LECTURE #4 - friction in the human body

Question 1

what is an example of friction in the human body ?

Answer 1

joints

Question 2

what is the sample coefficient for synovial joints in humans (static) ?

Answer 2

0.01

Question 3

what is the sample coefficient for synovial joints in humans (kinetic) ?

Answer 3

0.003

Question 4

does friction increase or decrease with reduction in AC and synovial fluid OA patients ?

Answer 4

increases

Question 5

what does TKR stand for ?

Answer 5

total knew replacement

Question 6

what is osteoarthritis ?

Answer 6

a degenerative disease that worsens over time, often resulting in chronic pain

Question 7

what is TKR coefficient of friction ?

Answer 7

TKR coefficient of friction is still 0.03-0.10

Question 8

what does the ACL do?

Answer 8

stops tibia from coming forward (anterior motion)

Question 9

what does ATT stand for?

Answer 9

anterior tibia translation

Question 10

what is coefficient of friction in OA patient ?

Answer 10

0.1 - 0.3

Question 11

what is the normal coefficient for a normal individual with healthy knee

Answer 11

0.1

Question 12

what is the normal coefficient for a patient elegable with OA ?

Answer 12

0.3

Question 13

how does one avoid slipping when walking on a surface with a low coefficient of friction

Answer 13

more vertical force going down and shorter steps
(smaller steps increase friction/normal force)

Question 14

TRUE OR FALSE

different skates manipulate friction

Answer 14

TRUE

Question 15

what is klapskate technology ?

Answer 15

a new skate during the early to mid 90s related to the developments of speed skating

Question 16

describe the developments of speed skating :

Answer 16

1960s - refrigerated facilities
1960s - ice preparation techniwues
1970s - tight fit suits
1980s - indoor rinks
1996/97 - klapskates

Question 17

why was klapskate technology invented ?

Answer 17

• speed skaters must suppress ankle plantar flexion (decreased know extension)
• eliminate pressing tip of blade into ice

Question 18

what makes the klapskate different from a conventional skates ?

Answer 18

• posterior aspect of blade detaches from boot
• “klap” refers to sound of blade slapping back into place

Question 19

talk abut klapskates & reduction ice friction :

Answer 19

• increasing μ from 0.004 to 0.006 results in decrease velocity by 0.3 m/s
  0 increase f 0.8 sec in 500 meter race ; 23.5 in 10,00 meter race

Question 20

summarize klapskates :

Answer 20

• have provided skaters ability to execute explosive plantar flexion
• no corresponding increase in ice friction
• allows skater to benefit from increased power output
• increased mechanical power output by as much as 12%