Lecture 4 - Biomechanics

Question 1

define biomechanics

Answer 1

uses laws of physics and engineering concepts to describe motion undergone by the various body segments and the forces acting on these parts during normal daily living

Question 2

define occupational biomechanics

Answer 2

study of the physical interactions of workers with their tools, machines, and materials so as to enhance the workers performance while minimizing the risk of musculoskeletal disorders

Question 3

goals of occupational biomechanics (consider what we understand)

Answer 3

We understand that:
- > people have mechanical limitations (i.e. strength, ROM, fatigue) and that peoples excessive loading leads to fatigue, downtime, and injury

it is a goal of occupational biomechanics to generate “tolerable, acceptable and optimal” working condisions

Question 4

Kinetics vs Kinematics

Answer 4

Kinematics
- > describes motion undergone by various body segments (displacement, vel, acc)
Kinetics
- > understand the forces acting on these segments (F=ma)

Question 5

issues that may lead to injury, fatigue, ect. in the workforce

Answer 5

• > awkward & static posture
• > Force/Load (too much)
• > Repetition
• > Duration
• > Vibrations

Question 6

define tendons and tendon sheaths (relate to biomechanics)

Answer 6

Tendon
- > ables transmitting muscle forces
Tendon Sheaths
- > pulley and sliding surfaces

Question 7

questions to consider when evaluating the biomechanics and therefore the ergonomics of a workplace

Answer 7

• > what are the forces required to produce a movement
• > does it overload the person
• > can the force or motion requirements be reduced

Question 8

what are the most common issue that we try and fix when we work for a workplace

Answer 8

Low back pain and Upper-extremity cumulative trauma disorder (CTD)

Question 9

what causes tendon related cumulative trauma disorder (CTD)

Answer 9

loss of blood supply to the tendons and increased tension in the tendons

Question 10

neuritis

Answer 10

damage to the nerves that can be caused by awkward posture and repeated use

Question 11

ischemia

Answer 11

the sensation of tingling and numbness, and is caused by obstruction of blood flow to tissue

Question 12

bursitis

Answer 12

the inflammation of a bursa sac, which contains viscous fluid and is located near joints

Question 13

what are the different types of cumulative trauma disorders (CTD)

Answer 13

• > tendon related CTD
• > neuritis
• > ischemia
• > bursitis

Question 14

parts of the musculoskeletal system

Answer 14

• > tendons
• > ligaments
• > fascia
• > cartilage
• > bone
• > muscle

Question 15

characteristics of connective tissue

Answer 15

cells: produce extracellular matrix
extracellular matrix: consistency determines connective tissue physical properties
- > ground substance (viscous fluid)
- > fibers

Question 16

fibroblasts

Answer 16

cells produce matrix of loose connective tissue (skin, tendons and ligaments)

Question 17

chondroblast

Answer 17

cells produce matrix of cartilage (transform to chondrocytes)

Question 18

osteoblasts

Answer 18

cells produce matrix of bone (transform to osteocytes)

Question 19

force hierarchy of muscle contractions

Answer 19

1. Eccentric
   - > works at optimum length
2. Isometric
   - > works at a non optimal length
3. Concentric
   - > works away from optimal length

Question 20

characteristics of tendons

Answer 20

• > connects muscle to bone
• > transmit muscle force
• > parallel collagen arrangements, minimal elastin
• > surrounded by fibrous tissue sheaths
• reduce friction

Question 21

types of tendon damage

Answer 21

• > torn
• > tendonitis
• > tenosynovitis

Question 22

characteristics of ligaments

Answer 22

• > provides stability to joints
• > non-parallel collagen arrangement, aligned in direction of imposed stress

Question 23

explain stress-strain relationships

Answer 23

Stress: applied load
Strain: deformation
Plastic region: permanent disruption
Ultimate strength: complete tear

Question 24

muscular endurance

Answer 24

ability of a muscle or group of muscles to sustain repeated contractions against a resistance for an extended period of time

Question 25

axial vs appendicular bones

Answer 25

Axial bones
- > skull, verts, sternum, ribs, pelvis
Appendicular bones
- > limbs

Question 26

functions of bone

Answer 26

• > provide support
• > allow movement
• > protection
• > mineral storage
• > blood cell formation

Question 27

types of bone

Answer 27

Long bones
- > shafts (diaphysis)
- > two expanded ends (epiphyses)
Cortical (compact)
- > provides cortex or lining of bone
Cancellous (spongy, trabecular)

Question 28

fractures

Answer 28

bone loaded to failure
- > can handle compressive loads (stronger compression than tension)
Traumatic fracture: single load
Stress fracture: repetitive loading

Question 29

how to find/what are bone “hot spots”

Answer 29

• > computed topography (CT)scan or magnetic resonance imaging (MRI) will be necessary
  bone scan will identify “hot spots”, which may indicate stress fractures or tumours

Question 30

fatigue

Answer 30

Net effect of the central fatigue and muscle fatigue and psychological factors resulting in a progressive decline of observed force production

Question 31

central vs muscle fatigue

Answer 31

central
- > reduction in MVC force not accompanied by same reduction in maximal evocable force
muscle
- > reduction in the capacity to generate force

Question 32

how do we quantify the magnitude of the loading over a given time (refer this to cumulative loading and CTD)

Answer 32

we observe the…
- > posture
- > repetition
- > duration
- > force

Question 33

main causes of CTD

Answer 33

• > inadequate recovery
• > awkward joint postures
• > excessive loads

Question 34

how can repeated submaximal loading cause injury

Answer 34

tissue tolerance will decrease and eventually fail

Question 35

how can sustained loading over time lead to injury

Answer 35

over time you will slowly degrade the tissue until your tolerance completely gives out