Acute neuromuscular responses to whole-body vibration in healthy individuals: A systematic review

Whole-body vibration (WBV) training has been employed alongside conventional exercise like resistance training to enhance skeletal muscle strength and performance. This systematic review examines the evidence regarding the effect of WBV on muscle activity, strength, and performance in healthy individuals. The Academic Search Ultimate, CINAHL, Cochrane CENTRAL, PubMed, ProQuest One Academic and SCOPUS databases were searched from 1990 to April 2023 to retrieve relevant studies. Methodological quality was assessed using the Modified Downs and Black checklist, while the level of evidence was evaluated through the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool. Even though the quality of the included studies was moderate to high, the level of evidence was very low owing to serious concerns with three or more GRADE domains (risk of bias, inconsistency, indirectness, imprecision, and publication bias) for each outcome of interest across studies. The review suggests that in WBV training, using moderate to high vibration frequencies (25-40 Hz) and high magnitudes (3-6 mm) can enhance muscle activation and strength in pelvis and lower limb muscles. However, findings regarding WBV effect on muscle performance measures were inconsistent. Future research with robust methodology is necessary in this area to validate and support these findings.

Whole-body vibration reduces hamstrings neuromuscular function in uninjured individuals

OBJECTIVES

Despite the growing use of whole-body vibration (WBV) to enhance quadriceps neuromuscular function, the hamstrings-specific response is unclear among those without neuromuscular impairment, which is important to inform performance-based recommendations. Our objective was to determine the immediate and prolonged effects of WBV on hamstrings and quadriceps neuromuscular function in uninjured individuals.

DESIGN

Crossover.

SETTING

Laboratory.

PARTICIPANTS

Nineteen, recreationally active individuals performed WBV and control exercise protocols, consisting of six 1-min repetitions of isometric squats, on separate days in a randomized order.

MAIN OUTCOME MEASURES

Electromyographic (EMG) amplitude, antagonist-to-agonist co-activation, rate of torque development, and peak torque of the hamstrings and quadriceps were measured pre-, immediately post-, and 20 min post-condition. Percentage change scores were calculated from baseline to each post-measurement.

RESULTS

A condition main effect indicated that WBV reduced agonist semitendinosus EMG amplitudes more than the control (-12.1% vs. -1.5%, p < .001). Antagonist vastus medialis EMG amplitudes were reduced immediately, but not 20 min following WBV (-7.1% vs. 3.5%, p < .001).

CONCLUSIONS

WBV induced an inhibitory effect on medial hamstrings activity during knee flexion contraction in a majority of our sample, yet this response was not uniformly observed and its functional relevance remains unclear in an uninjured population.

Effect of whole-body vibration on neuromuscular activation and explosive power of lower limb: A systematic review and meta-analysis

OBJECTIVE

The review aimed to investigate the effects of whole-body vibration (WBV) on neuromuscular activation and explosive power.

METHODS

Keywords related to whole-body vibration, neuromuscular activation and explosive power were used to search four databases (PubMed, Web of Science, Google Scholar and EBSCO-MEDLINE) for relevant studies published between January 2000 and August 2021. The methodology of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses was used. The eligibility criteria for the meta-analysis were based on PICOST principles. Methodological assessment used the Cochrane scale. Heterogeneity and publication bias were assessed by I2 index and funnel plots, respectively. The WBV training cycle is a random effect model. Publication bias was also assessed based on funnel plots. This study was registered in PROSPERO (CRD42021279439).

RESULTS

A total of 156 participants data in 18 studies met the criteria and were included in the meta-analysis for quantitative synthesis. Results of the meta-analysis showed significant improvements in lower limb neuromuscular activation immediately after WBV compared with the baseline (SMD = 0.51; 95% CI: 0.26, 0.76; p<0.001), and no significant heterogeneity was observed (I2 = 38%, p = 0.07). In addition, the highest increase in lower limb explosive power was observed (SMD = 0.32; 95% CI: 0.11, 0.52; p = 0.002), and no significant heterogeneity (I2 = 0%, p = 0.80) was noted.

CONCLUSIONS

WBV training could improve neuromuscular activation and explosive power of the lower limb. However, due to different vibration conditions, further research should be conducted to determine standardized protocols targeting performance improvement in athletes and healthy personnel experienced in training.

Effects of Whole-Body Vibration Training with Different Body Positions and Amplitudes on Lower Limb Muscle Activity in Middle-Aged and Older Women

Purpose

The present study was designed to investigate the electromyographic (EMG) response in leg muscles to whole-body vibration while using different body positions and vibration amplitudes.

Methods:

An experimental study with repeated measures design involved a group of community-dwelling middle-aged and older women (n = 15; mean age=60.8 ± 4.18 years). Muscle activity of the gluteus maximus (GM), rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and gastrocnemius (GS) was measured by surface electromyography, which participants were performing three different body positions during three WBV amplitudes. The body positions included static semi-squat, static semi-squat with elastic band loading, and dynamic semi-squat. Vibration stimuli tested were 0 mm, 2 mm, and 4 mm amplitude and 30 Hz frequencies. And the maximum accelerations produced by vibration stimuli with amplitudes of 2 mm and 4 mm are approximately 1.83 g and 3.17 g.

Results:

Significantly greater muscle activity was recorded in VL, BF, and GS. When WBV was applied to training, compared with the same training without WBV (P < .05). There were significant main effects of body positions on EMGrms for the GM, RF, and VM (P < .05). Compared to static semi-squat, static semi-squat with elastic band significantly increased the EMGrms of GM, and dynamic semi-squat significantly increased the EMGrms of GM, RF and VM (P < .05). And there were significant main effects of amplitudes on EMGrms for the GM, RF, and VM (P < .05). The EMGrms of the VL, BF, and GS at 4 mm were significantly higher than 0 mm, and the EMGrms of the VL and BF at 4 mm were significantly higher than 2 mm. There was no significant body interaction between body positions and amplitudes (P > .05).

Conclusions:

The EMG amplitudes of most leg muscles tested were significantly greater during WBV exposure than in the no-WBV condition. The dynamic semi-squat 4 mm whole-body vibration training is recommended for middle-aged and older women to improve lower limb muscle strength and function.

Effects of Low-Frequency Whole-Body Vibration on Muscle Activation, Fatigue, and Oxygen Consumption in Healthy Young Adults: A Single-Group Repeated-Measures Controlled Trial

CONTEXT

Whole-body vibration (WBV) training improves muscle strength and balance. Few studies have focused on the effects of WBV frequencies below 30 Hz. We aimed to investigate the effect of low-frequency WBV training on muscle activity, fatigue recovery, and oxygen consumption (VO2).

DESIGN

Prospective single-group, repeated-measures study.

METHODS

In this controlled laboratory setting study, 20 healthy adults (age 23.26 [1.66] y) performed half squats at 0, 4, 6, 8, 12, 16, 20, 24, and 30-Hz WBV. Muscle activity was evaluated using the root mean square and peak electromyography amplitude of 6 muscles (iliocostalis, rectus abdominis, rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius) obtained via surface electromyography. VO2 was measured during the squats using a gas analyzer, and fatigue recovery was evaluated using measurements of lactate after the squats and after a recovery period. Statistical significance was set at P < .05, and analysis of variance was conducted to determine differences in muscle activity, fatigue, recovery, and VO2, with post hoc analyses as appropriate.

RESULTS

Of the 6 muscles measured, the muscle activity of the gastrocnemius alone significantly increased from 0 Hz at 4, 8, 12, 16, 24, and 30 Hz based on the root mean square values and at 4, 8, 12, and 30 Hz based on the peak electromyography amplitude values. There were no significant differences in the other muscles. There were no significant differences in VO2 or in lactate levels.

CONCLUSIONS

Low-frequency WBV during squat exercises significantly increased the activity of the gastrocnemius medialis only at specific frequencies in healthy young adults. Low-frequency WBV is safe and has the potential to increase muscle activity.

Characterisation of the transient mechanical response and the electromyographical activation of lower leg muscles in whole body vibration training

The aim of this study is to characterise the transient mechanical response and the neuromuscular activation of lower limb muscles in subjects undergoing Whole Body Vibration (WBV) at different frequencies while holding two static postures, with focus on muscles involved in shaping postural responses. Twenty-five participants underwent WBV at 15, 20, 25 and 30 Hz while in hack squat or on fore feet. Surface electromyography and soft tissue accelerations were collected from Gastrocnemius Lateralis (GL), Soleus (SOL) and Tibialis Anterior (TA) muscles. Estimated displacement at muscle bellies revealed a pattern never highlighted before that differed across frequencies and postures (p < 0.001). After stimulation starts, muscle oscillation peaks, drops and further stabilises, suggesting the occurrence of a neuromuscular activation to reduce the vibration-induced oscillation. The oscillation attenuation at the SOL muscle correlated with its increased activation (rho = 0.29, p < 0.001). Furthermore, only specific WBV settings led to a significant increase in muscle contraction: WBV-induced activation of SOL and GL was maximal in fore-feet (p < 0.05) and in response to higher frequencies (30 Hz vs 15 Hz, p < 0.001). The analysis of the mechanical dynamics of lower leg muscles highlights a resonant response to WBVs, that for the SOL correlates to the increased muscle activation. Despite differing across frequencies and postures, this resonant behaviour seems to discourage the use of dynamic exercises on vibrating platforms. As for the most efficient WBV combination, calf muscle response to WBVs is maximised if those muscles are already pre-contracted and the stimulation frequencies are in the 25–30 Hz range.

Impact of Local Vibration Training on Neuromuscular Activity, Muscle Cell, and Muscle Strength: A Review

This paper presents a review of studies on the effects of local vibration training (LVT) on muscle strength along with the associated changes in neuromuscular and cell dynamic responses. Application of local/direct vibration can significantly change the structural properties of muscle cell and can improve muscle strength. The improvement is largely dependent on vibration parameters such as amplitude and frequency. The results of 20 clinical studies reveal that electromyography (EMG) and maximal voluntary contraction (MVC) vary depending on vibration frequency, and studies using frequencies of 28-30 Hz reported greater increases in muscle activity in terms of EMG (rms) value and MVC data than the studies using higher frequencies. A greater muscle activity can be related to the recruitment of large motor units due to the application of local vibration. A greater increase in EMG (rms) values for biceps and triceps during extension than flexion under LVT suggests that types of muscles and their functions play an important role. Although a number of clinical trials and animal studies have demonstrated positive effects of vibration on muscle, an optimum training protocol has not been established. An attempt is made in this study to investigate the optimal LVT conditions on different muscles through review and analysis of published results in the literature pertaining to the changes in the neuromuscular activity. Directions for future research are discussed with regard to identifying optimal conditions for LVT and better understanding of the mechanisms associated with effects of vibration on muscles.

The Effect of Cycling-specific Vibration on Neuromuscular Performance

PURPOSE

This study aimed to provide an understanding of how surface-induced vibrations in cycling interfere with short-term neuromuscular performance.

METHODS

The study was conducted as a cross-sectional single cohort trial. Thirty trained cyclists participated (mass = 75.9 ± 8.9 kg, body height = 1.82 ± 0.05 m, V˙O2max = 63 ± 6.8 mL·kg-1⋅min-1). The experimental intervention included a systematic variation of the two independent variables: vibration (Vib: front dropout, 44 Hz, 4.1 mm; rear dropout, 38Hz, 3.5 mm; NoVib) and cranking power (LOW, 137 ± 14 W; MED, 221 ± 18 W; HIGH, 331 ± 65 W) from individual low to submaximal intensity. Dependent variables were transmitted accelerations to the body, muscular activation (gastrocnemius medialis, gastrocnemius lateralis, soleus, vastus lateralis, vastus medialis, rectus femoris, triceps brachii, flexor carpi ulnaris, and lumbar erector spinae), heart rate, and oxygen consumption.

RESULTS

The main findings show that the root-mean-square of local accelerations increased with vibration at the lower extremities, the torso, and the arms-shoulder system. The activation of gastrocnemius medialis, gastrocnemius lateralis, soleus, triceps brachii, and flexor carpi ulnaris increased significantly with vibration. The activation of vastus lateralis increased significantly with vibration only at HIGH cranking power. Oxygen consumption (+2.7%) and heart rate (+5%-7%) increased significantly in the presence of vibration.

CONCLUSIONS

Vibration is a full-body phenomenon. However, the impact of vibration on propulsion is limited as the main propulsive muscles at the thigh are not majorly affected. The demands on the cardiopulmonary and respiratory system increased slightly in the presence of vibration.

Effects of whole body vibration exercise on lumbar-abdominal muscles activation for patients with chronic low back pain

Background

Whole body vibration (WBV) training as an intervention method can cure chronic low back pain (CLBP). Different WBV parameters exert different effects on lumbar-abdominal muscle performance. Currently, there is a lack of study researched the influence of WBV training on patients with CLBP by lumbar–abdominal muscle activity. Therefore, this study aimed to investigate how WBV and exercise and their interactions influence lumbar-abdominal muscle activity in patients with CLBP.

Methods

a group of ambulatory patients with chronic low back pain. Muscle activities of the multifidus (MF), erector spinae (ES), abdominal oblique externus muscle (AOE) and the rectus abdominis muscle (RA) were measured by surface electromyography, whereas participants performed 4 different exercises (single bridge, plank, side stay and V crunch) during three whole body vibration conditions and a no-vibration condition in a single experimental session.

Results

Compared with the same exercises without whole body vibration, muscle activity increased when whole body vibration was added to the exercises. MF; the WBV frequency (P = 0.002,) and exercise (P < 0.001) presented significant effects on the root mean square of MF, whereas exercise * frequency (P = 0.044) also resulted in significant interaction effects. ES: the significant differences were detected at WBV frequency (P < 0.001), exercise (P < 0.001), the interaction effect of exercise and frequency (P = 0.225) was no significant. RA: the significant difference was detected at WBV frequency (P = 0.018), the effect of exercise (P = 0.590) and the exercise * frequency interaction (P = 0.572) were no significant. AOE: the significant difference was detected at WBV frequency (P < 0.001), the effect of exercise (P = 0.152) and the exercise * frequency interaction (P = 0.380) were no significant.

Conclusion

Adding whole body vibration to exercise could increase muscle activation of lumbar–abdominal muscle in patients with CLBP. The optimum frequency for lumbar–abdominal muscles is 15 Hz. The best exercises include plank for multifidus and erector spinae, V crunch for rectus abdominis and single bridge for abdominal oblique externus.

Clinical registration

Trial registration: ChiCTR-TRC-13003708. Registered 19 October 2013.

The code of ethical approval

2014008.

The effect of road-bike damping on neuromuscular short-term performance

The aim of this study was to understand if and how surface-induced vibrations and road bike damping affect short-term neuromuscular performance in cycling. Thirty cyclists (mass 75.9 ± 8.9 kg, height 1.82 ± 0.05 m, Vo2max 63.0 ± 6.8 ml/min/kg) performed steady-state and maximum effort tests with and without vibration exposure (front dropout: 44 Hz, 4.1 mm; rear dropout: 38 Hz, 3.5 mm) on a damped and a nondamped bike. Transmitted accelerations to the musculoskeletal system, activation of lower extremity muscles (gast. med., soleus, vast. med., rec. fem.) and upper body muscles (erec. spinae, deltoideus, tric. brachii), oxygen uptake, heart rate and crank power output were measured. The main findings indicate a transmission of vibration to the whole body, but since no major propulsive muscles increase their activation with vibration, the systemic energy demand increases only marginally with vibration. Damping reduces vibrations at the upper body, which indicates an increase in comfort, but has no effect on the vibration transfer to the lower extremities. Therefore, road bike damping does not affect neuromuscular response of the propulsive muscle groups and energy demand. Consequently, short-term power output does not increase with damping.

The effects of patellar tendon vibration on quadriceps strength in anterior cruciate ligament reconstructed knees

OBJECTIVES

To examine the immediate effects of prolonged patellar tendon vibration on quadriceps strength in anterior cruciate ligament reconstructed (ACLR) knees with bone-patellar tendon-bone (BTB) grafts and non-BTB grafts, and healthy control knees.

DESIGN

Pretest-posttest design.

SETTING

Laboratory.

PARTICIPANTS

Young adult participants were stratified into one of three groups: non-BTB graft (n = 25), BTB graft (n = 26), and controls without ACLR (n = 21).

MAIN OUTCOME MEASURES

Maximum voluntary isometric contraction (MVIC) knee extension torque was measured at baseline and following a 20-min vibration intervention applied locally to the patellar tendon.

RESULTS

Our findings suggest there was no difference in the effects of vibration on knee extension torque between the three groups. Knee extension torque significantly increased (effect size = 0.52 [0.18 to 0.81]) from baseline to post-vibration across all three groups (0.30 ± 0.26 Nm/kg, 21.8 ± 20.0%). Both ACLR groups demonstrated significantly lower knee extension torque compared the control group.

CONCLUSIONS

The vibration intervention had a net excitatory effect on quadriceps strength in all three groups and there were no differences in the magnitude of change between the three groups. Vibration could become a useful tool for enhancing quadriceps strength in ACLR and healthy knees.

The Peculiarities of Remodelling Muscle Tissue of Rats Under the Vibration Influence

Study of the influence of vibration oscillations of different frequency, amplitude and vibration acceleration on the structural and functional state and mechanisms of muscle tissue remodelling. An experimental study was conducted on sexually mature male rats. The rats of the four experimental groups were subjected to vertical vibration oscillations of 15, 25, 50 and 75 Hz, respectively. It has been established that pathological changes in muscle tissue in the form of different variants of damage and remodelling tend to increase, which correlates with the frequency of vibration, amplitude and vibration acceleration level, as in the 2nd group, where the maximum permissible vibration levels did not exceed the established allowable norms, and in other groups of animals, where the permissible levels of total vibration were exceeded. By increasing vibration acceleration for more than 1.25 m/s2 (0.13 g, frequency more than 25 Hz and amplitude of 2 mm), severe damages are observed in the form of alterative changes of muscle fibres with the disappearance of transverse strain, homogenization of sarcoplasm, fragmentation with dissociation fibres on separate beams, partial and subtotal myocytolysis, and necrosis of separate fibres. Inflammation is rapidly increasing with the increase in the frequency of vibration and the level of vibration acceleration for more than 5.0 m/s2 (0.51 g).

Whole-Body Vibration Improves Early Rate of Torque Development in Individuals With Anterior Cruciate Ligament Reconstruction

Pamukoff, DN, Pietrosimone, B, Ryan, ED, Lee, DR, Brown, LE, and Blackburn, JT. Whole body vibration improves early rate of torque development in individuals with anterior cruciate ligament reconstruction. J Strength Cond Res 31(11): 2992-3000, 2017-The purpose of this study was to compare the effect of whole-body vibration (WBV) and local muscle vibration (LMV) on early and late quadriceps rate of torque development (RTD), and electromechanical delay (EMD) in individuals with anterior cruciate ligament reconstruction (ACLR). Twenty individuals with ACLR were recruited for this study. Participants performed isometric squats while being exposed to WBV, LMV, or no vibration (control) in a randomized order during separate visits. Early and late quadriceps RTD and EMD were assessed during a maximal voluntary isometric knee extension before and immediately after WBV, LMV, or control. There was a significant condition by time interaction for early RTD (p = 0.045) but not for late RTD (p = 0.11) or EMD of the vastus medialis (p = 0.15), vastus lateralis (p = 0.17), or rectus femoris (p = 0.39). Post hoc analyses indicated a significant increase in early RTD after WBV (+5.59 N·m·s·kg; 95% confidence interval, 1.47-12.72; p = 0.007). No differences were observed in the LMV or control conditions, and no difference was observed between conditions at posttest. The ability to rapidly produce knee extension torque is essential to physical function, and WBV may be appropriate to aid in the restoration of RTD after ACLR.

Effects of whole-body vibration on muscle strength, bone mineral content and density, and balance and body composition of children and adolescents with Down syndrome: a systematic review

The aim of this study is to verify the effects of whole-body vibration (WBV) training on the muscle strength of children and adolescents with Down syndrome. We searched MEDLINE, Cochrane, SciELO, Lilacs and PUBMED databases and included manual searches to identify randomised controlled trials to investigate the effects of WBV on the structure and body function of children and adolescents with Down syndrome. Two reviewers independently selected the studies and performed statistical analysis. In total, five studies with 171 patients that compared WBV with exercise and/or control were included. Two studies demonstrated a significant difference between the muscle strength of children and adolescents with Down syndrome who received WBV training and that of those who did not receive the intervention. The studies included in this systematic review showed that WBV training has positive effects on bone mineral density (BMD), body composition and balance. Results of this study showed that WBV training improves muscle strength, BMD, body composition and balance of children and adolescents with Down syndrome, and a more in-depth analysis of its effects on other variables in this population is required, as well as of parameters to be used.

Effect of Whole-Body Vibration on Sagittal Plane Running Mechanics in Individuals With Anterior Cruciate Ligament Reconstruction: A Randomized Crossover Trial

OBJECTIVE

To examine the effect of whole-body vibration (WBV) on running biomechanics in individuals with anterior cruciate ligament reconstruction (ACLR).

DESIGN

Single-blind randomized crossover trial.

SETTING

Research laboratory.

PARTICIPANTS

Individuals (N=20) with unilateral ACLR (age [± SD]=22.3 [±3.3] years; mass=71.8 [±15.3] kg; time since ACLR=44.9 [±22.8] months; 15 females, 10 patellar tendon autograft, 7 hamstrings autograft, 3 allograft; International Knee Documentation Committee Score=83.5 [±9.3]).

MAIN OUTCOME MEASURE

Participants performed isometric squats while being exposed to WBV or no vibration (control). WBV and control conditions were delivered in a randomized order during separate visits separated by 1-week washout periods. Running biomechanics of the injured and uninjured limbs were evaluated before and immediately after each intervention. Dependent variables included peak vertical ground reaction force (GRF) and loading rate (LR), peak knee flexion angle and external moment, and knee flexion excursion during the stance phase of running.

RESULTS

There was an increase in knee flexion excursion (+4.1°, 95% confidence interval [CI]: 0.65, 7.5°) and a trend toward a reduction in instantaneous LR after WBV in the injured limb (-4.03 BW/sec^-1, 95% CI -0.38, -7.69). No effect was observed on peak GRF, peak knee flexion angle, or peak external knee flexion moment, and no effect was observed in the uninjured limb.

CONCLUSIONS

Our findings indicate that a single session of WBV acutely increases knee flexion excursion. WBV could be useful to improve running characteristics in individuals with knee pathology.

Effect of 6-weeks WBVT on the behaviour of the lower limb muscle fibres during vertical jumping

The purpose of the current study was to examine the effect of 6 weeks of whole body vibration training (WBVT) on body composition, muscle activity of the gastrocnemius and vastus lateralis, gastrocnemius muscle architecture (static and dynamic) and ground reaction forces (performance jump) during the take-off phase of a countermovement jump in young healthy adult males. A total of 33 men (23.31 ± 5.62 years) were randomly assigned to a whole body vibration group (experimental group, EG_WBVT: n = 17; 22.11 ± 4.97 years) or a control group (CG: n = 16; 24.5 ± 6.27 years). The total duration of the intervention phase (WBVT) was 6 weeks with a frequency of 3 sessions per week. Statistically significant differences were observed (P ≤ 0.05) between pre- and post-test in the power peak (Δ 1.91 W · kg^-1; P = 0.001), take-off velocity (0.1 cm · s^-1; P = 0.002) and jump height (Δ 0.4 cm; P = 0.002) for EG_WBVT. There were no statistically significant differences in any of the body composition and muscle architecture variables. Moreover, no significant differences were found between EG_WBVT and CG nor changes in muscle activity during take-off phase of the gastrocnemius and vastus lateralis pre- versus post-training. This study suggests that a 6-week WBVT programme with increasing intensity improves jump performance but does not alter muscle activity nor muscle architecture in healthy young men.

Energy Expenditure and Substrate Oxidation in Response to Side-Alternating Whole Body Vibration across Three Commonly-Used Vibration Frequencies

Background and Aim

There is increasing recognition about the importance of enhancing energy expenditure (EE) for weight control through increases in low-intensity physical activities comparable with daily life (1.5–4 METS). Whole-body vibration (WBV) increases EE modestly and could present both a useful adjuvant for obesity management and tool for metabolic phenotyping. However, it is unclear whether a “dose-response” exists between commonly-used vibration frequencies (VF) and EE, nor if WBV influences respiratory quotient (RQ), and hence substrate oxidation. We aimed to investigate the EE-VF and RQ-VF relationships across three different frequencies (30, 40, and 50Hz).

Methods

EE and RQ were measured in 8 healthy young adults by indirect calorimetry at rest, and subsequently during side-alternating WBV at one of 3 VFs (30, 40, and 50 Hz). Each frequency was assessed over 5 cycles of intermittent WBV (30s vibration/30s rest), separated by 5 min seated rest. During the WBV participants stood on the platform with knees flexed sufficiently to maintain comfort, prevent transmission of vibration to the upper body, and minimise voluntary physical exertion. Repeatability was assessed across 3 separate days in a subset of 4 individuals. In order to assess any sequence/habituation effect, an additional group of 6 men underwent 5 cycles of intermittent WBV (30s vibration/30s rest) at 40 Hz, separated by 5 min seated rest.

Results

Side-alternating WBV increased EE relative to standing, non-vibration levels (+36%, p<0.001). However, no differences in EE were observed across VFs. Similarly, no effect of VF on RQ was found, nor did WBV alter RQ relative to standing without vibration.

Conclusion

No relationship could be demonstrated between EE and VF in the range of 30-50Hz, and substrate oxidation did not change in response to WBV. Furthermore, the thermogenic effect of intermittent WBV, whilst robust, was quantitatively small (<2 METS).

The effect of vertical whole-body vibration on lower limb muscle activation in elderly adults: Influence of vibration frequency, amplitude and exercise

OBJECTIVE

This study aimed to investigate how whole-body vibration (WBV) and exercise and their interactions influenced leg muscle activity in elderly adults.

STUDY DESIGN

An experimental study with repeated measures design that involved a group of ambulatory, community-dwelling elderly adults (n=30; 23 women; mean age=61.4±5.3years).

MAIN OUTCOME MEASURES

Muscle activity of the vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GS) was measured by surface electromyography (EMG), while participants were performing seven different exercises during 4 WBV conditions (condition 1: frequency=30Hz, amplitude=0.6mm, intensity=2.25 units of Earth's gravity (g); condition 2: 30Hz, 0.9mm, 3.40g; condition 3: 40Hz, 0.6mm, 3.65g; condition 4: 40Hz, 0.9mm, 5.50g) and a no-WBV condition in a single experimental session.

RESULTS

Significantly greater muscle activity was recorded in VL (3%-148%), BF (16%-202%), and GS (19% -164%) when WBV was added to the exercises, compared with the same exercises without WBV (p≤0.015). The effect of vibration intensity on EMG amplitude was exercise-dependent in VL (p=0.002), and this effect was marginally significant in GS (p=0.052). The EMG activity induced by the four WBV intensities was largely similar, and was the most pronounced during static erect standing and static single-leg standing.

CONCLUSIONS

The EMG amplitude of majority of leg muscles tested was significantly greater during WBV exposure compared with the no-WBV condition. Low-intensity WBV can induce muscle activity as effectively as higher-intensity protocols, and may be the preferred choice for frail elderly adults.

Vibration mechanosignals superimposed to resistive exercise result in baseline skeletal muscle transcriptome profiles following chronic disuse in bed rest

Disuse-induced muscle atrophy is a major concern in aging, in neuromuscular diseases, post-traumatic injury and in microgravity life sciences affecting health and fitness also of crew members in spaceflight. By using a laboratory analogue to body unloading we perform for the first time global gene expression profiling joined to specific proteomic analysis to map molecular adaptations in disused (60 days of bed rest) human soleus muscle (CTR) and in response to a resistive exercise (RE) countermeasure protocol without and with superimposed vibration mechanosignals (RVE). Adopting Affymetrix GeneChip technology we identified 235 differently transcribed genes in the CTR group (end- vs. pre-bed rest). RE comprised 206 differentially expressed genes, whereas only 51 changed gene transcripts were found in RVE. Most gene transcription and proteomic changes were linked to various key metabolic pathways (glycolysis, oxidative phosphorylation, tricarboxylic acid (TCA) cycle, lipid metabolism) and to functional contractile structures. Gene expression profiling in bed rest identified a novel set of genes explicitly responsive to vibration mechanosignals in human soleus. This new finding highlights the efficacy of RVE protocol in reducing key signs of disuse maladaptation and atrophy, and to maintain a close-to-normal skeletal muscle quality outcome following chronic disuse in bed rest.

The EMG activity-acceleration relationship to quantify the optimal vibration load when applying synchronous whole-body vibration

PURPOSE

To date are lacking methodological approaches to individualizing whole-body vibration (WBV) intensity. The aim of this study was: (1) to determine the surface-electromyography-root-mean-square (sEMG(RMS))-acceleration load relationship in the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), lateral gastrocnemius (LG) muscles during synchronous WBV, and (2) to assess the reliability of the acceleration corresponding to the maximal sEMG(RMS).

METHODS

Twenty-five sportsman voluntarily took part in this study with a single-group, repeated-measures design. All subjects postured themselves in an isometric half-squat during nine trials in the following conditions: no vibrations and random vibrations of different acceleration loads (from 0.12 to 5.72 g).

RESULTS

The sEMG(RMS) were dependent on the acceleration loads in the VL (p = 0.0001), LG (p = 0.0001) and VM (p = 0.011) muscles; while RF was not affected by the acceleration loads (p = 0.508). The comparisons among the sEMG(RMS)-accelerations relationships revealed a significant difference between the LG and the others muscles (p = 0.001). No significant difference was found between the different thigh muscles (p > 0.05). The intra-class correlation coefficient ranged from 0.87 to 0.99 for the measurements performed on the LG, VL and VM.

CONCLUSIONS

The sEMG(RMS)-acceleration relationship in the VL, VM and LG is a reliable test to individualize the WBV intervention.