PHLT 432 Exam 1

What is the definition of ergonomics?

The branch of science that is concerned with the achievement of optimal relationships between workers and their work environment

In a latin context, what does ergonomics mean?

The study of work.

Ergon = work

Nomikos = law

What is the golden rule of ergonomics?

Fit the job to the person, not the person to the job.

• What does this mean? Instead of expecting workers to physically or mentally force themselves to adapt to poorly designed tasks or hazardous environments, this principle means modifying the work environment to match human capabilities and limitations

Ergonomics is an interdisciplinary science. True or false?

True. It is connected to psychology, physics, math, science, antomy, epi, chemistry, engineering, etc.

Lagging factors

Retrospective - waiting on data to happen. Can’t collect anything until something happens

Leading indicators

Evaluating a task before an issue happens. Preventative and prospective. Going out to evaluate a system to find potential areas for injuries before they occur.

What is the primary objective of ergonomics?

To achieve an optimal relationship between people and their work environment

What are the greatest conflicts to ergonomics?

1. Worker’s productivity

2. Cost of implementation

3. Corporate buy-in

Worker’s productivity

A business wants to stay in business; if an intervention cuts production, nobody wants it. We need to keep people safe without decreasing production.

Cost of implementation

There are usually 3 levels:

• Cheap but fast, the problem still exists long-term

• Middle ground: spend more money to get a medium-term fix, risks are still there

• Completely get rid of the risk by spending as much money as possible

We need to find a balance between the money spent and the impact an intervention has. If there is no data to use as evidence that the intervention is important, the cost is harder to justify (this can be an issue with leading indicators)

Corporate buy-in

Organizations and workplaces will hire consultants. Anytime an ergonomist consultant goes to a workplace, they have to get them to buy into the intervention.

• At the end of the day, all interventions really just come down to money justification (similar to cost of implementation above). The language is business is money.

Ergonomic Risk

The primary objective is to maximize the area (buffer zone) between employee capabilities (the human side - personal factors, non-occupational factors, behavioral factors, etc.) and job requirements (the work side - occupational factors, workload demand, etc.).

• When job demands exceed human limits, ergonomic risk increases.

What is anthropometry?

• The human component of ergonomics

• The measurement of humans

What are the goals of anthropometric design?

We must design for those in the…

1. Range

2. Average

3. Extremes

Designing for the range

Designing for the most optimal person in a range of 5th percentile female and 95th percentile male. If they can do the task, most everybody can do it. This range allows us to optimize the amount of people that can do a task (covers about 90% of the population). Usually means using mechanical adjustments (standing desks, adjustable chairs)

Designing for the average

Designing a fixed dimension based on 50th percentile measurements. While cost-effective for short-use items (e.g., checkout counters or auditorium seating), ergonomists caution that “designing for the average designs for no one”—because an individual who is average in stature is rarely average in arm reach, leg length, or torso size

Designing for the extreme

Accounts ONLY for the 5th percentile female or ONLY for the 95th percentile male. Usually very expensive. Sets fixed upper or lower thresholds when adjustability is impractical.

• Ex: Airlines for athletes; private jets are completely customized for their long limbs

What are the 4 industrial applications?

1. Tool/equipment evaluation

2. Manufacturing/assembly lines

3. Limitations of human capabilities

4. Environmental effects on human capacity

Tool/equipment evaluation

Design, modification, replacement, and maintenance of equipment for enhanced productivity, and the work-life & product quality

Manufacturing/assembly lines

Design and modification of work spaces and workplace layout for ease and speed of operation, service, and maintenance

Limitations of human capabilities

Design and modification of work methods, including automation and task allocation between human operators and machines

• What tools are humans using, are they using them in the right way?

Environmental effects on human capacity

Controlling physical factors (heat, cold, noise, vibration, light) in the workplace for the best productivity and safety of employees

Occupational factors

1. Environmental conditions (temperature, light, noise)

2. Physical and mental requirements of a job

3. Worker’s exposure to hazardous materials

4. Interaction between worker and work equipment

Types of hazards

1. Physical

   1. Extremes of temperature, noise, vibration, and radiation

   2. Falling, slipping, tripping

2. Chemical

   1. Liquids, solids, gases, dusts, fumes, mists

   2. Can be inhaled, swallowed, or absorbed

3. Biological

   1. Healthcare industry: Blood, cooling liquids, bacteria

Anatomy

Branch of science which deals with the body’s structures (bones, muscles, tendons, ligaments, other structures)

• STRUCTURE

Physiology

Science of body’s functions, including metabolism, muscle mechanics, oxygen and nutrient distribution, temperature regulation, nerve transmission, other functional activities

• FUNCTION

What is anatomical position?

Standing erect, eyes looking forward to the horizon, arms by sides, palms of hands and toes directed forward

What are the 3 reference planes?

1. Sagittal

2. Coronal

3. Transverse

Saggital plane

• Vertical plane dividing the body into left and right parts

• Also known as the “median” (but isn’t necessarily in the middle)

• The mid sagittal plane divides into right and left halves

Coronal plane

• Vertical plane perpendicular to the median

• Divides body into FRONT and BACK

• Imagine you are wearing a CROWN on the front or back of your head

Transverse plane

• Horizontal plane that is perpendicular to the saggital and coronal planes

• Divides body into upper and lower parts (top and bottom)

Anterior

Refers to the front, nearer the surface of the body

Posterior

Refers to the back, nearer the back surface of the body

Superior

Above, upper, higher part of the body (near crown of head)

Inferior

Below, lower part of the body (near soles of the feet)

Medial

Nearer the median plane of the body (or body part)

Lateral

Farther from the median plane

Proximal

The end of a body member nearer the body; the point where a limb attaches

Distal

The end of a body segment farther from the body or point of attachment

Palmar or volar

Anterior surface of the hand or forearm

Dorsal

Pertaining to the back or nearer the back (of the foot, hand, and forearm)

• Similar to “posterior”

Plantar

Sole of the foot

Who said “People buy into the leader before they buy into the idea.”?

John Maxwell

What are the components of the skeletal system?

• Bone

• Cartilage

• Hemopoietic Tissues

• Tendons

• Ligaments

What are hemopoietic tissues responsible for?

Forming blood cells

What components of the skeletal system are connective tissue?

Tendons and ligaments (and technically fascia but that’s later in the slide)

How many bones are there in the human body?

206

How are bones classified?

By shape

Long bones

Arms, legs, fingers, toes

What is a characteristic of long bones?

They are strong vertically (long axis) but very weak horizontally. For example, the femur provides strong weight support, but a horizontal force would easily break it.

Short bones

Wrists and ankles

Characteristics of short bones

Can make a combined movement based on the capable movements of each bone, which can move in many different planes. Has a significant amount of movement capacity

Flat bones

Ribs, skull, etc.

Characteristics of flat bones

To provide protection to internal organs like the lungs and brain

Irregular bones

Vertebrae, sacrum, etc

Characteristics of irregular bones

To allow mobility, support, nerve escape (which is why there are holes in the sacrum)

Their purpose is to provide function. Function controls the design.

Right now you need to go back in the lecture slides (PPT 2) and memorize all of the bones on the “bones to know” slide

I did it!

Connective tissue is made up of…

Ligaments, tendons, and fascia

Ligaments

Connects bone to bone and stabilizes joint structures

What does a ligament connect?

Bone to bone

Tendons

Transmits force from muscle to bone

What do tendons connect?

Muscle to bone

Fascia

General connective tissue

Where might fascia be found?

Cavity lining. It is internal connective tissue.

Axial skeleton

Skull, spone, ribs and sternum, and pelvis. Basically everything connected to the spine.

Appendicular skeleton

Arms, legs, collarbone

• Upper extremeties

  • Clavicle and scapula, humerus, radius, ulna, wrist, hand bones

• Lower extremeties

  • Femur, patella, fibula, tibia, foot bones

Functions of the skeletal system

• Supporting body’s framework (preventing collapse into soft tissue)

  • Provides physical framework upon which to apply force

• Protection of vital organs, like the ribcage and skull

• Allow movement of body (provides mechanical levers for skeletal muscles)

• Housing bone marrow which produces red blood cells

• Storing calcium and phosphorous

Cartilage

Cushions the ends of bones and acts as a shock absorber

• Found between joints of spinal column (disks), at joint surface of limbs, at end of ribs

  • Ex: Between the ribs and sternum, there is cartilage

• Firm, elastic, flexible, and capable of rapid growth

• Avascular (Nutrients and oxygen reach cells only by diffusion. It can’t replenish itself)

What are the 3 types of cartilage?

Hyaline

Fibrous

Elastic

Hyaline cartilage tissue

• Covers articular surfaces

• Cushions joints against impact effects

• Hyaline = glassy

• Can be found in fingers because it is a lubricant fluid = lots of movement

Fibrous cartilage tissue

• Greatest rigidity and tensile strength

• Ribcage, intervertebral disks

• Resistant to wear + tear and compression

Elastic cartilage tissue

• Elasticity and firmness

• Ears and nose (maintains shape of anatomical structures)

Cartilage microstructure

Similiar to bone in that…

• Has more intercellular substance than cells

• Collagenic fibers reinforce the matrix of tisuse

  • This makes it resistant to stretching and gives it tensile strength

Different from bone in that…

• Fibers are imbedded in a firm gel instead of calcified matrix (bones are calcified/ossified)

• Flexibility rather than rigidity

Fiber orientation: Tendons

• Pattern: The fibers are arranged completely in parallel, straight lines

• Purpose: Tendons connect muscle to bone

  • Because muscles pull in one specific direction (toward the MUSCLE), this parallel alignment gives the tendon maximum tensile strength along a single axis to transmit force efficiently without stretching

Fiber orientation: Ligaments

• Pattern: The fibers are mostly parallel with interwoven, crisscrossing fibers

• Purpose: Ligaments connect bone to bone to stabilize joints

  • Since joints experience forces from varying angles during movement, the slight cross-weaving allows the ligament to withstand primary pulling forces while providing stability against multi-angle stress.

Fiber orientation: Skin

• Pattern: The fibers are arranged in a random, crisscrossed, multidirectional web

• Purpose: Skin must stretch, flex, and resist friction or forces coming from any direction without tearing, so a mesh pattern provides elasticity and flexibility in all directions

What are the 3 types of joints?

• Fibrous/suture

• Cartilaginous

• Synovial

Fibrous/suture joints

• Sutures in skull and pelvis

• Strong, inflexible

Cartilaginous joints

• Intervertebral disks, sternum

• Shock absorption

• Moderate degree of movement

Synovial joints

• Finger, elbow, knee

• Wide range of movement between articular surfaces

• Limited movement based on number of axes

• Enclosed by a joint capsule made up of bone, articular cartilage, supporting ligaments, the synovium, and lubricating synovial fluid

• Moves smoothly for fine motor control (Hinge and ball-and-socket joints in the fingers, elbows, and knees)

Vertebrae

Cervical

Thoracic

Lumbar

Sacral

Cervical

7 vertebrae in the neck area

Thoracic

12 vertebrae behind the ribcage

Lumbar

5 vertebrae in the lower back

Sacral

5 fused vertebrae below the lower back

Coccyx (not as important lol)

4-5 fused vertebrae near the tailbone

What are the vertebrae numbers down the back?

7

12

5

5

Spinal structure

Vertebrae separated by intervertebral disks

• The disks are tough, fibrous rings filled with gel-like substances that act as shock absorbers, provide flexibility, and are the most fragile part of the spine

• Ex: That’s why a herniated disk hurts so much, because it puts constant pressure on the nerve.

Types of spinal curvature

Scoliosis, kyphosis, lordosis

Scoliosis

Abnormal lateral (away from the trunk) curvature

Kyphosis

Abnormal posterior (to the back) curvature of the thoracic spine

Lordosis

Abnormal anterior (to the front) curvature of the lumbar spine

Microscopic structure of bone

• Bone consists of living cells and non-living intercellular substance

  • Intercellular matrix is non-living, calcified, and rigid

  • The living cells are osteoblasts, osteoclasts, and osteocytes (trapped osteoblasts)

    • Build, breakdown, monitor

• Two types of long bone structures

  • Compact (dense): Shafts of long bones (diaphysis) and outer shell of bone structures

  • Cancellous (spongy): Enlarged ends of long ends (epiphysis), the surface for muscle connection

Where is bone marrow stored?

Medullary cavity

Diaphysis

Main shaft of long bone, provides support without excess weight (hollow cylinder)

Epiphysis

Extremities of long bones, provides for muscle attachments and stable joints

Articular cartilage

Thin layer of hyaline cartilage covering articular surface if epiphysis - cushions joint

Medullary cavity

Runs length of diaphysis, contains bone marrow

Wolff’s Law

Bone will deposit where needed (for structural support) and be reabsorbed where not needed based upon the mechanical stresses placed on it.

Implications of Wolff’s Law

• Healing broken bones

• Space travel

• Bed-ridden patients (osteoporosis)

• Lifting jobs