## A-Z

A-Z Golfing Biomechanical Terms

Dr Paul Hurrion
www.quintic.com

ACCELERATION
The rate of change of velocity in relation to time: ANGULAR ACCELERATION
Angular acceleration refers to the rate at which the angular velocity of a body changes in relation to time.

BALANCE
(i) A state where things are of equal weight or force;
(ii) If someone or something is off balance, they are in a position where they are likely to fall or be knocked down:
(iii) A state of equilibrium or equipoise; equal distribution of weight, amount, etc. A state resulting in bodily equilibrium or counterpoise.

CENTRE OF PRESSURE
Force platforms measure the position of the point of application of force (centre of pressure) on the platform. This is the point at which the force can be considered to act, although the pressure is distributed over the platform (and foot or feet). There may actually be no pressure acting at the centre of pressure, for example, when it is below the arch of the foot or between the feet during a double stance position (Address in the golf swing)

DISPLACEMENT
The distance from the initial to the final position of a body moved from one position to another due to the action of a force. Displacement is a VECTOR in that it possesses magnitude and direction.

ENERGY
The capacity for doing work. In any system, this capacity cannot be destroyed, but energy can be transformed from one form to another.

· Kinetic Energy : that component of the mechanical energy of a body resulting from its motion.
· Potential Energy : that component of the mechanical energy of a body resulting from its position.

FORCE
A vector quantity that describes the action of one body on another.

Force – Velocity Relationship
At any given length, the speed of shortening or lengthening of a muscle that is stimulated at a constant level will depend on the force that is applied to the ends of the muscle. The Hill equation, best known of the force-velocity equations, describes mathematically the fact that light loads can be lifted quickly but heavy loads only slowly although it is often stated that maximal muscle force is available at zero velocity (isometric action), the highest loads are achieved during eccentric muscle action.

Ground Reaction Force
The forces that act on the body as a result of interaction with the ground.

GRAVITY
Gravitational acceleration 9.81ms-2 is the acceleration of a body (of negligible mass compared to the earth) towards the centre of the earth. During the golf swing, the golfer exploits gravitational acceleration and changes in moments of inertia.

HUMAN MOVEMENT
A philosophy that emphasises the ability of the human body to move as a means for expressing, exploring, developing and interpreting one’s own self and one’s relationship to the world. Aims to teach the athlete to move effectively and efficiently with minimising the risk of injury. (Human Biomechanics!)

INERTIA
The resistance offered to a body to change its state of rest or motion. For example, centrifugal force in a rotating co-ordinate system (golf club during the downswing)
Every body perseveres in its state of being at rest or of moving uniformly straight ahead, except in so far as it is compelled to change its state by forces impressed.

Rotational Inertia: Refers to the fact that a rotating rigid body maintains its state of uniform rotational. Its ANGULAR MOMENTUM is unchanged, unless an external TORQUE is applied; this is also called conservation of angular momentum.

JOINT REACTION FORCE
The net force acting across a joint in the body. It follows Newton’s 3rd law that there must be an equal and opposite force acting at each joint.

KINEMATICS
The study of the motion of bodies without reference to the forces associated with that motion. KINETICS is the study of the motion of bodies with reference to the forces associated with that motion.

LEVER
A lever is a system that tends to change the mechanical advantage of an applied force. Basically, it consists of two forces and a fulcrum or hinge. The two forces are called an effort force (such as a muscular force) and a resisting force (such as a weight held in the hand or a ground reaction force). The perpendicular distance of each force from the fulcrum is called the lever arm.

MASS
The quantity of matter in an object. The mass of an object will remain constant regardless of location or gravitational conditions (e.g., earth or moon gravity). Weight, however, varies under these two conditions. The importance of mass in mechanics is that it represents, in linear terms, the resistance to a change of state (a speeding up or slowing down).

CENTRE OF MASS : The point at which the mass of the body acts at (point representing the mean position of the matter in a body).

NEWTONS LAWS
1. Newton’s first law states that a body will maintain a state of rest or uniform motion unless acted on by a net force.
2. Newton’s second law states that the change in momentum of the body under the action of a resultant force will be proportional to the product of the magnitude of the force and the time for which it acts (i.e., the impulse). The second law also states that the change in momentum will be in the direction of the resultant force.
3. Newton’s third law states that action and reaction are equal and opposite.

OVERUSE INJURIES

POWER
The rate of doing work. Power is equal to the work done divided by the time during which the work is being done: P = W/t.

QUINTIC
Of the fifth degree or an equation of the fifth degree. A Quintic Spline is a mathematical term for a line through points on a graph frequently used in mathematical calculation of speeds and accelerations.

ROTATIONAL RESISTANCE
Spinning, turning or rotating speed.
The effort needed to produce movement involves interplay between:

· the length of the limb & the compactness of the body
· the mass of the limb
· the joint around which the limb moves.

It is found by multiplying the mass by the square of the radial length.

STABILITY
Stability is concerned within the body where all forces counteract each other to produce a zero force therefore balance is achieved. Both situations rely on the position on the Centre of Gravity relative to the base of support.

Dynamic Stability: the balance of the body while in motion.
Static Stability: the balanced position of the body when it is still.

TORQUE
The moment of a force. The measure of a force’s tendency to produce torsion and rotation about an axis, equal to the vector product of the radius vector from the axis of rotation to the point of application of the force and the force vector. A turning or twisting force.

UNITS
The base dimensions of the Système Internationale d’Unités (SI system) are mass (kilograms) length (metres), angle (radians), time (seconds) and temperature (kelvins)

VELOCITY
The velocity is a physical quantity of an object’s motion. Velocity is speed that has a clearly stated direction; e.g., “5 miles per hour” is not a vector, whereas “north at 5 miles per hour” is a vector. If the motion is in a straight line in only one direction, it is the same as speed. The average velocity (v) of an object moving a displacement (s) in a straight line during a time interval (t) is described by the formula

WORK
Work is done when a force moves an object through a distance. Whenever a constant force exists and motion takes place in a straight line, then work equals the magnitude of the force (F) times the distance (d) through which the object moves: W = F x d.

X-FACTOR
The term X-Factor was introduced by Jim McLean in a 1992 Golf Magazine article titled “Widen the Gap”. It is used to describe the relative rotation of shoulders with respect to hips during the golf swing, specifically at the top of back swing. The majority of tour players begin the down swing with the hips leading the shoulders. Approximately 70 percent of Tour players rotate their hips first in the down swing, this action actually increases the X-Factor during the transition and results in faster club-head speed.

YIPS
In golf, the yips is a movement disorder known to interfere with putting and or chipping. The term yips is said to have been popularized by Tommy Armour a golf champion and later golf teacher — to explain the difficulties that led him to abandon tournament play. In describing the yips, golfers have used terms such as twitches, staggers, jitters and jerks.

ZENZIC
The square of a number, for example: 5 x 5 = 25