Transmission of whole body vibration - Comparison of three vibration platforms in healthy subjects

The Effects of Vibration Exposure on Lower-Limb Extensor Muscles' Stiffness, Elasticity, and Strength Responses in Untrained Young Individuals: A Randomized Controlled Trial

OBJECTIVES

The whole-body vibration (WBV) effects on muscle strength show inconsistent results. Moreover, there is no study about the WBV effect on stiffness, elasticity, and muscle strength. Therefore, the study aimed to examine the effect of WBV exposure with static squat posture on the stiffness, elasticity, and strength of the lower-limb extensor muscles.

MATERIAL AND METHODS

Forty healthy untrained young adults were divided into WBV and control groups. The experimental group received WBV exposure on 2 nonconsecutive days of the week, for 6 weeks. The MyotonPRO device was used for the assessment of the knee extensor and the ankle dorsiflexors' stiffness and elasticity. Isometric muscle strength was evaluated with a hand-held dynamometer. All measurements were done by the same assessor at baseline, and the following 6 weeks.

RESULTS

Significant group-by-time interactions were found for the elasticity scores of the right (d = 0.84, P = .01) and left (d = 0.77, P = .02) ankle dorsiflexors. Similar to the elasticity measurements, significant group-by-time interactions were observed in the muscle strength scores of the right (d = 0.45, P = .046) and left (d = 1.25, P < .001) ankle dorsiflexors. No significant effects were observed in any of the evaluated muscle stiffness measurements (P > .05), and there was no significant group-by-time interaction in knee-extensor muscle strength and elasticity scores (P > .05).

CONCLUSIONS

The study results indicate that if the ankle dorsiflexor strength and elasticity are desired to be increased, the 6-week WBV exposure in a static squat posture can be used in healthy individuals.

Effectiveness of whole-body vibration on bone mineral density in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials

The present study observed significant effects of whole-body vibration (WBV) on bone mineral density (BMD) in postmenopausal women, with high-quality evidence for high-frequency, low-magnitude, and high-cumulative-dose use. The aim was to update a previous systematic review with meta-analysis to observe the effects of WBV on BMD in postmenopausal women. For the meta-analysis, the weighted mean difference between WBV and control groups, or WBV and conventional exercise, was used for the area of bone mineral density (aBMD) of the lumbar spine, femoral neck, total hip, trochanter, intertrochanter, and Ward's area, or volumetric trabecular bone mineral density (vBMDt) of the radius and tibia. Methodological quality was assessed using the PEDro scale and the quality of evidence using the GRADE system. In total, 23 studies were included in the systematic review and 20 in the meta-analysis. Thirteen studies showed high methodological quality. WBV compared with control groups showed significant effects on aBMD in the primary analysis (lumbar spine and trochanter), sensitivity (lumbar spine), side-alternating vibration (lumbar spine and trochanter), synchronous vibration (lumbar spine), low frequency and high magnitude (lumbar spine and trochanter), high frequency and low magnitude (lumbar spine), high frequency and high magnitude (lumbar spine, trochanter, and Ward's area), high cumulative dose and low magnitude (lumbar spine), low cumulative dose and high magnitude (lumbar spine and trochanter), and positioning with semi-flexed knees (trochanter). Of these results, only high frequency associated with low magnitude and high cumulative dose with low magnitude showed high-quality evidence. At this time, considering the high quality of evidence, it is possible to recommend WBV using high frequency (≈ 30 Hz), low magnitude (≈ 0.3 g), and high cumulative dose (≈ 7000 min) to improve lumbar spine aBMD in postmenopausal women. Other parameters, although promising, need to be better investigated, considering, when applicable, the safety of the participants, especially in vibrations with higher magnitudes (≥ 1 g).

Short-term effects of side-alternating Whole-Body Vibration on cognitive function of young adults

Recent research in rodents and humans revealed that Whole-Body Vibration (WBV) is beneficial for cognitive functions. However, the optimal WBV conditions are not established: contrary to vertical WBV, side-alternating WBV was not investigated before. The present study investigated the short-term effects of side-alternating WBV in standing and sitting posture on specific cognitive function of young adults. We used a balanced cross-over design. Sixty healthy young adults (mean age 21.7 ± 2.0 years, 72% female) participated. They were exposed to three bouts of two-minute side-alternating WBV (frequency 27 Hz) and three control conditions in two different sessions. In one session a sitting posture was used and in the other session a standing (semi-squat) posture. After each condition selective attention and inhibition was measured with the incongruent condition of the Stroop Color-Word Interference Test. WBV significantly (p = 0.026) improved selective attention and inhibition in the sitting posture, but not in the standing posture. The sitting posture was perceived as more comfortable, joyous and less exhaustive as compared to the standing posture. This study demonstrated that side-alternating WBV in sitting posture improves selective attention and inhibition in healthy young adults. This indicates that posture moderates the cognitive effect of WBV, although the effects are still small. Future studies should focus on the working mechanisms and further optimization of settings, especially in individuals who are unable to perform active exercise.

The effect of whole-body vibration in osteopenic patients after total knee arthroplasty: a randomized controlled trial

BACKGROUND

Total knee arthroplasty (TKA) is an important treatment for knee osteoarthritis, but the result of whole-body vibration (WBV) in knee function rehabilitation and bone loss with osteopenia was unknown. Therefore, the purpose of this study is to study whether low-frequency, low-amplitude WBV can improve the clinical outcome of knee osteoarthritis.

METHODS

This study was randomized and included 67 osteopenic patients (55-90 years, 85% women) for TKA surgery (control group N = 32, WBV group N = 35). All selected patients after TKA surgery tested clinical results, such as knee function and bone mass in baseline, 3 months after surgery, and 6 months after surgery.

RESULTS

Compared to the control group, the WBV group improved pain scores, thigh circumference, lower limb muscle strength, joint activity, and joint function in 6 months after surgery. WBV intervention also improves bone density in the spine, the microstructure of the radius and tibia, and the bone turnover marker. At 3 months after TKA surgery, the WBV group had no significant effect on knee function and bone loss.

CONCLUSIONS

Whole-body vibration for osteopenic patients with knee arthroplasty showed good therapeutic results in 6 months after TKA surgery, but the long-term therapeutic effect still needs to be further observed.

Prediction of the natural frequencies of different degrees of degenerated human lumbar segments L2-L3 using dynamic finite element analysis

BACKGROUND AND OBJECTIVE

Chronic exposure to resonant environment may cause more serious injuries to human lumbar spine than other vibrations. On the condition that the natural frequency of human lumbar spine is known, excitation frequency from an external vibration source can be optimized to keep away from the natural frequency and thus avoid lumbar resonance. Therefore, this study aimed to present an approach to predict the natural frequency of the human lumbar spine.

METHODS

Four poroelastic finite element models of human L2-L3 spinal motion segments with different degrees of degeneration were established. Dynamic finite element analyses of these models during 1 h of vibration were then conducted. The mechanical parameters of these models under vibrations at different excitation frequencies were predicted. The excitation frequencies that resulted in the greatest changes in the lumbar mechanical parameters were identified as the natural frequencies of the established L2-L3 spinal motion segments.

RESULTS

Simulation results showed that the natural frequencies of the healthy and mildly degenerated L2-L3 spinal motion segments, moderately degenerated L2-L3 spinal motion segments, and seriously degenerated L2-L3 spinal motion segments were in the range of 5-7, 3-5, and 1-3 Hz, respectively.

CONCLUSIONS

The predicted results indicated that the natural frequencies of the human L2-L3 spinal motion segments gradually decreased with the severity of degeneration. These phenomena may be related to changes in the lumbar structures and materials because of degeneration. This study provided a feasible method to predict the lumbar natural frequencies for different populations, which may be helpful in optimizing external vibration sources to avoid lumbar resonance.

The Endothelium as a Therapeutic Target in Diabetes: A Narrative Review and Perspective

Diabetes has reached worldwide epidemic proportions, and threatens to be a significant economic burden to both patients and healthcare systems, and an important driver of cardiovascular mortality and morbidity. Improvement in lifestyle interventions (which includes increase in physical activity via exercise) can reduce diabetes and cardiovascular disease mortality and morbidity. Encouraging a population to increase physical activity and exercise is not a simple feat particularly in individuals with co-morbidities (obesity, heart disease, stroke, peripheral vascular disease, and those with cognitive and physical limitations). Translation of the physiological benefits of exercise within that vulnerable population would be an important step for improving physical activity goals and a stopgap measure to exercise. In large part many of the beneficial effects of exercise are due to the introduction of pulsatile shear stress (PSS) to the vascular endothelium. PSS is a well-known stimulus for endothelial homeostasis, and induction of a myriad of pathways which include vasoreactivity, paracrine/endocrine function, fibrinolysis, inflammation, barrier function, and vessel growth and formation. The endothelial cell mediates the balance between vasoconstriction and relaxation via the major vasodilator endothelial derived nitric oxide (eNO). eNO is critical for vasorelaxation, increasing blood flow, and an important signaling molecule that downregulates the inflammatory cascade. A salient feature of diabetes, is endothelial dysfunction which is characterized by a reduction of the bioavailability of vasodilators, particularly nitric oxide (NO). Cellular derangements in diabetes are also related to dysregulation in Ca²⁺ handling with increased intracellular Ca²⁺overload, and oxidative stress. PSS increases eNO bioavailability, reduces inflammatory phenotype, decreases intracellular Ca²⁺ overload, and increases antioxidant capacity. This narrative review and perspective will outline four methods to non-invasively increase PSS; Exercise (the prototype for increasing PSS), Enhanced External Counterpulsation (EECP), Whole Body Vibration (WBV), Passive Simulated Jogging and its predicate device Whole Body Periodic Acceleration, and will discuss current knowledge on their use in diabetes.