i. Broad base of support: for greater stability increase the area of the base and lower the centre of gravity as much as is consistent with the activity involved. Examples:
a. a basketball player stops, spreads his feet wide as shoulder line and lowers his CG to dodge the opponent.
b. Defence position of the player in volleyball.
c. Wide stance of a golfer.
d. tackling position of a player in football.
ii. Stability is directly proportional to the weight of the body: the object or a person with heavy weight will have greater stability as compared to person with less weight.
Example: it is difficult to move a heavier person as compared to less heavier person.
On the basis of this principle, wrestling, boxing, judo, etc. are organized according to different age groups.
iii. Direction of an acting force: to start quickly in one direction, keep the CG as high as possible and as near as possible to the edge of the base nearest to the direction of intended motion.
Example: the crouched position in starting a race, the CG is kept high by not bending the knees extremely and by keeping the hips high, also the lean of the body is towards the hands so that the weight rest on the hands. From this position, the movement hands are raised from the ground; motion starts by reason of the pull gravity. This pull is added to the force exerted against the starting block by the feet and thus aids in a quick start.
iv. When the body is free in the air, if the head and feet move down, the hip move up and vice versa.
Example:
a. This principle is applied in the high jump in western or velley roll technique at the take of, the head and one foot is thrust up as high as possible. As the head and one leg clear the bar, they are dropped which raises the hips to clear the bar. As the hips are lowered, the opposite leg is raised to clear the bar.
b. This is also used in pole vault, hurdles and jacknife, dive in swimming.
