Question

Take each of the above individually and provide a specific example of how each are responsible in human motion. Please use specific joints and musculature in the examples.

1. Magnitude of force

2. orientation of force

3. direction of force

4. point of application of the force

5. length of muscle and length/tension relationship

6. velocity of movement and force/velocity relationship

7. Fiber arrangement and fast/slow twitch fiber ratio.

Here are a couple examples:

1. The orientation of force: This refers to the angle between the line of action and the center of the joint. When the angle is between 1 and 90 degrees there will be a stabilizing force. When the orientation is between 91 and 180 degrees, there will be a dislocating force.

2. The magnitude of force: The greater the magnitude of force, the greater will be the ability to overcome greater and greater resistances. This is especially important when longer levers are involved.

Answer 1

1. The magnitude of force: The greater the magnitude of force, the greater will be the ability to overcome greater and greater resistances. This is especially important when longer levers are involved.

2. The orientation of force: This refers to the angle between the line of action and the center of the joint. When the angle is between 1 and 90 degrees there will be a stabilizing force. When the orientation is between 91 and 180 degrees, there will be a dislocating force.

3. Direction of force: Direction of exerting force plays an important role in achieving desired motion. Applying same magnitude of force but in different directions can lead to a different results for example if you apply force forward on a object it will move forward and vice versa. To walk forward we exert force on ground backwards and in return ground exerts an equal and opposite force and pushes us forward. Instead if we exert force forward then ground will push us back making us go backward.

4. Point of application of force: The point of application is the exact location at which a force is applied to a body. For levers the point of application of force plays a key role as it determines the force needed to produce the desired torque to move objects.

5. Length of muscle: Tendons are organs that attach our skeletal muscles to our bones. When our muscles are resting, they are not contracted instead they are actually stretched to a point called resting length. The natural resting length maximizes the ability of the muscle to contract when stimulated. The effect of resting fiber length on muscular contraction is called as length-tension relationship.

6. Velocity of movement: It is velocity at which muscle contract when force is applied. The force-velocity relationship describes how muscle force depends on the velocity of movement or vice versa. The graph between force and velocity shows an inverse relationship between the two meaning in force would cause decrease in velocity and vice versa.

7. Human muscles contain a genetically determined mixture of both slow (type I) and fast (type II) fiber types. Slow-twitch muscles help enable long-endurance feats such as distance running, while fast-twitch muscles fatigue faster but are used in powerful bursts of movements like sprinting. On average, people have about 50 percent slow twitch and 50 percent fast twitch in most of the muscles used for movement but the ratio varies depending on the profession.