Biomechanics

Question 1

Biomechanics

Answer 1

• Application of mechanical laws to living structures, specifically to the locomotor system of the human body.

Question 2

6 Uses of Biomechanical Analyses

Answer 2

• Improvement of sports skill techniques
• Design of sports equipment
• Prevention of injuries
• Clinical analysis of movement pathologies
• Design of prostheses
• Design of rehabilitation devices

Question 3

qualitative analysis

Answer 3

• Non-numerical description of a movement based on direct observation. (coaches)

Question 4

quantitative analysis

Answer 4

• Movement is analyzed numerically based on measurements from data collected during the performance of the movement. (researchers)

Question 5

mass

Answer 5

• Quantity of matter contained in an object.

Units = kilograms (kg)

Question 6

force

Answer 6

• Mass X acceleration.

Units = Newtons (N
1 N = (1 kg) (1 m/s2))

Question 7

weight

Answer 7

• Amount of gravitational force exerted on a body
(Weight = mass X acceleration of gravity = m*g)
• Acceleration of gravity = 9.81 m/s^2

(Units of weight – Newtons)

Question 8

torque (rotary force)

Answer 8

• Product of force and the perpendicular distance from the force’s line of action to the axis of rotation.

(Units = Newton-meters (N∙m))

Question 9

moment arm

Answer 9

• Perpendicular distance between the force’s line of action and the axis of rotation.

Question 10

mechanical advantage of a lever

Answer 10

• Ratio of force arm length to resistance arm length.

Question 11

volume

Answer 11

• Amount of space that a body occupies

Question 12

pressure

Answer 12

• Force distributed over a given area.

Units = N/cm2; P = F/A

Question 13

compression

Answer 13

• Pressing or squeezing force directly axially through a body.

Question 14

tension

Answer 14

• Pulling or stretching force directly axially through a body.

Question 15

shear

Answer 15

• Force directed parallel to a surface

Question 16

mechanical stress

Answer 16

• F/A: similar to pressure.

Question 17

8 Tips on Lifting a Heavy Object From the Floor

Answer 17

1. Get someone to help you on heavy lifts.
2. Ensure that you have a stable base of support; facing the object with your feet flat on the floor, at shoulder width, and pointing straight ahead.
3. Avoid twisting and the simultaneous generation of high twisting torques; face the object in the direction which you intend to move with it.
4. Keep the object as close to your body = minimize the reaction torque on lower back.
5. Firm grip on the object to keep it under control.
6. Bend at hips and knees; neutral spine.
   (minimizing L5/S1 disc compressive force and ligament strain)
7. Lift using knees and hip extensor muscles, not by pulling upwards with the arms and back.
8. Carry the object close to your center of gravity.

Basically bro, just don’t lift or stretch right after you woke up, and warm up before activities if you have been sitting/inactive. Also bro, brace, and keep neutral spine to reduce the risk of hernia/ligament damage, bro.

Question 18

Center of Gravity

Answer 18

• CG is approximately 5 cm anterior to the second sacral vertebra, or 6 cm below the belly button.
• CG higher in male.
– 57%(m) versus 55%(f) of height.

• The exact location varies depending on body proportions.
• Influenced by body/limb positions.
• Addition of external weight (backpack) relocates CG.
• Segmentally each body area contains its own center of gravity.

Question 19

3 Reasons Why It Is Useful to Determine CG

Answer 19

1. Describes the movement of the body through space
2. Important for stability
3. Important factor in calculation of amount of work done.

Question 20

2 Ways of Locating Center of Gravity

Answer 20

1. Reaction board method
   (for static position)
   • Assume that the center of gravity is the fulcrum, apply the Principle of Levers.
2. Segmental method
   (for body in motion)

Question 21

Balance and Stability

Answer 21

• CG must remain over the base of support.

* More stability when a weight is close to the body’s CG.

Question 22

Stability

Increasing Stability

Answer 22

• Firmness of balance - can be increased by:

1. Increasing body mass.
2. Increasing the size of the base of support in the direction of the line of action of an external force.
3. Positioning the CG as low as possible
4. Increasing friction between the body and the surface contacted
5. Positioning the CG near the edge of the base of support towards the oncoming external force

Question 23

Newton’s Laws of Motion

Answer 23

• First Law - The amount of inertia a body possesses is directly proportional to its mass.
• Second Law - Law of Acceleration - “force equals mass X acceleration”
• Third Law - Law of Reaction - “equal and opposite reaction”

Question 24

momentum

Answer 24

• A mechanical quantity that is important in situations involving collisions.

(Momentum = mass X velocity)

Question 25

Work and Power Relationships

Answer 25

• Work = force X distance
(Units of work - 1.0 Nm = 1.0 J (joule))

• Power = work per unit of time = force X velocity
(Units of power = watt; 1.0 W = 1.0 J/sec)

Question 26

Walking Versus Running

Answer 26

• Differences between walking and running:

1. In running there is a period when both feet are off the ground. (series of jumps)
2. In running, there is no period when both feet are in contact with the ground at the same time
3. In running, the stance phase is a much smaller portion of the total gait cycle than in walking.

Question 27

Running speed

Answer 27

• stride length X stride rate

Question 28

length of stride

Answer 28

• Dependent primarily upon leg length and the power of the stride.

Question 29

leg speed (frequency)

Answer 29

• Mostly dependent on speed of muscle contraction and neuromuscular coordination (skill) in running.

Question 30

foot contact while running

Answer 30

• At slow running speeds, complete foot contact is used. As running speed increases, the amount of foot contact becomes less.

Question 31

posture when running

Answer 31

• At slower running speeds, runners tend to run more erectly, whereas at full speed, the typical sprinter leans forward at about 15 degrees from the perpendicular.