Module 3. Workload Flashcards
Estimates the extent of physical activity
Energy Expenditure
All energy in the body utilized during physical activity produces ___
Heat
Strenuous activity means ___ energy requirement
Greater
5 ways to measure/estimate energy expenditure
- Direct Calorimetry
- Indirect Calorimetry - O2 Analysis
3.Indirect Calorimetry - CO2 Analysis - Calculations of Energy Expenditures
- Heart-rate Measurement
- Body heat output as a measure of energy expenditure
- Body heat output is measured under laboratory conditions
- Can be impractical due to the required setup
Direct Calorimetry
- Measurement of oxygen uptake
- Requires information on volume of expired air
- Analysis of oxygen content in expired air
- Air volume determined through a spirometer
- Estimation of energy based on equation by -J. B. Wier
Indirect Calorimetry – O2 Analysis
Formula for Indirect Calorimetry - O2 Analysis
Energy = (Vstp [Oi - Oe])/20
Where
Energy is in kcal/min
Vstp = volume of air expired in L/min
Oi and Oe = Percentages of oxygen in inspired and expired air, respectively
Gas analysis of carbon dioxide content in expired air
* Most methods use infrared properties of carbon dioxide with an instrument, capnograph
Indirect Calorimetry – CO2 Analysis
Two things to take note for this calculation:
* Accurate account of all activities and time spent for each in a day
* Metabolic cost of each activity
What type of method in estimating energy expenditure?
Calculation of Energy Expenditures
Formula for Total Energy Expenditure
Total Energy Expenditure = E time spent per activity (min) x metabolic cost per activity (kcal)
How are activities recorded in calculating energy expenditures
Detailed questionnaire – might be unreliable (dependent on memory; may exaggerate)
* Diary techniques – subject records daily activities in a diary (minute by minute or 5-minute periods); an observer may be employed to log activities
Indirect measurement of energy expenditure
* ___ and energy expenditure are related
* - May greatly vary based on activities (e.g., lifting a sack of rice vs lifting piece of paper)
* - May also vary based on muscle groups used (e.g., walking vs lifting weights)
* - Can also be affected by physical fitness (e.g., athletes expend more energy)
* - Emotion, body temperature, type of drinks can also affect ___
* Range of variation among population is large
* - Solution is to group/subdivide people
Heart-rate Measurement
Heart-Rate Measurement Formulas
Male = -55.0969 + (0.6309HR) + (0.1998Weight) + (0.2017*Age) / 4.184
Female = -20.4022 + (0.4472HR) - (0.1236Weight) + (0.074*Age) / 4.184
HR in bpm; Weight in lbs; Age in years
Normal Resting Heart rate of a healthy adult is between ___ to ___ bpm
60 - 100
Healthy athletes have even lower normal resting heart rate – can go as low as __
40
Heart rate guidelines based on intensity of activity
Moderate intensity physical activity = 64% - 76% of Max HR
Vigorous intensity physical activity = 77% - 93% of Max HR
Estimation of Max Heart Rate
220 - age
- A scale used to know perceived intensity of an activity, such as exercise or physical/manual labor
- Developed by Gunnar ___ for rating exertion and breathlessness during physical activity
- Reflects how hard the activity is through heart rate and respiration, perspiration and muscle exertion
Borg Rating of Perceived Exertion (RPE)
Original Borg RPE has a scale of __ to ___
6 to 20
Later revised to ____ or ____, has a scale of __ to ___
Category Ratio Scale (CR10 Scale)
Modified Borg Dyspnoea Scale
0-10
Method of Use of Borg RPE
- Participants are asked to rate their exertion of activity based on the scale
- Taking into consideration feelings of physical stress or fatigue
- Focusing only feeling of exertion, not on the pain experienced
- Number in scale connotes intensity of activity; tells us if participant should speed up or slow down movements/activity
Occupational and non-occupational risk factors can lead to ___ and ___
musculoskeletal disorder (MSD)
work-related musculoskeletal
disorder (WMSD)
Factors that can result in the formation of MSD or WMSD
- Local soft tissue fatigue
- Sufficient blood flow in these soft tissues
- Sufficient recovery from fatigue
Three factors must be considered to evaluate work or tasks
- Force / Forceful exertion
- High task repetition
- Sustained awkward posture
Higher force requirement = ___
Higher Risk and higher muscle effort and higher muscle fatigue
Control Methods for forceful exertion
- Engineering controls – mechanical assists, adjustable height lift tables and workstations, powered tools, ergonomic tools
- Work practice controls – carts and dollies to reduce lifting/carrying, sliding objects instead of lifting/carrying, eliminating reaching obstruction
Higher task repition = ___
Higher Risk
General cycle time that makes tasks repetitive
≤ 30 seconds = repetitive
Control Methods for High Task Repetition
- Engineering controls – goes hand-in-hand with improvements in other factors
- Work practice controls – proper work technique to minimize MSD risk
- Job rotation – to reduce duration, frequency and severity of MSD risk
- Counteractive stretch breaks – for recovery from fatigue
High Awkward posture =
higher force on joints; overload muscles and tendons
Joints most efficient when operating closest to ___
mid-range of motion of the joint
Repetitive and Outside mid-range of motion = ___
higher MSD risk
Control Methods for Sustained Awkward posture
Engineering controls – modify workplace to reduce awkward posture
* Work practice controls – proper techniques in doing a task; work procedures following proper posture should be implemented
* Job rotation and job enlargement – increasing variety of work reduces repeated or sustained awkward postures
* Counteractive stretch breaks – rests and stretching to allow recovery from fatigue
What is awkward posture?
- Body position is non-neutral
- Extreme ends of range of motion
- Joints eventually become weaker; muscles out of balance
- Tasks become even more physically demanding; adds unnecessary stress to the body
Where is the power zone?
- Close to the body
- Between mid-thigh and mid-chest height
- Arms and back can lift the most with least amount of effort
- Lifting outside power zone → risks and injuries ↑
Occurs if tools and materials are placed outside the “Power Zone”
Awkward Posture
2 different methods in evaluating posture in the workplace
- Rapid Upper Limb Assessment (RULA)
- Rapid Entire Body Assessment (REBA)
- developed in England in 1993
- Only in 1998 it was first applied
- Tool focuses only on posture
- Using the tool can help predict risk of upper extremity MSD
- Hand
- Wrist
- Elbow
- Shoulder
- Back
The tool uses a scoresheet to derive a ___ “score”
A composite score is calculated based on individual components in the tool
Rapid Upper Limb Assessment (RULA)
RULA is mostly applicable in ergonomic assessment of ___
seated tasks, high repetition tasks or continual such as
- office workers in the workstation
- Assembly workers in an assembly line
predicts the risk of developing MSD or WMSD but for entire body (which includes lower limbs)
Rapid Entire Body Assessment (REBA)
REBA evaluates
- Required or selected body postures
- Forceful exertion
- Type of movement, action, repetition, and coupling
the institution that provided the lifting equation guidelines for evaluating two-handed manual lifting tasks
National Institute of Occupational Safety and Health
- is the weight of the load that nearly all healthy workers can lift over a substantial period (e.g., 8-hour work shift)
- recommendation for preventing an increased risk of developing lower
back pain
Recommended Weight Limit
Maximum weight to be lifted under ideal conditions is ___
23 kg
RWL considers six factors for lifting weight to reduce the maximum of 23 kg
- A load of 51 lbs / 23 kg
- Lifted in the sagittal plane
- The load is at a height of 75 cm above the floor
- The load is held 25 cm in front of the body
- The load is to be lifted no more than 25 cm vertically
- There is good coupling of the load
Six coefficients to reduce RWL to account for task factors
Determined using biomechanical models of spinal loading
H = horizontal distance of hands from midpoint between ankles in cm
V = vertical height of the hands from the ground in cm
D = vertical distance of lifting vertically (where the load is being lifted to) in cm
F = frequency or time between lifts, in mins or secs
A = angle of asymmetry of the load in relation to the body, in degrees
C = hand-to-load coupling (quality of grasp based on type of handle)
RWL equation
LC x HM x VM x DM x AM x FM x CM
Where
LC = load constant
HM = horizontal multiplier
VM = vertical multiplier
DM = distance multiplier
AM = asymmetric multiplier
FM = frequency multiplier
CM = coupling multiplier
Load Constant
23 kg
Horizontal Multiplier
25/H cm
Vertical Multiplier
1 - 0.003 |V-75| cm
Distance Multiplier
0.82 + (4.5/D) cm
Asymmetric Multiplier
1 - 0.0032A degrees
Frequency Multiplier and Coupling Multiplier
refer to tables, FM - lifts/min
Answers the question, “Is the weight too heavy for the task?”
Recommended Weight Limit (RWL)
Answers the question, “How significant is the risk?”
Lifting Index (LI)
Lifting Index based on results of the RWL equation
Lifting Index = Actual Load/ RWL
where actual load is in kg
If LI < 1.0
the task does not increase the risk of injury
- If LI ≥ 1.0
some workers are at risk of injury
If LI > 3.0
many/most workers are at high risk of injury, leading to low back pain and injury
Higher Lifting Index = ___
Higher risk of injury
If RWL < Actual Weight of load, determine which factor(s) contributes the highest risk, then modify lift
Lowes multiplier values = factors of highest risk
The lifting (or lowering) equation and LI can only be used when
- Task/work involves two-handed lifting
- Worker is in comfortable lifting posture
- The environment is comfortable enough for lifting, including the floorings
Limitations of the LI Formula
- Only one hand is used
- > 8 hours
- When seated or kneeling
- In a restricted workspace
- Unstable objects (e.g., buckets, liquid containers)
- Involving pushing or pulling
- Using wheelbarrows or shovels
- Objects of extreme temperature
- Poor footing/foot coupling (may cause risk or fall)
