Muscles are the driving force of all movement in your body. Your muscles control everything you do from lifting, running, walking, and even organ functions. The muscular system consists of three major muscle types. Number one: cardiac muscles which are responsible for your heart and blood flow; number two: smooth muscles which are responsible for the movement of all your other organs functions; and lastly number three: skeletal muscles which are responsible for the movement and protection of your bones. Both smooth and cardiac muscles work involuntary which means they move by themselves or subconsciously, without you even knowing; while skeletal muscles move and function voluntary and are under our conscious control. There are three different muscle fiber types known as type 1, type 2a, and type 2x fibers. These muscle types are classified by size, color, speed, force, and energy source.
Type 1 fibers or slow-twitch muscle fibers as it is more commonly called are the smallest type and are a darkish red color, it has a very slow twitch speed and produces a small amount of force when contracted. it has large amounts of mitochondria, which use O2 to produce energy. although the force generated is very small type 1 muscle fibers are highly fatigue resistant allowing for them to be active for long periods of time. these muscles are used in the acts of running, jogging, or aerobics. Type 2a fibers or moderate fast twitch fibers, are also red but are intermediate in size. These larger fibers typically use a combination of oxygen and glucose to create energy. This combination allows for a quicker contracting speed and force output compared to type 1 fibers. However the fatigue resistance isn't as high. These types of fibers are primarily active during aerobic activities that are moderate in duration such as a mile run, swimming, and short distance cycling. Type 2x fibers or fast-twitch fibers are white in color due to the low oxygen capacity, and are by far the largest fiber type. This fiber makes up for the lack or oxygen capacity by having extremely high levels of glucose or its stored form glycogen to create energy. This allows the type of muscle fiber to have the fastest speed and the most force. The downside to this is fibers fatigue quickly burning out after fifteen to thirty seconds. High impact heavy resistance activities such as lifting weights and sprinting will activate type 2x fibers the most.
For any activity your muscles follow a specific recruitment order the slow-twitch low force fatigue resistant type one fibers are always activated first. When type one fibers are maxed out type 2a fibers are activated and after those have been maxed out, type 2x fibers are activated. This order known as the Henneman's size principle, and it helps minimize fatigue and allows size motor control by using no more force necessary to complete a movement.
Everyone has a genetically determined amount of each muscle fiber type, some people are born with a predominant amount of a certain muscle fiber. Making them affected differently with activities that favor those fibers. There have been some findings that suggest that type 2x fibers can change into type 2a fibers with proper training however this might simply be to type two x fibers showing higher oxegen capacity through physical adaptations, but they are ultimately still type type 2x fibers. Muscle fibers are the cells or basic building block of the muscle. There are a few different types of muscle fiber, each designed for a specific type of muscle activity. Some muscle fibers are good for endurance exercises, other work best for the short bursts of strength exercises.
YOUR GOING TO HAVE TO WRITE AN INTRODUCTION PARAGRAPH AND CONCLUDING PARAGRAPH BUT THIS IS THE BASICS.
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