Work-Related Musculoskeletal Disorders (WMSDs) PDF

Work-Related Musculoskeletal Disorders (WMSDs): Risk Factors, Causes, and Symptoms Work-related musculoskeletal disorders (WMSDs) develop gradually due to repeated trauma from repetitive movements, awkward postures, forceful exertions, and environmental factors. These disorders primarily affect mus...

Work-Related Musculoskeletal Disorders (WMSDs): Risk Factors, Causes, and Symptoms Work-related musculoskeletal disorders (WMSDs) develop gradually due to repeated trauma from repetitive movements, awkward postures, forceful exertions, and environmental factors. These disorders primarily affect muscles, tendons, and nerves, leading to pain, weakness, and reduced function. Muscles control movement and essential functions like respiration and digestion. They work by contracting and extending, powered by chemical energy conversion from ATP. Types of Muscular Effort: Isotonic (Dynamic) Effort: Involves muscle contraction and relaxation, increasing blood supply and facilitating work. Isometric (Static) Effort: Involves prolonged muscle tension without movement, restricting blood flow, leading to fatigue and pain. During dynamic work, the muscle acts as a pump, increasing the blood supply to the muscle by 10 to 20 times the amount present when the muscle is at rest. A muscle performing dynamic work is continuously supplied with energy (sugar) and oxygen provided in the blood while waste products are simultaneously removed. In contrast, in muscles maintaining a static contraction (prolonged tensing of the muscles), the blood vessels are compressed by the internal pressure of the muscle tissue so that blood no longer flows through the muscle. Therefore, the muscle must depend on reserves of sugar and oxygen already present. Metabolic waste (lactic acid and carbon dioxide) builds up, cutting off the oxygen supply to the muscle. Waste products are not removed as efficiently, and the accumulation of waste products eventually results in pain and fatigue. The static effort also leads to a raised heart rate, and longer rest periods are needed. Examples of static work include: Jobs that involve bending the back forward or sideways. Holding things in the hands. Manipulations that require the arms to be held stretched out or raised above shoulder height. Putting the weight on one leg while the other works a pedal.  Standing in one place for long periods. Pushing and pulling heavy objects. Tilting the head strongly forward, backward, or to the side. Raising the shoulders for long periods. Most tasks involve both static and dynamic work. A particular task, such as keyboard operation, can be partly static and partly dynamic. A static effort is more arduous than a dynamic effort and frequently results in local muscle fatigue and pain, even for short- duration activities. Dynamic work duration is often measured in minutes and hours, while acceptable time periods for static work duration are measured in seconds and minutes. Therefore, avoiding static efforts for long periods of time is an important human engineering task. 1. Risk Factors for WMSDs WMSDs occur due to a combination of personal, job-related, and environmental risk factors: Personal Risk Factors Physical conditioning – Poor strength and endurance increase fatigue and injury risk. Body size and proportions – Mismatched workstations and tools can force awkward postures. Pre-existing conditions – Arthritis, previous injuries, and other health issues heighten susceptibility. Work habits and posture – Poor lifting techniques and prolonged static postures contribute to strain. Health - Age, weight, height, sex, and smoking status all factor into the potential risk for developing musculoskeletal disorders. Job-Related Risk Factors Static work – Holding a position for too long (e.g., prolonged holding, standing or sitting).  Repetitive movements – Repeating motions frequently without rest (e.g., typing, assembly work). Forceful exertions – Lifting, pushing, or gripping with excessive force. Localized pressure on soft tissues – Tools or surfaces pressing against the body (e.g., wrists resting on a desk edge). Fast-paced work with insufficient recovery time – Tasks requiring continuous motion without breaks. Environmental Risk Factors Heat – High temperatures cause fatigue, increase sweating, and reduce grip strength, making injuries more likely. Cold – Low temperatures reduce muscle flexibility, slowing reaction time and increasing stiffness, which raises the risk of strains and sprains. Vibration – Prolonged use of vibrating tools (e.g., power drills, jackhammers) can damage blood vessels, nerves, and muscles, leading to conditions like Hand-Arm Vibration Syndrome (HAVS). These risk factors interact to create conditions that lead to WMSDs over time. 2. How WMSDs Occur WMSDs develop gradually as muscles, tendons, and nerves experience repeated trauma due to repetitive motion, poor ergonomics, and environmental stressors. Muscle Injuries Muscles contract using chemical energy and produce by-products like lactic acid. Prolonged muscle contractions reduce blood flow, preventing proper waste removal. Accumulation of irritating substances causes pain and muscle fatigue. Tendon Injuries Tendons attach muscles to bones and can be damaged by repetitive movements and awkward postures. Tendons with sheaths (hands and wrists):  o Overuse can cause lubrication failure, leading to friction, swelling, and inflammation (tenosynovitis). o Severe cases can form ganglion cysts. Tendons without sheaths (shoulders, elbows, forearms): o Repetitive tension causes micro-tears, thickening, and inflammation (tendonitis). o Bursa inflammation (bursitis) may develop when tendons rub against bones. Nerve Injuries Nerves carry signals for movement, sensation, and other functions. Repetitive motion, awkward postures, and vibration can cause swelling of surrounding tissues, leading to nerve compression. Symptoms include muscle weakness, numbness, tingling, poor circulation, and dry skin. Carpal Tunnel Syndrome is a common nerve injury caused by median nerve compression in the wrist. 3. Symptoms and Progression of WMSDs Stages of WMSDs Stage Symptoms Aching and tiredness appear during work but disappear with rest. No Early Stage performance reduction. Intermediate Symptoms persist after work, reducing ability to perform repetitive Stage tasks. Chronic pain, fatigue, and weakness, even at rest. Difficulty sleeping Late Stage and performing light tasks. Without intervention, WMSDs can become irreversible. 4. Common WMSDs, Risk Factors, and Symptoms Disorder Occupational Risk Factors Symptoms Repetitive wrist and shoulder motions, sustained Pain, weakness, swelling, Tendonitis/Tenosynovitis hyperextension, prolonged burning, dull ache shoulder load Epicondylitis (Elbow Repeated or forceful forearm Same as tendonitis Tendonitis) rotation with wrist bending Repetitive wrist motions, Pain, numbness, tingling, awkward hand positions, strong Carpal Tunnel Syndrome burning, muscle wasting gripping, mechanical stress, at thumb base, dry palm vibration Repetitive hand twisting and De Quervain’s Disease Pain at thumb base forceful gripping Prolonged shoulder flexion, Pain, numbness, hand Thoracic Outlet Syndrome overhead work, carrying loads on swelling shoulder Tension Neck Syndrome Prolonged restricted posture Neck pain Heavy lifting, awkward posture, Lower Back Pain Back pain whole-body vibration Numbness, tingling, Hand-Arm Vibration reduced grip strength, Prolonged use of vibrating tools Syndrome (HAVS) poor circulation in hands and fingers