How do we actually run? How is our running affected by our muscle structure and function? The essential physiological event that allows us to run are our muscle contractions. Our heart or cardiac muscle, skeletal muscle, and smooth muscle are the 3 types of muscle in our bodies. For the focus of this article, I will be discussing our skeletal muscles structure and function.
There are a vast number of muscle cells that are put together to make up our skeletal muscle. Each divided by one another by connective tissue that contains blood vessels and nerves. In the human body, slow twitch fibers and fast twitch fibers are our 2 different muscle fiber types. Each muscle in our body is mixed with slow twitch and fast twitch fibers. Nerve supplies and capillaries surround each of our muscle cells which supply our working muscle with blood. The number of capillaries increase through training, but on average each muscle cell is surrounded by 5 capillaries.
Inside each of our muscle cells contains a mitochondria. The mitochondria is the "powerhouse of the cell" and produces the energy we need to power our muscle contractions. This gives us our running ability and exercise and is related to the total metabolic capacity of all the mitochondria a runner has. The more muscle cells, the more mitochondria, the more total energy produced.
How does the mitochondria produce energy? Through our nutrition and the food we eat! Each mitochondria consists of enzymes that change the food we each into energy - ATP! With the presence of an adequate oxygen supply, the mitochondria can function to produce the energy we need while running and exercising. The mitochondria can not produce ATP without sufficient oxygen. Lucky for us there are emergency energy systems in the body that allow us to run and exercise without oxygen. This type of exercise is anaerobic exercise which uses our stored glycogen in our muscle and blood glucose as an energy source.
Our muscle can also use fat droplets in our muscle cells as a fuel source. These fat droplets are consist of triglyceride molecules, a form in which fat is stored in the body. Excessive accumulation of these fatty acid molecules is known as cellulite. Once the free fatty acids are broken down, they must be transported to the muscle cell, to the mitochondria where is can be used for energy fuel. The liver can also use stored glycerol molecules to produce new glucose units for the body to use as energy. Glycogen is the only form in which both muscles and liver store the carbohydrates eaten in our diets.
For example, lower intensity exercise will utilize more fat during exercise. With the presence of oxygen, the body can break down the fatty acids that are stored as body fat and use them as energy. To lose body fat & cellulite, you must be able to use fat as energy! Also, the more fat we use, the more energy we have stored as glycogen in our muscle and liver to use during longer bouts of exercise. This becomes important with performance. Considering our body needs energy sources to feed our mitochondria and produce our muscle contractions, I would say different types of training intensities and our nutrition becomes extremely important when fueling our body for performance and changing our body composition.
Our body is an amazing machine, that uses many different metabolic pathways to produce the energy it needs through running and exercise! Different types of training intensities and our nutrition affect the amount of energy we have and the fuel sources used during exercise. No matter what your goals are in terms of health and fitness, knowing what types of exercise to do and how to fuel your body, will give you the best results.
Feel free to comment or ask questions!!
Happy Energized Muscle for Happy Running :)
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