Tour De Lance: Cycling Physics

Tour De Lance: Cycling Physics – Lance Armstrong

Nicole Dyer

What does it take to be the fastest and most resilient rider on two wheels? Sheer devotion to cycling and physics! Take a spin with Lance Armstrong as he speeds through a winning day in the 2001 Tour de France.

On July 29, 2001, world-champion cyclist Lance Armstrong became the firs American to win three consecutive victories in the Tour de France, the world’s most grueling and popular cycling race. The three-week, 3,489-kilometer (2,168-mile) Tour is divided into 20 “mini-races” called stages. They include speed battles up and down brutally steep French mountains (see map).

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The 29-years-old Texan conquered the entire course in a total time of 86 hours, 17 minutes, 28 seconds–the third-fastest Tour in the race’s history. “Nobody can beat him,” says former victor Eddy Merckx. Even more remarkable: Armstrong’s latest victory comes three years after a near-death struggle with testicular, brain, and lung cancer.

July 17, 2001: MORNING RUSH HOUR

Armstrong climbs out of bed at 7:00 a.m. and joins his eight-member team for breakfast. What’s on the menu? Pasta. “Let’s face it, spaghetti firs thing in the morning isn’t exactly my idea of a fun breakfast,” Armstrong says. But the champ knows pasta is crammed with complex carbohydrates, chemical starches that will power him through today’s race: a 208-km (129-mi) sprint from the village of Aix-Les-Bains and up the mountain L’Alpe D’Huez. The stage is considered the Tour’s most punishing, including two steep 14-km (9-mi) climbs, and a hair-raising 60-mph descent.

Meanwhile, one million fans line the roads, waiting to catch a glimpse of the famous maillot jaune–French for “yellow jersey”–which is worn only by the Tour’s overall leader. This morning the jersey belongs to Australian Stuart O’Grady–but Lance has plans to change that.

Armstrong thrives on steep climbs, having spent the last year training six to eight hours a day in the mountainous terrain of the Alps and Pyrencees. As a result, his cardiovascular system (heart and blood vessels) functions like a well-oiled engine: his [VO.sub.2] max–the maximum amount of oxygen the lungs can retain during one hour of exercise per kilogram of body weight–tops the charts at 84 milliliters. An average human registers less than 40.

LET THE GAMES BEGIN

An official swings a checkered flag and the day’s race takes off. Immediately, cyclist swarm together in a beehive-like formation called the peleton (French for “pack”). Lance cruises comfortably in the middle. Why not race ahead? As his team’s strongest rider, he needs to conserve his energy for an explosive finish. Pedaling an average of 25 mph is hard enough. And the faster you ride, the harder you need to pedal to overcome wind resistance or drag, the force acting against you as you glide forward.

To reduce drag, racers take advantage of a team-orchestrated physics trick called drafting–in bike language “wheel sucking”–in which teammates take turns shielding each other from the wind. A rider tucked just 15 cm (6 in.) behind another rider expends almost 30 percent less energy than the front runner. Increase that distance to 61 cm (24 in.) and energy savings are slashed to just 10 percent.

DRIVE-THROUGH LUNCH

Each minute Lance cranks his pedals, he burns 17.5 calories (units of energy in food). after three hours his body has consumed a staggering 3,150 calories–which translates into digesting six Big Macs, and more fuel than the average teen expends in a day. To maintain his energy output, he’ll need to recharge. But how do you eat and drink while riding a bike? Think high-speed drive-through.

Lance’s team car pulls up beside his speeding bike and his coach hands him a “feed bag,” a cotton pouch with shoulder straps. It’s crammed with energy-rich foods: a peanut butter and banana sandwich, energy bars, two honey cookies (Lance’s favorite), and a sports drink. The nourishment restores Lance’s depleted glycogen, linked sugar molecules stored in the body’s muscles, which are later broken down and used as fuel.

HOME STRETCH

The most torturous part of the race looms just ahead: a legendary 1-km (3,500-ft) uphill climb over 15 km (9 mi) to a mountaintop finish on L’Alp d’Huez. The ascent reduces most riders to a slow-motion crawl–but Lance feels right at home.

Armstrong’s strength is due in part to his loss of 8 kilograms (18 lbs) after chemotherapy, a regimen of powerful cancer-fighting drugs. The weight loss altered his weight-to-power ratio, or how much energy (measured in watts) Lance needs to pump into his pedals to move one kilogram of weight uphill.

To win, Lance has to generate 6 watts of power per kilogram. At a trim 68 kilograms (150 lbs), that adds up to 408 watts of power–enough to light a room! “A heavier rider needs to put out more watts than a lighter one,” explains Coach Chris Carmichael. “If you added 18 pounds to Lance’s frame, he’d finish 3 minutes, 47 seconds slower on the Alpe d’Huez climb.”

FINAL SHOWDOWN

Lance decides it’s time to cash in the energy he conserved hiding in the peleton. At the base of L’Alpe d’Huez, his legs spring to life and he explodes past the pack. Armstrong chases down main rival Jan Ullrich from Germany, looks him straight in the eyes, then bursts past him for a 15-km (9-mi) solo sprint to the finish line.

Lance cranks his pedals an average of 90 revolutions per minute to win this particular stage in just 6 hours, 23 minutes, and 47 seconds. The victory puts Lance within striking distance of the overall Tour lead–and the revered yellow jersey.

TOUR DE FORCE

Armstrong goes on to win three more stages, and finally nabs the Tour victory. He proudly completes 10 laps around the Arc de Triomphe in Paris. “This is a good time to be Lance Armstrong,” he says.

MAN OR MACHINE?

FITNESS LANCE AVERAGE MALE

[VO.sub.2] max 84 [O.sub.2]/kg/hour 40 [O.sub.2]/kg/hour

Resting heart 32-24 72

rate beats/min beats/min

Stroke volume 200 ml 100 ml

(amount of

blood sent to

body with

each

heartbeat)

RELATED ARTICLE: HANDS-ON SCIENCE

BUILT TO LAST

Think Lance felt “stressed” during the Tour de France? Consider his bike frame: It supports his weight and absorbs jarring ground forces. That’s why a good bike frame is both strong and flexible. Engineers evaluate these properties when searching for bike frame materials:

1 elasticity (ability to bend and return to original shape)

2 yield strength (amount of force needed to bend material to a point where it no longer returns to original shape)

3 ultimate strength (amount of force needed to break material)

YOU NEED: plastic comb * rubber band * ballpoint pen * paper clip * wooden pencil

TO DO:

1. Try to bend and stretch each object.

2. On a scale of 1 to 10, rate each object’s flexibility, yield strength, and ultimate strength.

3. Determine which material would make the best bike frame.

CONCLUSIONS:

Which material has the greatest elasticity? Yield strength? Ultimate strength? Is there a materials for which yield strength and ultimate strength are close? Can a material have a low elasticity and a low yield strength, and still have a high ultimate strength? Why?

RELATED ARTICLE: Physical/Life Science: Drafting * Cardiovascular System

Cross-Curricular Connection

Language Arts: Write a short story in which the main character overcomes a tremendous obstacle to achieve his or her goal.

Did You Know?

* An average bicycle wheel is designed to support 400 times its own weight, making it one of the strongest man-made objects in the world.

* An average bike built in the 1800s–crafted almost entirely of steel tubing and Cast iron–weighed about 80 lbs.

* During the Tour de France, Lance Armstrong’s heart beat 2,153,600 times; he burned 132,000 calories.

* On average, it takes a professional cyclist less than 9 seconds to repair a flat tire.

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National Science Education Standards

Grades 5-8: motions and forces * structure and function in living systems * regulation and behavior * abilities of technological design

Grades 9-12: the cell * motions and forces * matter, energy, and organization in living systems * abilities of technological design

Resources

“Lance Armstrong Has Something to Get Off His Chest,” by Michael Hall, Texas Monthly, July 2001 Peak Performance: Sports, Science, and the Body in Action, by Emily Isberg, Simon & Schuster, 1989

The Exploratorium’s Science of Cycling Web site: www.exploratorium.edu/cycling

Lance Armstrong’s Web site: lancearmstrong.com

COPYRIGHT 2001 Scholastic, Inc.

COPYRIGHT 2001 Gale Group