Re: would a persons height affect their leg strength?

Cheryl -

Your question implies that there is some correlation between muscle length & strength & that is not exactly true! I am sure that you realize that out of the over 600 skeletal muscles in the human body, not all of them are of the same shape, size or design. This results in our amazing ability to manipulate our environment with just the correct amount of power and precision.

In order to understand about muscle strength, you have to know a little about levers. There are 3 classes of levers that are of use to us in explaining human muscle activity.

• A class 1 lever is one that is designed like a "seesaw". This is one that has its fulcrum somewhere in between the force (the pull of a muscle or muscles) and the weight that the muscle is going to move. The force of the muscle will cause the weight to move in the opposite direction. An example is the trapezius muscle that allows you to look up at the sky.
• A second class lever is one that has its weight located in between the fulcrum & the force. A wheelbarrow is like this. The gastrocnemius - the muscle along the calf of the leg- is like this in that it causes our heel to raise off the floor when contracted.
• The last type is a class 3 lever & this type has the force in between the fulcrum & the weight. Carrying a shovel full of dirt it like this system. Most of our muscles are designed like this. If you contract the bicep brachii of your arm, your forearm will undergo flexion. A weight in your hand will then be lifted, just as the dirt in a shovel. Your elbow serves as the fulcrum in this example. The strength of this system is, in part, determined by the relative lengths between the fulcrum & the source of the force compared to the length from the fulcrum to the weight. The former is called the power arm & the latter is the weight arm. A longer power arm leads to greater strength & a longer weight arm leads to a faster reaction.