Biomechanical theory and concepts

Learning goals We are learning the basics of biomechanics. We are learning the types of rotation. We are learning to apply Newtonian physics to the body.

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biomechanics the science examining the internal and external forces acting on a human body and the effects produced by these forces internal forces produced by muscles and tendons working against external forces of gravity, air resistance, water resistance and friction

aim Medicine Biomedical Engineering Sport Equipment Design Rehabilitation Ergonomics

background movement of the body is produced by the rotation of body segments around joints movement of joints occur when muscles contract (ex . biceps) the skeleton is the structural framework; muscles move body segments movement is caused by forces

background force is a push or pull causes movement or a change in movement or direction vector quantities because have both a size and direction standard unit of force is the Newton - N the amount of force and speed muscles can produce depends on size of the muscles angle of pull type of resistance training

Types of motion Linear or Translation movement in a particular direction; linear force acting on an object, resulting in a straight line Angular or Rotary movement around an axis; force acts “off-centre” causing spin General combination of linear and angular (most motion)

Determining motion centric force: force applied directly through the centre of an object or body and it results in linear motion only the object or body will move linearly in the direction of the applied force. eccentric (off-centre) force: force directed through a point other than the centre of the object or body always results in rotational motion (and sometimes linear motion, too).

Humans and rotational motion rotations of projectiles or other objects (e.g., the swing of a hockey stick) rotations of the entire human body about one of three axes (e.g., the tumble of a gymnast) rotations of individual body segments (e.g, the throwing motion of a softball pitcher’s arm)

Newton’s laws

newton 3 laws established foundations of classical mechanics see Costella for a brief and likely interesting history!

1st Law of inertia “An object remains at rest or in a state of constant motion unless acted upon by an unbalanced external force.” the heavier an object is, the harder it is to change it’s motion. this resistance to a change in motion is called inertia.

examples car skidding off icy road on a curve gymnast maintaining a stationary pose on balance beam curling rock if on a frictionless surface

2nd law of acceleration “In the presence of an unbalanced external force, an object will accelerate in the direction of that force”. the heavier the body, the smaller the acceleration.

examples F = ma as more mass is added to a blocking sled, a football lineman must generate more force for the sled to accelerate at the same rate. proper technique and strength allow professional tennis players to apply more force when they hit the ball, causing the ball to accelerate faster.

3rd law “Every action has an opposite and equal reaction”. if one object exerts a force on a second object, the second object exerts the exact same force on the first but in the opposite direction.

examples punch a wall, it punches back with the same force… you break your hand. kick a table, it kicks you back with the same force… you stub your toe. basketball or volleyball player jumping sprinter in starting blocks

Learning goals We are learning basics of biomechanics. We are learning the types of rotation. We are learning to apply Newtonian physics to the body.

Please complete Newton Law HO