Principles of Stability, biomedical physics , stability, physical therapy

It is all about principles of stability with examples , applications , how to use it for physical therapy students .

1. PRINCIPLES OF STABILITY Prepared by – JOYAL TEJPAL

2. COG (centre of gravity) The main force acting on all parts of the body is GRAVITY. As a consequence it must be centred somewhere in the body, this is known as the COG (centre of gravity) COG is defined as “ the point in the body at which all parts of the body are in balance, or the point at which gravity is centered. Try and balance a pen on your finger!

3. COG When we stand in the anatomical position our COG is located around the hip region. When we produce rotation as a consequence of force being applied, the body rotates about the COG. These are called “the axes of rotation”

4. LOG (Line of Gravity) The line of gravity is the vertical line that passes through the COG to the ground The line of gravity is important when determining the stability of an object If the line of gravity falls within the objects base of support the object is relatively stable If the line of gravity falls outside the objects base of support the object is relatively unstable.

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7. Base of Support Base of support is the area within an objects point of contact with the ground. The bigger the base = the more stable Who is the most stable?

8. Principle I Other things being equal, the lower the center of gravity, the greater will be the stability. 12/6/2018 8 Principles of Stability

9. Applications The easiest & safest pyramids for beginners are those in which the participants are on their hands & knees. 12/6/2018 9 Principles of Stability

10. In canoeing the kneeling position represents a compromising position which combines the advantages of stability & ease of using the arms for paddling. 12/6/2018 10 Principles of Stability

11. A performer on a balance beam quickly squats when she feels herself losing her balance. 12/6/2018 11 Principles of Stability

12. A wrestler tries to remain as stable as possible by lowering his center of gravity. 12/6/2018 12 Principles of Stability

13. Principle II Greater stability is obtained if the base of support is widened in the direction of the line of force. 12/6/2018 13 Principles of Stability

14. Applications This helps an individual to keep from being thrown off balance when he punches with force, pushes a heavy object or throws a fast ball. 12/6/2018 14 Principles of Stability

15. In pushing and pulling heavy furniture, he can put his whole body into the act without loss of balance 12/6/2018 15 Principles of Stability

16. While catching a fast moving object like a baseball or a heavy one like a medicine ball, widening the base in the direction of the force enables the catcher to “give” as he catches and in this way to provide a greater distance in which to reduce or stop the motion of the object. 12/6/2018 16 Principles of Stability

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18. The military “at ease” is more stable than the position of “attention”. 12/6/2018 18 Principles of Stability

19. Keeping one’s balance when standing on a bus or train which is accelerating of decelerating is facilitated by widening the stance in the direction that the vehicle is moving, that is, in a forward-backward direction in relation to the vehicle. 12/6/2018 19 Principles of Stability

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21. Principle III For maximum stability the line of gravity should intersect the base of support at a point which will allow the greatest range of movement within the area of the base in the direction of forces causing motion. 12/6/2018 22 Principles of Stability

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24. Applications A football player knowing he will be pushed from in front, should lean forward so that he can “give” in a backward direction without losing his balance. 12/6/2018 25 Principles of Stability

25. A person in a tug-of-war line leans backward in preparation for absorbing a strong forward pull from opponent. 12/6/2018 26 Principles of Stability

26. A tennis player anticipating her opponent’s return will keep her line of gravity centered so that she can shift her center of gravity in any direction without loss of balance. 12/6/2018 27 Principles of Stability

27. Dragging a heavy box forward on a high shelf and then lifting it down is an activity in the home to which this principle applies. Assuming a forward-backward stance and leaning forward for this act gives the individual a wider distance for receiving the weight of this forward moving object. This decreases the likelihood of his being thrown off balance when the box suddenly comes free. 12/6/2018 28 Principles of Stability

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31. Principle IV Other things being equal, the greater the mass of a body, the greater will be its stability 12/6/2018 32 Principles of Stability

32. Application In sports in which resistance to impact is a factor, heavy, solid individuals are more likely to maintain their equilibrium than lighter ones. This provides one basis for selecting linemen in football. 12/6/2018 33 Principles of Stability

33. Principle V Other things being equal, the most stable position of a vertical segmented body (such as a column of blocks or the erect human body) is one in which the center of gravity of each weight-bearing segment lies in a vertical line centered over the base of support or in which deviations in one direction are exactly balanced by deviations in the opposite direction. 12/6/2018 34 Principles of Stability

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35. Applications This applies to postural adjustments for achieving a pleasing, well-balanced alignment of the body segments, both with and without external loads. 12/6/2018 36 Principles of Stability

36. In pyramid building and other balance stunts in which one person for group of persons supports the weight of another person or persons, the chief problem is one of either aligning or balancing the several center of gravity over the center of the base of support. 12/6/2018 37 Principles of Stability

37. Principle VI Other things being equal, greater the friction the between supporting surface and the parts of the body in contact with it, the more stable the body will be. 12/6/2018 38 Principles of Stability

38. Application The wearing of cleats and rubber-soled shoes for sport activities not only aids in locomotion but also serves to increase one’s stability in positions held momentarily between quick or forceful movements, as in basketball , fencing, football, field hockey, lacrose and other sports. 12/6/2018 39 Principles of Stability

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41. Principle VII Other things being equal, a person has better balance in locomotion under difficult circumstances when he focuses his vision on stationary objects rather than on disturbing stimuli. 12/6/2018 42 Principles of Stability

42. Application Beginners learning to walk on a balance beam or perform balance status and others who for any reason have difficulty in keeping their balance can minimize disturbing visual stimuli by fixing their eyes on a stationary spot in front of them, either at eye level or somewhat above eye level. 12/6/2018 43 Principles of Stability

43. Principle VIII There is a positive relationship between one’s physical and emotional state and the ability to maintain balance under difficult circumstances. 12/6/2018 44 Principles of Stability

44. Application Persons should not be permitted to attempt dangerous balance stunts or activities requiring expert balance ability when their physical or emotional health is impaired. 12/6/2018 45 Principles of Stability

45. Principle IX Regaining equilibrium is based on the same principles as maintaining it. 12/6/2018 46 Principles of Stability

46. Applications After an unexpected loss of balance, such as when starting to fall or after receiving impetus when “off balance” equilibrium may be more quickly regained if a wide base of support is established and the center of gravity is lowered. 12/6/2018 47 Principles of Stability

47. Upon lending from a downward jump, stability may be more readily regained if the weight is kept evenly distributed over both feet or over the hands and feet, and if a sufficiently wide base of support is provided. 12/6/2018 48 Principles of Stability

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50. Upon landing from a forward jump, the balance may be more readily regained if one lands with the weight forward and uses the hands if necessary in order to provide support in the direction of motion. 12/6/2018 51 Principles of Stability

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53. REFERENCE: Basics of Kinesiology – Wells 54 12/6/2018 Principles of Stability