Gymnasts must attain extreme ranges of flexibility to execute performance requirements, thus effective stretching proves vital to advancement in the sport. This study examined the acute effects of whole-body vibration (WBV) on passive and dynamic flexibility in young, female gymnasts. Participants (n = 27, Junior Olympic levels 5-10) served as their own control. Measurements of passive and dynamic flexibility were obtained using the TOPS forward split testing method to examine passive flexibility and dynamic flexibility was measured via split jumps that were analyzed with video and Dartfish software. According to randomized order, all participants completed a stretching protocol either with the WBV platform turned on (VIB) or off (C) separated by 48 h. Participants performed 4 sets of three stretches on the WBV platform. An ANCOVA was performed (using height, weight, age, years of experience, and gymnastics level as covariates). Significant improvements were found in passive flexibility for both VIB and C conditions, but there was no significant difference between the two stretching conditions (p = 0.17). The maximum split jump decreased significantly from pre to post measurement in both the VIB (p < 0.0001) and C (p = 0.04) conditions. VIB decreased the split jump significantly more than C. Based on the results of our study, an acute session of static stretching or stretching with WBV immediately before performance decreases split jump performance. Therefore, this WBV protocol is not recommended immediately prior to gymnastics competition.

No description available.

Low back pain is a leading cause of disability and is associated with whole-body vibration exposure in industrial workers and military personnel. The pathophysiological mechanisms by which whole-body vibration causes low back pain have been studied in vivo, but there is little data that improve diagnosis of low back pain. The overall objective of this research was to elucidate diagnostic biomarkers associated with whole-body vibration. Hence, a rat model for vibration-induced inflammatory responses was developed. Von Frey filaments were used to determine the withdrawal threshold of the hind paw as a surrogate behavioral marker for pain. The concentration of nerve growth factor in the serum was measured every four days using an assay as a potential diagnostic biomarker for low back pain. In the first study, whole-body vibration was applied using a modified commercially available device at 8 or 12 Hz every other day for two weeks, following which animals recovered for one week. At the conclusion of the study, intervertebral discs were graded histologically for degeneration. The nerve growth factor concentration increased threefold in the 8 Hz group and twofold in the 12 Hz group and returned to baseline by the end of the recovery period for 12 Hz, but not 8 Hz. Mechanical sensitivity appeared to change over time due to habituation and not any effect of vibration and was inconclusive. There was no difference in intervertebral disc degeneration scores between groups. In the second study, rats were vibrated at 8 Hz every other day for two or four weeks. The concentrations of nine cytokines were determined in the longissimus muscle, spleen, and thymus using a multiplex assay. These cytokines were ranked according to their ability to differentiate vibrated and non-vibrated animals, and classification models were compared. Nerve growth factor serum concentration peaked on day 13, then returned to baseline on day 17. The withdrawal threshold in vibrated animals decreased throughout the study indicating greater sensitivity to the stimulus, a surrogate for increased pain. Several longissimus muscle and spleen cytokines were important in distinguishing vibrated animals from non-vibrated, while thymus cytokines and weeks of exposure were not significant.

No description available.

This paper will present an online approach for friction approximation to be utilized in con- cert with whole body control on humanoid robots. This approach allows humanoid robots with ankle mounted force-torque sensors to extrapolate information about the friction constraints at the hands during multi-contact poses without the addition of hardware to the platform. This is achieved by utilizing disturbance detection as a method of monitoring active forces at a single external point and deriving available friction force at said contact point in accordance with Coulomb's Law of Friction. First, the rigid body dynamics and required compliant humanoid model optimization are established which allow incorporation of friction constraints. These friction constraints are then informed by monitoring of external forces, which can be used as an indicator of slip based on tangential force. In practice, the robot with operational multi-contact whole body control is navigated to the desired contact surface and normal force only contact is initiated. Using an iterative coefficient estimation based on the achieved system forces, the robot tests the boundaries of its operable force range by inducing slip. Slip detection is utilized as the basis for coefficient estimation, which allows the robot to further understand its environment and apply appropriate forces to its contact points. This approach was implemented on a simple 3 link model to verify expected performance, and then on both the simulated model of Virginia Tech's ESCHER robot and in practice on the actual ESCHER platform. The proposed approach was able to achieve estimation of slip parameters, based largely on time spent measuring, actual friction coefficient, and the available contact force. Though the performance of the proposed approach is dependent on a number of variables, it was able to provide an operational parameter for the robot's whole body controller, allowing expansion of the support region without risking multi-contact slip. / Master of Science / This paper presents an approach for humanoid robots to use their hands to approximate the friction parameters of contact surfaces without prior knowledge of those parameters. This is accomplished as part of the robot’s control system and integrated into its balancing and movement operating system so that it may determine these parameters without ceasing operation. The proposed approach relies on the force sensors typically embedded in the ankles of bipedal robots as its sole force input, so no additional hardware need be added to the robot in order to employ this functionality. Once placed in contact, the robot is able to approximate the forces at its hand with these sensors, and use those approximate values as the basis for estimating the static friction coefficient of the system, in accordance with Coulomb’s Law of Friction. The robot’s onboard controller is able to utilize this information to ensure that it does not overestimate the available force that may be applied at the contact point, using prior knowledge of the robot model’s range of motion. In practice, the robot with this functionality is navigated to the desired contact surface and a hand contact that does not risk slip is initiated. Using an iterative coefficient estimation based on the achieved system forces, the robot tests the boundaries of its operable force range by inducing slip. Slip detection is utilized as the basis for coefficient estimation, which allows the robot to further understand its environment and apply appropriate forces to its contact points. This approach was implemented on a simple 3 link robot model to verify expected performance, and then on both the simulated model of Virginia Tech’s ESCHER robot and in practice on the actual ESCHER platform. The proposed approach was able to achieve estimation of slip parameters, based largely on time spent measuring, actual friction coefficient, and the available contact force. Though the performance of the proposed approach is dependent on a number of variables, it was able to provide an operational parameter for the robot’s whole body controller, allowing expansion of the support region without risking multi-contact slip.

With the recent interest in single fraction Stereotactic Body Radiation Therapy and the emerging prominence of the Rapid Arc radiotherapy technique capable of delivering a fast and accurate treatment, the in-field primary dose and out-of-field dose assessments are becoming increasingly important. Currently, full physics Monte Carlo calculations for dose calculations have been regarded as a ‘gold standard’ for dose assessments of the target and OAR (organ at risk). However, these Monte Carlo calculations require very long computation times. The current treatment planning methods provide shorter calculation times, but issues such as heterogeneities and model-based parameter calculations cause challenges and affect dose calculation accuracy. This thesis describes a new and fast dose estimation method leveraging parallel computing called EDK-SN, “Electron Dose Kernel-Discrete Ordinates”. This new method uses hybrid electron dose kernels driven by linear Boltzmann (discrete ordinates) photon transport method to carry out dose calculations. The method has proven effective for fast and accurate computations of out-of-field whole body dose calculations benchmarked to Monte Carlo with isotropic monoenergetic photon sources. This thesis accomplishes adaptation of clinical Varian phase space data for use with general Monte Carlo codes including MCNP, and mapping accurate phase space data into the application of optimized EDK-SN dose calculation method with a 15-year-old patient phantom. The EDK-SN method with improved source term modeling is demonstrated to fall within accuracy of the measured golden beam data for a clinical water phantom.

Vibration exposure can occur at work, commuting between home and work, and in leisure activities. Any form of transportation will expose humans to some degree of vibration. Exposure to vibration can cause health problems, but more likely comfort problems. Health problems are normally related to back pain. Comfort on the other hand is related to both physiological and psychological factors, which can have a wide range of effects from a general annoyance to a reduced work capability. The standard ISO 2631-1 (1997) provides a guidance, which can be used to measure, evaluate and assess effects of whole-body vibration to discomfort. The standard allows several interpretations, which can lead to different results, as the standard does not provide an explicit guidance for selecting which axes and locations to measure and which averaging method to use for evaluating the axes. The suggested averaging method is the root mean square (r.m.s.) method, but additionally vibration dose value (VDV) can be used. This can lead to different results, as VDV emphasises shocks more than the r.m.s. method. The standard guides to measure and evaluate at least the seat translational axes, but the additional nine axes from the seat, backrest and floor are not mandatory. However, this can result in a different comfort value, as the values from the measured axes are combined. So taking into account all possible interpretations the assessment can vary significantly for the same environment. The selection of the averaging method is not a technical issue, as both methods are supported by all commercial equipment. However, it is rare that more than three axes are possible to be measured with typical whole-body vibration measurement equipment, thus the majority of studies have published results based on only the seat translational axes. Especially the rotational axes have been missing in most studies. The full method (i.e. using all possible axes to calculate the comfort value) of ISO 2631-1 (1997) has been rarely used and there is very little information on how accurate the method is for assessing discomfort in a multi-axis environment. There are only a few studies that have used the full method, but there are no known studies which have actually validated the full ISO 2631-1 method. The objective of the thesis was to validate and, if necessary, to improve the full method of the ISO 2631-1 standard for evaluating discomfort from whole-body vibration in a multi-axis environment. It was assumed that the ISO 2631-1 method can be used to predict discomfort in practice, but there are a relatively low number of studies to confirm this. Frequency weightings have been the focus of many published studies and it was assumed that these are broadly correct. Other aspects of the ISO 2631-1 method are the focus of this thesis. The goal was to keep a backward compatibility to previous studies and the current commercial equipment, thus several limitations were defined for the improvement of the standard. Several laboratory experiments, field measurements, and field and laboratory trials were conducted to validate the standard method. At first it was concluded that practical equipment for measuring 12-axis data was needed as there was no commercial system available. The equipment and software was validated in two experiments, which showed that simple and affordable components could be used to develop equipment for the full method. Even though the standard does not include information about a six-axis sensor for measuring both translational and rotational axes, there was a method to validate the sensor. The first field study included measuring several machines using all twelve axes. The analysis showed that the seat and backrest translational axes will contribute about 90 % of the overall vibration total value of the standard method, thus very little justification was found for including the seat rotational and floor translational axes. Similar results were found based on the data from the previous 12-axis studies. It was also found that the neglected axes could be compensated with a factor for estimating the overall vibration total value including all twelve axes. As the overall vibration total value is directly related to the number of used axes, the compensating factors can be used to compare results which used different axes. The laboratory trial confirmed the results from the field study, and it was concluded that sufficient accuracy to predict discomfort can be achieved using just the seat translational axes, even though the correlation improved when more axes were included. It was found that the evaluation of discomfort was improved by the use of the frequency weighting curves and the r.m.s. averaging method. However, as the multiplying factors degraded correlation, it was concluded that a new set of factors should be calculated. The new factors showed that a higher emphasis on the seat horizontal axes should be given (x=2.7, y=1.8 and z=1.0). The new factors improved the correlation systematically for all subjects. The field trial showed a similar trend, where optimised multiplying factors improved the correlation, but it was also noted that different multiplying factors are required for different environments, thus a procedure to optimise the standard method to different environments was developed. The trial showed systematic behaviour and the optimised multiplying factors were best for all subjects and groups. Keywords: Discomfort, whole-body vibration, standard, ISO 2631-1, multi-axis, multiplying factors

MPH, Occupational Hygiene, Faculty of Health Sciences, University of the Witwatersrand / Introduction Locomotive operators in the mining industry are exposed to high levels of noise and vibration. There is currently limited information indicating whole-body vibration exposure levels conducted over an 8-hour time weighted average (TWA) exposure period; most of the available data are based on instantaneous measurements. The 10-Ton New Era locomotive was specifically designed with the focus on areas such as ergonomics, safety, future automation, productivity and flexibility of use. The locomotive has a single cab and can be driven and controlled with maximum visibility in the direction of travel. Most mining houses are converting from the use of the 10 Ton Goodman battery operated locomotive to the 10Ton New Era locomotive, hence the focus of noise and vibration measurements on the latter. Objectives This research report documents a project to measure noise and whole-body vibration exposure levels of locomotive operators working in an underground platinum mine. The objectives of the study are: • to describe the eight hour time weighted average occupational noise exposure levels of locomotive operators operating the 10-Ton New Era locomotive in an underground platinum mine over 2008 and 2009; • to describe personal whole-body vibration exposure levels of locomotive operators operating the 10-Ton New Era locomotive in an underground platinum mine over 2008 and 2009; and 5 • to determine whether personal noise and whole-body vibration exposure levels of locomotive operators operating the 10-Ton New Era locomotive in an underground platinum mine over 2008 and 2009 comply with national and international standards. Methods Personal noise and whole-body vibration exposure measurements were obtained from 21 underground locomotive operators. Measurements were conducted in accordance with the procedures described in the SANS 10083 standard for personal noise dosimetry and the ISO 2631-1 standard for whole-body vibration. Determination of likely health risks for the operators were based on a comparison of the measured time-weighted noise exposure levels with the South African OEL and the ACGIH threshold limit value; whole-body vibration levels were compared with the HGCZ limits presented in Annex B of the ISO 2631-1 standard and the EU directive daily exposure limits. Results The measured noise and whole-body vibration levels taken over an 8-hour TWA exposure period were higher when compared to national and international standards. The mean LTWA levels for noise was 66.5 dB(A) with 12.5% of the measurements exceeding the South African OEL of 85dB(A). 45% of the wholebody vibration measurements fell within the HGCZ indicating that whole-body vibration exposure on locomotive operators presents a moderate probability for an adverse health outcome. Discussion and Conclusion Locomotive operators are exposed to potentially harmful levels of noise and whole-body vibration. The Mine Health and Safety Act requires an employer to assess the health and safety risks that hazards pose to their employees, and to take reasonably practicable steps towards eliminating or controlling those risks. Like any other risks at a workplace, noise and whole-body vibration needs to be 6 identified and controlled, and the approach to be taken is one of a risk management

Vehicle occupants are typically exposed to unpleasant whole-body vibration (WBV) for extended period of time. It is well known that the transmission of unwanted vibration to the human body can lead to fatigue and discomfort. Moreover, the unwanted vibration normally distributed in the low-frequency range has been found as the main risk factor for lower back pain and lumbago, which seriously affect the health and working performance of occupants. Thus vibration cancellation on seats has attracted considerable interest in recent years. So far, for most vehicle seats, vibration isolation is achieved passively by using seat cushions and conventional energy absorbers, which have very limited performance in the low-frequency range. The work presented in this thesis forms a successful development and experimental study of an active seat and control algorithm for occupants’ WBV reduction under low frequency excitations. Firstly, a modelling study of the seat human subjects (SHS) and an extensive experimental measurement of the vibration transmissibility of a test dummy and vehicle seat are carried out. The biodynamic responses of SHS exposed to uncoupled vertical and fore-and-aft WBV is modelled. A comparison with the existing models is made and the results show that an improved fit with the aggregated experimental data is achieved. Secondly, an active seat is developed based upon the observations and understanding of the SHS and seat system. The characteristics of the active seat dynamics are identified through experimental tests found suitable for the development of an active seat to attenuate the vibration experienced by vehicle occupants. The vibration cancellation performance of the active seat is initially examined by feedforward plus proportional-integral (PI) control tests. Through these tests, the effectiveness of the actuators control authority is verified, but the limitations are also revealed. Because the active seat system is subject to non-linear and time-varying behaviour, a self-tuning fully adaptive algorithm is a prime requirement. The Filtered-x Least-Mean-Square (FXLMS) algorithm with the Fast-block LMS (FBLMS) system identification technique is found suitable for this application and is investigated through experimental tests. Substantial vibration reductions are achieved for a variety of input vibration profiles. An excellent capability of the active seat and control system for efficiently reducing the vibration level of seated occupants under low-frequency WBV is demonstrated.

Thermogenic brown adipose tissue generates heat via mitochondrial uncoupling protein-1 (UCP-1), increases whole-body energy expenditure and may protects against obesity and metabolic disorders. White adipocytes store excess energy in the form of triglycerides. UCP-1 positive adipocytes develop within white adipose tissue (beige or brite adipocytes) in response to cold exposure or β3 adrenergic agonists. It was known that beige adipocytes arise from a distinct lineage compared with brown adipocytes, but the developmental origin of the beige adipocytes is still unclear. Signaling pathways that control beige adipocyte determination and formation are essentially unknown. Here, we identified a novel signaling pathway that regulates the lineage specification of beige adipocytes. Bone morphogenetic protein 7 (BMP7), a known brown adipogenesis inducer, suppresses Rho-GTPase kinase (ROCK) and depolymerizes F-actin (filamentous actin) into G-actin (globular actin) in mesenchymal stem cells. G-actin regulates myocardin-related transcription factor A (MRTFA) that co-transactivates serum response factor (SRF) and promotes smooth muscle cell differentiation in various organs. Subcutaneous white adipose tissue from MRTFA-/- mice had enhanced accumulation of UCP-1+ adipocytes and elevated levels of brown-selective proteins. Compared with wild type (WT) controls, MRTFA-/- mice exhibited improved metabolic profiles and were protected from diet-induced obesity and insulin resistance, suggesting that the beige adipocytes are physiologically functional. Compared to WT mice, stromal vascular cells from MRTFA-/- mice expressed higher levels of distinct beige progenitor markers and reduced levels of smooth muscle markers. Our studies demonstrate a novel ROCK-actin-MRTFA/SRF pathway that contributes to the development of beige adipocytes.