Physiology Of Stretching Essay

* A stretch reflex is a contraction of a muscle when an attached tendon is pulled. Stretch reflexes are important in maintaining proper posture. Stretch reflexes are used to determine which areas of the body the central nervous system are not responding to. For example, if you tap your knee to check for reflex and the leg doesn’t move, you then know that the peripheral nerves that lead to the knee are nonresponsive and/or the brain is not receiving a signal from that particular area.

Skeletal Muscle Structure.The cells of skeletal muscles are long fiber-like structures. They contain many nuclei and are subdivided into smaller structures called myofibrils. Myofibrils are composed of 2 kinds of myofilaments. The thin filaments are made of 2 strands of the protein actin and one strand of a regulatory protein coiled together. The thick filaments are staggered arrays of myosin molecules.

The fibers in both cells are striated, and the fibers are long and each muscle cell is fused to one another. This is why so many nuclei are included. Also, the fibers are almost threadlike, with dark and light colored striations.

Muscle fibres, as shown in Diagram 1, consist of myofibrils, which contain the proteins, actin and myosin, in specific arrangements . The diagram illustrates how a muscle is made up of many fascicles, which in turn are made up of many endomysiums, and within them, many muscle fibres. Each muscle fibre is made up of many myofibrils that consist of sarcomeres bound end on end . Actin is a thin filament, about 7nm in diameter, and myosin is a thick filament, about 15nm in diameter , both of which reside in the sarcomere. They are held together by transverse bands known as Z lines . Diagram 2 shows actin and myosin filaments within a sarcomere, and the Z lines that connect them.

My whole life has been centered around the field of kinesiology. Since I was about four years old I have been involved in some sort of sport or physical activity and I have never wanted to change that. When I learned that there was a major that could revolve around sports and activity of which I love so much, I decided to throw myself fully into it. I have always been one to throw myself into whatever I am doing and challenge myself and set high goals. Therefore, I have chosen to go to medical school after my undergraduate education and become an orthopedic surgeon. Within the next ten years I hope to be on a hospital staff, improving my skills as a surgeon for sports medicine.

When a muscle contracts, myosin heads in thick filaments bind to actin in thin filaments and pulls the thin filament, shortening the length of the muscle fiber. However, without Ca++ when troponin binds to actin, the tropomyosin moves into a position that

Actin and myosin are contractile proteins that are essential for muscle contraction (Powers). A contraction is triggered by a series of events called the crossbridge cycle. In a muscle fiber, the functional unit of contraction is called a sarcomere (Powers). A sarcomere contains myofibrils, which consist of actin and myosin myofilaments. The sarcomere shortens when myosin heads and thick myofilaments form crossbridges with actin molecules and thin myofilaments. The formation of a crossbridge is initiated when calcium ions released from the sarcoplasmic reticulum bind to troponin. An action potential triggers this release of these ions. The binding of calcium ions causes troponin to change shape. Tropomyosin moves away from the myosin binding cites on actin, allowing the myosin head to bind actin and form a crossbridge. When ATP on the myosin head has not been hydrolyzed yet, the myosin head is inactivated, or in the uncocked position. The myosin head has to be activated before a crossbridge cycle can begin (Powers). This occurs when ATP binds to the myosin head and is hydrolyzed to Adenosine Diphosphate (ADP) and an inorganic phosphate. The enzyme that breaks this ATP down is called myosin ATPase, which is located on the myosin head. The energy from the hydrolysis activates the myosin head putting it into the cocked position. The activated myosin head binds to actin forming a crossbridge. Then inorganic

Actin and myosin filaments can be found in skeletal muscle and are the smallest units that form a sarcomere, which is the smallest contractile unit in muscle (Baechle, 2008). The Sliding Filament Theory states that the actin filaments slide inward on the myosin filaments, pulling on the boundaries of the sarcomere, causing it to shorten the muscle fiber, also known as a concentric muscular contraction (Baechle, 2008). The Sliding Filament Theory is composed of five steps: the “Resting Phase”, the “Excitation-Contraction Coupling Phase”, the “Contraction Phase”, the “Recharge Phase”, and the “Relaxation Phase” (Baechle, 2008). During the Resting Phase, the actin and myosin filaments are lined up with no cross-bridge binding of the two filaments. During the Excitation-Contraction Coupling Phase, Calcium is released from the sarcoplasmic reticulum and binds to troponin, causing a shift in tropomyosin where the binding cites are exposed (Baechle, 2008). When the binding cites are exposed, the myosin cross-bridge head attaches to actin. During the Contraction Phase, ATP bonds break, releasing energy that is used to allow the myosin head to flex, causing the actin filaments to move toward the M-bridge. During the Recharge Phase, there is a continuous repetition of the Excitation-Contraction Coupling Phase and the Contraction Phase in order to produce muscular

INCREASES FLEXIBILITY AND CIRCULATION: Providing a gentle stretch to the tendons and ligaments in the

When you get the strong tendon and its outstretched it will be in a lot of stress so it can return to it’s original state.

Is stretching a positive or negative thing for athletes? I readed two passages that tells you that if stretching is a positive or negative thing to do. The first passage opinion in“Stretching: The Right Way’’ uses a way to think that stretching is a positive way because it said that a “rubber band are like muscles’’. The author shows how stretching is the best if you don’t want injuries, in the passage it said that ‘‘muscles are like a rubber band if you slowly stretch the rubber band until it can go not further and then hold it for a few seconds the rubber band will not become looser and it will snap’’.

As a trainer, I have found that clients seeking to improve their flexibility complain about tight hamstrings more than any other muscle group. Time and time again, clients are consistently surprised to find that hamstring flexibility can be improved without stretching at all.

Before exercise it is crucially important that you take the time to stretch your muscles and to warm up. As a general rule, dynamic stretches before a WOD are useful, and longer extended sessions of static stretches should be kept for the end of your training. These are a great way to improve your flexibility and cool down after an intensive workout.

To keep these muscles from turning out to be "tight," it is essential to extend them quickly prior and then afterward running any measure of separation.

1. Why does the force begin to decrease with time? Note that a decrease in force indicates muscle fatigue.