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Vibration (resulting from driving) and lifting cause back, neck, and shoulder pain, whereas inability to work seems affected by stress at work.

The models suggest that, by altering placement of the artificial disc in the anteroposterior direction, a surgeon can modulate motion-segment flexuralstiffness and posterior load-sharing, even though the specific disc replacement design has no inherent rotational stiffness.

Sixteen subjects were exposed to fatiguing (vibration) and restorative (walking) interventions to assess their response to sudden loads. Unexpected loads, which people often experience, can lead to high forces in the spine and may be a cause of low irack injury. Erector spinae responses to sudden load were mediated by exposure to vibration and walking. Reaction time was affected by fatigue. Vertical vibration exposure significantly increased the muscle response time. Walking was able to ameliorate that effect. Sudden loads can exacerbate fatigue effects. Walking after driving, reduces the risk to the back due to handling unpredictable loads.

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IntroductionRear-end collisions typically occur in dense traffic at very low speeds. The vehicle is subjected to a forward acceleration during which the occupants are pushed forward by the seatbacks. The head lags behind forcing the neck into extension. This head motion continues until the neck hits the headrest or reaches its maximum range of motion, or is counteracted by the muscles. The head then reacts by moving forward into a flexed neck posture. This is the typically described injurious extension-flexion motion of the neck called "whiplash motion" [12]. Hypertranslation of the head was suggested by Penning as being the primary mechanism of whiplash injury [16]. The translatory motion takes place in the upper cervical spine followed by an angular extension in the lower part, forming as S-shape of the cervical spine. This means that the upper cervical spine is undergoing a flexion motion while the lower cervical spine is undergoing an extension motion. When the upper cervical spine reaches its limit for maximum flexion, the lower cervical spine reaches its limit for full extension. The cervical spine then goes into full extension and stops before the motion is reversed [22].The hyperextension of the cervical spine results in compressive forces on the posterior structures, such as the Abstract Whiplash motion of the neck is characterized by having an extension-flexion motion of the neck. It has been previously assumed that muscles do not play a role in the injury. Eight healthy males were seated in a car seat mounted on a sled. The sled was accelerated by a spring mechanism. Muscle electromyographic (EMG) activity was measured by wire electrodes in semispinalis capitis, splenius capitis, and levator scapulae. Surface EMG activity was measured over trapezius and sternocleidomastoideus. Wavelet analysis was used to establish the onset of muscle activity with respect to sled movement. Shorter reaction times were found to be as low as 13.2 ms from head acceleration and 65.6 ms from sled acceleration. Thus the muscles could influence the injury pattern. It is of interest that clinical symptoms are often attributed to muscle tendon injuries.