to everyone who rides. Most cyclists agree that cycling not only improves their physical health but their mental outlook. A sense of accomplishment and a feeling of independence are feelings every cyclist shares. Perhaps that's why cycling for many is more than a sport or even a mode of transportation--it's a passion.

  Mount Tam


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