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  HEALTH TIPS  
  The 5 L's of Lifting:
   LOAD: Always test the weight of the load before lifting . . . if something is too heavy, get help!

   LEVER: Keep the load close to your body with your back in the upright position, thereby reducing
      the lever arm.

   LORDOSIS: Maintain the hollow in your back throughout the lift.

   LEGS: Always use your legs and not your back while lfting. Move your feet to avoid twisting while
      moving objects.

   LUNGS: Just pior to lifting the load, inhale, set your abdominals and as you lft, breathe out through
      pursed lips.

Physiology of Overuse Injuries and Ergonomics Outline

I. DEFINITIONS

A.Musculoskeletal Disorders (MSD’s)

www.cdc.gov/niosh/ergopage.html

B. Overuse Injuries (cumulative trauma disorders – CTD’s)

www.osha.gov

C. Ergonomics

1.The study of the interaction between human beings and the objects they use and the environments in which they function. (human beings, objects, environments, complex interactions amongst each)

2.Wojciech Jastrzebowski, (Polish educator/ scientist) introduced the term in mid-nineteenth century. Ergon, meaning work, and nomos, meaning laws.1

3.Human factors or human factors engineering.

4.Human engineered.

5.Design for human use (human-made objects, equipment, machines, and systems).

6.Sanders & McCormick2 comprehensive definition: (three pronged)

    1. Central focus
        1. Consideration of human beings in the design of objects, machinery, and environments.
    2. Objectives
        1. To increase the effectiveness of the resulting human-machine system while maintaining human well-being.
    3. Central approach
        1. Systematic application of available data on human characteristics (capabilities, limitations) to the design of such systems or procedures.

D.Biomechanics concerned with mechanical elements of living organisms.

E.Occupational biomechanics deals with mechanical and motion characteristics of the human body and its elements

II.Assumptions

A.We can link the efficiency of person-object systems to the efficiency of human functions in those systems.

B.People achieve more if they are properly motivated.

1.Meaningful work;

2.Opportunity for advancement;

3.People allowed to play important roles.

 

III.Costs of Ignoring Ergonomics3

A.Less production output;

B.Increased lost time;

C.Higher medical costs;

D.Increased absenteeism;

E.Low-quality work;

F.Injuries, strains;

G.Increased probability of accidents and errors;

H.Increased labor turnover;

I.Less spare capacity to deal with emergencies.

IV.Potential Gains of Ergonomics

A.Tangible (reverse of the above);

B.Intangible;

1. Job satisfaction;

2. Work acceptance.

V.Ten Leading Work-Related Diseases and Injuries in the United States4

  1. Occupational lung disease;
  2. Musculoskeletal injuries;
  3. Occupationalcancers;
  4. Amputations, fractures, eye loss, lacerations, and traumatic deaths;
  5. Cardiovascular diseases;
  6. Diseases of reproduction;
  7. Neurotoxic disorders;
  8. Noise-induced loss of hearing;
  9. Dermatologic conditions;
  10. Psychologic disorders.

(Bolded/Italics indicates ergonomics related.)

VI.Musculoskeletal Disorders

A. Physical work capacity

1. Worker’s capacity for energy output, a function of energy available to the person in form of food, oxygen, sum of energy provided by aerobic and anaerobic processes.

2. Age limits maximum increase in heart rate and oxygen consumption.

3. Working more than 30-40% of one’s maximum aerobic power in an eight-hour shift causes notable muscular fatigue.5

 

B. Energy costs of work on specific activities

1. Energy consumption in humans is measured in kilocalories.

2. Good relationship between the two (energy consumption & kilocalories), energy consumption of work is measured indirectly by oxygen comsumption.

3. For every liter of oxygen consumed, there is an average 4.8 kcal of energy expended.

4. Variables affecting calories expended on task:

    1. age;
    2. posture;
        1. where is the center of gravity during the task?
    3. body weight;
        1. with increasing body weight there are increasing energy costs.
    4. intensity of activity;
        1. as activity increases, so does the energy costs.

5. Keeping energy costs within acceptable limits. (6,7)

a. For men:
  1. Maximum time-weighted average 5 kcal/min due to activity energy cost of work;
  2. Maximum time-weighted heart rate average of 100 beats/min.
b. For women:
  1. Maximum time-weighted average of 4 kcal/min due to activity energy cost of work;
  2. Maximum time-weighted heart rate average of 90 beats/min.

C. Fatigue

1. Volle et.al. (8) fatigue effects of a compressed workweek (40 hours in 4 days) compared with the usual schedule of 40 hours in 5 days. (right hand strength deterioration)

2. Astrand (9) rise in heart rates in subjects who worked at loads corresponding to about 50% of the individual’s maximum oxygen uptake during a period of about 8 hours. (circadian rhythms?)

3.Yates et.al. (10) strenuous lifting tasks indicate that lactate production may be a good predictor of fatigue and exhaustion.

 

D.Strength and endurance

1.Strength is the maximum force that one can exert voluntarily. Two types:

    1. Static
    2. Dynamic

2.Endurance is the ability to maintain activity over time. (maintenance of effort)

3.Research suggests that people can maintain their maximum effort only briefly (11,12).

a. Static effort can be maintained at only 20% of its peak over time, whereas 30% of peak forces can be maintained over extended periods in dynamic work.

b. Several other characteristics of strength (13):
  1. Strength is at its peak by the late twenties, and shows continuous decline from then on. At age 65, one has only 75% of the strength of a youth.
  2. On the average, women have two-thirds the strength of men.
  3. Exercise can increase strength and endurance by as much as 50%.
  4. Peak grip strength occurs with shoulder abducted zero degrees, elbow flexed 135 degrees, and the wrist at neutral posture. Deviations in elbow and wrist angles may result in up to 36% decrement in grip strength.

E. Safe performance of physical activity depends to a large extent on the person’s capacity and job demands.

VII. Cumulative Trauma Disorders

A.OSHA emphasis on repetitive-trauma cases.

B.Ramazzini notes in 1717.

C.Causes and Prevention Techniques

  1. Unnatural joint posture:
    1. Risk CTD’s increases
    2. Straight wrist (neutral) unnatural hand postures
    3. Risk increases when joint extremes are involved in motion.14
  2. Forceful application:
    1. Application of forces through hinge joints (wrist) notably increases injury potential.
    2. Pivot joints (elbow) also at risk.
    3. Hand force of 39.2 N (4.448N/lb)or 174.4 pounds more may cause CTD’s.15
    4. Exceeding 1/3 of worker’s static muscle strength available may be a causative factor.
  3. Repetition of activity:
    1. High repetition tasks with short duration (less than 30 seconds) pose more risk. Performed over months and years, CTD risk increases significantly.
  4. Individual factors:
    1. Pre-existing conditions
      1. Neuropathy
      2. Arthritis
      3. Peripheral circulatory disorders
      4. Reduced estrogen levels
      5. Small hand/wrist size
  5. Other:
    1. Localized pressure (ex. Blade pressure at base of palm in slabbing)
    2. Vibration
    3. Cold
    4. Lumbricals flexed
  6. Prevention:
    1. Administrative control
      1. Job rotation
      2. Warming exercises
      3. Controlling pre-existing conditions
      4. Remove time and pace pressures
      5. Training, selection
    2. Engineering controls
      1. Automation
      2. Job & workplace redesign
      3. Tool redesign
      4. Work/rest cycle
    3. Job strength index = job demand/operator capacity (1978, 1982)
      1. JSI <1.0, operator capacity exceeding job demand.
      2. JSI = 1.0, good match between job demand & operator capacity.
      3. JSI >1.0, truly dangerous jobs for CTD’s

 

VIII.Physiological Change & Adaptation to Exercise in the Older Adult

A.Cardiovascular function

  1. Resting cardiovascular(CV) function does not change with aging.
  2. Submaximal exercise (minimal to moderate response in CV):
    1. Oxygen consumption response is unchanged with age;
    2. Oxygen consumption is linearly related to exercise intensity;
    3. Submax heart rate(HR) is linearly related to exercise intensity;
    4. Increasing abilities to deliver oxygen during exercise depend on:
      1. HR
      2. Stroke volume(SV)
      3. Arteriovenous oxygen differences
    5. Maximum exercise capacity
      1. Undergoing exercise in which the individual can no longer exercise.
      2. Maximal oxygen consumption & HR are reached
  3. The maximum ability of the body to use oxygen during exercise(max. oxygen consumption) declines with age.(16)
  4. Factors that contribute to decline in oxygen use:
    1. HRmax
    2. SVmax
    3. Arteriovenous oxygen difference max
  5. Maximal HR during exercise does decrease with age. (220-age=estimated predicted HRmax) Inaccurate but indicates direct relationship between HR & age.
    1. Expected HRmax decreases with age.
    2. HRmax for a 25 y/o 195 beats/min (BPM).
    3. Healthy 75 y/o 165 BPM
    4. Implication is that the aging worker has lower exercise capacity and reaches intense level of exercise at lower pulse rates than the young.
  6. Maximum stroke volumes were 10% to 20% smaller for the older subjects compared with younger exercisers.
    1. This is controversial as level of fitness is associated with stroke volume at any age.
    2. Factors influencing stroke volume: diastolic filling, myocardial contractility, perfusion of myocardium, peripheral vascular resistance.

 

B.Pulmonary function

  1. There is a decrease in the functional ability of the lung to move air in and out as we age.
  2. The vital capacity of a 65 y/o is about 77% the value of a 25 y/o, due to loss of elastic recoil in the lung, rigidity of rib cage, declining strength of respiratory muscles (must breath more often for the same oxygen).
  3. Exercise training has improved the efficiency of the muscle metabolism and maximal ventilation.

C.Musculoskeletal function:

  1. There is a decline in muscle strength as people age.
  2. More notable decreases beyond age 60 and accelerates at 80 and older.
  3. Changes in strength associated with decrease in size of muscles occurring with aging.
    1. Reduced cross sectional area of muscles in upper and lower extremities for both men and women.
    2. Loss of gross number of muscle fibers and size of individual muscle fibers.
    3. Capacity for both aerobic and anaerobic metabolism in skeletal muscle does not seem to decline with aging.
    4. Mitochondria number remains stable but volume decreases as we age.
  4. Bone mineral density declines as people age.
    1. Declines at rate of 1% per year for men and women beyond age 60.
    2. Reduced bone mineral density of 20% (men) and 30% (women) who survive to 90.
    3. Exercise decreases bone loss as we age

IX.Inflammatory Response

A.Cause of inflammation

  1. Body’s response is the same regardless of the location or agent.
  2. Agents:(17)
    1. Physical injury
    2. Injury from light, heat, laser beams
    3. Bacterial & viral effects
    4. Endotoxin shock
    5. Antigen-antibody reactions
    6. Chemical injury
  3. Joints are most often affected (18)
    1. Physical trauma (direct & indirect)
    2. Infections
    3. Metabolic disease (gout)
    4. Neuopathies
    5. Systemic diseases
    6. Local joint disturbances

B.Definition of trauma

  1. Results from direct blow (direct) or forcing a joint or causing abnormal joint motion (indirect).

C.Types of trauma to the joints

  1. Focus in indirect
    1. Acute inflammation has same characteristic responses as seen in other body cavities and tissues.
    2. Chemical, metabolic, vascular changes occur resulting:
      1. Increased vascular permeability
      2. Leukocyte infiltration
      3. Cellular repair
    3. Goal of inflammatory process is to rid area of results of the injury:
      1. Cellular debris
      2. Necrotic tissues

D.Effects of trauma

  1. Whether produced by a blow or stretching and tearing of joint tissues
    1. Direct damage to cells of structural tissues:
      1. Muscles
      2. Tendons
      3. Ligaments
    2. Associated tissues:
      1. Nerves
      2. Capillaries
      3. Blood vessels
  2. Torn vessels allow bleeding into interstitial spaces
    1. Release of cellular debris
    2. Exposure of sub-cellular matrix promotes
      1. Adhesion
      2. Activation of blood platelets (hematoma)
  3. Cells undergo structural changes that may lead to cell death
  4. As cells degenerate, they release substances capable of producing vascular changes – serotonin and histamine
    1. Cause rapid increase in vascular permeability (15-30 minutes).
    2. Vessel wall cells contract, leaving gaps through which fluid and blood cells escape.
    3. Increased permeability occurs in non-disrupted blood vessels in adjacent areas.
    4. Results in the passage of plasma proteins, colloids, water primarily from venules into interstitial spaces, producing swelling and edema.
  5. Within the blood vessel
    1. Increase in concentraton RBC’s/WBC’s
    2. Increase in viscosity of blood
    3. Slowing of blood flow.
  6. Histamine-mediated response
    1. Immediate reaction to injury appearing within minutes
    2. Produces coagulation cascade activated during clot formation
      1. Fibrinopeptides which introduce immediate increases in vascular permeability
  7. Goal of post-injury
    1. Mobilize and transport the defense components of the blood the WBC’s to the injury site
      1. Margination
      2. Diapedesis
      3. chemotaxis

E.Phagocytosis

  1. clean up of cellular debris via polymorphonuclear leukocytes (PMN’s)
  2. PMN’s compose 60-70% of circulating WBC’s and are formed in blood marrow, lungs are a large reservoir
  3. Neutrophils (mature)
  4. Monocytes (macrophages)

F.Repair

  1. healing process begins
  2. Resolution when the injury is limited
  3. replacement with the normal cell type being replaced by connective tissue (fibrosis)
  4. formation of an abscess (by infection)
  5. progression of chronic inflammation
    1. influenced by persistent injury or predisposing factors

G.Symptoms 19

  1. Skin sensitivity is a major key with neurological tissue involvement, sensory change may present as:
    1. Hypoesthesia – decreased light touch, pain, or heat sensation.
    2. Anesthesia – complete loss of light touch, pain, or heat sensation.
    3. Dyesthesia – the substitution of one sensation (usually pain) for another.
    4. Hyperesthesia – increased non-nociceptive sensation.
    5. Allodynia – the sensation of pain with a non-noxious stimulus.
  2. Each of theses neurological sensory change symptoms can occur with a multitude of insult or disease process:
    1. Ischemia – (Gr. ischein to suppress + emia) deficiency of blood in a part, usually due to a functional constriction or actual obstruction of a blood vessel.20
    2. Infarction –
    3. Compression – (L. compression from comprimere to squeeze together) the act of compressing together; an action exerted upon a body by an external force which tends to diminish its volume and augment its density.20
    4. Traction – (L. tractio) the act of drawing or exerting a pulling force, as along the long axis of a structure.20
    5. Neuromas –
    6. CNS neuromas –
    7. Neuritis – (neur- + -itis) inflammation of a nerve, with pain and tenderness, anesthesia and paresthesias, paralysis, wasting, and disappearance of the reflexes.20
    8. Vibration – (L. vibratio, from vibrare to shake) a rapid movement to and fro; oscillation.20
  3. The most common lesion seen affecting sensation is compression of the spinal nerve or root by a disk herniation.
  4. The amount of sensory loss depends on the degree of pressure exerted on the neural tissue, if compression is the cause, the amount of ischemia if that is the cause, and the length or amount of contact with the nerve nucleus, if this is a factor.

X. The Good, the Bad and the Ugly - Ergonomics

A.Pulp Make Down

The foreman and the two employees initially present stated that the pulp bales weigh approximately 500 pounds, that the PMD is operating 1-2 times per week now (weekly). The employees indicated that the forklift operator is in charge of cutting the two baling wire strands holding each bale together. That the forklift operator would then pick up the 5 bales high stack and transport it (5 bale high stack) to the transfer table. That if the bales were not placed on the transfer table appropriately (by the forklift operator) and were placed with the Mead pulp sticker on top (when lowered mechanically), the bales when advanced and wires removed would be difficult to push over. They stated that this was very important in how the job is done. This has been communicated to the other forklift operators but not always performed due to considerations. It was mentioned that the bales break up during transport and that the operator must get off the forklift and physically remove the bale, usually takes 10-15 handfuls to remove and is heavy and bulking. Usually this breaking of bales occurs over one time per day. Bales were held together in the past by a material that did not require the removal of the structures, simplifying the process but that since the bales were made ahead of time and stored that the other type of holding structure disintegrated, causing many bales to fall apart in transport. The employee advancing the bales to remove the baling wire and pushing over the bales from the upright position will push one bale every 10 seconds or 360 pulp bales per hour. This information was substantiated with the foreman in attendance. Also during the process of removing and positioning the bales flat on the conveyor, some of the bales do not fall appropriately. This requires the employee to stop the process and physically reposition the bale, so as to advance up the conveyor or cause the others to mal-position also. The working shifts are 8 hours in duration.

OBJECTIVE:

Observation:

Activity- All employees rotate from operating forklift to cutting baling wire to operating transport tables at the hardwood and softwood areas. Noted frequent standing, squatting, pushing, pulling, and lifting, carrying, hand-eye-foot coordination of equipment. Limited sitting. Transport and position of bales of pulp individually weighing 500#, and stacks of 5 bales weighing up to 2500 pounds.

Forklift operator

Bilateral use of hands and arms in operating forklift controls and using a wire cutter to cut baling wire 10 times for each stack of 5 pulp bales. The operator then climbs into the forklift cab and transports the stack to the transport table to be lowered to the other employee at the transport table.

Conveyor operator

Advances the 500-pound bales with a foot pedal on his right foot. At this time the baling wire is removed as the bale is pushed by the operator to lay flat on the conveyor. The baling wire is placed in a dumpster located approximately 2-3 feet to the operators right. As the bales are pushed the operator is forced to perform a twisting action creating a shear force on the spine.

Physical Requirements-

1.Standing sustained time period on synthetic rubber mat up to 8 hours duration, physical therapist noted two hours without sitting.

2.Reaching one to two feet laterally and twisting to grab two cut baling wires and remove from the pulp bale. Occurs once every 10 seconds.

3.Pulling baling wire from bales wedged together. Physical therapist noted pull pressure requirement 20 to 80 pounds depending on pulp bale positioning. 20 pounds average (every 10 seconds) and 80 pounds peak force (every 5-10 minutes). This accumulative force on the human body is approximately average 7200 pounds of force average per hour and the peak force at every 10 minutes would be an additional 480 pounds in addition total approximately 7680 pounds of force in one hours duration.

PT: 7200# force/hr. ave., 7680# force/hr. peak.

4.Pushing pulp bales over from the upright position to the flat position. Physical therapist noted push pressure with hand dynamometer to be 48 to 56 pounds per bale every 10 seconds. 360 bales per hour (management has indicated maximum bales is one every 15-18 seconds, not 10 seconds; TPD rate of 600 is maximal rate, that is 120 bales/hour not 360 bales). This accumulative force on the human body is approximately 17,280 pounds of force average per hour (management numbers indicate 5,760 pounds of force average per hour) and 20,160 pounds of force peak per hour (management numbers indicate 6,720 pounds of force peak per hour). Physical therapist attempted with limited efficiency and considerable use of force, as each bale was unpredictable.

Labor: push one bale/10 seconds, 360 bales/hr., 17,280#/hr average, 138,240#/8hr.

Mgmt: push one bale/15-18sec., 120 bales/hr., 5760#/hr ave., 46,080#/8hr.

5.Repositioning mal-positioned bales on the conveyor. Physical therapist noted occurrence once every 5-10 minutes, requiring 85 to 95# of pressure to push and re-position. This accumulative force on the human body is approximately average force of 540 pounds and low range of 510 pounds and high range of 570 pounds. Physical therapist attempted with very limited success, poor efficiency and considerable use of force.

PT: 540# force/hr. ave. Range: 510# force/hr. to 570# force/hr.

6.Cutting wires on each pulp bale times 2. Physical therapist noted requires 14 to 22# of force to cut wires with cutters, 2 wires per bale, 5 bales per stack, and 360 bales per hour management indicates one bale/15-18 seconds or 120 bales/hr). Accumulative force on the human body is average 6480 pounds and low ranges 5040 pounds and high range 7920 pounds.

Labor: 6480#/hr. ave., range 5040# force/hr. to 7920# force/hr.

Mgmt: 1680#/hr to 2640#/hr.

 

7.Operating a forklift and positioning pulp bale stacks for optimal work performance and safety of employee operating transport table.

Accumulative Forces:

Average accumulated force requirement for the table operator would be 25,500 pounds per hour or 204,000 pounds during 8-hour shift of this work task. Good or bad ergonomics?

Average accumulated force cutting pulp bale wires would be 6480 pounds per hour or 51,840 pounds of force during an 8-hour shift of this work task. Good or bad ergonomics?

PROBLEMS:

1.Poor task and worker interface of forces. Average accumulated force requirement for the table operator would be 25,500 pounds per hour or 204,000 pounds during 8-hour shift of this work task. Average accumulated force cutting pulp bale wires would be 6480 pounds per hour or 51,840 pounds of force during an 8-hour shift of this work task.

RECOMMENDATION: Significantly reduce the forces currently required of the employees by decreasing physical contact with the pulp bales with improved engineering of current technology on-site. Investigate why work order to decrease the force required to topple bales (at hardwood conveyor) has not been acted on within a year’s time frame. Eliminate the pulling of the wires from the bales of pulp. ONGOING.

2.Poor floor mat resiliency to absorb forces transmitted from concrete during physical activity. RECOMMENDATION: Change out old flooring mats and replace with matting with air cells that cover more of the working area. ADDRESSED.

3.Poor dust control.

RECOMMENDATION: Place fans on the break shack aimed at the work area that dust is produced when stacked bales are lowered and pushed over to decrease dust inhalation and increase work comfort.

4.Limited employee concern for fellow employee safety and energy conservation.

RECOMMENDATION: Back safety presentations to the staff and management, voluntary fitness evaluations, remediation as necessary, company sponsored time to work under physical therapist supervised program to improve readiness for heavy duty work. Quarterly testing of employee readiness to work and interface with tasks. ONGOING.

5.Questionable employee-management relations.

RECOMMENDATIONS: Improve relations to increase cooperative effort, safety, and productivity. ONGOING.

B. Progressive Resistance Workout at Mead Fitness Center

  1. Seated chest press, 50#, 1 set of 10 repetitions. 500 # force.
  2. Seated overhead press, 40#, 1 set of 10 repetitions. 400# force.
  3. Seated preacher curls, 30#, 1 set of 10 repetitions. 300# force.
  4. Standing Lat pulldown, 30#, 1 set of 10 repetitions. 300# force.
  5. Supine leg press, 90#, 1 set of 10 repetitions. 900# force.

Total accumulative force through the body: 2400# in one session.

Three sessions/week: 7200# force accumulative.

Six week training routine: 43,200# force accumulative.

C. Fitness of Mead Management and Labor Force and Ergonomics
  1. Management
    1. Trunk curls
    2. Trunk extensions
    3. Hip 90/90
    4. Hamstring flexibility
    5. Hip muscle flexibility
  2. Labor
    1. Trunk curls
    2. Trunk extensions
    3. Hip 90/90
    4. Hamstring flexibility
    5. Hip muscle flexibility
  3. Ergonomics and work positioning.
    1. Center of mass:
      1. Over legs - Good
      2. Forward of knees - Bad
      3. Laterally - Ugly
    2. Head positioning:
      1. Neutral – Good
      2. Extended/flexed – Bad
      3. Rotated with extension/flexion – Ugly
    3. Shoulder/arm positioning:
      1. Average use between shoulder height and hip height - Good
      2. Average use overhead – Bad
      3. Average use shoulder height/overhead and laterally – Ugly
    4. Back positioning
      1. Neutral – weight over legs, 3 curves evident in spine - Good
      2. Forward bent average use – Bad
      3. Forward bent and twisting laterally – Ugly
    5. Working radius

 

 

References:

1.Amos,JM, et.al., 1981, Management for Engineers. Prentice Hall, Englewood Cliffs, NJ.

2.Peters,TJ, et.al., 1982, In Search of Excellence. Harper & Row, New York.

3.Pulat,BM, 1997, Fundamentals of Industrial Ergonomics.Waveland Press, Inc., Prospect Heights, Il.

4.Centers for Disease Control. 1983. Leading Work-Related Diseases and Injuries – United States. Morbidity and Mortality Weekly Report, 32, pp. 24-26.

5.Dukes-Dobos, FN, et.al., 1976, Cardiopulmonary Correlates of Subjective Fatigue. Proceedings of 20th Annual Meeting of the Human Facors Society, July 11-16, pp. 24-27.

6.Bonjer,FH, 1962, Actual Energy Expenditure in Relation to Physical Working Capacity. Ergonomics, 5, pp.467-470.

7.Brouha,L, 1960, Physiology in Industry. Pergamon Press, Elmsford, NY.

8.Volle,M, et.al., 1979, Compressed Work Week: Psycho-Physiological and Psychological Repercussions. Ergonomics, 22(9), p.1001.

9.Astrand,I., 1960, Aerobic Work Capacity in Men and Women in Special Reference to Age. Acta Physiologica Scandinavica, 49 (Suppl. 169).

10.Yates,JW, et.al., 1990, High Frequency Lifting and Blood Lactate Production. In Advances in Industrial Ergonomics and Safety II. Das,B. (Ed.). Taylor & Francis, London.

11.Astrand,PO,et.al., 1979, Textbook of Work Physiology. McGraw-Hill, New York.

12.Kroemer,KHE, 1979, Human Strength: Terminology, Measurement, and Interpretation of Data. Human Factors, 12(3), pp. 297-313.

13.Fredericks,TK, et.al., 1995, Is Grip Strength Maximum in the Neutral Posture? In Advances in Industrial Ergonomics and Safety VII. Bittner, AC, and Hampney,PC. (Eds.). Taylor & Francis, London, pp. 561-568.

14.Silverstein,BA, 1985. The Prevalence of Upper Extremity Cumulative Trauma Disorders in Industry. PhD. Dissertation. University of Michigan, Ann Arbor.

15.Silverstein,BA, 1986. Hand Wrist Cumulative Trauma Disorders in Industry. British Journal of Industrial Medicine, 43, pp. 779-784.

16.Kasch,FW, 1985. Effects of 18 years of endurance exercise on the physical work capacity of older men. J Cardiac Rehabil, 5:308-312.

17.Irwin, JW, 1979. Inflammation, Bibl Anat, 17:72.

18.Turek,SL, 1977. Orthopaedics: Principles and Their Application, Lippincott, Philadelphia, pp. 17-29.

19.Meadows,JTS, 1999,Orthopedic Differential Diagnosis in Physical Therapy, McGraw-Hill, pp. 73.

20.Dorland’s Illustrated Medical Dictionary, 28th Ed., 1994. W.B. Saunders Co., Philadelphia.

 

 		 
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