Biomechanics Flashcards
(37 cards)
Biomechanics:
Uses laws of physics and engineering concepts to describe motion undergone by the various body segments and the forces acting on these parts during normal daily living
Occupational Biomechanics:
Study of the physical interaction of workers with their tools, machines and materials so as to enhance the worker’s performance while minimizing the risk of musculoskeletal disorders
The goals of occupational biomechanics are to generate: - - - Working conditions
- tolerable
- acceptable
- optimal
Why/how is biomechanics concerned or related with ergonomics?
People have mechanical limitation (strength, range of motion, fatigue) and that excessive loading leads to fatigue, downtime and injuries
Ergonomic issues that are related to biomechanics:
- awkward static postures
- force/load
- repetition
- duration
- vibration
Techniques of biomechanics involve kinematics and kinetics, kinematic variables are _______ and kinetic variables are ________.
Kinematic: time and space variables
Kinetic: force and energy variables
Suggestions for manual materials handling include:
- Loads should be kept close to the body
- Loads should be presented at thigh or waist height
- Lifting should minimize twisting
- Frequency of lifting should be minimized
Suggestions for seated work:
- Curvature of spine should be kept
- Back support (lumbar) should be given to support the body and help keep S curve of spine
Common forms of cumulative trauma disorders (CTD):
- Tendon-related CTD, caused by loss pf blood supply to the tendons and increased tension
- Neuritis is damage to the nerves that can be caused by awkward posture and repeated use
- Ischemia is the sensations of tingling and numbness, is caused by obstruction of blood flow and tissue damage
- Bursitis is inflammation of bursa sac, which contains viscous fluid and is located between joints
Stress-Strain Relationships:
Stress:
Strain:
Plastic region:
Ultimate Strength:
Stress: applied load
Strain: deformation
Plastic Region: permanent disruption
Ultimate Strength:
Complete tear
Muscle fatigue:
Reduction in the capacity to generate force
Central fatigue:
Reduction in maximal voluntary contraction force not accompanied by same reduction in maximal evocable force
Excessive loads, awkward joint postures, and inadequate recovery are all possible causes for…
cumulative trauma disorder
Factors affecting performance and injury include:
- individual
- task
- environment
What are the two methods of classifying and evaluating manual work:
Traditional and contemporary
Traditional methods of manual work included describing manual activities with reference to standard categories of _____ to classify and evaluate manual work.
Effort
Traditional methods of classifying and evaluating manual work were based on…
improving efficiency without major concern for safety
With contemporary biomechanical job analysis systems, worker is…
critical importance
Physical stress checklists and surveys help to identify…
why the safety procedure is not being followed by employees
1981 NIOSH Study major findings…
Overexertion causing low back pain (significant), overexertion injuries account for large amount of reported occupational injuries
- Load
- Dimensions
- Distribution of load
- Couplings
- Stability of load
These are all examples of ________ characteristics that affect ___________.
Material/container characteristics that affect manual material handling systems
What are three strategies to prevent overexertion injury:
- Design the task for all workers
- Select workers believed to be at low risk
- Train workers to reduce personal risk levels
Be careful not to implement bias however!
The 1981 NIOSH equation to evaluate sagittal plan lifting produces and objective method to determine __________
safe load
To use to NIOSH equation, need to define 4 job attributes:
- Location of Centre of Mass (handgrip center) of the object in horizontal direction (H)
- Location of Centre of Mass (handgrip center) in vertical direction at start of lift
- Vertical travel distance of the hands
- Frequency of lifting (lifts/minute) averaged over period
