Musculoskeletal loading

An important component of the workstation that can help reduce musculoskeletal loading is a document holder. When properly designed and proportioned, document holders reduce awkward incli-... 

Guidelines for Occupational Musculoskeletal Load as a Basis for Intervention A Critical Review Author(s) Westgaard RH/ WINKEL J Source Applied Ergonomics V.27 NO. 2, PP. 79-88, Apr 1996... 

Because muscle, ligament, and joint-contact forces cannot be measured noninvasively in vivo, estimates of these quantities have been obtained by combining mathematical models with either the inverse-dynamics or the forward-dynamics approach (Sec. 6.6). Below we review the levels of musculoskeletal loading incurred in the lower-limb during rehabilitation exercises, such as isokinetic knee extension, as well as during daily activity such as gait. 

Wu J, An K-N, Cutlip R et al. (2008) Analysis of musculoskeletal loading in an index finger during tapping. Journal of Biomechanics 41 668-676... 

The choice of an agent for use as an antipyretic or analgesic is seldom a problem. Drugs with more rapid onset of action and shorter duration of action probably are preferable for simple fevers accompanying minor viral illnesses or pain after minor musculoskeletal injuries, whereas a longer duration of action may be preferable for postoperative pain management. Sometimes a loading dose of such NSAIDs may be required. 

Vogel KG. Tendon structure and response to changing mechanical load. J Musculoskelet Neuronal Interact 2003 3 323-325. 

As a minimum, a 15-minute break from working should be taken after 2 hours of continuous computer work (CDC 1980 NIOSH 1981). Breaks should be more frequent as visual, muscular, and mental loads are high and as users complain of visual and musculoskeletal discomfort and psychological stress. With such intense, high-workload tasks, a work break of 10 minutes should be taken after 1 hour of continuous computer work. More frequent breaks for alternative work that does not pose demands similar to the primary computer work can be taken after 30 minutes of continuous computer work. Rest breaks provide an opportunity for recovery from local visual, musculoskeletal, and mental fatigue, to break from monotonous activities, or to engage in activities that provide variety in sensory, motor, and cognitive requirements. 

The nervous system can learn to achieve desired levels of accuracy by adjusting control signals to accommodate factors such as changing musculoskeletal geometry, and dynamics. For example, when an object is grasped and lifted with fingers, the grip force varies directly in an anticipation of the load force as determined by mass and acceleration of the object [ 13-16]. 

Women generally report more musculoskeletal problems than men. The reason for this is not quite elear, but there are several possible erqrlanations (a) Women have less physical strength than men and gender diffeienees in terms of muscle fiber composition may be of importance (b) compared to men, women are overrepresented in jobs with a high incidence of muscular problems (e.g., repetitive assembly work) and they tend to stay longer in these jobs and (c) employed women are often exposed to more work overload and role conflicts than men, due to the combined load from paid and unpaid duties. As a consequenee, women have fewer opportunities than men for off-work relaxation and their muscles may therefore remain activated too long without rest and restitution. 

The role of psychosocial factors in the development of musculoskeletal disorders seems to be consistent with the allostatic load model. Cashiers working in the supermarket have an unfavorable work-rest pattern with increased muscle activity and very few periods of rest during a 2-hour work shift (Sandsjo, 1997). Jobs involving repetitive exposure to mental and physical demands (e.g., Lundberg et al., 1989), lack of relaxation onorofifthejob(Frankenhaeuser, Lundberg,... 

The equations of motion are dynamic expressions relating kinematics with forces and moments. In a musculoskeletal biodynamic system, the forces and moments will consist of joint reactions internal forces, such as muscle, tendon, or ligament forces and/or externally applied loads. Consequently, the equations of motion can provide a critical understanding of the forces experienced by a joint and effectively model normal joint function and joint injury mechanics. They can yield estimates for forces that cannot be determined by direct measurement. For example, muscle forces, which are typically derived from other quantities such as external loads, center of mass locations, and empirical data including anatomical positioning and/or electromyography, can be estimated. 

Another property of the physiologic arm is that it has give, that is, it is compliant or springlike. This compliance is not a fixed quantity but can be varied depending on the task requirements a stiff arm for bracing oneself against an expected blow or a relaxed arm for playing the piano. This inherent compliance of the human arm also provides protection for the joints and musculo-skeletal system. Because the musculoskeletal system is compliant, it can withstand external shock loads far better than can a stiff-jointed equivalent. 

In human bodies, all movement is possible due to the application of load and stress to biological levers. The field of biomechanics, which teaches about joints, bones, and muscles, provides safety professionals with an understanding of how the musculoskeletal levers of the body are designed to work. This awareness can be applied to identify and eliminate unnatural movements resulting in ergonomic problems. Evaluation activities such as monitoring frequency and duration of... 

The occurrence and severity of low back and other musculoskeletal injuries increases directly with increase in the distance of the centre of gravity of the load fiom the handler s body, whether this increase is occasioned by bulk of load or workplace layout. Refer again to Fig. 11.1. 

Musculoskeletal In two cases of osteolysis in hips with third-generation alumina ceramic-on-ceramic couplings, periarticular tissue contained titanium wear debris (from impingement of the neck of the titanium femoral component against the rim of the titanium shell) and ceramic debris (from edge loading wear of the ceramic) [63 ]. The authors could not decide whether the titanium debris, the ceramic debris, or both had caused the osteolysis. 

The high incidence of musculoskeletal disorders has as main cause the negligence in the postures and handling of excessive loads during the workday, which contributes to decreasing productivity, increasing the absenteeism and a decreasing the life quality of workers involved in this activity (Couto, 1996). For situations like of these, the... 

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