True or False 1. A single motor unit contains muscle fibers that are all of the

Question

True or False

1. A single motor unit contains muscle fibers that are all of the same type in terms of contractile properties, but the oxidative capacities of some of the fibers may be 100% greater than oxidative capacities of other fibers of the same motor unit.

2. To be an elite, world-class endurance athlete, it is an absolute prerequisite that muscles involved in the endurance performance have at least 90% Type I fibers.

3. Most musculoskeletal levers in the human body favor speed of movement rather than force development.

4. The frequencies at which motor units are stimulated affect the velocity of a muscle's contraction but do not affect the magnitude of force developed by the muscle.

Explanation / Answer

Answers:

1. True

Explanation: Within a single motor unit, despite having all the muscle fibers with the same contractile property; the oxidative properties for some fibers might vary. For few of the muscle fibers oxidative property with approximately be 100% more than others.

The muscle contraction begins with the working of Troponin C of the thin myofilaments. This in turn activates other proteins of the thin myofilaments. Which means that the recruitment pattern of the different proteins within the myofilaments is different. Likewise their mode of action also is scrutinized and hence their redox potentials varies.

2. True.

Explanation: Skeletal muscles are classified into two types; slow twitch (Type 1 muscle fibers) and fast twitch (Type 2 muscle fibers).

Slow twitch muscles are also called as red muscle fibers as they bear oxygen carrying pigment; myoglobin. Also, very importantly they contain a cell organelle ; mitochondria; known as the power house of the cell. This organelle is involved in producing ATP which provides the energy. Since the muscle fibers are actively involved in energy formation; these are mainly utilized for the endurance exercises like distance running. And that is why; in world class endurance athlete; the muscles mainly involved in the endurance performance; 90% of the muscle fibers involved are type 1.

3. False

Explanation: Muscoskeleton system of our body comprises of the bones and the muscles along with the joints and the tendons. Muscles in our body show movements and they are exhibited either per our will or directly per the will of nervous system. Biomechanics is a branch of science which applies the concepts and fundamentals of Physics over the muscle movement.

This explains how some joints work like a lever or a pulley. Most common principle applied for the muscle movement is the lever system.

Lever is defined as a body which is meant to rotate an object by exerting a force over it. It comprises of a stationary fulcrum and a rigid bar.

Fulcrum of muscles is the axis between the joints and the levers are referred to as the bones. Levers are classified as the first class lever, second class lever and the third class lever. This classification is done using the parameters fulcrum, force applied, and the resistance against the force applied.

Also, an increase in the length of the lever not just increases the speed of the muscles joints; it also increases the force which is required for the muscles to move.

4. False

Explanation: As the stimulus frequency of the muscle fiber increases; not just the velocity, force developed by the muscles also gets affected.

Each time the muscle frequency varies, the force developed within the muscles for their contraction or relaxation first increases; and then starts to decrease. This can easily be monitored by the generation of an electrical signal as a result of the muscle contraction. This is monitored by placing electrodes over the slin surface. And the fluctuation in the reading depicts the changes in the muscular force.

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