Temporary threshold shift of vibratory sensation induced by a vibrating handle and its gripping force

Abstract

•Objective This study examines the effect of the force with which a vibrating handle is gripped on the temporary threshold shift of vibratory sensation (TTS_v) induced by hand-arm vibration. •Methods Six healthy subjects gripped a handle vibrating with a 1/3 octaveband vibration, with a central frequency of 200 Hz and an intensity of 39.2 m/s². Exposure was for 1 min and 10 min, respectively. Gripping forces for the 1-min exposure were 5 N, 10 N, 40 N and 80 N, respectively, with 0 N push-pull force. Gripping forces for the 10-min exposure were the same as for the 1-min exposure, but omitting 80 N. The vibratory sensation threshold at 125 Hz was measured before and after exposure of an exposed fingertip to vibration. The differences measured determine TTS_v,t at timet. TTS_v,t determines TTS_v,0, that is, the temporary threshold shift of vibratory sensation immediately after exposure to vibration according to the estimate made on the basis of the preceding study. The same experimental conditions were repeated 3 times on different days in a soundproof and thermoregulated room. •Results Our findings show that TTS_v increases significantly with increasing gripping force. We also determined the quantitative relationships between TTS_v,0 and gripping force as described by the equationEquationSource % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuqr1ngBPrgarmqr1ngBPrgitL% xBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2D% aeHbuLwBLnhiov2DGi1BTfMBaebbfv3ySLgzGueE0jxyaibaieYlf9% irVeeu0dXdh9vqqj-hEeeu0xXdbba9frpe0db9Lqpepeea0xd9q8as% 0-LqLs-Jirpepeea0-as0Fb9pgea0lrP0xe9Fve9Fve9qapdbaqaae% GaciGaaiaabeqaamaaeaqbaaGcbaGaeeivaqLaeeivaqLaee4uam1a% aSbaaSqaaiabbAha2bqabaGccqqGSaaldaWgaaWcbaGaeeimaadabe% aakiabg2da9iGbcwgaLjabcIha4jabcchaWjabcIcaOiabbUgaRnaa% BaaaleaacqqGMbGzaeqaaOGaey41aqRaemOrayKaey4kaSIaem4yam% 2aaSbaaSqaaiabdAgaMbqabaGccqGGPaqkcqGGSaalaaa!5B91!<InlineEquation ID="IE1"> <EquationSource Format="MATHTYPE"> <![CDATA[{\text{TTS}}_{\text{v}} {\text{,}}_{\text{0}} = \exp ({\text{k}}_{\text{f}} \times F + c_f ),$$ wherek _f andc _f are constants andF is gripping force. •Conclusion This study revealed the importance of ergonomic design in reducing the force with which a vibrating handle is gripped to prevent an adverse effect of local vibration. The equation devised may help in the quantitative assessment of the effect of reduced gripping force.