Biology 105
Biology of Exercise
Spring 2003

Learning objectives:

• How do speed and force of muscle contraction interact?
• Can muscles be strong and fast?
• How do muscles and bones interact?

Diagrams

• sliding filament model
• velocity-force relationship
• velocity-power relationship
• muscle and bone interaction
• lever mechanics

"The Sweet Spot in Time" (J. Jerome).

• Concentric muscle action- production of force when the muscle is shortening. Today's discussion refers to concentric contractions.
• Eccentric muscle action - production of force when the muscle is lengthening.
• tradeoff between velocity (distance / time) and force
• Cross bridge cycling
• power = force * velocity

Biomechanics

• the lever concept
• in and out lever arms (Li and Lo) and a pivot point
• in and out force (Fi and Fo)
• in force is generally created by muscle contraction
• an out force is created at a distant point
• Fo = Fi * Li / Lo
• in and out velocities (Vi and Vo)
• Vo=Vi * Lo / Li
• there is a tradeoff between force and velocity
• i.e. a long out level will decrease out force but increase out velocity