Vascular Responses to Vibration Are Frequency Dependent

A Review of Hand–Arm Vibration Studies Conducted by US NIOSH since 2000

“…This allowed us to test the hypothesis that injury or dysfunction would be increased with exposure to vibration frequencies that induced a greater biodynamic response (or resonance). Vascular responses to vibration were frequency-dependent; although exposures at all frequencies resulted in an increase in oxidative stress, anti-oxidant enzyme concentrations, inflammation and cellular factors that play a role in vascular remodeling, morphological measures of the ventral tail artery demonstrated that vibration exposure at frequencies that generated greater resonance of the tissue (62.5 < 125 < 250 Hz) resulted in a reduction in the internal diameter of the artery, a thickening of the vascular smooth muscle of the artery ( Figure 15 ), and an increased expression of a marker indicative of oxidative-induced tissue damage, nitrotyrosine [ 206 ]. This increased and maintained vasoconstriction is similar to that seen in biopsy samples collected from the fingers of workers with HAVS [ 207 ].…”

“…Exposure to HTV results in changes in blood flow and in sensory perception in the local tissues directly exposed to vibration [ 132 , 239 ]. However, exposure to HTV or segmental vibration has also been shown to induce systemic effects that may be the result of changes in sensitivity to autonomic nervous system signaling [ 240 – 243 ] and possibly various metabolic processes [ 206 , 244 ]. Because results from animal models show segmental vibration exposure is associated with changes in transcript levels of genes associated with an increased risk for developing cancer and heart disease [ 206 , 244 ], additional epidemiological studies looking at the prevalence of these diseases in workers exposed to HTV would help determine if the vibration is a significant risk factor in the development of these diseases.…”

“…However, exposure to HTV or segmental vibration has also been shown to induce systemic effects that may be the result of changes in sensitivity to autonomic nervous system signaling [ 240 – 243 ] and possibly various metabolic processes [ 206 , 244 ]. Because results from animal models show segmental vibration exposure is associated with changes in transcript levels of genes associated with an increased risk for developing cancer and heart disease [ 206 , 244 ], additional epidemiological studies looking at the prevalence of these diseases in workers exposed to HTV would help determine if the vibration is a significant risk factor in the development of these diseases. Experimental studies can also contribute by identifying characteristics of vibration that are most likely to contribute to physiological changes associated with the development of these diseases, determine which tissues or biological systems are most sensitive to the effects of vibration, and identify early biomarkers of disease progression so that interventions might be developed and used to prevent disease progression.…”

“…On day 20 of exposure, the amplitude of the pulse was reduced in both restraint controls and vibration exposed. However, the fact that the reduction in the pulse amplitude occurred sooner, and the magnitude of the reduction was more pronounced in animals exposed to vibration, suggests that vibration resulted in an increase in stiffness of the artery, which could be due to a thickening of the smooth muscle wall [ 204 , 206 , 252 , 304 ]. These findings are consistent with those seen in humans that have been exposed to vibration [ 255 , 256 , 299 ] and with changes in vascular morphology indicative of vascular dysfunction [ 204 , 206 ].…”

Examination of Vibration Characteristics, and Reported Musculoskeletal Discomfort for Workers Exposed to Vibration via the Feet

“…When exposed to higher frequency vibration believed to be linked to HAV injury in humans, structural damage has been documented to occur within the muscle fibres of animals [12,13]. Vascular responses to vibration of the tail in rats have been shown to be frequency dependent, with the greatest risk of injury at 250 Hz [14]. If miners experience localized damage to their feet from direct vibration exposure, it is plausible that this would occur when the dominant vibration frequency is within the range associated with hand-arm vibration syndrome.…”