Dr. Katie CahillScience 295

Light and Moderate WorkBasic metabolic functions work the same as with

hard labor, but at a lower levelByproducts dissipated through the skin and

respirationBlood flow is not a limiting factor; the demands

require an ability to perform endurance tasks with attention to detail during possibly long shifts

Environment contributes to our perception of workPsychosocial environment - getting along with co-

workers and supervisorsPhysics environment – temperature, humidity, noise

and lighting, arrangement of working hours (shiftwork)

Physiological and psychological principlesMost jobs are sedentary and require little

physical effort Many people with sit-down jobs try to bring

up daily expenditures by doing demanding leisure activities to avoid weight gain from unneeded food intake

Physiological and psychological principlesStairs and ramps

Use the stairs instead of the elevator to make up for sedentary day

Energy use depends on step design and stair steepness (Figure 11.2)

Measuring work and load effectsHeart rate is the most useful indicator during light

work because it responds to static muscle loadingHR may also respond to emotional excitement,

emotions; HR may reflect more than just physical work

Other possible techniques: EMGs, EEGs, eyelid closure frequencies, simple observation

Physiological and psychological principlesScaled judgments

A way to assess satisfaction is to ask for employee opinions Usually done through questionnaires:

1. Paired descriptors (p. 218)2. Ordinal scales – pain on a scale of 1-103. Interval scales4. Ratio scales – allow for mathematical calculations

Subjective, not objective informationStudies may generate awareness of problems

at work, which management may want to avoid

Physiological and psychological principlesNordic questionnaire

(figure 11.3)2 parts:

1. General information2. Area focused on

specific regions of the body-Body is divided into 9 regions and the person indicates where they experience musculoskeletal problems

Tiredness, boredom and alertness at workTiredness – the state in which we feel unable

or disinclined to continue a taskFatigue – the physiological effect of having

spent our energy, or overstrain of our muscles so that our body needs to rest

Boredom – the psychological or emotional condition in which a lack of events lulls us into a state of sluggishness

Bottom line: In everyday life we feel tired as a result of physical fatigue or psychological boredom

Tiredness, boredom and alertness at workDiversity vs. monotony

Monotony - the quality of constancy, routine, and lack of variety Some individuals enjoy jobs that have diverse parts

-challenges mental and physical capabilities-keeps workers interested-Workers find satisfaction in successful solutions

For others, job/task predictability is appealing-find satisfaction in skillful repetition

For most people, performance and job satisfaction is best when the job is not overly simple or overly complex

Tiredness, boredom and alertness at workVigilance and event frequency

Ability to maintain concentration was found to be very important during WWII Noticed that the frequency with which radar

watchers reported submarines decreased with the longer they watched; alertness decreased with time on watch

Frequency of signals influences number of reported signals-too few signals – observers becomes bored and pays

less attention-too many signals – observer becomes overwhelmed

and cannot report them all- It has to be just right! (figure 11.5)

Tiredness, boredom and alertness at workPerformance decreases

with timeif the time intervals are too longIf the observer is fatigued or mentally stressedIf the environment is too hot or loud

Tiredness, boredom and alertness at workMonotonous jobs

Tayloristic approach During the 1920s, industrial workers were

responsible for small, highly repetitive tasks Good because the worker became highly skilled Bad because led to repetition injuries and boredom

Tiredness, boredom and alertness at work

Satisfaction at work Work preferences differ, but everyone wants to feel

successful in their job This requires communication between a manager

and employees Managerial control: higher level, focused on work

design, organization and administration Detail control: task level, workplace arrangement,

tools and procedures Having control over a task at work is empowering;

lack of control/understanding can be stressful Communication between team members can create

a highly productive and stimulating social environment

Suitable postures at workNo static work

Fatigue in light to moderate work occurs as a result of maintaining a constant posture over a long period of time

Muscles are under constant contraction, blood cannot flow through the tissue and metabolic wastes accumulate

Muscles fatigue and have to restBlood can flow through the tissue, remove the

metabolic wastes and recover

Suitable postures at workAvoiding fatiguing body postures

Standing, stooping and kneelingExamples of fatiguing conditions at work?

Sitting at workLess tiring than standingDifferent seated positions are suitable for

different tasksToo much sitting

Truck drivers and military pilotsPatients on bed rest – bedsoresMoving is essential for well-being and comfort

Accurate, fast, skillful activitiesExact manipulations

Light work is performed best in a work area at about waist height

Exact manipulations may require arm restsMicroscope work is difficult because neck muscles remain

static – images can now be projected onto a monitorSeeing what we are doing

Having to twist your neck to see what you are doing at work results from poor ergonomic planning

Normal LOS is angled downwardEye movements 15 degrees above and below the LOS are

comfortable (figure 11.16)Therefore a viewing task works best within a well lit 30

degree range

Accurate, fast, skillful activitiesBetter Tools

Constant bending results from improper designFlaws in design must be adjusted (figures 11.17,

11.18)Repetitive Work

Leads to injuries of muscle, CT and jointsAffects both physical laborers and desk workersHuman body is not designed for repetitive actions

(Table 11.2)Low back, wrists, shoulders and elbows are the

most common areas affected by repetition

Accurate, fast, skillful activitiesRest breaks

Both physiologically and psychologically beneficial

Many short breaks are more beneficial than few longer breaks

Breaks help to avoid monotony, prevent overload, allow for social interaction and a chance to restore energy supplies with food

Summary Light and moderate tasks don’t impose heavy physical burdens

but require attention to detail for long periods HR is a useful indicator of physical strain, but can also be

affected by emotions; questionnaires can also be used Some people enjoy consistency and repetition in their jobs;

others enjoy challenging, diverse tasks Job satisfaction is greatest when the job is neither too complex

nor too simple Physical fatigue can result from static positions as well as

overexerting muscles Viewing tasks are best performed within a 30 degree cone in

front of the body Repetition increases skill level but puts the worker at risk for

repetition injuries Breaks are both physiologically and psychologically beneficial Many short breaks are more beneficial than few longer breaks