Cycling Biomechanics

Question 1

Aerodynamic Drag

Answer 1

Aerodynamic drag is a product of air density, velocity, coefficient of drag and frontal area.
Aerodynamic drag increases with higher air density, velocity, coefficient of drag and the amount of frontal area.
The cyclist contributes 80% of aerodynamic drag.
Cyclists can most effectively reduce drag by adopting a more aerodynamic body position.

Question 2

Aerodynamic Drag and Positioning

Answer 2

1. Tops
   Riding upright with hands on top of the handlebars increases aerodynamic drag. The average drag coefficient (1.15) is highest in this position.
2. Hoods
   An athlete who places his hands on the brake hoods of drop handlebars has an average drag coefficient of 1.0., which is slightly less than the upright position.
3. Drops
   Placing the hands in the lower part of the drops reduces the total frontal area, compared to placing the hands on the hoods. The average drag coefficient in this position is 0.88.
4. Aerobars
   Using aerobars reduces the average drag coeffient to 0.70. To reduce drag the cyclist’s body position must be as tight and narrow as possible, and the head should be in line with the back and neck.

Question 3

Aerodynamic Drag and Gear

Answer 3

To minimize aerodynamic drag, clothing, gear and the bicycle should not catch or disrupt the flow of air.
Tight fitting clothing, and using the time trial style helmet can help to combat excess aerodynamic drag forces.

Question 4

Body Mass and Gravity

Answer 4

the amount of power required to cycle uphill increases with mass; so a heavier cyclist and/or bicycle will increase the amount of power required, and therefore energy needed, to overcome this resistance.
Power-to-weight ratio is a formula used to determine the athlete’s strength compared to his or her body weight. It is calculated by dividing the body weight (in kilograms) by power (in watts).
The higher the power-to-weight ratio, the faster the athlete.

Question 5

Review: Propulsion

Answer 5

The athlete is fastest in a position where he or she can produce power.
Propulsion occurs when force is applied to the pedals, turning the crank and powering the bicycle.
Propulsion is a positive force, combating drag as the athlete propels forward.
It is a smooth combination of downward push (power) and upward pull (torque).

Question 6

Biomechanics of a Pedal Stroke

Answer 6

To keep an object in motion in the presence of drag requires an ongoing exertion of energy.
The forces applied to the pedals vary throughout the pedal stroke.
A full pedal stroke is 360 degrees.
0 degrees (12 o’clock) is top dead center
90 degrees (3 o’clock) is the middle of the down stroke
180 degrees (6 o’clock) is the bottom dead center
270 degrees (9 o’clock) is the middle of the up stroke
360 degrees is again at the top of the stroke