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Effect of Vibration
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
J. E. Smeathers, P. S. Helliwell
The preferred unit for describing the magnitude of a particular vibration is acceleration in (m/s2). Acceleration is the rate of change of velocity, which in turn is the rate of change in displacement. So for a given acceleration a at frequency f, the velocity ν and displacement d will be
Acceleration physiology
Published in Nicholas Green, Steven Gaydos, Hutchison Ewan, Edward Nicol, Handbook of Aviation and Space Medicine, 2019
Nicholas Green, Steven Gaydos, Hutchison Ewan, Edward Nicol
Linear acceleration: Change of speed without change in direction.For example, aircraft takeoff, spacecraft re-entry.
Data smoothing, filtering and processing
Published in Paul Grimshaw, Michael Cole, Adrian Burden, Neil Fowler, Instant Notes in Sport and Exercise Biomechanics, 2019
A further problem with using noisy data, such as that depicted in Figure G8.1, for an analysis is that the error that is present in this measure will ultimately influence the accuracy of other measures that are derived from it. For example, just as velocity is the rate of change of displacement, acceleration is the rate of change of velocity. As such, when acceleration data are derived from erroneous velocity data, these errors are further magnified in the accelerations.
Multi-scale numerical simulation on mechano-transduction of osteocytes in different gravity fields
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Chaohui Zhao, Haiying Liu, Congbiao Tian, Chunqiu Zhang, Wei Wang
Bone loss cannot fully prevented by relying solely on adversarial exercises or nutritional supplements while in space (White and Averner 2001).Therefore, fundamental understanding of the mechanical factors of continuous bone loss under microgravity is required. The exertion of various physiological functions of osteocytes is inextricably linked to their perception and response to the changes of the surrounding mechanical microenvironment. In addition, osteocytes are very sensitive to the surrounding environment, and the changes in micro-environmental structure, biochemical composition and mechanical stimulation can greatly impact the structure and function of osteocytes (Ren et al. 2014). During space flight, the weight of the human body provides only centripetal acceleration for its circular motion in orbit. Therefore, a part of bodily fluids transfer from the legs to the upper body as a result of losing the influence of gravity, which directly leads to the decrease of the vascular content and pressure in the legs and the increase of the related parameters in the upper body (Watenpaugh 1996). Under microgravity conditions, the gravity gradient in the load-bearing bones disappears and the mechanical micro-environment of osteocytes changed. In addition, the ability of osteocytes to conduct mechanical signals decreases, which leads to osteoporosis due to the imbalance of bone remodeling regulated by osteocytes.
Pulsatile flow of thixotropic blood in artery under external body acceleration
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Louiza Cheffar, Abdelhakim Benslimane, Djamel Sadaoui, Adel Benchabane, Karim Bekkour
In most cases, arteries are assumed to be immobile, i.e. under normal physiological conditions. In this case, blood flow is driven by a biological pump: the heart producing a pulsatile pressure gradient in the cardiovascular system (Shit and Roy 2011). However, this excludes other important situations that occur in daily human life, in which the human body is subjected to external body acceleration, e.g. running, driving a vehicle, traveling in an airplane. A long exposure of body to such acceleration in time can leads to many health problems namely: increase in pulse rate, abdominal pain, venous pooling of blood in the extremities (Frolov et al. 2018). To this end, several researchers (Sud et al. 1983; Misra and Sahu 1988; Srivastava et al. 1994; Massoudi and Phuoc 2008) focused their studies on understanding blood flow in arteries under periodic body acceleration.
Accelerometer assessed upper limb activity in people with stroke: a validation study considering ambulatory and non-ambulatory activities
Published in Disability and Rehabilitation, 2022
Lucian Bezuidenhout, Conran Joseph, Ulrika Einarsson, Charlotte Thurston, Maria Hagströmer, David Moulaee Conradsson
Objective assessment through the use of accelerometers has therefore been proposed as a complimentary quantitative method for upper limb assessment [1,7–14]. Accelerometers measure mechanical movement (acceleration changes) due to body movement and yield primarily quantitative information such as frequency, duration and intensity of an activity [15]. The benefit of this method is its ability to monitor arm use in daily life over a prolonged period which may provide a more robust marker of the level of upper limb activity than clinical assessment of function at a single time point. Most previous studies exploring the use of accelerometers for upper limb assessment post stroke have used the vector magnitude (VM) for analyses, which incorporates all three directional components (vertical, horizontal and perpendicular) of arm movements in daily life [16]. The vector magnitude ratio (VMR, i.e., the relation of the VM of the affected side to the VM of the unaffected side with a value of 1 reflecting equal use of both limbs) is generally used when measuring upper limb activity in individuals post-stroke [17,18].