Body Systems in Movement:
To move, the human body goes through a complex series of interactions that involve different body systems. Even the smallest of movements requires coordination and communication between the muscular, skeletal, and nervous systems.
Muscular system: Muscles are connected to bones. When a muscle contracts, it creates tension which often produces movement around a joint. Sometimes, muscle contraction does not produce movement, but instead holds and supports the body, increasing stability.
Concentric contraction: Tension while the muscle shortens
Eccentric contraction: Tension while the muscle lengthens
Isometric contraction: Tension without muscle length change
Skeletal system: The human skeleton is the framework that supports the human body. Without bones, you could not stand, sit, or walk.
Nervous system: Every movement you make is controlled by the nervous system. The brain and spinal cord (central nervous system) interprets signals from the body and sends messages to the muscles to move. These messages travel through the nerves of the nervous system until they reach their destinations.
Planes of movement:
The movements available to your body can be broken down into 3 planes or axis: Sagittal, Horizontal, and Frontal planes.
Sagittal Plane:
Bisects the body from front to back, dividing it into left and right halves. Flexion and Extension movements usually occur in this plane.
Horizontal Plane:
Divides the body horizontally into Superior and Inferior halves. Rotational movements usually occur in this plane.
Frontal Plane:
Bisects the body laterally from side to side, dividing it into front and back halves. Abduction and Adduction movements occur in this plane.
The physical world is 3 dimensional and so is our movement. It’s not just in sporting situations that we are required to rotate from the trunk (horizontal plane), drive our legs up and down (sagittal plane), and push our arms out (frontal plane) at the same time (eg fending in rugby). Even daily activities like putting on clothes require the use of many planes, occurring simultaneously or at least in quick succession.
Your body is capable of so many different movements in so many different directions, that it can be hard to train for all of them optimally. A balanced exercise program should contain movements that occupy a variety of these planes.
Newton’s Laws of Motion
These define all types of motion, including the movement of the body.
Law of inertia:
An object at rest will stay at rest and an object in motion will stay in constant linear motion unless acted on by an outside force. If a ball is rolling, it will keep rolling forever unless something stops it. In the same way, if a ball is at rest, it will stay at rest until a force pushes it to move.
Law of acceleration:
The acceleration of an object is directly proportional to the force acting on it and inversely proportional to the mass of the object. As the force acting upon an object increases, the acceleration of the object also increases. As the mass of an object increases, the acceleration of the object decreases for a fixed force.
Law of action and reaction:
For every action there is an equal and opposite reaction. When one object exerts a force on a second object, the second object reacts by exerting an equal force in the opposite direction on the first object. For example, when you walk, your body pushes down on the ground to move yourself forward. The ground “pushes back” against you with the same magnitude of force (compression), propelling you forward.
The movement of the human body follows Newton’s laws of motion. The body moves when internal and external forces act on it. Internal forces are generated within the body. When a muscle concentrically contracts, it applies an internal pulling force on a bone (tension), which causes movement. External forces are generated outside of the body. For example, gravity is constantly pulling you down.