Greater seated postural reactions are provoked by double-sided compared to single-sided mechanical shocks
(English)Manuscript (preprint) (Other academic)
Study design: Human volunteers were exposed experimentally to single-sided mechanical shocks (SSMS) and double-sided mechanical shocks (DSMS) while seated.
Objective: To describe seated postural reactions due to SSMS and DSMS in healthy male adults.
Summary of Background Data: Mechanical shocks, caused when driving on irregular terrain are suggested to be hazardous to the spine and may be associated with the reported musculoskeletal disorders of the back and neck among professional drivers.
Methods: Twenty healthy male subjects (18-43 years old) were exposed while seated to 5 SSMS and 15 DSMS in lateral directions. The second acceleration in the DSMS was in the opposite direction to the first acceleration and divided into fast, medium and slow depending on the speed of direction change. Surface electromyography (EMG) was recorded in upper neck, trapezius, erector spinae and external oblique and kinematics were recorded with inertial sensors for the neck, trunk and pelvis. Muscle activity evoked by the shocks was normalized to maximum voluntary contractions (MVC).
Results: The EMG amplitudes were significantly higher (0.6-1%; p<0.001) for the fast DSMS compared to all other shocks. Range of motions of the neck and trunk were greater from the DSMS compared to the SSMS. Muscle activity in the erector spinae and upper neck was sparse while the most intense muscle activity was found in the external obliques > 10% MVC, with elements of co-contraction.
Conclusion: Fast DSMS in lateral directions appear more demanding compared to SSMS and increase seated postural reactions, especially activity in the external oblique muscles. Still, the extent of range of motions in the neck and trunk and muscle activities alone, do not suggest a high risk for musculoskeletal overload.
Postural balance, Posture, Electromyography, Musculoskeletal pain, Whole-body vibration
Research subject Physiotherapy
IdentifiersURN: urn:nbn:se:umu:diva-117167OAI: oai:DiVA.org:umu-117167DiVA: diva2:905685