Each cyclist must convert the energy stored in his or her muscles into torque to move the pedals. To go uphill, the necessary rate of work (power) increases as does the required torque. (Corbis Corporation)

Pressure is force divided by the area over which the force acts:

or
In the metric system, pressure has a unit of newtons per square meter, which is called a pascal (Pa). Although the pascal is the scientific unit and is preferred, pounds per square inch (lbs/in²) is common in the United States. For example, in most of Europe, tire pressure is recorded in pascals (typically 220,000 Pa), whereas tire pressure in American cars is measured in pounds per square inch (typically 32 lbs/in²). As a point of reference, the pressure that the earth's atmosphere exerts on anything at the earth's surface is roughly 100,000 Pa or 15 lbs/in².

A large pressure does not...