Principles of Force in Sports
Force is the product of the mass (weight) and acceleration of an object or person. Principles of force offer guidance for teaching sport techniques and leveraging training strategies that require the development of force--pushing or pulling. These principles and examples concern (a) general applications, (b) athlete-produced force, and (c) force dissipation.
General Principles of Force
1. Total force (velocity) is the sum of all the forces contributed by each body part. In any explosive skill, each force in sequence should be applied at the peak of the previous force. Examples include throwing a ball and performing a power clean.
2. Force is used more economically when it is applied constantly and evenly. For example, a swimmer moves more efficiently when moving at constant speed and with smooth application of force.
3. All forces should be applied in the intended direction. Deviations from the required line of force waste energy. For example, a runner who points his toes outward or bounces excessively exerts wasted force and energy.
4. Greater velocity is generated if force is applied over a longer distance. For example, an outfielder can generate greater force for throwing to home plate by using a long winding up, rotating the trunk, shifting body weight from the back leg to the front, and following through.
Principles Concerning Athlete-Produced Force
5. To achieve maximum force, use larger muscles in the lower body before actions of the trunk and upper body. For example, the force of a punch in boxing or throwing is greater when initiated from the lower body and hips, rather than from the shoulders.
6. Maintain a firm base of support to develop maximum force for throwing and striking. For example, a tennis player can generate a more powerful stroke if the feet are firmly set against the surface of the court.
7. Force generated by muscles can be increased by increasing initial tension before a contraction. This increase in force production is called elastic recoil, or the stretch-shortening cycle. For example, drawing the arm back to pitch a ball or throw a javelin places the muscles of the throwing arm on stretch, increasing the force of contraction upon the initiation of the throw.
8. Executing a follow through at the end of a throwing or striking action maximizes force generation and eliminates the tendency to decelerate prematurely. For example, reversing the feet at the end of the shot put or discus maximizes acceleration while helping prevent fouling.
Principles Concerning Force Absorption
9. The force of a blow can be diminished by distributing the force over a greater time, distance, or area. For example, flexing the joints or rolling on the ground can help an athlete absorb the shock of landing at the end of jump or fall.
10. Transferring momentum from vertical to horizontal can reduce force over a longer time and greater surface area. For example, football players fall and roll to dissipate the force of hitting the ground.
11. Catching objects should be accomplished by extending the arms and fingers, flexing to absorb force and reduce the velocity of the object, and grasping with the fingers to secure the object.
In addition to these principles of force, see other rules that govern athletic skills:
Newton's Laws of Motion
Principles of Stability and Balance
Projectiles in Sports
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