The Multisystem Effects of Simulated Agricultural Whole Body Vibration on Acute Sensorimotor, Physical, and Cognitive Performance.
Ann Work Expo Health. 2018 Jun 14;:
Authors: Yung M, Tennant LM, Milosavljevic S, Trask C
Background: 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.
Objective: 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.
Method: 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.
Results: 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).
Conclusion: 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.
PMID: 29905767 [PubMed - as supplied by publisher]
Improved osseointegration with as-built electron beam melted textured implants and improved peri‑implant bone volume with whole body vibration.
Med Eng Phys. 2018 Jun 11;:
Authors: Ruppert DS, Harrysson OLA, Marcellin-Little DJ, Dahners LE, Weinhold PS
Transcutaneous osseointegrated prostheses provide stable connections to the skeleton while eliminating skin lesions experienced with socket prosthetics. Additive manufacturing can create custom textured implants capable of interfacing with amputees' residual bones. Our objective was to compare osseointegration of textured surface implants made by electron beam melting (EBM), an additive manufacturing process, to machine threaded implants. Whole body vibration was investigated to accelerate osseointegration. Two cohorts of Sprague-Dawley rats received bilateral, titanium implants (EBM vs. threaded) in their tibiae. One cohort comprising five groups vibrated at 45 Hz: 0.0 (control), 0.15, 0.3, 0.6 or 1.2 g was followed for six weeks. Osseointegration was evaluated through torsional testing and bone volume fraction (BV/TV). A second cohort, divided into two groups (control and 0.6 g), was followed for 24 days and evaluated for resonant frequency, bone-implant contact (BIC) and fluorochrome labeling. The EBM textured implants exhibited significantly improved mechanical stability independent of vibration, highlighting the benefits of using EBM to produce custom textured surfaces. Bone formation on and around the EBM textured implants increased compared to machined implants, as seen by BIC and fluorescence. No difference in torque, BIC or fluorescence among vibration levels was detected. BV/TV significantly increased at 0.6 g compared to control for both implant types.
PMID: 29903535 [PubMed - as supplied by publisher]