Canadian Centre for Health & Safety in Agriculture, College of Medicine, University of Saskatchewan, Clinic Place, Saskatoon, Saskatchewan, Canada.
School of Physical Therapy, College of Medicine, University of Saskatchewan, Clinic Place, Saskatoon, Saskatchewan, Canada.
Ann Work Expo Health. 2018 Aug 13;62(7):884-898. doi: 10.1093/annweh/wxy043.
Exposure to whole body vibration (WBV) is common in construction, agriculture, mining, and transportation. There is strong epidemiological evidence linking WBV with adverse health outcomes in the long-term, including low back pain. Fortunately, WBV exposure guidelines to prevent long-term musculoskeletal disorders and discomfort exist. In the shorter-term, it has been speculated that occupational levels of WBV may lead to increased risk of vehicle accidents and falls during egress; however, the acute effects of different vibration intensities remain poorly understood and it is uncertain whether established standards protect the worker from injurious short-term effects.
The aim of this study was to investigate the acute sensorimotor, physical, and cognitive effects of occupationally-relevant, simulated whole body vibration (WBV) at levels equivalent to international standard guideline thresholds for long-term discomfort and musculoskeletal disorder risk.
Eighteen participants were recruited to perform four, 60-min conditions: (i) Control-no vibration, (ii) Low vibration-equivalent to the exposure action value, (iii) Shock-transient impacts at 1-min intervals superimposed on the Low condition, and (iv) High vibration-equivalent to the exposure limit value. Whole body vibration was simulated using data based on field-collected accelerations experienced by rural workers while operating an all-terrain vehicle. This vibration signal was manipulated to achieve required intensities for each condition and simulated with a 6 degree-of-freedom hexapod platform. Before and after each condition, we collected: rating of perceived body discomfort, rating of perceived headache, postural sway, blink frequency, King-Devick test, and psychomotor vigilance task. Pre- and post-condition data in each condition were submitted to either a paired t-test (parametric) or Wilcoxon signed-rank test (non-parametric). To determine differences between conditions, each condition's post-condition data was normalized to its pre-condition value and entered as the dependent variable in a repeated measures analysis of variance.
All conditions, including Control, led to increased upper body discomfort when compared to pre-exposure baseline. The Low condition led to increased discomfort in seven body locations, headache (91% increase from baseline; t = -2.44, P = 0.03), and postural imbalance (53% increase from baseline; t = -2.88, P = 0.01), but the effect on cognitive functioning was less clear. Shock condition led to whole body discomfort, specifically at nine upper body and lower body locations. The High condition led to increased whole body discomfort at all 10 body locations, headache (154% increase from baseline; t = -2.91, P = 0.01), postural imbalance (61% increase from baseline; t = -2.57, P = 0.02), and decrements in vigilance (mean reaction time: 6% increase from baseline, t = -3.27, P = 0.005; Number of lapses: 100% increase from baseline, S = -42.5, P = 0.002).
Although the number of pre-post condition effects increased with higher vibration intensity, these effects were not significantly different from sitting without vibration. Therefore, current guideline thresholds might not protect the worker from acute WBV effects. However, further research is needed to discern these effects from other sources of WBV. Based on this study, future WBV interventions and action controls should not only address vibration reduction, but also consider potential effects from prolonged sitting.
全身振动（WBV）暴露在建筑、农业、采矿业和交通运输等行业中很常见。有强有力的流行病学证据表明，WBV 与长期的健康后果有关，包括下背痛。幸运的是，存在预防长期肌肉骨骼疾病和不适的 WBV 暴露指南。在短期，有人推测职业水平的 WBV 可能会增加车辆事故和出口时跌倒的风险；然而，不同振动强度的急性影响仍知之甚少，也不确定既定标准是否能保护工人免受短期伤害。
本研究旨在调查与国际标准指南长期不适和肌肉骨骼疾病风险阈值等效的职业相关模拟全身振动（WBV）的急性感觉运动、身体和认知影响。
招募了 18 名参与者，进行四项 60 分钟的条件：（i）对照-无振动，（ii）低振动-相当于暴露动作值，（iii）冲击-在 1 分钟间隔内叠加的瞬态冲击低振动条件，以及（iv）高振动-相当于暴露限值。全身振动使用基于农村工人在操作全地形车时经历的现场采集加速度的数据进行模拟。这种振动信号被操纵以达到每个条件所需的强度，并使用 6 自由度六足平台进行模拟。在每个条件前后，我们收集了：身体不适的感知评级、头痛的感知评级、姿势摆动、眨眼频率、King-Devick 测试和精神警觉任务。每个条件的前后条件数据均提交给配对 t 检验（参数）或 Wilcoxon 符号秩检验（非参数）。为了确定条件之间的差异，将每个条件的后条件数据归一化为前条件值，并作为重复测量方差分析的因变量。
与暴露前基线相比，所有条件（包括对照）都导致上半身不适增加。低振动条件导致七个身体部位的不适增加、头痛（比基线增加 91%；t = -2.44，P = 0.03）和姿势失衡（比基线增加 53%；t = -2.88，P = 0.01），但对认知功能的影响不太清楚。冲击条件导致全身不适，特别是在上半身和下半身的九个部位。高振动条件导致所有 10 个身体部位的全身不适增加，头痛（比基线增加 154%；t = -2.91，P = 0.01）、姿势失衡（比基线增加 61%；t = -2.57，P = 0.02）和警觉性下降（平均反应时间：比基线增加 6%，t = -3.27，P = 0.005；失误次数：比基线增加 100%，S = -42.5，P = 0.002）。
尽管随着振动强度的增加，前后条件的效果增加，但这些效果与不振动时没有显著差异。因此，当前的指南阈值可能无法保护工人免受急性 WBV 影响。然而，需要进一步的研究来区分这些影响与其他来源的 WBV。基于这项研究，未来的 WBV 干预和行动控制不仅应减少振动，还应考虑长时间坐着可能带来的潜在影响。
