Application of Biomechanics - Running, swimming, lifting
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How does normal running gait differ from normal walking gait?
- Requires greater balance;Requires greater muscle strength;
- Requires greater range of motion;
- Direction of driving force is more horizontal and stride is longer;
- Body has greater forward incline;
- Increased rotary action of spine and pelvis;
- Arm actions are higher and more vigorous;
- Increased stride length and frequency;
Why does running require greater stability?
Because of absense of double support period and presence of "flight phase when both feet are out of contact with supporting surface
Why does running require greater muscle strength than walking?
Because of many muscles contracting more rapidly and with greater force
Why does running require a greater range of motion?
Because of greater joint angles at the extremes of the movement.
What is the flight phase?
Period of non-support, where both feet are not in contact with the supporting surface
How are running and walking similar?
- The normal gait cycle is similar;
- both utilize CL and CR
What are GRF patterns in running over 6 m/s?
Between 2 and 3 times the body weight; forces are realized at heel strike as an impact peack during push-off as an active peak
Most common problem with abnormal running gait?
Involve rear foot motion during heel strike and push-off (pronation and supination of the foot)
What is pronation, in terms of the foot? When is it greatest, and how can it be affected?
- Combo of abduction, eversion, and dorsiflexion;
- Greatest at mid-stance;
- Affected by running speed and shoe hardness and design
What are shoe patterns of overpronation?
What is supination, in terms of the foot? What are the repercussions of oversupination?
- Combo of adduction, inversion and plantarflexion;
- At take-off, may impair running performance because of mis-direction of propulsive forces.
What are shoe patterns of oversupination?
Excessive wear on the lateral side
What are the basic concepts of swimming?
- Propelling Forces
- Resistive forces
What is buoyancy?
The tendency of a body to float when submerged in fluid
What is buoyancy of the body dependent on and why?
The percentage of weigh composed of bone and muscle, because these structures are more dense (less buoyant) than other body tissues like fat
What is Archimedes' principle?
A body immersed in fluid is buoyed up with a force equal to the weight of the displaced fluid.
What causes propelling forces during swimming, and what do they cause?
- Stroke and kick;
- Cause forward progress, not vertical or lateral movement
What should the hands, feet, and arms do during the propelling phase of swimming?
Presents a large surface to the water and should push against the water.
What do resistive forces in swimming result from?
- Skin resistance (friction);
- Wave-making resistance cause by up-and-down body movement;
- Eddy current resistance
What components of biomechanics are important in applying the laws of motion to lifting, reaching, pushing, pulling, and carrying of objects?
- Effects of:
- Muscular force;
- External resistance
What are the basic principles of good body mechanics?
- 1) Assume a position close to the object;
- 2) Position the COG as close to the object's COG as possible;
- 3) Widen the BOS;
- 4) Position the feet according to direction of movement;
- 5) Avoid twisting;
- 6) Push, pull, roll, or slide an object rather than lift;
- 7) Use the Power Position;
What does assuming a position close to the object do, in terms of lifting?
- Allows use of upper extremeties in a shortened position (short lever arms);
- Lowers torque required to lift object, allowing muscles to function more efficiently;
What does positioning the COG as close to object's COG do, in terms of lifting?
Reduces torque and energy requirements
How do you widen the BOS?
Lowering the COG and maintaining the COG within the BOS
What is the Power Position?
- Knees sightly bent;
- Body bent forward from the hips;
- Back straight;
- Chest and head upright
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