Work Physiology and Aerobic work capacity

WORK PHYSIOLOGY AND AEROBIC CAPACITY

Work physiology is a term associated with industrial engineering that is concerned how the human body copes with physical stress, work strain, and the working environment.

 

Work physiologists apply their understanding in evaluating and designing work spaces that reduce physical fatigue, eliminate occupational injuries, and increase overall productivity. They need to understand how the body performs under a variety of environmental conditions, the amount of rest it requires, and when it is able to work at peak levels.

 

Capacity for physical work

An individual’s physical tolerance to physical work is usually determined by the capacity of his or her cardiovascular and respiratory system sto deliver oxygen to the working muscles and to metabolize chemically stored energy.

 

Metabolism, respiration, and circulation are just a few of the body systems that physiologists study. They also take into account skeletal, muscular, and cardiovascular activity. Work physiologists are concerned with the metabolic cost of work and attempt to minimize it by making the work space as ergonomic as possible. 

 

A work physiology laboratory has all the equipment necessary to measure parameters like heart rate, oxygen consumption, and core temperature. This branch of physiology also studies the changes that result in the human body as a result of being exposed to single or multiple instances of work stress.Knowledge obtained from work physiology is used to design work spaces that suit a wide variety of people.

The goal of work physiology is to ensure that the worker performs his or her task safely in the most efficient manner possible within the work environment. Human beings come in all sizes and shapes, and this makes it challenging for work physiologists to design environments suited to every type. Normally, the environment isn't a controlled one — there may be loud noises, flying dust particles, and heat, for example, which the body has to deal with. This branch of physiology monitors the amount of energy people spend on their task and ensures that they aren't pushed beyond their physical capacity to work.

 

Matching people and their work

Obviously, it is important to match human capabilities with the related requirement of a given job. If the job demands equal the worker’s capabilities or if they exceed them, the person will be under much strain and may be not able to perform task. Hence, various functional stress tests, which are administered by a physician, have been developed to assess an individual’s capability to perform physically demanding work.

 

Work capacity or fitness level of an individual can be determined in laboratory by measuring the VO₂ max.  VO2 max is indicative of aerobic fitness level.

 

Aerobic work capacity is the highest amount of oxygen consumed during maximal exercise in activities that use the large muscle groups in the legs or arms and legs combined. Aerobic capacity, aerobic power, functional capacity, functional aerobic capacity, maximal functional capacity, cardiorespiratory fitness, cardiovascular fitness, maximal oxygen intake, and maximal oxygen uptake are terms that are often used interchangeably.

 

Aerobic capacity is commonly described by the o₂max, or maximal oxygen uptake. This measurement is an indication of (1) the ability of the cardiovascular system to provide oxygen to working muscles and (2) the ability of those muscles to extract oxygen for energy generation in the form of adenosine triphosphate (ATP).

 

VO_2max is a measure of the maximum amount of oxygen that an individual can use per unit of time during strenuous physical exertion at sea level. It is an important measure for several reasons:

(1) It serves as an index of cardiovascular and pulmonary function;

(2) It characterizes the functional capacity of the cardiopulmonary system to transport oxygen to the working muscles; and

(3) It is one of the limiting factors in endurance performance.

 

Men who are 20 years of age have an average maximal capacity of 3-3.5L/min; women of the same age have an average capacity of 2.3-2.8 l/min. At age of 60 the capacity is diminished to about 2.2-2.5 L/min. for men and 1.8-2.0 L/min for women.

 

An individual’s VO_2max can be measured or estimated by a variety of techniques, including treadmill running, cycle ergometry, arm cranking, and stair stepping, rowing, and walking.

 

The most common way to measure VO_2max is by open-circuit spirometry, whereby the individual breathes in ambient air and then the exhaled air is measured and analyzed. The amount of oxygen consumed (VO₂) can be computed on the basis of the composition of the inspired air by quantifying the volume (V) and oxygen (O₂) content of the expired air.

Work/rest cycles: Fatigue is an overexertion phenomenon that leads to a temporary decrease in physical performance. In order to avoid the fatigue and especially the chronic fatigue, rest pauses must be taken. Frequent short rest periods reduce cumulative fatigue better than a few long breaks. 

ERGONOMICS

 

ERGONOMICS

§  Derived from the Greek words ‘Ergon’ meaning work and ‘nomos’ meaning laws.

§  Thus, ergonomics can be simply defined as the how workplace and equipment can be best used and designed for comfort, safety, efficiency and productivity.

§  Simply, ergonomics is the branch of science that deals with the people and their working environment.

§  It can also be understood as the study of worker in their working environment.

§  Ergonomics is concerned with designing or arranging workplaces, products and systems so that they fit the people who use them and the maximum output can be obtained from them

§  Ergonomics extends beyond the proper posture of the workers.

 

Types of Ergonomics

 

·        Physical ergonomics is concerned with the way the body interacts with the worker’s tools (anything from shovels to chairs to personal computers) and their effects on the body such as posture, musculoskeletal disorders, repetitive disorders, workplace layout and workplace health and safety.  

·        Cognitive Ergonomics relates to the way the mind processes information, memory usage, decision-making and other mental workloads.

·        Organizational Ergonomics is concerned with optimizing the workplace, teamwork, performance assessment and quality management. It includes office design, shift (work hours) management, teamwork, virtual organizations, tele-work, addressing communication, and quality management in the workplace.

Elements of Ergonomics

ANTHROPOMETRY

Anthropometry is the science of measurement of the human body. It can be applied to ensure that workers have sufficient space to perform their tasks and they can reach necessary equipment and tools. 

Structural anthropometry also referred to as static anthropometry or static dimensions. These are measurements with the body in a still or fixed position; for example, stature or height, weight, head circumference. 

Dynamic Anthropometry : The dimensions are taken with the body at work, in motion or in workspace attitudes.

The human body is measured with anthropometric measuring tools. Basic components include the anthropometer, personal scale, spreading caliper, pelvimeter, sliding caliper, soft metric tape and caliper.

Anthropometric measurements are a series of quantitative measurements of the muscle, bone, and adipose tissue used to assess the composition of the body. The core elements of anthropometry are height, weight, body mass index (BMI), body circumferences (waist, hip, and limbs), and skin fold thickness.

 There are several factors that affect the dimensions of the human body are namely:

1. Age: The first factor is age. In each person’s measurement, the age of the person must be known. This can happen because basically, every age has different body dimensions. The dimensions of the human body will grow and grow with age.

2. Gender: Besides using age as a variation of data, gender also determines other variations. Basically, the dimensions of the male body size are generally larger than women. So it is important to group measurements through gender.

3. Ethnic groups/ Racial: Every ethnic or ethnic group will have physical characteristics that will differ from one another.

4. Profession

Biomechanics is the science of movement of a living body, including how muscles, bones, tendons, and ligaments work together to produce movement.

Engineers and occupational therapists use biomechanics to design work tasks and equipment to prevent overuse injuries related to specific jobs.

The applications of biomechanics to human movement can be classified into two main areas: the improvement of performance and the reduction or treatment of injury.

Importance of ergonomics:

a) Increases productivity

§  Best ergonomic solution enhances the productivity

§  Ergonomic reduces the unwanted tension, awkward position of the body.

§  Ergonomic is focused in making the work your easier and comfortable, this thereby reduces any kind of stress, risk and enhances the satisfaction and productivity.

b) Reduces the cost

§  Ergonomics can be considered as the one-time investment

§  As ergonomics is focused about marinating the better health of the worker it can further reduce the cost of compensation that would be made by the injured or unhealthy staffs.

§  It also reduces the indirect and the opportunity cost that could have incurred due to injury.

c) Improves the quality of the work

§  Improved ergonomics favors the favorable environment where the workers can work efficiently.

§  As the ergonomics improves, level of satisfaction in the quality of the work increases.

d) Others

§  Helps to reduce the absenteeism due to more comfort, safety and healthy working environment

§  Assurance to the worker as their workplace is safer (acts as the motivation)

§  More focus on the working environment and worker’s health makes them feel valued and boost of moral.

Principles of Ergonomics

There are 12 fundamental principles of ergonomics which are:

1- Keep everything in easy reach

2- Work at proper heights

3- Reduce excessive force

4- Work in good postures

5- Reduce excessive repetition

6- Minimize fatigue

7- Minimize direct pressure

8- Provide adjustability and change posture

9- Provide clearance and access

10- Maintain a comfortable environment

11- Enhance clarity and understanding

12- Improve work organization

Ergonomic Risk Factors:

The major workplace ergonomic risk factors to consider are:

Awkward Postures 

Posture determines which joints and muscles are used in an activity. It also affects the amount of force required to perform a job. For example, more stress is placed on spinal discs when lifting, lowering or handling objects when the back is bent or twisted than when the back is straight. 

Tasks requiring repeated or sustained twisting of the wrists, knees, hips or shoulders create increased wear and tear on joints and muscles in those areas.

Forceful Exertions 

Work that involves forceful exertions—such as lifting, pulling, pushing, gripping or pinching—place higher loads on muscles, tendons, ligaments, joints, cartilage, and spinal discs. Prolonged or frequent activities with high amounts of force can cause fatigue. If there is inadequate time for rest and recovery, these activities can lead to musculoskeletal problems. Force requirements may increase with: 

• Increased weight and bulkiness of the load being handled or lifted
• Increased speed or acceleration of movement (e.g., jerkiness)
• Presence of localized or whole-body vibration
• Use of the index finger and thumb to forcefully grip an object (i.e., a pinch grip compared to a power grip)
• Use of small or narrow tools that limit grip capacity. 

Repetitive Motions

If motions are repeated frequently and for long periods of time, like an eight-hour shift, a buildup of fatigue and muscle tendon strain can occur resulting in repetitive strain injuries(RSIs). Repetitive motion is especially dangerous when combined with other risk factors, such as awkward postures or forceful exertions. 

Ergonomic Risk Controls

Some Ways to Reduce Ergonomic Risks Engineering Improvements.

Engineering controls include rearranging, modifying, redesigning, or replacing tools, equipment, workstations, packaging, parts, or products. These improvements can be very effective because they may reduce or eliminate contributing factors. (For example, if your job requires sitting for long periods of time, having an adjustable seat or foot stool so that your knees are higher than your hips helps protect your lower back.)

Administrative controls. Administrative improvements include changing work practices or the way work is organized.

•      Providing variety in jobs

•      Adjusting work schedules and work pace

•      Providing recovery time (i.e., muscle relaxation time)

•      Modifying work practices

• Ensuring regular housekeeping and maintenance of work spaces, tools, and equipment

•     Encouraging exercise

Personal Protective Equipment. Safety gear, or personal protective equipment (PPE), includes gloves, knee and elbow pads, footwear, and other items that employees wear.

ErgonomicInjuries/Musculoskeletal Disorder (MSDs):

§  Ergonomic injuries or MSDs can affect the muscles, nerves, tendons, ligaments, joints, cartilage and spinal discs.

§  Musculoskeletal disorder (MSDs) is also known as the repetitive motion injury.

§  MSDs are the condition that can affect muscles, joints and bones.

§  MSD are caused due to individual risk factor or ergonomic risk factor.

§  MSDs are the single largest category of workplace injuries and are responsible for almost 30% of all worker’s compensation costs

§  Individual risk factor include age, nutrition, activity, etc., while ergonomic risk factors includes:

§  High task repetition

§  Awkward body posture for longer period

§  Sitting in same posture

§  Lifting heavy weights.

 WMSDS/ MSDS – Work-Related Musculoskeletal Disorders

MSDs, or musculoskeletal disorders, are injuries and disorders of the soft tissues (muscles, tendons, ligaments, joints, and cartilage) and nervous system. They can affect nearly all tissues, including the nerves and tendon sheaths, and most frequently involve the arms and back. Occupational  safety and health  professionals  have called these  disorders a variety  of names, including  cumulative trauma disorders(CTDs),  repeated trauma and repetitive stress injuries(RSIs). These painful and often disabling injuries generally develop gradually over weeks, months, and years. MSDs usually result from exposure to multiple risk factors that can cause  or aggravate the disorders,  not from  a single  event.

MSDs  can  cause  a  number  of  conditions,  including  pain,  numbness,  tingling,  stiff  joints,  difficulty  moving, muscle  loss, and  sometimes  paralysis. Frequently, workers must lose time from work to recover;  some never  regain full  health. These disorders include carpal tunnel syndrome,  tendinitis, herniated discs,  and low  back pain. MSDs do not include injuries resulting from slips, trips, falls, or similar accidents