Basic Biomechanical Factors and Concepts
The study of mechanics as it relates to the functional and anatomical analysis of biological systems is known as biomechanics. Human movement is quite complex. In order to to make recommendations for its improvement, we need to study movements from a biomechanical perspective, both qualitatively and quantitatively. |
Machines in the Body
We use muscles to apply force to our bones upon which they attach to cause, control or prevent movement in the joints that they cross. In turn we use the bones of our body to pull, push or hold onto an object while we use a series of bones and joints to apply force via the muscles to affect the position of the object. In doing so we are utilizing a series of simple machines. These "machines are used to increase or multiply the applied force in performing a task or to provide a mechanical advantage. This helps us apply a small force or resistance to a much larger object. Ultimately Machines Function in 4 ways. First is to balance multiple forces. Second is enhance for in attempt to reduce the total force needed to overcome a resistance. Third to enhance range of motion and speed of movement so that the resistance may be moved farther or faster and last to alter the resulting direction of the applied force.
Levers
Human movement occurs through organized use of a system of levers. These levers cannot be changed but when their purpose is understood we can maximize the muscular efforts of the body and use them more efficiently. All levers have 3 main parts. First is an axis of rotation, or fulcrum. This is the point of rotation about which the lever moves. Second the lever rotates around the fulcrum as a result of a force being applied against a (third) resistance. In our body the bones function as the lever, whereas the joint is the fulcrum and the muscle contracts to apply the force.
1st Class Lever
A first class lever has an axis of rotation between force and resistance. The force arm and resistance arm move in opposite directions. This provides balanced movement, speed and range of motion, and force motion. An example would be of the Triceps in extending the elbow or the head. This lever is designed to produce balance balanced movements when the axis is midway between the force. I good example would be of "quick feet." When alternating feet putting weight on one and switching to the other you Force and resistance are constantly changing, Being a 1st class lever this helps you stay balanced and not fall down when performing this exercise.
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Second Class Lever
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In this type of lever the resistance is between the axis and the force. The resistance arm and force arm move in the same direction. This lever is designed to provide forced movements and a large resistance can be moved by a relatively small force. A good example of this type of lever would be plantar flexion of the ankle or calf raises. This lever is not very prevalent in our bodies.
3rd Class Lever
In a third class lever the force is between the axis and resistance. The resistance arm and force arm move in the same direction very much like a 2nd class lever. This lever is designed for speed and range of motion. This lever is the most popular in our bodies. The bicep is a good example of this type of lever. The forearm is also a good example. It pulls the ulna just below the elbow, and since the ulna cannot rotate, the pull is direct and true. |
Torque and Length of Lever Arms
Torque is a moment of force that is the turning effect on the eccentric point. The amount of torque can be determined by multiplying the amount of force by the force arm. The perpendicular distance between the location of the force application and the axis is known as the force arm, moment arm or torque arm. It is the shortest distance from the line of action to the force. The greater the distance the greater the torque.
The end of a longer lever travels faster than a shorter lever when moved over the same degree in the same amount of time. The farther the resistance is from the axis, the farther it is moved and the more force delivered to it, resulting in the resistance moving at a greater velocity.
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In softball it is better to hit the ball at then end of the bat on the sweet spot than it would be to hit it on the part of the bat closest to your hands. The longer the distance from the force the greater the velocity.
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Throwing
Throwing is also a good example of a lever arm. This is why infielders and outfielders throw two different ways. The shoulder to the fingers is one giant lever. Infielders making a play do not have to throw the ball as hard or far as an outfielder. In this case it is more important for the infielder to initiate and complete the throw as soon as possible than to deliver as much velocity as to the ball as possible. This is why they make a shorter motion only pulling the ball to their ear. In the outfielders case they use their whole body to gain as much velocity as possible. In this instance the lever can be as long as the distance from the feet to the hand.
Wheel‐Axles
Wheels and axles are primarily used to enhance range of motion and speed of movement. Together they can function as a form of a lever. When either the wheel or axle turns the other must turn as well. The radius of both respond to the force arms; if the radius of the wheel is greater than the radius of the axle, then due to longer force arm, the wheel has a mechanical advantage over the axle. With
minimal humerus rotation, the hand
& wrist travel a great distance. An example of this would be of the arm in a pitching motion. The shoulder moves in a small circular motion and the hand moves in a circular motion with a much larger diameter.
Pulleys
A single pulley has a fixed axis and its function is to change the effective direction of the force application. Their mechanical advantage is to apply a small amount of force to a large amount of weight. Single pulleys are move-able and can be combined to form a compound pulley. Every additional pulley added to the single pulley increases the mechanical advantage by 1. An example of this in the body would be provided by the lateral malleolus, acting as a pulley around which the tendon of the peroneus longus runs. As this muscles contracts, it pulls toward its belly, which is towards the kneed. This action results in eversion or plantarflexion of the foot. In softball we use the pulley system when we do wrist rollups. We use our wrist and forearms to roll a bar that is attached to a weight by a string. This exercise helps pitchers strengthen their wrist which provides better wrist snaps in the overall pitching motion.
Balance and Stability
Balance is the ability to control equilibrium, either static or dynamic. This refers to the state of zero acceleration in the body where there is no change in speed or direction of the body. For us to control equilibrium and achieve balance we need to maximize our stability. Stability is the resistance to a change in the body's acceleration or the resistance to a disturbance of the body's equilibrium. Balance is important for the resting body as it is for the moving body. In softball one of the most important time to be balanced is at the plate. With a good balanced stance you will get a greater increase in power when you hit the ball then when you are unbalanced. A person has balance when the center of gravity falls within the base of support. The large the base of support the more balanced you are. Balance is less if the center of gravity is near the edge of the the base. This is why in softball we stand with our feet shoulder width apart. This ultimately split of center of gravity, which in women is our pelvis, in half between both feet.