Evaluation of Vibration Analysis to Assess Bone Mineral Density in Children

The effectiveness of vibration analysis to assess bone mineral density (BMD) in children with suspected reduction in bone density was studied. A system was designed that measured the ulna's vibration responses in vivo. The system was evaluated on the ulnae of 48 children (mean age=12.0, std=3.5 years), 31 of whom had been confirmed to have osteogenesis imperfecta (OI). All children had dual energy X-ray absorptiometry (DXA) scan as part of their routine clinical care and vibration analysis was performed on the same day. Frequency spectra of the ulnae's vibration responses were obtained and processed by principal component analysis. Four main principal components were selected and together with age, sex and right hand ulna's length were used in a regression analysis to estimate BMD. Regression analysis was repeated using the children's leave-one-out and partitioning methods. The percentage similarity and correlation between the DXA-derived and vibration analysis estimated BMDs using the leave-one-out were 80.34% and 0.59 and for partitioning were 74.2% and 0.64 respectively. There was correlation between vibration analysis BMD readings and those derived from DXA however a larger study will be needed to better establish the extent to which vibration analysis can assist in assessing bone density in clinical environments

Understanding nonlinear vibration behaviours in high-power ultrasonic surgical devices

Ultrasonic surgical devices are increasingly used in oral, craniofacial and maxillofacial surgery to cut mineralized tissue, offering the surgeon high accuracy with minimal risk to nerve and vessel tissue. Power ultrasonic devices operate in resonance, requiring their length to be a half-wavelength or multiple-half-wavelength. For bone surgery, devices based on a half-wavelength have seen considerable success, but longer multiple-half-wavelength endoscopic devices have recently been proposed to widen the range of surgeries. To provide context for these developments, some examples of surgical procedures and the associated designs of ultrasonic cutting tips are presented. However, multiple-half-wavelength components, typical of endoscopic devices, have greater potential to exhibit nonlinear dynamic behaviours that have a highly detrimental effect on device performance. Through experimental characterization of the dynamic behaviour of endoscopic devices, it is demonstrated how geometrical features influence nonlinear dynamic responses. Period doubling, a known route to chaotic behaviour, is shown to be significantly influenced by the cutting tip shape, whereas the cutting tip has only a limited effect on Duffing-like responses, particularly the shape of the hysteresis curve, which is important for device stability. These findings underpin design, aiming to pave the way for a new generation of ultrasonic endoscopic surgical devices

Fatiguing Effects of Indirect Vibration Stimulation in Upper Limb Muscles- pre, post and during Isometric Contractions Superimposed on Upper Limb Vibration

© 2019 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/ , which permits unrestricted use, provided the original author and source are credited.Whole-body vibration and upper limb vibration (ULV) continue to gain popularity as exercise intervention for rehabilitation and sports applications. However, the fatiguing effects of indirect vibration stimulation are not yet fully understood. We investigated the effects of ULV stimulation superimposed on fatiguing isometric contractions using a purpose developed upper limb stimulation device. Thirteen healthy volunteers were exposed to both ULV superimposed to fatiguing isometric contractions (V) and isometric contractions alone Control (C). Both Vibration (V) and Control (C) exercises were performed at 80% of the maximum voluntary contractions. The stimulation used was 30 Hz frequency of 0.4 mm amplitude. Surface-electromyographic (EMG) activity of the Biceps Brachii, Triceps Brachii and Flexor Carpi Radialis were measured. EMG amplitude (EMGrms) and mean frequency (MEF) were computed to quantify muscle activity and fatigue levels. All muscles displayed significantly higher reduction in MEFs and a corresponding significant increase in EMGrms with the V than the Control, during fatiguing contractions (p < 0.05). Post vibration, all muscles showed higher levels of MEFs after recovery compared to the control. Our results show that near-maximal isometric fatiguing contractions superimposed on vibration stimulation lead to a higher rate of fatigue development compared to the isometric contraction alone in the upper limb muscles. Results also show higher manifestation of mechanical fatigue post treatment with vibration compared to the control. Vibration superimposed on isometric contraction not only seems to alter the neuromuscular function during fatiguing efforts by inducing higher neuromuscular load but also post vibration treatment.Peer reviewedFinal Published versio

Piezo-electromechanical smart materials with distributed arrays of piezoelectric transducers: Current and upcoming applications

This review paper intends to gather and organize a series of works which discuss the possibility of exploiting the mechanical properties of distributed arrays of piezoelectric transducers. The concept can be described as follows: on every structural member one can uniformly distribute an array of piezoelectric transducers whose electric terminals are to be connected to a suitably optimized electric waveguide. If the aim of such a modification is identified to be the suppression of mechanical vibrations then the optimal electric waveguide is identified to be the 'electric analog' of the considered structural member. The obtained electromechanical systems were called PEM (PiezoElectroMechanical) structures. The authors especially focus on the role played by Lagrange methods in the design of these analog circuits and in the study of PEM structures and we suggest some possible research developments in the conception of new devices, in their study and in their technological application. Other potential uses of PEMs, such as Structural Health Monitoring and Energy Harvesting, are described as well. PEM structures can be regarded as a particular kind of smart materials, i.e. materials especially designed and engineered to show a specific andwell-defined response to external excitations: for this reason, the authors try to find connection between PEM beams and plates and some micromorphic materials whose properties as carriers of waves have been studied recently. Finally, this paper aims to establish some links among some concepts which are used in different cultural groups, as smart structure, metamaterial and functional structural modifications, showing how appropriate would be to avoid the use of different names for similar concepts. © 2015 - IOS Press and the authors

Vibration as an exercise modality: how it may work, and what its potential might be

Whilst exposure to vibration is traditionally regarded as perilous, recent research has focussed on potential benefits. Here, the physical principles of forced oscillations are discussed in relation to vibration as an exercise modality. Acute physiological responses to isolated tendon and muscle vibration and to whole body vibration exercise are reviewed, as well as the training effects upon the musculature, bone mineral density and posture. Possible applications in sports and medicine are discussed. Evidence suggests that acute vibration exercise seems to elicit a specific warm-up effect, and that vibration training seems to improve muscle power, although the potential benefits over traditional forms of resistive exercise are still unclear. Vibration training also seems to improve balance in sub-populations prone to fall, such as frail elderly people. Moreover, literature suggests that vibration is beneficial to reduce chronic lower back pain and other types of pain. Other future indications are perceivable

RECORDING TECHNIQUES AND ANALYSIS OF THE ARTICULAR CRACK: A Critical Review of the Literature

Objective: To review the available literature pertaining to the recording and analysis of the joint crack/cavitation sound produced as a result of spinal manipulative therapy. A critical appraisal of the recording and analysis techniques is presented

Effects of different vibration frequencies, amplitudes and contraction levels on lower limb muscles during graded isometric contractions superimposed on whole body vibration stimulation

Background: Indirect vibration stimulation, i.e., whole body vibration or upper limb vibration, has been investigated increasingly as an exercise intervention for rehabilitation applications. However, there is a lack of evidence regarding the effects of graded isometric contractions superimposed on whole body vibration stimulation. Hence, the objective of this study was to quantify and analyse the effects of variations in the vibration parameters and contraction levels on the neuromuscular responses to isometric exercise superimposed on whole body vibration stimulation. Methods: In this study, we assessed the 'neuromuscular effects' of graded isometric contractions, of 20%, 40%, 60%, 80% and 100% of maximum voluntary contraction, superimposed on whole body vibration stimulation (V) and control (C), i.e., no-vibration in 12 healthy volunteers. Vibration stimuli tested were 30 Hz and 50 Hz frequencies and 0.5 mm and 1.5 mm amplitude. Surface electromyographic activity of the vastus lateralis, vastus medialis and biceps femoris were measured during V and C conditions with electromyographic root mean square and electromyographic mean frequency values used to quantify muscle activity and their fatigue levels, respectively. Results: Both the prime mover (vastus lateralis) and the antagonist (biceps femoris) displayed significantly higher (P < 0.05) electromyographic activity with the V than the C condition with varying percentage increases in EMG root-mean-square (EMGrms) values ranging from 20% to 200%. For both the vastus lateralis and biceps femoris, the increase in mean EMGrms values depended on the frequency, amplitude and muscle contraction level with 50 Hz-0.5 mm stimulation inducing the largest neuromuscular activity. Conclusions: These results show that the isometric contraction superimposed on vibration stimulation leads to higher neuromuscular activity compared to isometric contraction alone in the lower limbs. The combination of the vibration frequency with the amplitude and the muscle tension together grades the final neuromuscular output.Peer reviewe

Vibration transmission through the human spine during physical activity

Osteoporosis causes bone to become fragile. Pharmacological treatments of osteoporosis are burdened with adverse effects and increase bone mineral density (BMD) only between 1% and 15% depending on the drug and time used. Thus non pharmacological treatments are needed to complement pharmacological ones. Physical activity is a non pharmacological treatment of osteoporosis and is essential for maintaining bone health at any age. However, physical activities have been identified to produce a modest improvement of spinal strength or just preserve it. In addition, it is not known how much exercise is optimal and safe for people with spinal osteoporosis. Most research employs conflicting definitions of physical activity and measure the effect of exercise on BMD alone instead of combining it with measurements of three dimensional bone strength. There is the need to offer a technique to measure the effect of physical activity on the overall strength of the spine, not only on its bone mineral content. Vibration transmissibility is a measurement of the mechanical response of a system to vibration expressed as stiffness or damping, thus offering a variable that represents structural strength. It can be employed to measure the mechanical response of the human spine during physical activity by attaching inertial sensors over the spine. However, it has not been employed to characterize the way vibration is transmitted through the osteoporotic spine during physical activity. Understanding the effects of osteoporosis and ageing on vibration transmission is important since such effects are related to the stiffness of the spine and thus very likely to the incidence of vertebral fractures. It is also often recommended that fast walking is beneficial to the bone, yet it is not known if fast walking affects the mechanical response of the spine of people with osteoporosis. The aims of this study were (1) to evaluate the feasibility of employing inertial sensors and a skin correction method to measure vibration transmission through the spine during physical activity (2) to characterize the transmission of vibration in the lumbar and thoracic spines of people with and without osteoporosis during physical activities, (3) to characterize the effect of osteoporosis on vibration transmissibility at levels of the thoracic spine which are known to fracture and (4) to investigate the effects of fast walking on vibration transmissibility. 100 young and healthy and older volunteers with and without osteoporosis were recruited. Participants were asked to perform straight walking, stair negotiation and turning while having inertial sensors attached to the skin over the spinous process of the first sacral (S1), twelfth (T12), eighth (T8) and first thoracic vertebrae (T1). Vibration transmissibility was calculated as the square root of the acceleration of the output (T12 for the lumbar and T1 for the thoracic spine) over the input (S1 for the lumbar and T12 for the thoracic spine) in the frequency spectrum. Vibration transmissibility was corrected for the movement of the skin-sensor interface and for the inclination of the sensor over the spine of every subject. All physical activities were performed at self selected normal and fast walking speeds. Lumbar and thoracic curvatures were determined with an electromagnetic device and BMD was measured through quantitative ultrasound. Skin measurement of transmission of vertical vibration is feasible with the inertial sensors and correction method presented. Vibration transmissibility through the human spine is significantly different between dissimilar physical activities and frequency dependent. Ageing significantly alters the vibration transmissibility of the spine. Osteoporosis has a minimal effect on vibration transmissibility of the spine. The effect of ageing and osteoporosis are frequency dependent. Older lumbar spines may receive greater stimulation than young and healthy ones, whereas older thoracic spines may receive lower stimulation during fast walking. There are significant differences in vibration transmissibility between lumbar and thoracic spines. A percentage of vibration transmission of the lumbar and thoracic spines is determined by their curvatures. This thesis has provided a technique that future research can employ to correlate vibration transmissibility with mechanotransduction signals in bone as well as volumetric bone health measurements and the risk of vertebral fractures. Until then it will be possible to prescribe physical activity taking into account individual capabilities, bone strength and differences in mechanical response between lumbar and thoracic sections

Nonlinear model identification and spectral submanifolds for multi-degree-of-freedom mechanical vibrations

In a nonlinear oscillatory system, spectral submanifolds (SSMs) are the smoothest invariant manifolds tangent to linear modal subspaces of an equilibrium. Amplitude-frequency plots of the dynamics on SSMs provide the classic backbone curves sought in experimental nonlinear model identification. We develop here a methodology to compute analytically both the shape of SSMs and their corresponding backbone curves from a data-assimilating model fitted to experimental vibration signals. Using examples of both synthetic and real experimental data, we demonstrate that this approach reproduces backbone curves with high accuracy.Comment: 32 pages, 4 figure