The effects of whole-body vibration on the cross-transfer of strength

This study investigated whether the use of superimposed whole-body vibration (WBV) during cross-education strength training would optimise strength transfer compared to conventional cross-education strength training. Twenty-one healthy, dominant right leg volunteers (21±3 years) were allocated to a strength training (ST, m = 3, f = 4), a strength training with WBV (ST + V, m = 3, f = 4), or a control group (no training, m = 3, f = 4). Training groups performed 9 sessions over 3 weeks, involving unilateral squats for the right leg, with or without WBV (35 Hz; 2.5mm amplitude). All groups underwent dynamic single leg maximum strength testing (1RM) and single and paired pulse transcranial magnetic stimulation (TMS) prior to and following training. Strength increased in the trained limb for the ST (41%; ES = 1.14) and ST + V (55%; ES = 1.03) groups, which resulted in a 35% (ES = 0.99) strength transfer to the untrained left leg for the ST group and a 52% (ES = 0.97) strength transfer to the untrained leg for the ST + V group, when compared to the control group. No differences in strength transfer between training groups were observed (P = 0.15). For the untrained leg, no differences in the peak height of recruitment curves or SICI were observed between ST and ST + V groups (P = 1.00). Strength training with WBV does not appear to modulate the cross-transfer of strength to a greater magnitude when compared to conventional cross-education strength training.

Whole-body vibration and occupational physical performance: a review

Introduction: In the occupational environment, there are a considerable number of stressors that can affect physical performance in job tasks. Whole-body vibration (WBV), which arises from vehicle transit, is one such stressor that has been demonstrated to alter human function in several ways. This study identifies the known physical changes to human function which result from WBV, to comment on changes which may translate to performance in physically demanding occupational tasks. Methods: A systematic review is performed on the literature relating to changes in the neuromuscular, physiological and biomechanical properties of the human body, when exposed to WBV. Selection criteria are constructed to synthesise articles which strictly relate to in-vehicle WBV and physical responses. Results: In total, 29 articles were identified which satisfied the criteria for inclusion. A range of physical responses produced from WBV are presented; however, little consistency exists in study design and the responses reported. Discussion: Given the inconsistency in the reported responses, the precise changes to human function remain unknown. However, there is sufficient evidence to warrant the design of studies which investigate occupationally relevant physical performance changes following WBV.

Maximal muscular vascular conductances during whole body upright exercise in humans

[EN] That muscular blood flow may reach 2.5 l kg(-1) min(-1) in the quadriceps muscle has led to the suggestion that muscular vascular conductance must be restrained during whole body exercise to avoid hypotension. The main aim of this study was to determine the maximal arm and leg muscle vascular conductances (VC) during leg and arm exercise, to find out if the maximal muscular vasodilatory response is restrained during maximal combined arm and leg exercise. Six Swedish elite cross-country skiers, age (mean +/-s.e.m.) 24 +/- 2 years, height 180 +/- 2 cm, weight 74 +/- 2 kg, and maximal oxygen uptake (VO(2,max)) 5.1 +/- 0.1 l min(-1) participated in the study. Femoral and subclavian vein blood flows, intra-arterial blood pressure, cardiac output, as well as blood gases in the femoral and subclavian vein, right atrium and femoral artery were determined during skiing (roller skis) at approximately 76% of VO(2,max) and at VO(2,max) with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise) and leg skiing (predominantly leg exercise). During submaximal exercise cardiac output (26-27 l min(-1)), mean blood pressure (MAP) (approximately 87 mmHg), systemic VC, systemic oxygen delivery and pulmonary VO2(approximately 4 l min(-1)) attained similar values regardless of exercise mode. The distribution of cardiac output was modified depending on the musculature engaged in the exercise. There was a close relationship between VC and VO2 in arms (r= 0.99, P < 0.001) and legs (r= 0.98, P < 0.05). Peak arm VC (63.7 +/- 5.6 ml min(-1) mmHg(-1)) was attained during double poling, while peak leg VC was reached at maximal exercise with the diagonal technique (109.8 +/- 11.5 ml min(-1) mmHg(-1)) when arm VC was 38.8 +/- 5.7 ml min(-1) mmHg(-1). If during maximal exercise arms and legs had been vasodilated to the observed maximal levels then mean arterial pressure would have dropped at least to 75-77 mmHg in our experimental conditions. It is concluded that skeletal muscle vascular conductance is restrained during whole body exercise in the upright position to avoid hypotension.

Continuous versus intermittent stochastic resonance whole body vibration and its effect on pelvic floor muscle activity

To determine the optimal stochastic whole body vibration (SR-WBV) load modality regarding pelvic floor muscle (PFM) activity in order to complete the SR-WBV training methodology for future PFM training with SR-WBV.

Whole-body vibration exposure study in U.S. railroad locomotives--an ergonomic risk assessment

Whole-body vibration exposure of locomotive engineers and the vibration attenuation of seats in 22 U.S. locomotives (built between 1959 and 2000) was studied during normal revenue service and following international measurement guidelines. Triaxial vibration measurements (duration mean 155 min, range 84-383 min) on the seat and on the floor were compared. In addition to the basic vibration evaluation (aw rms), the vector sum (av), the maximum transient vibration value (MTVV/aw), the vibration dose value (VDV/(aw T1/4)), and the vibration seat effective transmissibility factor (SEAT) were calculated. The power spectral densities are also reported. The mean basic vibration level (aw rms) was for the fore-aft axis x = 0.18 m/sec2, the lateral axis y = 0.28 m/sec2, and the vertical axis z = 0.32 m/sec2. The mean vector sum was 0.59 m/sec2 (range 0.27 to 1.44). The crest factors were generally at or above 9 in the horizontal and vertical axis. The mean MTVV/aw was 5.3 (x), 5.1 (y), and 4.8 (z), and the VDV/(aw T1/4) values ranged from 1.32 to 2.3 (x-axis), 1.33 to 1.7 (y-axis), and 1.38 to 1.86 (z-axis), generally indicating high levels of shocks. The mean seat transmissibility factor (SEAT) was 1.4 (x) and 1.2 (y) and 1 (z), demonstrating a general ineffectiveness of any of the seat suspension systems. In conclusion, these data indicate that locomotive rides are characterized by relatively high shock content (acceleration peaks) of the vibration signal in all directions. Locomotive vertical and lateral vibrations are similar, which appears to be characteristic for rail vehicles compared with many road/off-road vehicles. Tested locomotive cab seats currently in use (new or old) appear inadequate to reduce potentially harmful vibration and shocks transmitted to the seated operator, and older seats particularly lack basic ergonomic features regarding adjustability and postural support.

Acute effects of stochastic resonance whole body vibration

AIM: To investigate the acute effects of stochastic resonance whole body vibration (SR-WBV) training to identify possible explanations for preventive effects against musculoskeletal disorders. METHODS: Twenty-three healthy, female students participated in this quasi-experimental pilot study. Acute physiological and psychological effects of SR-WBV training were examined using electromyography of descending trapezius (TD) muscle, heart rate variability (HRV), different skin parameters (temperature, redness and blood flow) and self-report questionnaires. All subjects conducted a sham SR-WBV training at a low intensity (2 Hz with noise level 0) and a verum SR-WBV training at a higher intensity (6 Hz with noise level 4). They were tested before, during and after the training. Conclusions were drawn on the basis of analysis of variance. RESULTS: Twenty-three healthy, female students participated in this study (age = 22.4 ± 2.1 years; body mass index = 21.6 ± 2.2 kg/m2). Muscular activity of the TD and energy expenditure rose during verum SR-WBV compared to baseline and sham SR-WBV (all P < 0.05). Muscular relaxation after verum SR-WBV was higher than at baseline and after sham SR-WBV (all P < 0.05). During verum SR-WBV the levels of HRV were similar to those observed during sham SR-WBV. The same applies for most of the skin characteristics, while microcirculation of the skin of the middle back was higher during verum compared to sham SR-WBV (P < 0.001). Skin redness showed significant changes over the three measurement points only in the middle back area (P = 0.022). There was a significant rise from baseline to verum SR-WBV (0.86 ± 0.25 perfusion units; P = 0.008). The self-reported chronic pain grade indicators of pain, stiffness, well-being, and muscle relaxation showed a mixed pattern across conditions. Muscle and joint stiffness (P = 0.018) and muscular relaxation did significantly change from baseline to different conditions of SR-WBV (P < 0.001). Moreover, muscle relaxation after verum SR-WBV was higher than after sham SR-WBV (P < 0.05). CONCLUSION: Verum SR-WBV stimulated musculoskeletal activity in young healthy individuals while cardiovascular activation was low. Training of musculoskeletal capacity and immediate increase in musculoskeletal relaxation are potential mediators of pain reduction in preventive trials.

Stochastic Resonance Whole-Body Vibration Improves Postural Control in Health Care Professionals: A Worksite Randomized Controlled Trial

Slip, trip, and fall injuries are frequent among health care workers. Stochastic resonance whole-body vibration training was tested to improve postural control. Participants included 124 employees of a Swiss university hospital. The randomized controlled trial included an experimental group given 8 weeks of training and a control group with no intervention. In both groups, postural control was assessed as mediolateral sway on a force plate before and after the 8-week trial. Mediolateral sway was significantly decreased by stochastic resonance whole-body vibration training in the experimental group but not in the control group that received no training (p < .05). Stochastic resonance whole-body vibration training is an option in the primary prevention of balance-related injury at work.

Electromyographic activity of back muscles during stochastic whole body vibration

OBJECTIVES: Stochastic resonance whole body vibrations (SR-WBV) may reduce and prevent musculoskeletal problems (MSP). The aim of this study was to evaluate how activities of the lumbar erector spinae (ES) and of the ascending and descending trapezius (TA, TD) change in upright standing position during SR-WBV. METHODS: Nineteen female subjects completed 12 series of 10 seconds of SR-WBV at six different frequencies (2, 4, 6, 8, 10, 12Hz) and two types of "noise"-applications. An assessment at rest had been executed beforehand. Muscle activities were measured with EMG and normalized to the maximum voluntary contraction (MVC%). For statistical testing a three-factorial analysis of variation (ANOVA) was applied. RESULTS: The maximum activity of the respective muscles was 14.5 MVC% for the ES, 4.6 MVC% for the TA (12Hz with "noise" both), and 7.4 MVC% for the TD (10Hz without "noise"). Furthermore, all muscles varied significantly at 6Hz and above (p⋜0.047) compared to the situation at rest. No significant differences were found at SR-WBV with or without "noise". CONCLUSIONS: In general, muscle activity during SR-WBV is reasonably low and comparable to core strength stability exercises, sensorimotor training and "abdominal hollowing" in water. SR-WBV may be a therapeutic option for the relief of MSP.

Effects of whole body vibration on strength and jumping performance in volleyball and beach volleyball players

The primary aim of this study was to examine the effects of 6-week strength training with whole body vibration (WBV) on leg strength and jumping performance in volleyball and beach volleyball players. Twenty-three sub-elite male volleyball (VB; n=12) and beach volleyball players (BVB; n=11) aged 21.2±3.0 years were divided into two groups and subjected to 6 weeks of strength training (three one-hour sessions per week): (I) 12 players (6 VB and 6 BVB players) underwent training with WBV (30-40 Hz, 1.7-2.5 mm, 3.0-5.7 g), and (II) 11 players (6 VB and 5 BVB players) underwent traditional strength training. Squat jump (SJ) and countermovement squat jump (CMJ) measurements by the Ergo Tester contact platform and maximum leg press test (1RM) were conducted. Three-factor (2 time x 2 WBV use x 2 discipline) analysis of variance for SJ, CMJ and 1RM revealed a significant time main effect (p<0.001), a WBV use effect (p<0.001) and a discipline effect (p<0.001). Significantly greater improvements in the SJ (p<0.001) and CMJ (p<0.001) and in 1RM (p<0.001) were found in the WBV training groups than in traditional training groups. Significant 3-way interaction effects (training, WBV use, discipline kind) were also found for SJ, CMJ and 1RM (p=0.001, p<0.001, p=0.001, respectively). It can be concluded that implementation of 6-week WBV training in routine practice in volleyball and beach volleyball players increases leg strength more and leads to greater improvement in jump performance than traditional strength training, but greater improvements can be expected in beach volleyball players than in volleyball players.

Analysis of an Intervention to Reduce Truck Drivers' Exposure to Whole-Body Vibration

Thesis (Master's)--University of Washington, 2016-06

A lumped parameter model for the analysis of the motion of the muscles of the lower limbs under whole-body vibration

Through a lumped parameter modelling approach, a dynamical model, which can reproduce the motion of the muscles of a human body standing in different postures during Whole Body Vibrations (WBVs) treatment, has been developed. The key parameters, associated to the dynamics of the motion of the muscles of the lower limbs, have been identified starting from accelerometer measurements. The developed model can be usefully applied to the optimization of WBVs treatments which can effectively enhance muscle activation. © 2013 IEEE.