Your muscle cells produce enough heat every day to boil almost 2 pints of water for an hour.
When you shiver, your muscles contract involuntarily. This releases energy that keeps your body warm.
You use your muscles to stand still. Try it. Stand as still as you can. Gravity will make you sway, but your muscles will pull you straight.
Your tireless heart beats more than 4500 times each hour.
Smile! You've just used about 30 muscles. Muscles control your eyelids, nostrils and brow. They work together to show the slightest change in your emotions.
Believe it or not our one and only cardiac muscle never gets tired. Just imagine how much pressure we apply on it every little thing requires more blood to somewhere. It is working when your sleeping, when your playing sport, even when your in the toilet. It is working beating on average 80 beats per minute. The secret is that the mitochondria, the mitochondria is the fuel plants for cardiac cells.
They then make adenosine triphosphate or ATP this a major source of energy to the heart. Furthermore, lactate is converted into fuel by cardiac muscles. This means even if the entire body besides the heart is starving. The heart will always have food or fuel. This is one of the most prominent aspects of the cardiac muscle functions.