Whole-body vibration (WBV) may positively influence performance acutely through the potentiation of the muscle’s series elastic components and neuromuscular mechanisms. The purpose of this investigation was to examine the acute effects of WBV on sprint performance in NCAA Division I collegiate male sprinters and jumpers. Twenty-one athletes (n=21) completed a control or WBV protocol (30 seconds, 50 Hz, low amplitude ~3mm) one minute before a 30 m flying sprint. Each athlete participated in three separate trials using randomized treatment sessions (1 treatment per session) over 12 weeks of preparation training prior to the indoor season. The control condition consisted of no vibration, while treatment 1 (T1) and treatment 1 repeated (T1-R) incorporated vibration. The vibration-sprint protocol was repeated after a five minute rest period following the first sprint (test-re-test ICC≥0.81). The sprint consisted of a 15 m run-in from a standing start and a 30 m flying sprint with a total distance of 45 m. A two-way factorial ANOVA with repeated measures (p ≤ 0.05) was used to compare treatments. Statistics showed no differences between the treatments at all distances (average sprint time of control vs. T1, control vs. T1-R, and T1 vs. T1-R). The results of this study indicate that WBV at 50 Hz and low amplitude has no potentiation effect on sprint times (15, 30, 45, or 30 m fly). Further research is needed to determine if different WBV protocols may elicit enhanced results in 30 m flying sprint performance. The present WBV protocol does not appear to have practical acute value for sprinting.

Studies of human response to whole-body vibration, such those encountered in heavy machinery and ground and aerial transportation, have highlighted the critical role of the head-neck posture of seated human occupants and the role of the transport system of a supine human on the severity of the transmitted vibration to the human body. Novel passive and muscle-based models are introduced in this work to predict the biodynamical response of the human under whole-body vibration in seated and supine postures. Planar and three-dimensional models representing the human head-neck system under different seated postures and fore-aft and multiple-axis whole-body vibration are first introduced. In these models, the head-neck system is represented by rigid links connected via spring-damper components representing the soft-tissue and connecting elements between the bones. Additional muscle components are added to some models. The muscle components comprise additional mass, spring, and damper elements arranged in a special order to capture the effect of changes in the displacement, velocity, acceleration, and jerk. The results show that the proposed models are able to predict the displacement and acceleration of the head under different vibration files, with the muscle-based models showing better performance than the passive models. The second set of models is introduced in this work to investigate the effect of the underlying transport system conditions on the response of supine humans under vertical and multiple-axis whole-body vibration. In these models, the supine human body is represented by three rigid links representing the head, torso/arms, and legs. The links are connected via rotational and translational joints, and therefore, it is expected that the models can capture the coupling effects between adjacent segments. The joints comprise translational and rotational spring-damper components that represent the soft tissue and the connecting elements between the segments. The contact surfaces between the supine human and the underlying transport system were modeled using spring-damper elements. Two underlying transport systems were considered, including a rigid support and a long spinal board attached to a military litter. The results showed that the proposed models were able to predict the effect of the transport systems on the human response under different vibration conditions.

O setor de mineração registrou de 2011 até 2013 o maior número de acidentes entre as indústrias extrativas, evidenciando a relevância da preocupação com os controles dos riscos e doenças ocupacionais. Atividades intrínsecas do setor, como perfuração manual, transporte de minério e estéril com caminhões ou carregadeiras, locomoção com veículos dentro do site, manutenção e amostragem com o uso de serras circulares, entre outros, são caracterizadas por presença e alta intensidade de vibração. O objetivo do trabalho consiste em avaliar a exposição ocupacional à vibração de corpo inteiro em operadores de equipamentos frequentes em minerações a céu aberto, além de comparar os resultados obtidos com a legislação brasileira vigente e apresentar sugestões para a redução dos valores de vibração de corpo inteiro (VCI) encontrados. O autor pesquisou artigos sobre vibração de corpo inteiro na mineração e em outros setores, números de casos de doenças ocupacionais associadas ao agente em território nacional, tipos de assento disponíveis no mercado e legislações nacionais e internacionais europeias e norte-americanas. Foram visitadas três pedreiras na região metropolitana de São Paulo, onde realizaram-se avaliações preliminares da exposição seguidas de levantamento quantitativo de parâmetros aren (aceleração resultante da exposição normalizada) e VDVR (valor dose de vibração resultante). Ao todo, foram analisados 22 equipamentos envolvendo caminhões fora-de-estrada, escavadeiras, pás-carregadeiras, perfuratrizes, rompedores pneumáticos e caminhões pipa. Os equipamentos estudados em sua maioria ficaram acima do nível de ação estabelecido pela NHO-09 (norma de higiene ocupacional) e alguns acima do limite de exposição. Os equipamentos com os maiores índices de Vibração de Corpo Inteiro encontrados foram as pás-carregadeiras e os menores, perfuratrizes. / The mining sector registered the greatest number of accidents among the extractive industries from 2011 to 2013, highlighting the relevance of the concern with occupational risks and diseases control. Intrinsic activities of it such as manual drilling, ore and / or waste transportation with truck or loaders, locomotion with vehicles inside the mine site, maintenance and sampling with the use of circular saws are characterized by presence and high intensity of vibration. The objective of this study is to evaluate the whole-body vibration in common open pit machinery operators, comparing values obtained with current Brazilian legislation and to suggest improvements to reduce whole-body vibration (WBV) in the studied sites. The author researched articles on whole body vibration in and out of mining, numbers of occupational diseases associated with the agent in the national territory, types of seats available in the market and international laws in Europe and the United States. Three quarries were visited in the metropolitan region of São Paulo, where preliminary exposure assessments were performed followed by a quantitative survey of aren factors (acceleration resulting from normalized exposure) and VDVR (resulting dose of vibration). Altogether, it was analyzed 22 equipment involving off-road trucks, excavators, shovel loaders, drills, breakers and water trucks. Most of the equipment studied was above the action level established by the NHO-09 (occupational hygiene standard) and some even above the exposure limit. The equipment with the highest indexes of Whole-Body Vibration found were the loader and the lowest, drills.

Lower back disorders due to whole-body vibration (WBV) are the most common injuries reported by professional drivers. Such injuries often have long-term complications leading to significant personal and societal costs. An improved mathematical model of the whole human body would contribute to a better understanding of the mechanisms of lower back injury and be valuable in injury prevention research. Current biodynamic human models reported in the literature lack detailed information for predicting the non-linearity due to vibration amplitude of transmission of vibration from seat to a human. Therefore, one of the primary objectives of this research has been to develop and validate a detailed threedimensional biodynamic human model, with special attention given to the incorporation of active trunk muscles with non-linear stiffness properties. These muscles have been incorporated into an existing spine and neck model of a MADYMO 50th percentile male occupant model. A detailed multi-body human model has been developed, called MODEL ONE. This thesis shows that incorporating non-linear stiffness functions and energy dissipation using hysteresis or damping into a human model is appropriate for predicting non-linear biodynamic responses in arbitrary excitation functions. A major advantage of MODEL ONE compared to other multi-body models and lumped mass models is its ability to predict nonlinear seat-to-human transmissibility. However MADYMO 50th male occupant models use simplified geometry and rigid bodies to represent the lower lumbar spine. These simplified spinal models have no ability to simulate the internal stresses and deformations of soft tissues, even if these are the apparent cause of lower back pain (LBP). Therefore a detailed finite element human lower lumbar spine model - with appropriate material properties and capable of simulating internal stresses⎯is necessary, in order to better understand spinal injuries under WBV. A three-dimensional finite element model of a lower lumbar spine motion segment - called MODEL TWO - has thus been developed for the present study. MODEL TWO comprises a detailed geometric description of vertebrae, nucleus pulposus, endplates, and intervertebral discs. The intervertebral discs lump together the annulus fibrosus, ground substance and ligaments. The vertebrae have been assumed to be rigid. The material properties of the intervertebral discs of MODEL TWO were obtained from test matrices and from various parameter data reported in the literature. MODEL TWO has been validated against cadaveric experiments reported in the literature. The mechanical behaviour and stress distribution within the MODEL TWO intervertebral disc agree reasonably well with the cadaveric experiments. MODEL TWO was integrated into MODEL ONE to form a new human model, called MODEL THREE, which was subsequently dynamically validated against volunteers� responses to WBV reported in the literature. MODEL THREE, as presented in this thesis, consists of a multi-body human model with detailed representation of a finite element (FE) lower lumbar spine. As far as the author is aware, MODEL THREE is the first model with detailed representation of a FE lower lumbar spine to successfully demonstrate that it is capable of simulating the stress profile of the entire intervertebral disc and endplate region due to WBV. The simulated results revealed abnormal stress concentrations in both the posterior and xviii the posterolateral annulus. The stresses increased most in the posterolateral intervertebral discs region during WBV, suggesting a possible mechanism for disc mechanical overload leading to fatigue fracture and degeneration. The results from MODEL THREE are promising and lead to a more comprehensive understanding of the behaviour of the intervertebral disc under WBV. MODEL THREE has also provided a good foundation for the development of a bio-fidelity human model. However, implementation of currently unavailable and/or inadequate in vitro and in vivo experimental studies is needed to further validate and develop MODEL THREE. A better understanding of injury mechanisms and the clinical significance of LBP will ultimately be arrived at using a combination of analytical models with in vitro and in vivo experimental data.

An emerging non-pharmacological treatment for bone degenerative diseases is whole body vibration (WBV), a mechanical signal composed of low-magnitude, high-frequency (LMHF) vibrations that when applied to bone, have osteogenic and anti-resorptive effects. Currently, the cellular and molecular mechanism underlying the effect of WBV on bone is unclear. In this study, we investigated the response of osteocytes, the putative mechanosensor in bone, under LMHF vibration. As bone cells differentiate from mesenchymal stromal cells (MSCs), we also studied the osteogenic differentiation of rat MSCs in the presence of vibration loading. We found that vibrated osteocytes show gene and protein expression changes suggestive of an anti-osteoclastogenic response, and secrete soluble factors that inhibit osteoclast formation and activity. In contrast, rat MSCs showed moderate to no response to LMHF vibration during osteogenic differentiation. Our data suggest that in vivo effects of LMHF vibration are mediated through mechanosensing and biochemical responses by osteocytes.

An emerging non-pharmacological treatment for bone degenerative diseases is whole body vibration (WBV), a mechanical signal composed of low-magnitude, high-frequency (LMHF) vibrations that when applied to bone, have osteogenic and anti-resorptive effects. Currently, the cellular and molecular mechanism underlying the effect of WBV on bone is unclear. In this study, we investigated the response of osteocytes, the putative mechanosensor in bone, under LMHF vibration. As bone cells differentiate from mesenchymal stromal cells (MSCs), we also studied the osteogenic differentiation of rat MSCs in the presence of vibration loading. We found that vibrated osteocytes show gene and protein expression changes suggestive of an anti-osteoclastogenic response, and secrete soluble factors that inhibit osteoclast formation and activity. In contrast, rat MSCs showed moderate to no response to LMHF vibration during osteogenic differentiation. Our data suggest that in vivo effects of LMHF vibration are mediated through mechanosensing and biochemical responses by osteocytes.

Low back disorders (LBDs) are the most common musculoskeletal problem among farmers, with higher prevalence rates than in other occupations. Operators of tractors and other farm machinery such as combines and all terrain vehicles (ATV) can have considerable accumulation of exposure to whole body vibration (WBV). The causal relationship between LBDs and WBV is not fully clear; however, it may be different among farmers as their work context and exposure is unique. Objectives: The objectives of the two studies which form two manuscripts or chapters in this thesis were to: 1) investigate the associations between WBV and LBDs among farmers using a) systematic review (manuscript 1) and cohort studies (manuscript 2). Methods: Objective 1: Nine databases were searched using groups of terms for two concepts: ‘farming’ and ‘low back disorder’. Screening, data extraction and quality assessment was performed by two reviewers independently. The population was adult farmers or agricultural workers globally irrespective of sex. The intervention was considered to be WBV exposure, such tractor, combine and ATV use. The control was no exposure or low exposure to WBV and the outcome was low back disorders. No limits in date of publication and type of study design were applied in the literature search, and only full text, English language studies were considered. Objective 2: The data source was the Saskatchewan Farm Injury Cohort Study. In 2007, baseline data were collected on accumulated yearly tractor, combine, ATV operation, as well as several biopsychosocial covariates thought to be associated with LBDs. Follow-up data on LBDs and related symptoms were collected during 2013 (6 year follow-up) and 2014 (1-year). This resulted in two datasets for each of two cohorts: 1) the first cohort with 1,149 farm people who had been followed for six years, and 2) the second with 605 participants who had been followed for one year. Generalized estimating equation-modified Poisson regressions were performed with low back and hip symptoms as the outcome. Results: Objective 1: After 276 full texts screened, we found 12 articles which analyzed WBV as a risk factor for LBD. Three were case-control, 6 cross-sectional and 3 retrospective cohorts. Four studies showed no association between WBV and LBDs, 4 studies showed a positive association and for the remaining 4 studies, results were mixed depending on the exposure or the outcome measure. Objective 2: The adjusted model in cohort 1 found LBDs to be associated to tractor operation for 1-150 hrs/year (RR=1.23, 95%CI 1.05-1.44), 151-400 hrs/year (RR=1.32, 95%CI 1.14-1.54) and 401+ hrs/year (RR=1.34, 95%CI 1.15-1.56). In addition, tractor operation for 151-400 hrs/year (RR=1.95, 95%CI 1.45-2.62) and 401+ hrs/year (RR=1.79, 95%CI 1.32-2.45) was also found to be related to hip symptoms. Although combine operation ≥ 61 hrs/year and ATV operation 81+ days/year was related to LBD in the bivariate analysis in cohort 1, this association did not persist after adjustment for confounders. Due to limited power, no significant bivariate association was found between WBV and either LBDs and hip symptoms in cohort 2. Conclusions: Objective 1: A firm conclusion is difficult due to heterogeneity in statistical strategy, LBDs definition, type of farm commodity, and study design. Direct comparisons and synthesis were not possible. Although retrospective cohort studies tended to show a relationship, future studies with a prospective cohort design can help clarify this association further. Objective 2: Although duration of tractor operation and older age showed with both LBDs and hip symptoms in farmers in cohort 1, the true prospective cohort 2 found no significant association between WBV and LBDs.

No description available.

Introduction: Occupational drivers of terrain vehicles are exposed to several risk factors associated with musculoskeletal symptoms in the lower back as well as in the neck and upper limbs. Vibration has been suggested to be a main risk factor. These drivers are exposed to both whole-body vibration (WBV) and hand-arm vibration (HAV). Aim: This study establishes the association between driving terrain vehicles and musculoskeletal disorders (MSDs) in the neck and upper limbs as well as hand-arm vibration syndrome (HAVS). In addition, this study examines the effect on muscles in the neck and upper limbs of the type of vibration exposure that occurs in occupational driving of terrain vehicles. Methods and results: In Paper I, a cross-sectional questionnaire study on occupational drivers of terrain vehicles, increased Prevalence Odds Ratios (POR) were found for numbness, sensation of cold and white fingers (POR 1.5-3.9) and for MSDs in the neck (POR 2.1-3.9), shoulder (POR 1.8-2.6) and wrist (POR 1.7-2.6). For the shoulders, neck and elbow, there appears to be a pattern of increased odds with increasing exposure time. In Paper II, an experimental study on the trapezius muscle, which included 20 men and 17 women, the mean frequency of the electromyography signal (EMGMNF) decreased significantly more in a three minute sub-maximal contraction without vibration (-3.71Hz and -4.37Hz) compared to with induced vibration (-3.54Hz and -1.48Hz). In Paper III, a higher initial increase of the mean of the root-mean-square of the electromyography signal (EMGRMS) was seen in a three minute sub-maximal contraction with vibration exposure compared to without vibration (0.096% vs. 0.045%). There was a larger mean EMGMNF decrease for NV compared to V in the total three minutes, and a larger decrease also in the first time period was seen for the NV compared to V. A small gender effect was also noticed. In Paper IV, the combination of HAV and WBV was studied in laboratory settings and resulted in a higher trapezius EMGRMS compared to the HAV and WBV separately. Conclusion: Occupational drivers of terrain vehicles are likely to experience symptoms related to HAVS and musculoskeletal symptoms in the neck and upper limbs. Local vibration does not seem to have any negative acute effects on trapezius muscle fatigue. Vibration exposure seems to cause an initial increase in muscle activity in the trapezius that could be related to recruitment on new motor-units. A combination of HAV and WBV causes a larger muscular demand on the trapezius muscle.

No description available.