MadSci Network: General Biology

Re: How are muscles built through weight lifting?

Date: Fri Mar 26 15:56:01 1999
Posted By: Richard Mondak, Staff, Physician Assistant, PA Provider Services
Area of science: General Biology
ID: 920851860.Gb

Voluntary skeletal muscle tissue is composed of layers of fibers, like a hemp rope, for example. First the individual fibers grouped into fibrils then strands then bundles.(look closely at a piece of lean meat). Not all of the fibers move at the same time or in the same direction, they sort of "slide" alternatingly, but usually in a coordinated motion (with some help from the parts of the brain that control different types of muscle motion). The muscle fibers are made up of proteins (like that steak).

There are two specific components of the muscle fibers, called MYOSIN and ACTIN, which control the contraction (when muscles become shorter and bulkier) and relaxation (muscle appears longer and thinner). Attached to myosin is a chemical called Adenosine Triphosphate (or ATP) which is the energy source for the muscles.

Now you have ATP giving energy to the muscles because you ate a well-balanced diet and are USING energy. Through repeated use you can increase the muscle mass. Is that all there is to it? No way,Jose! I mean, Jesse.There is another part of this process called the second messenger system. The pattern of developing muscle size and shape through the second messenger system is determined through genes passed from your parents.

When you use your muscles through weight lifting exercises, the muscles are actually injured and a "message" filters down to alter the pattern of protein expansion, or growth and repair of the muscle cells (this occurs during rest). When a weight lifting program is done properly, the muscle cells become larger, although some new muscle cells may be added. It may take two or more MONTHS before you actually notice a change in muscle bulk. More info:

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