Class 3 levers are always mechanically disadvantageous. Output velocity can be increased by decreasing the length of the input lever arm, increasing the length of the output lever arm, or both. Distinguish between plantigrade, digitigrade, and unguligrade locomotion, and briefly explain how they are related to running speed. Unguligrade locomotors orient all foot and digit bones parallel to the limb and support their weight on specialized toenails, resulting in longer effective limb length and greater running speed. Explain why longer muscles, all other things being equal, have a greater velocity of contraction than shorter muscles.
Long muscles have more sarcomeres linked end to end.
The total distance of contraction of an entire muscle fiber is the sum of the individual distances of contraction of all the sarcomeres in the fiber, so a longer fiber has a greater sum of distances. The velocity of contraction of sarcomeres is the same in a long or short muscle, so the longer muscle is contracting a greater distance in the same period of time, hence a higher velocity of contraction.