A human traveling on a bicycle at , using only the power required to walk, is the most energy-efficient means of human transport generally available. Air drag, which increases with the square of speed, requires increasingly higher power outputs relative to speed , power increasing with the cube of speed as power equals force times velocity . A bicycle in which the rider lies in a supine position is referred to as a recumbent bicycle or, if covered in an aerodynamic fairing to achieve very low air drag, as a streamliner. Racing bicycles are light in weight, allow for free motion of the legs, keep the rider in a comfortably aerodynamic position, and feature high gear ratios and low rolling resistance. On firm, flat ground, a person requires about 60 watts to walk at . That same person on a bicycle, on the same ground, with the same power output, can travel at using an ordinary bicycle, so in these conditions the energy expenditure of cycling is one-third that of walking  . Uphill and downhill speeds vary according to the slope of the incline and the effort of the rider. Uphill cycling requires more effort or energy to overcome gravity and speeds are therefore lower and heartrate is higher than the average riding conditions. With medium effort a cyclist can pedal 8 - 10 km/h up a gentle incline. Riding on grass, sand, mud, or snow will also slow a rider down. Without pedaling downhill a bicycle rider can easily reach speeds of 20 - 40 km/h down a gentle \% 5 slope and dangerous speeds exceeding 50 km/h on steeper inclines. Energy output Active humans can produce between 1.5 Watts /kg (untrained), 3.0 W/kg ( threshold for the medical definition of “fit” ), and 6.6 W/kg (top-class male athletes). 5 W/kg is about the level reachable by the highest tier of male amateurs for longer periods.Power profiling data table version 4.0 by Andy R. Coggan Maximum sustained power levels during one hour range from about 200 W (NASA experimental group of "healthy men") to 500 W (men's world hour record).
A human traveling on a bicycle at , using only the power required to walk, is the most energy-efficient means of human transport generally available. Air drag, which increases with the square of speed, requires increasingly higher power outputs relative to speed . A bicycle in which the rider lies in a supine position is referred to as a recumbent bicycle or, if covered in an aerodynamic fairing to achieve very low air drag, as a streamliner. Racing bicycles are light in weight, allow for free motion of the legs, keep the rider in a comfortably aerodynamic position, and feature high gear ratios and low rolling resistance. On firm, flat ground, a person requires about 60 watts to walk at . That same person on a bicycle, on the same ground, with the same power output, can travel at using an ordinary bicycle, so in these conditions the energy expenditure of cycling is one-third that of walking the same distance . Uphill and downhill speeds vary according to the slope of the incline and the effort of the rider. Uphill cycling requires more power to overcome gravity and speeds are therefore lower and heartrate is higher than during flat riding conditions. With medium effort a cyclist can pedal 8-10 km/h up a gentle incline. Riding on grass, sand, mud, or snow will also slow a rider down. Without pedaling downhill a bicycle rider can easily reach speeds of 20-40 km/h down a gentle 5 \% slope and speeds exceeding 50 km/h on steeper inclines. Energy output Active humans can produce between 1.5 Watts per kilogram of body mass (untrained), 3.0 W/kg ( fit ), and 6.6 W/kg (top-class male athletes). 5 W/kg is about the level reachable by the highest tier of male amateurs for longer periods.Power profiling data table version 4.0 by Andy R. Coggan Maximum sustained power levels during one hour range from about 200 W (NASA experimental group of "healthy men") to 500 W (men's world hour record).
D
, power increasing with the cube of speed as power equals force times velocity
A
the same distance
R
effort or energy
power
R
the average
during flat
R
8 - 10
8-10
R
20 - 40
20-40
D
\%
R
slope and dangerous
\% slope and
R
/kg
per kilogram of body mass
R
threshold for the medical definition of “fit”
fit