on 31-Dec-2018 (Mon)

Manual materials handling (MMH) means moving or handling things by lifting, lowering, pushing, pulling, carrying, holding, or restraining.

Approximately 25% of accidents reported in industry each year are related to MMH

60% of overexertion injuries are due to lifting and lowering

Low-back-pain overexertion injuries with significant lost time results in less than one-third of the patients eventually returning to their previous work

Overexertion injuries in the U.S. occur to about 500,000 workers per year. One in every 200 workers is afflicted by such disorders

The 25-44 age group has the highest incidence rate

Total annual cost for back pain reaches $56 billion

Chronic back pain resulting from 1. Strains and cramps in the back muscles 2. Tears in the tendons connecting the back muscles to the spine, or from sprains 3. Tears in the ligaments interconnecting the vertebrae (bones of the spine)

It is the repetition, as in manual handling, that contributes most to the occurrence of injuries

Lifting loads over 20 kilograms results in an increased number and severity of back injuries

Epidemiological: – Try to derive significant trends by using historical records that may lead to injuries

Biomechanical: Upper limit – Calculating forces and moments on various body elements

Psychophysical: – Subjects adjust the load and characteristics in order to arrive at a setup that is acceptable to them

Ensure an adequate work/rest schedule. In extreme cases that require heavy MMH in temperatures above 30C, rest periods or light work load tasks may account for 75 percent of the work time.

Illuminate the work area for MMH tasks at the level of 200 lux.

Tolerable work conditions Do not pose known dangers to human life or health

Acceptable conditions People can voluntarily agree, according to current scientific knowledge and under given sociological, technological, and organizational circumstances

Optimal conditions So well adapted to human characteristics, capabilities, and desires

Ergonomics’ fundamental aim is that all human-made tools, devices, equipment, machines , and environments should advance, directly or indirectly, the safety, well being, and performance of human beings

About 400 B.C., Hippocrates described a scheme of four body types (moist, dry, cold, and warm)

In the 15 th and 17 th centuries, Leonardo da Vinci and Alfonso Giovanni Borrelli, and Mimar Sinan (anatomy, physiology, and equipment design)

In the early 1800s, in France, Lavoisier, Duchenne, Amar, and Dunod researched energy capabilities of the working body

Marey developed methods to describe human motions at work

Bedaux made studies to determine work payment systems

In England, the Industrial Fatigue Research Board considered theoretical and practical aspects of the human at work

In Italy, Mosso constructed dynamometers and ergometers to research fatigue

In Scandinavia, Johannsson and Tigerstedt developed scientific discipline of work physiology

In the U.S., Benedict and Catchcard described the efficiencies of muscular work

The physical and physiological aspects were studied mainly in Europe and the psychological and social aspects in North America

Anatomy: the build of the human body

Orthopedics: the skeletal system

Physiology: functions and activities of the living body

Medicine: illnesses and healing

Psychology: the science of mind

Sociology: development of behavior

Anthropometry: the measuring and description of the physical dimensions of the human body

Biomechanics: the physical behavior of the body in mechanical terms

Work Physiology: people’s behavior and attitude at work

Human beings receive stimuli from many resources

People can sense those level of stimuli that are within the spectra to which they are sensitive

Five classic senses (vision, audition, smell, taste, and touch) are known as the exteroceptors

Proprioceptors are stimulated by the actions of the body itself, such as a reach or a sudden turn. They are embedded within the muscles and tendons, around the joints, and in the inner ear.

Light is visually evaluated radiant energy

People require 80% of the information through the visual channels

Six muscles attach to the eyeball move the eyeball

Cones are highly sensitive to bright light and are used for daylight vision.

Rods are sensitive in low levels of illumination and are used for nightvision.

Visual Acuity: – It is the sharpness of vision

As an object is brought close to the eyes, after some point, the object will be seen as two objects. This point is known as the near point of accommodation.

As high as 15 to 20% of the population has some degree of color blindness

Monochromats: truly colorblind people (various shades of gray)

Deuteranopes: lack the green catching pigment in their cones (red and green are confused

Protanopes: lack the red catching pigment (red and green are confused)

Tritanopes: lack the blue catching pigment (blue and green are confused)

The near point of accommodation at age 60 averages around 83 cm

The light-adapted eye is maximally sensitive to light, with a wavelength of about 555 nm, the dark-adapted eye, to 505 nm. This shift is known as the Purkinje shift, is attributed to the fact that the pigments in the rods and cones differ in their selective absorption of wavelengths of light.

With no eye or head movements, it is estimated that human beings have a vertical visual field of about 160 degrees and a horizontal field of 208 degrees.

Color is perceived well within ±62 degrees of the normal line of sight (NLS) for a horizontal visual field, ±35 degrees of NLS for a vertical visual field