Improved methods of hand-arm vibration exposure measurement have been defined by ISO 5349 as the ones using additional factors such as contact force in order to decrease the uncertainty of exposure time.
Contemporary, very small force transducers can be fitted right next to the MEMS-technology-based vibration accelerometer in a form of hand-arm adapter as specified by ISO 5349-2 and ISO 10819. With such an effective solution it became possible to perform continuous measurements through the whole working day which decreases the uncertainty of the sample limitation. The time-history of contact force values proved important in determining the true exposure time by simple selection of the force threshold level and this was backed up by the analysis of spectrograms.
Simultaneous measurement of coupling forces and vibration is necessary because different coupling forces applied by operators on handheld vibrating tools influence differently the stage of transmission of vibration in the upper limbs. Coupling forces modify exposure to vibration and the health effects it causes. Moreover, the synergic impact of force and vibration on the cardiovascular system, nervous system and the joints and muscles should be considered.