Explain how muscle use leads to hypertrophy or atrophy through changes in muscle fiber mass

Answer 1

To start out let's define the terms. Atrophy is a decrease in muscle strength due to a decrease in muscle mass, or the fibers that make up muscle. Hypertrophy is an increase in muscle strength due to an increase in the number and size of muscle cells, which can be increased by doing things such as strength training.

Atrophy can be caused by multiple factors, most of which revolve around one central theme; decreased muscle use. This can be caused by diseases such as AIDS, a sedentary lifestyle (if someone is bed ridden), starvation, or simply aging. The body breaks down muscles that aren't being used due to the simple fact that if the body is not using a muscle, it won't put in the work to keep that muscle in top condition and therefore the muscle fibers will begin to degrade. Think of it like a junker car. If you leave a car outside without doing things like changing the oil, checking tire pressure, routine maintenance, etc., that car will begin to degrade until it's nothing but a pile of rusted metal. The body works in the same way.

On the other hand, hypertrophy is the build up muscle, usually brought about by strength training. Strength training works to cause tiny tears in the muscle fibers. The body then sees these tears, says "hey this muscle is torn maybe I should build it up stronger next time so it won't tear so easily" and proceeds to do so. Overtime, this cycle of tearing and repairing the muscle fibers leads to the development of bigger and stronger muscle.

I hope this helps, please reach out if you are still confused.