Analysis of Vibration Frequency and Direction for Facilitating Upper-Limb Muscle Activity

We aimed to determine the effect of vibration frequency and direction on upper-limb muscle activation using a handheld vibrator. We recruited 19 healthy participants who were instructed to hold a handheld vibrator in their dominant hand and maintain the elbow at 90° flexion, while vertical and horizontal vibrations were applied with frequencies of 15, 30, 45, and 60 Hz for 60 s each. Surface electromyography (EMG) measured the activities of the flexor digitorum superficialis (FDS), flexor carpi radialis (FCR), extensor carpi ulnaris (ECU), extensor carpi radialis (ECR), biceps, triceps, and deltoid anterior muscles. EMG changes were evaluated as the difference in muscle activity between vibration and no-vibration (0 Hz) conditions. Muscle activity was induced under vibration conditions in both vertical and horizontal (p < 0.05) directions. At 45 Hz, FDS and FCR activities increased during horizontal vibrations, compared with those during vertical vibrations. ECU activity significantly increased under 15-Hz vertical vibrations compared with that during horizontal vibrations. Vibrations from the handheld vibrator significantly induced upper-limb muscle activity. The maximum muscle activations for FDS, ECR, ECU, biceps, and triceps were induced by 45-Hz horizontal vibration. The 60-Hz vertical and 30-Hz horizontal vibrations facilitated maximum muscle activations for the FCR and deltoid anterior, respectively.

Effects of Skin Stimulation on Sensory-Motor Networks Excitability: Possible Implications for Physical Training in Amyotrophic Lateral Sclerosis

Background

Many different trials were assessed for rehabilitation of patients with amyotrophic lateral sclerosis (ALS), with non-unique results. Beside the effects on muscle trophism, some of the encouraging results of physical training could be ascribed to the modulation of cortical excitability, which was found hyperexcited in ALS.

Objective

The effects of tactile skin stimulation in the modulation of the sensory-motor integrative networks in healthy subjects were assayed through the paired associative stimulation (PAS) protocol.

Methods

In total, 15 healthy subjects were enrolled. In the standard PAS session, the average amplitude of the motor evoked potential (MEP) after 10 stimuli of transcranial magnetic stimulation (TMS) was measured at the baseline and after the PAS protocol (0, 10, 20, 30, and 60 min). In the skin stimulation session, the average amplitude of the MEP was measured before and after 10 min of skin stimulation over the hand. Subsequently, each subject underwent the PAS stimulation and the measure of the average amplitude of the MEP (0, 10, 20, 30, and 60 min).

Results

The tactile skin stimulation on healthy subjects increases the PAS-induced sensory-motor network hyperexcitability in healthy subjects.

Conclusion

Skin stimulation should be avoided in the physiotherapeutic approaches for patients with ALS, given the possible hyperexciting effects on the already upmodulated sensory-motor networks. They can be taken into account for diseases characterized by downregulation of cortical and transcortical networks.

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.

Local plantar vibration for the treatment of diabetic neuropathy: a case report

PURPOSE

One of the most common and debilitating complications of diabetes is peripheral neuropathy. Physical modalities such as whole-body vibration are used to treat diabetic peripheral neuropathy (DPN), but there are limted studies on the effectiveness of local vibration for the treatment of PDN. In this study, we aimed to evaluate the effectiveness of local vibration in treating a patient with DPN.

METHODS

The local vibration was applied on the plantar side of both feet. The patient received 10 min of local vibration with 62.5 Hz frequency for five sessions. We used brief BESTest for balance evaluation, Numerical Pain Rating Scale (NPRS) for pain assessment, monofilament examination score for protective sensation evaluation, vibration threshold, and skin temperature to evaluate the effects of local vibration, which were measured before the treatment, after one session  of treatment, and after 5th session of treatment.

RESULTS

There was a 62.5% reduction in pain severity after five sessions of treatment. Vibration threshold of both patient's feet and protective sensation of right foot returned to normal after treatment. Skin temperature was increased in all evaluated points of both patient's feet, brief BESTest score increased by six points after five treatment sessions, indicating improvements in the blood flow of feet and balance, respectively.

CONCLUSIONS

Local plantar vibration was effective in improving the symptoms of DPN.

Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but Not Corticospinal Pathways

The use of upper limb vibration (ULV) during exercise and rehabilitation continues to gain popularity as a modality to improve function and performance. Currently, a lack of knowledge of the pathways being altered during ULV limits its effective implementation. Therefore, the aim of this study was to investigate whether indirect ULV modulates transmission along spinal and corticospinal pathways that control the human forearm. All measures were assessed under CONTROL (no vibration) and ULV (30 Hz; 0.4 mm displacement) conditions while participants maintained a small contraction of the right flexor carpi radialis (FCR) muscle. To assess spinal pathways, Hoffmann reflexes (H-reflexes) elicited by stimulation of the median nerve were recorded from FCR with motor response (M-wave) amplitudes matched between conditions. An H-reflex conditioning paradigm was also used to assess changes in presynaptic inhibition by stimulating the superficial radial (SR) nerve (5 pulses at 300Hz) 37 ms prior to median nerve stimulation. Cutaneous reflexes in FCR elicited by stimulation of the SR nerve at the wrist were also recorded. To assess corticospinal pathways, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation of the contralateral motor cortex were recorded from the right FCR and biceps brachii (BB). ULV significantly reduced H-reflex amplitude by 15.7% for both conditioned and unconditioned reflexes (24.0 ± 15.7 vs. 18.4 ± 11.2% M max ; p < 0.05). Middle latency cutaneous reflexes were also significantly reduced by 20.0% from CONTROL (-1.50 ± 2.1% Mmax) to ULV (-1.73 ± 2.2% Mmax; p < 0.05). There was no significant effect of ULV on MEP amplitude (p > 0.05). Therefore, ULV inhibits cutaneous and H-reflex transmission without influencing corticospinal excitability of the forearm flexors suggesting increased presynaptic inhibition of afferent transmission as a likely mechanism. A general increase in inhibition of spinal pathways with ULV may have important implications for improving rehabilitation for individuals with spasticity (SCI, stroke, MS, etc.).

Whole-body vibration training versus conventional balance training in patients with severe COPD-a randomized, controlled trial

BACKGROUND

Whole-body vibration training (WBV) performed on a vibration platform can significantly improve physical performance in patients with chronic obstructive pulmonary disease. It has been suggested that an important mechanism of this improvement is based on an improvement in balance. Therefore, the aim of this study was to investigate the effects of WBV compared to conventional balance training.

METHODS

48 patients with severe COPD (FEV₁: 37 ± 7%predicted) and low exercise performance (6 min walk distance (6MWD): 55 ± 10%predicted) were included in this randomized controlled trial during a 3 week inpatient pulmonary rehabilitation. All patients completed a standardized endurance and strength training program. Additionally, patients performed 4 different balance exercises 3x/week for 2 sets of 1 min each, either on a vibration platform (Galileo) at varying frequencies (5-26 Hz) (WBV) or on a conventional balance board (BAL). The primary outcome parameter was the change in balance performance during a semi tandem stance with closed eyes assessed on a force measurement platform. Muscular power during a countermovement jump, the 6MWD, and 4 m gait speed test (4MGST) were secondary outcomes. Non-parametric tests were used for statistical analyses.

RESULTS

Static balance performance improved significantly more (p = 0.032) in favor of WBV (path length during semi-tandem stand: - 168 ± 231 mm vs. + 1 ± 234 mm). Muscular power also increased significantly more (p = 0.001) in the WBV group (+ 2.3 ± 2.5 W/kg vs. - 0.1 ± 2.0 W/kg). 6MWD improved to a similar extent in both groups (WBV: 48 ± 46 m, p < 0.001 vs. BAL: 38 ± 32 m; p < 0.001) whereas the 4MGST increased significantly only in the WBV-group (0.08 ± 0.14 m/s², p = 0.018 vs. 0.01 ± 0.11 m/s², p = 0.71).

CONCLUSIONS

WBV can improve balance performance and muscular power significantly more compared to conventional balance training.

TRIAL REGISTRATION

Clinical-Trials registration number: NCT03157986; date of registration: May 17, 2017. https://clinicaltrials.gov/ct2/results?cond=&term=NCT03157986&cntry=&state=&city=&dist  = .

The Acute Effects of Whole Body Vibration on Isometric Mid-Thigh Pull Performance

The purpose of the present investigation was to examine the acute effects of whole body vibration (WBV) on isometric mid-thigh pull force–time curve (FTC) characteristics. Eleven recreationally trained subjects were randomly assigned to three treatment conditions: sham no vibration protocol (T1), vibration protocol 30 Hz 2–4 mm amplitude (T2), and vibration protocol 30 Hz 2–4 mm (T3). After completing a standardized warm-up, the subject stood on a vibration platform with the knee at a 120° angle and performed one of the three interventions. Each treatment condition required the subject to stand on the platform for thirty-second treatments, each separated by thirty seconds of recovery. Five minutes after the completion of the treatment conditions, the subjects performed the isometric mid-thigh pull. All FTCs were analyzed with standardized procedures for peak force (PF) and peak rate of force development (PRFD). A 1 × 3 repeated measures analysis of variance (ANOVA) was used to compare the three treatments. Additionally, coefficients of variance (CV), as well as intraclass and interclass correlations, were performed. There were no significant differences (p > 0.05) for any of the FTC analyses performed in this investigation. The CV and the 95% confidence interval (CI) indicate that the WBV protocol resulted in trivial changes in PF and beneficial changes in PRFD. A 30 Hz 2–4 mm amplitude WBV does not result in a significant increase in isometric mid-thigh pull performance.

Whole-body vibration modulates leg muscle reflex and blood perfusion among people with chronic stroke: a randomized controlled crossover trial

This study aimed to investigate the acute effect of whole-body vibration (WBV) on the reflex and non-reflex components of spastic hypertonia and intramuscular blood perfusion among individuals with chronic stroke. Thirty-six people with chronic stroke (age: 61.4 ± 6.9 years) participated in this randomized controlled cross-over study. Each participant underwent two testing conditions: static standing for 5 minutes with WBV (30 Hz, 1.5 mm) or no-vibration. We assessed the soleus H-reflex, shear modulus (ultrasound elastography) and vascular index (color power Doppler ultrasound) of the medial gastrocnemius (MG) muscle on either paretic or non-paretic side at baseline and every 1-min post-intervention up to 5 minutes. The results revealed a significant inhibition of the H/M ratio bilaterally for the WBV condition (absolute change on paretic side: 0.61 ± 0.35, p = 0.001; non-paretic side: 0.34 ± 0.23, p = 0.001), but not the control condition. The inhibition of H-reflex was sustained up to 4 minutes and 3 minutes on the paretic and non-paretic side, respectively. The vascular index of MG muscle was significantly increased only for the WBV condition [paretic: from 0.55 ± 0.07 to 1.08 ± 0.18 (p = 0.001); non-paretic: from 0.82 ± 0.09 to 1.01 ± 0.13 (p < 0.001)], which lasted for 3 minutes and 5 minutes, respectively. No significant change of the shear modulus in the MG muscle was observed, regardless of the testing condition. Based on our results, WBV had an acute effect on modulating spastic hypertonia dominated by hyperreflexia in people with chronic stroke and facilitating greater intramuscular blood perfusion. No acute effect on passive muscle stiffness was observed.

Whole body vibration showed beneficial effect on pain, balance measures and quality of life in painful diabetic peripheral neuropathy: a randomized controlled trial

Purpose

The aim of the study was to determine the efficacy of whole body vibration (WBV) therapy on pain, neuropathy disability score, balance, proprioception and quality of life (QOL) in patients with painful diabetic peripheral neuropathy (PDPN).

Methods

Twenty-six (16 males and 10 females) patients with PDPN were selected on the basis of inclusion and exclusion criteria. Subjects were randomly allocated to an experimental group (n = 13, age = 60.69 ± 5.08) and a control group (n = 13, age = 59.54 ± 4.25). The experimental group was given WBV therapy for six weeks (3 days/week) in addition to standard medical care, dietary advice and lifestyle modifications. Control group was provided only standard medical care, dietary advice and lifestyle modifications. Outcome measures included numeric pain rating scale (NPRS), Leeds assessment of neuropathic symptoms and signs (LANSS), vibration perception threshold (VPT), neuropathy disability score (NDS), proprioception, single-leg stance test (SLST), timed up and go test (TUGT) and short form 36 questionnaire (SF-36).

Results

NPRS, LANSS, NDS, SLST and TUGT showed significant time effect (p ≤ 0.022) and time×group interaction (p ≤ 0.007), whereas group effect was found to be significant only in LANSS (p = 0.001). VPT showed significant group effect (p ≤ 0.045) and time×group interaction (p ≤ 0.007) at great toe, metatarsal head and total average score. SF-36 was found to be significant time effect (p ≤ 0.024) in all domains except limitations due to physical health (p = 0.461). SF-36 average score was found be significant for group effect (p = 0.002) and time×group interaction (p < 0.001).

Conclusion

WBV improves sensory sensations like pain and vibration perception, neuropathy disability score, balance measures and health-related QOL in PDPN.

Motoneuron Function Does not Change Following Whole-Body Vibration in Individuals With Chronic Ankle Instability

CONTEXT

Following a lateral ankle sprain, ∼40% of individuals develop chronic ankle instability (CAI), characterized by recurrent injury and sensations of giving way. Deafferentation due to mechanoreceptor damage postinjury is suggested to contribute to arthrogenic muscle inhibition (AMI). Whole-body vibration (WBV) has the potential to address the neurophysiologic deficits accompanied by CAI and, therefore, possibly prevent reinjury.

OBJECTIVE

To determine if an acute bout of WBV can improve AMI and proprioception in individuals with CAI.

DESIGN AND PARTICIPANTS

The authors examined if an acute bout of WBV can improve AMI and proprioception in individuals with CAI with a repeated-measures design. A total of 10 young adults with CAI and 10 age-matched healthy controls underwent a control, sham, and WBV condition in randomized order.

SETTING

Biomechanics laboratory.

INTERVENTION

WBV.

MAIN OUTCOME MEASURES

Motoneuron pool recruitment was assessed via Hoffmann reflex (H-reflex) in the soleus. Proprioception was evaluated using ankle joint position sense at 15° and 20° of inversion. Both were assessed prior to, immediately following, and 30 minutes after the intervention (pretest, posttest, and 30mPost, respectively).

RESULTS

Soleus maximum H-reflex:M-response (H:M) ratios were 25% lower in the CAI group compared with the control group (P = .03). Joint position sense mean constant error did not differ between groups (P = .45). Error at 15° in the CAI (pretest 0.8 [1.6], posttest 2.0 [2.8], 30mPost 2.0 [1.9]) and control group (pretest 0.8 [2.0], posttest 0.6 [2.9], 30mPost 0.5 [2.1]) did not improve post-WBV. Error at 20° did not change post-WBV in the CAI (pretest 1.3 [1.7], posttest 1.0 [2.4], 30mPost 1.5 [2.2]) or control group (pretest -0.3 [3.0], posttest 0.8 [2.1], 30mPost 0.6 [1.8]).

CONCLUSION

AMI is present in the involved limb of individuals with CAI. The acute response following a single bout of WBV did not ameliorate the presence of AMI nor improve proprioception in those with CAI.

Whole body vibration of different frequencies inhibits H-reflex but does not affect voluntary activation

This study aimed to investigate the effects of whole-body vibration (WBV) at a frequency spectrum from 20 to 50 Hz on the Hoffmann (H) reflex and the voluntary motor output of ankle plantar-flexor muscles. A single-group (n: 8), repeated measures design was adopted with four conditions: standing (no vibration), 20, 35 and 50 Hz, each lasting one minute. H-reflex of the soleus muscle, maximal voluntary contraction (MVC) and central activation ratio (CAR) of the plantar-flexors were evaluated before, 1 and 5 min after each frequency condition. H-reflex decreased by 36.7% at 20 Hz, by 28% at 35 Hz, and by 34.8% at 50 Hz after one minute from WBV compared to baseline. Neither MVC nor CAR changed after WBV at all frequency conditions. The short-term, acute inhibition of the H-reflex after WBV at 20, 35 and 50 Hz suggested that decreased excitability of spinal motoneurons is not frequency dependent. On the other hand, the lack of vibration induced effects on MVC and CAR indicated that a 1-min WBV stimulus is not sufficient to affect the voluntary motor output.

Effects of vibration-induced fatigue on the H-reflex

Vibration exercise (VE) has been suggested as an effective training for improving muscle strength and coordination. However, the underlying physiological adaptation processes are not yet fully understood, limiting the development of safe and effective exercise protocols. To better understand the neuromuscular responses elicited by VE, we aimed at investigating the acute effects of superimposed vibration on the Hoffmann reflex (H-reflex), measured after fatiguing exercise. Twenty-five volunteers performed four isometric contractions of the right Flexor Carpi Radialis (FCR) with baseline load at 80% of their maximal voluntary contraction (MVC), both with no vibration and with superimposed vibration at 15, 30, and 45 Hz. Fatigue was estimated by MVC test and estimation of electromyographic spectral compression. H-reflex suppression was estimated as the relative decrease after exercise. Our results show that fatiguing exercise determined a decrease in H-reflex amplitude compared to rest condition while vibration determined a lower H-reflex suppression as compared to no vibration. The superimposition of 30-Hz vibration determined the largest acute reduction in force generating capacity (36 N, p < 0.05) and the lowest H-reflex suppression (20%, p < 0.05). These results suggest VE to be particularly suitable in rehabilitation programs for rapid restoration of muscle form and function after immobilization periods.

Effects of adding whole-body vibration to routine day activity program on physical functioning in elderly with mild or moderate dementia: a randomized controlled trial

OBJECTIVE

To evaluate the effects of whole-body vibration (WBV) added to a routine activity program on lower limb strength, balance, and mobility among community-dwelling individuals with mild or moderate dementia, compared with the routine program alone.

METHODS

Fifty-four older adults (40 women; mean (SD) age: 79.8 (6.1) years) with mild or moderate dementia were recruited from two daycare centers. The participants were randomly allocated to undergo a routine day activity program combined with WBV training (WBV at 30 Hz, 2-mm peak-to-peak amplitude) or the routine program only without WBV for 9 weeks (18 sessions). The primary outcome was functional mobility, measured using the timed up-and-go test. The following secondary outcomes were evaluated: Berg Balance Scale, Tinetti balance assessment, time to complete 5 repetitions of sit-to-stand, Quality of Life in Alzheimer's disease questionnaire, and Activities-specific Balance Confidence scale. The attendance rate and incidence of adverse events were also recorded.

RESULTS

The attendance rate for the training was high (86.0%). The incidence of adverse events was low, with only two of the 27 participants in the WBV group reporting mild knee pain. While significant improvement in timed up-and-go, Berg Balance Scale, and Tinetti balance score was found in both groups, none of the outcomes demonstrated a significant group by time interaction.

CONCLUSIONS

WBV training is feasible and safe to use with people with mild or moderate dementia. However, it did not lead to further improvement in physical function and quality of life than the usual activity program provided at the daycare centers. Copyright © 2017 John Wiley & Sons, Ltd.

Transmissibility and waveform purity of whole-body vibrations in older adults

BACKGROUND

This study examined the transmission power and waveform purity of vertical (synchronous) whole-body vibrations upon its propagation in the human body among older adults.

METHODS

Forty community-dwelling older adults participated in the study (33 women; mean age: 60.3 (SD 5.7) years). Four vibration frequencies (25, 30, 35, 40Hz), two amplitudes (0.6 and 0.9mm), and six different postures were tested. Skin-mounted tri-axial accelerometers were placed at the medial malleolus, tibial tuberosity, greater trochanter, third lumbar vertebra, and forehead. The transmissibility of vibration was computed as the ratio of the root-mean-square-acceleration at different body sites to that of the platform. Signal purity was expressed by the percentage of total transmitted power within 1Hz of the nominal frequency delivered by the platform.

FINDINGS

Vibration frequency and amplitude were inversely associated with transmissibility in all anatomical landmarks except the medial malleolus. Amplification of signals was noted at the medial malleolus in most testing conditions. The effect of posture on whole-body vibration transmission depends on its frequency and amplitude. In general, toe-standing led to the lowest transmissibility. Single-leg standing had the highest vibration transmission to the hip, while erect standing had the highest transmissibility to the head. The purity of waveform of the vibration signals was well conserved as the vibrations were transmitted from the feet to the upper body.

INTERPRETATION

Whole-body vibration transmissibility was highly influenced by signal frequency, amplitude and posture. These parameters should be carefully considered when prescribing whole-body vibration to older adults.

The Influence of an Acute Bout of Whole Body Vibration on Human Postural Control Responses

The use of vibrating platforms has become increasingly available, and popular at sports and rehabilitation institutes. Given the discrepancies in the literature regarding whole body vibration (WBV) and human reflexive responses, the purpose of this study was to examine the acute effects of WBV on postural response latencies, as well as associated electromyography measures of the lower extremities during balance perturbations. Reflexive responses during backward and forward balance perturbations were examined before, after, and 10 min after a bout of WBV. The findings suggest that following an acute bout of whole body vibration, muscle activity of the lower extremities is decreased during a reflexive response to an unexpected perturbation, and may be associated with faster reaction time.

Effects of whole-body vibration therapy on perception thresholds of type 2 diabetic patients with peripheral neuropathy: a randomized controlled trial

[Purpose] The aim of this study was to investigate the effect of whole-body vibration training on perception thresholds in type 2 diabetic patients with peripheral neuropathy. [Subjects and Methods] Fifty-nine patients with diabetic neuropathy participated in the study. They were randomly divided into the experimental group (n=29) and the control group (n=30). The experimental group performed whole-body vibration training, whereas the control group performed only lower body training in the same posture without using whole-body vibrator for 6 weeks. Perception threshold variables were measured to examine the effect of training. [Results] Warm and cold pain thresholds did not show significant changes in both groups before and after training. Vibration perception threshold showed significant improvement in the experimental group. [Conclusion] Our findings suggest that whole-body vibration training can improve vibration perception threshold of type 2 diabetic patients with peripheral neuropathy.

Alleviation of Motor Impairments in Patients with Cerebral Palsy: Acute Effects of Whole-body Vibration on Stretch Reflex Response, Voluntary Muscle Activation and Mobility

INTRODUCTION

Individuals suffering from cerebral palsy (CP) often have involuntary, reflex-evoked muscle activity resulting in spastic hyperreflexia. Whole-body vibration (WBV) has been demonstrated to reduce reflex activity in healthy subjects, but evidence in CP patients is still limited. Therefore, this study aimed to establish the acute neuromuscular and kinematic effects of WBV in subjects with spastic CP.

METHODS

44 children with spastic CP were tested on neuromuscular activation and kinematics before and immediately after a 1-min bout of WBV (16-25 Hz, 1.5-3 mm). Assessment included (1) recordings of stretch reflex (SR) activity of the triceps surae, (2) electromyography (EMG) measurements of maximal voluntary muscle activation of lower limb muscles, and (3) neuromuscular activation during active range of motion (aROM). We recorded EMG of m. soleus (SOL), m. gastrocnemius medialis (GM), m. tibialis anterior, m. vastus medialis, m. rectus femoris, and m. biceps femoris. Angular excursion was recorded by goniometry of the ankle and knee joint.

RESULTS

After WBV, (1) SOL SRs were decreased (p < 0.01) while (2) maximal voluntary activation (p < 0.05) and (3) angular excursion in the knee joint (p < 0.01) were significantly increased. No changes could be observed for GM SR amplitudes or ankle joint excursion. Neuromuscular coordination expressed by greater agonist-antagonist ratios during aROM was significantly enhanced (p < 0.05).

DISCUSSION

The findings point toward acute neuromuscular and kinematic effects following one bout of WBV. Protocols demonstrate that pathological reflex responses are reduced (spinal level), while the execution of voluntary movement (supraspinal level) is improved in regards to kinematic and neuromuscular control. This facilitation of muscle and joint control is probably due to a reduction of spasticity-associated spinal excitability in favor of giving access for greater supraspinal input during voluntary motor control.

Acute and chronic neuromuscular adaptations to local vibration training

Vibratory stimuli are thought to have the potential to promote neural and/or muscular (re)conditioning. This has been well described for whole-body vibration (WBV), which is commonly used as a training method to improve strength and/or functional abilities. Yet, this technique may present some limitations, especially in clinical settings where patients are unable to maintain an active position during the vibration exposure. Thus, a local vibration (LV) technique, which consists of applying portable vibrators directly over the tendon or muscle belly without active contribution from the participant, may present an alternative to WBV. The purpose of this narrative review is (1) to provide a comprehensive overview of the literature related to the acute and chronic neuromuscular changes associated with LV, and (2) to show that LV training may be an innovative and efficient alternative method to the 'classic' training programs, including in the context of muscle deconditioning prevention or rehabilitation. An acute LV application (one bout of 20-60 min) may be considered as a significant neuromuscular workload, as demonstrated by an impairment of force generating capacity and LV-induced neural changes. Accordingly, it has been reported that a training period of LV is efficient in improving muscular performance over a wide range of training (duration, number of session) and vibration (frequency, amplitude, site of application) parameters. The functional improvements are principally triggered by adaptations within the central nervous system. A model illustrating the current research on LV-induced adaptations is provided.

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.

Cardiopulmonary response during whole-body vibration training in patients with severe COPD

Several studies in patients with chronic obstructive pulmonary disease (COPD) have shown that whole-body vibration training (WBVT) has beneficial effects on exercise capacity. However, the acute cardiopulmonary demand during WBVT remains unknown and was therefore investigated in this study. Ten patients with severe COPD (forced expiratory volume in 1 s: 38±8% predicted) were examined on two consecutive days. On day one, symptom-limited cardiopulmonary exercise testing was performed on a cycle ergometer. The next day, six bouts of repeated squat exercises were performed in random order for one, two or three minutes either with or without WBVT while metabolic demands were simultaneously measured. Squat exercises with or without WBVT induced comparable ventilatory efficiency (minute ventilation (VE)/carbon dioxide production (V'_CO2 ): 38.0±4.4 with WBVT versus 37.4±4.1 without, p=0.236). Oxygen uptake after 3 min of squat exercises increased from 339±40 mL·min^-1 to 1060±160 mL·min^-1 with WBVT and 988±124 mL min^-1 without WBV (p=0.093). However, there were no significant differences between squat exercises with and without WBVT in oxygen saturation (90±4% versus 90±4%, p=0.068), heart rate (109±13 bpm versus 110±15 bpm, p=0.513) or dyspnoea (Borg scale 5±2 versus 5±2, p=0.279). Combining squat exercises with WBVT induced a similar cardiopulmonary response in patients with severe COPD compared to squat exercises without WBVT. Bearing in mind the small sample size, WBVT might be a feasible and safe exercise modality even in patients with severe COPD.

Neuromuscular responses of the plantar flexors to whole-body vibration

Enhanced physical performance following whole-body vibration (WBV) has been attributed to increased muscle activity; however, few studies have measured the mechanisms underlying these changes. The objective of this study was to measure the responsiveness of the Ia pathway as well as contractile properties in 16 young adults (24±2 years, eight men, eight women) following repeated bouts of acute WBV (45 Hz, 2 mm). Hoffman reflexes (H-reflex), compound muscle action potentials (M-wave), and twitch contractile properties were measured prior to and immediately following five 1-minute WBV exposures, and at 3, 5, 10, and 20 minute post-WBV. M-wave and H-reflex amplitudes decreased by 8% (P<.001) and by 46% (P<.05), respectively, whereas peak twitch torque decreased by 9% (P<.01) and rate of twitch torque development slowed 8% (P<.05). Percent voluntary activation and maximal plantar flexor torque were unchanged as a consequence of WBV (P>.05). In response to acute WBV, the root mean square of the soleus electromyography signal (EMG_RMS ) increased by 8%, while the EMG_RMS of the lateral gastrocnemius increased by 3% (P<.05). These data indicate that the responsiveness of the Ia pathway is diminished and contractile function is impaired immediately following WBV, and that the neural mechanisms underlying improved performance following WBV lie in alternative hypotheses possibly involving spindle disfacilitation or Golgi afferent modulation.

Effects of whole body vibration on muscle spasticity for people with central nervous system disorders: a systematic review

Objectives:

To examine the effects of whole-body vibration on spasticity among people with central nervous system disorders.

Methods:

Electronic searches were conducted using CINAHL, Cochrane Library, MEDLINE, Physiotherapy Evidence Database, PubMed, PsycINFO, SPORTDiscus and Scopus to identify randomized controlled trials that investigated the effect of whole-body vibration on spasticity among people with central nervous system disorders (last search in August 2015). The methodological quality and level of evidence were rated using the PEDro scale and guidelines set by the Oxford Centre for Evidence-Based Medicine.

Results:

Nine trials with totally 266 subjects (three in cerebral palsy, one in multiple sclerosis, one in spinocerebellar ataxia, and four in stroke) fulfilled all selection criteria. One study was level 1b (PEDro⩾6 and sample size>50) and eight were level 2b (PEDro<6 or sample size ⩽50). All three cerebral palsy trials (level 2b) reported some beneficial effects of whole-body vibration on reducing leg muscle spasticity. Otherwise, the results revealed no consistent benefits on spasticity in other neurological conditions studied. There is little evidence that change in spasticity was related to change in functional performance. The optimal protocol could not be identified. Many reviewed studies were limited by weak methodological and reporting quality. Adverse events were minor and rare.

Conclusion:

Whole-body vibration may be useful in reducing leg muscle spasticity in cerebral palsy but this needs to be verified by future high quality trials. There is insufficient evidence to support or refute the notion that whole-body vibration can reduce spasticity in stroke, spinocerebellar ataxia or multiple sclerosis.

Acute Effect of Whole-Body Vibration Warm-up on Footspeed Quickness

Donahue, RB, Vingren, JL, Duplanty, AA, Levitt, DE, Luk, H-Y, and Kraemer, WJ. Acute effect of whole-body vibration warm-up on footspeed quickness. J Strength Cond Res 30(8): 2286-2291, 2016-The warm-up routine preceding a training or athletic event can affect the performance during that event. Whole-body vibration (WBV) can increase muscle performance, and thus the inclusion of WBV to the warm-up routine might provide additional performance improvements. The purpose of this investigation was to examine the acute effect of a WBV warm-up, using a vertical oscillating platform and a more traditional warm-up protocol on feet quickness in physically active men. Twenty healthy and physically active men (18-25 years, 22 ± 3 years, 176.8 ± 6.4 cm, 84.4 ± 11.5 kg, 10.8 ± 1.4% body fat) volunteered for this study. A 2 × 2 factorial design was used to examine the effect of 4 warm-up scenarios (no warm-up, traditional warm-up only, WBV warm-up only, and combined traditional and WBV warm-up) on subsequent 3-second Quick feet count test (QFT) performance. The traditional warm-up consisted of static and dynamic exercises and stretches. The WBV warm-up consisted of 60 seconds of vertical sinusoidal vibration at a frequency of 35 Hz and amplitude of 4 mm on a vibration platform. The WBV protocol significantly (p ≤ 0.0005, η = 0.581) augmented QFT performance (WBV: 37.1 ± 3.4 touches; no-WBV: 35.7 ± 3.4 touches). The results demonstrate that WBV can enhance the performance score on the QFT. The findings of this study suggest that WBV warm-up should be included in warm-up routines preceding training and athletic events which include very fast foot movements.

Whole-Body Vibration as a Modality for the Rehabilitation of Peripheral Neuropathies: Implications for Cancer Survivors Suffering from Chemotherapy-Induced Peripheral Neuropathy

The objective was to study the effect of whole-body vibration (WBV) on strength, balance and pain in patients with peripheral neuropathies and to consider its significance for the rehabilitation of patients suffering from chemotherapy-induced peripheral neuropathy (CIPN). Using a broad search strategy, PubMed was searched for clinical trials on WBV interventions aimed at improving strength, balance or pain in patients with peripheral neuropathies, which were published in English until 5(th) June 2014. The search was performed by the first author and generated a total of 505 results, which yielded 5 articles that met the inclusion criteria, being studies: i) published in English; ii) involving adult human subjects' peripheral neuropathies; iii) evaluating the effect of WBV as a therapeutic intervention; and iv) reporting findings for at least one of the following outcomes: strength, balance or pain. Methodological quality of included studies was assessed independently by first and second author, using the physiotherapy evidence database scale. The overall methodological quality of included studies was low. Two studies found a beneficial effect of WBV on neuropathic pain, but another study failed to find the same effect. One study found significant improvements in both muscle strength and balance, while another study found improvements only in some, but not all, of the applied tests to measure muscle strength and balance. The results of this literature search suggest insufficient evidence to assess the effectiveness for the effects of WBV on neuropathic pain, muscle strength and balance in patients with peripheral neuropathies. More high-quality trials are needed to guide the optimization of rehabilitation programs for cancer survivors with CIPN in particular.

Effect of whole-body vibration therapy on health-related physical fitness in children and adolescents with disabilities: a systematic review

PURPOSE

To summarize the current literature regarding the effects of whole-body vibration (WBV) therapy on the health-related physical fitness of children and adolescents with disabilities.

METHODS

A literature search using MEDLINE-PubMed, SPORT DISCUS, and EMBASE databases was conducted up to August 2013. A total of 22 articles were included in this review (eight randomized controlled trials, four non-randomized controlled trials, three case reports, and seven reviews).

RESULTS

Most of the studies showed positive effects of WBV on health-related physical fitness in children and adolescents with disabilities. Overall, 10-20 minutes at least three times per week, for a minimum of 26 weeks, with high frequency (between 15 and 35 Hz) and low amplitude (no more than 4 mm of peak-to-peak displacement) might be an appropriate protocol to achieve improvement in body composition and muscular strength.

CONCLUSIONS

Because no serious adverse events have been observed, WBV might be defined as a safe treatment to be applied in children and adolescents with disabling conditions. Further research is recommended to explore the minimum dose of exposure to WBV required to elicit an optimal response in children and adolescents for improving health-related physical fitness. These may be translated into a more specific WBV protocol.

Effects of real and sham whole-body mechanical vibration on spinal excitability at rest and during muscle contraction

We examined the effects of whole-body mechanical vibration (WBV) on indices of motoneuronal excitability at rest and during muscle contraction in healthy humans. Real and sham WBV at 30 Hz had no effect on reflexes measured during muscle contraction. Real WBV at 30 and 50 Hz depressed the H-reflex ∼45%. These depressions diminished across the five inter-bout rest intervals. The depression converted to 27% and 7% facilitation over the 15-min long recovery period following real WBV at 30 and 50 Hz, respectively. The depression, measured during the inter-bout rest, correlated r = 0.48 (P = 0.007) with the subsequent facilitation, measured during the follow-up. The depression produced by sham vs real WBV was significant but less (23%), recovered faster, and the facilitation was absent in the 15-min long follow-up period. WBV produced time-varying depression followed by facilitation of the H-reflex at rest. A lack of change in volitional wave suggests that WBV did not affect the efferent neural drive.

Whole body vibration training--improving balance control and muscle endurance

Exercise combined with whole body vibration (WBV) is becoming increasingly popular, although additional effects of WBV in comparison to conventional exercises are still discussed controversially in literature. Heterogeneous findings are attributed to large differences in the training designs between WBV and "control" groups in regard to training volume, load and type. In order to separate the additional effects of WBV from the overall adaptations due to the intervention, in this study, a four-week WBV training setup was compared to a matched intervention program with identical training parameters in both training settings except for the exposure to WBV. In a repeated-measures matched-subject design, 38 participants were assigned to either the WBV group (VIB) or the equivalent training group (CON). Training duration, number of sets, rest periods and task-specific instructions were matched between the groups. Balance, jump height and local static muscle endurance were assessed before and after the training period. The statistical analysis revealed significant interaction effects of group×time for balance and local static muscle endurance (p<0.05). Hence, WBV caused an additional effect on balance control (pre vs. post VIB +13%, p<0.05 and CON +6%, p = 0.33) and local static muscle endurance (pre vs. post VIB +36%, p<0.05 and CON +11%, p = 0.49). The effect on jump height remained insignificant (pre vs. post VIB +3%, p = 0.25 and CON ±0%, p = 0.82). This study provides evidence for the additional effects of WBV above conventional exercise alone. As far as balance and muscle endurance of the lower leg are concerned, a training program that includes WBV can provide supplementary benefits in young and well-trained adults compared to an equivalent program that does not include WBV.

Side-alternating vibration training for balance and ankle muscle strength in untrained women

CONTEXT

Side-alternating vibration (SAV) may help reduce the risk of falling by improving body balance control. Such training has been promoted as a strength-training intervention because it can increase muscle activation through an augmented excitatory input from the muscle spindles.

OBJECTIVE

To determine the effect of SAV training on static balance during 3 postural tasks of increasing difficulty and lower limb strength.

DESIGN

Randomized controlled clinical trial.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 21 healthy women were divided into training (n = 11; age = 43.35 ± 4.12 years, height = 169 ± 6.60 cm, mass = 68.33 ± 11.90 kg) and control (n = 10; age = 42.31 ± 3.73 years, height = 167 ± 4.32 cm, mass = 66.29 ± 10.74 kg) groups.

INTERVENTION(S)

The training group completed a 9-week program during which participants performed 3 sessions per week of ten 15-second isometric contractions with a 30-second active rest of 3 exercises (half-squat, wide-stance squat, 1-legged half-squat) on an SAV plate (acceleration = 0.91-16.3g). The control group did not participate in any form of exercise over the 9-week period.

MAIN OUTCOME MEASURE(S)

We evaluated isokinetic and isometric strength of the knee extensors and flexors and ankle plantar flexors, dorsiflexors, and evertors. Static balance was assessed using 3 tasks of increasing difficulty (quiet bipedal stance, tandem stance, 1-legged stance). The electromyographic activity of the vastus lateralis, semitendinosus, medial gastrocnemius, tibialis anterior, and peroneus longus was recorded during postural task performance, baseline and pretraining, immediately posttraining, and 15 days posttraining.

RESULTS

After training in the training group, ankle muscle strength improved (P = .03), whereas knee muscle strength remained unaltered (P = .13). Improved ankle-evertor strength was observed at all angular velocities (P = .001). Postural sway decreased in both directions but was greater in the mediolateral (P < .001) than anteroposterior (P = .02) direction. The electromyographic activity of the peroneus longus increased during the sharpened tandem (P = .001) and 1-legged tasks (P = .007). No changes were seen in the control group for any measures.

CONCLUSIONS

The SAV training could enhance ankle muscle strength and reduce postural sway during static balance performance. The reduction in mediolateral sway could be associated with the greater use of ankle evertors due to their strength improvement.

Local metabolic rate during whole body vibration

Whole body vibration (WBV) platforms are currently used for muscle training and rehabilitation. However, the effectiveness of WBV training remains elusive, since scientific studies vary largely in the vibration parameters used. The origin of this issue may be related to a lack in understanding of the training intensity that is imposed on individual muscles by WBV. Therefore, this study evaluates the training intensity in terms of metabolic rate of two lower-extremity muscles during WBV under different vibration parameters. Fourteen healthy male subjects were randomly exposed to 0 (control)-, 10-, 17-, and 28-Hz vibrations while standing upright on a vibration platform. A near-infrared spectrometer was used to determine the gastrocnemius medialis (GM) and vastus lateralis (VL) muscles' metabolic rates during arterial occlusion. The metabolic rates during each vibration condition were significantly higher compared with control for both muscles (P < 0.05). Each increase in vibration frequency translated into a significantly higher metabolic rate than the previous lower frequency (P < 0.05) for both muscles. The current study showed that the local metabolic rate during WBV at 28 Hz was on average 5.4 times (GM) and 3.7 times (VL) of the control metabolic rate. The substantial changes in local metabolic rate indicate that WBV may represent a significant local training stimulus for particular leg muscles.

Study protocol: the effect of whole body vibration on acute unilateral unstable lateral ankle sprain- a biphasic randomized controlled trial

BACKGROUND

Ankle sprains often result in ankle instability, which is most likely caused by damage to passive structures and neuromuscular impairment. Whole body vibration (WBV) is a neuromuscular training method improving those impaired neurologic parameters. The aim of this study is to compare the current gold standard functional treatment to functional treatment plus WBV in patients with acute unilateral unstable inversion ankle sprains.

METHODS/DESIGN

60 patients, aged 18-40 years, presenting with an isolated, unilateral, acute unstable inversion ankle sprain will be included in this bicentric, biphasic, randomized controlled trial. Samples will be randomized by envelope drawing. All patients will be allowed early mobilization and pain-dependent weight bearing, limited functional immobilization by orthosis, PRICE, NSARDs as well as home and supervised physiotherapy. Supervised physical therapy will take place twice a week, for 30 minutes for a period of 6 weeks, following a standardized intervention protocol. During supervised physical therapy, the intervention group will perform exercises similar to those of the control group, on a side-alternating sinusoidal vibration platform. Two time-dependent primary outcome parameters will be assessed: short-term outcome after six weeks will be postural control quantified by the sway index; mid-term outcome after one year will be assessed by subjective instability, defined by the presence of giving-way attacks. Secondary outcome parameters include: return to pre-injury level of activities, residual pain, recurrence, objective instability, energy/coordination, Foot and Ankle Disability Index and EQ 5D.

DISCUSSION

This is the first trial investigating the effects of WBV in patients with acute soft tissue injury. Inversion ankle sprains often result in ankle instability, which is most likely due to damage of neurological structures. Due to its unique, frequency dependent, influence on various neuromuscular parameters, WBV is a promising treatment method for patients with acute unstable inversion ankle sprains.

TRIAL REGISTRATION

NCT01702597.

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; 2.5 mm 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.

Acute effects of Achilles tendon vibration on soleus and tibialis anterior spinal and cortical excitability

Prolonged vibration is known to alter muscle performance. Attenuation of Ia afferent efficacy is the main mechanism suggested. However, changes in motor cortex excitability could also be hypothesized. The purpose of the present study was therefore to analyze the acute and outlasting effects of 1 h of Achilles tendon vibration (frequency, 50 Hz) on the soleus (SOL) and tibialis anterior (TA) neuromuscular excitability. Spinal excitability was investigated by means of H-reflexes and F-waves while cortical excitability was characterized by motor evoked potentials (MEPs) obtained by transcranial magnetic stimulation. Twelve subjects performed the experimental procedures 3 times: at the beginning of the testing session (PRE), immediately after 1 h of Achilles tendon vibration (POST), and 1 h after the end of vibration (POST-1H). Prolonged vibration led to acute reduced H-reflex amplitudes for SOL only (46.9% ± 7.7% vs. 32.8% ± 7%; p = 0.006). Mainly presynaptic inhibition mechanisms were thought to be involved because of unchanged F-wave persistence and amplitude mean values, suggesting unaffected motoneuronal excitability. While no acute effects were reported for SOL and TA cortical excitability, both muscles were characterized by an outlasting increase in their MEP amplitude (0.64 ± 0.2 mV vs. 0.43 ± 0.18 mV and 2.17 ± 0.56 mV vs. 1.26 ± 0.36 mV, respectively; p < 0.05). The high modulation of Ia afferent input by vibration led to changes in motor cortex excitability that could contribute to the enhancement in muscular activation capacities reported after chronic use of tendon vibration.

Changes in postural sway frequency and complexity in altered sensory environments following whole body vibrations

Studies assessing whole body vibration (WBV) have produced largely positive effects, with some neutral, on postural control with frequencies between 25 and 40 Hz. However no conclusive evidence indicates that 25-40 Hz elicits the optimal beneficial effects. To address this issue, a larger range of vibration intensity (10-50 Hz at peak-to-peak amplitudes of 2 and 5mm) was employed while increasing the postural complexity (altered somatosensory and/or visual information) to assess acute effects of 4-min of WBV on postural control. Twelve healthy young adults underwent postural assessment at four time intervals (prior to, immediately following and 10 and 20 min post WBV). Findings revealed both postural sway frequency and sway complexity/regularity were affected by WBV. Baseline posture demonstrated increased sway frequency (p=.04) following WBV with no changes in sway complexity. When the support surface was altered, changes in both the frequency and complexity of sway were elicited (p=.027, .002, respectively). When both somatosensory and visual information were altered delayed improvements in postural control were elicited (p=.05 and .01, for frequency and complexity, respectively). Given the differential acute effects as a function of postural task complexity, future longitudinal studies could determine the overall training effect on sway frequency and complexity.

Whole-body vibration influences lower extremity circulatory and neurological function

Whole-body vibration (WBV) is currently used to enhance performance and treat injuries even though we lack an understanding of how WBV influences physiological processes. An improved understanding of the physiological effects of WBV could lead to protocols to speed healing or treat pathologies. This study examined the acute effects of WBV on peripheral blood perfusion, muscle oxygenation, motoneuron pool excitability, and sensory nerve conduction velocity. Fourteen healthy participants [9 women (21.7 ± 2.4 years); 5 men (20.8 ± 1.1 years)] completed a 5 min bout of WBV (50 Hz, 2 mm amplitude). Measures were assessed pre-treatment and at 0, 5, 10, 15, and 20 min post-treatment. WBV significantly increased superficial skin temperature (P < 0.0005) and total hemoglobin (P = 0.009), had no effect of oxyhemoglobin (P = 0.186), increased deoxyhemoglobin (P < 0.0005), inhibited the soleus Hoffmann reflex (P = 0.007), and had no effect on sural sensory nerve conduction velocity (P = 0.695). These results suggest that an acute bout of WBV influences physiological processes in both the circulatory and the nervous systems.

The sports performance application of vibration exercise for warm-up, flexibility and sprint speed

Since the turn of the 21st century, there has been a resurgence of vibration technology to enhance sport science especially for power and force development. However, vibration exercise has been trialled in other areas that are central to athlete performance such as warm-up, flexibility and sprint speed. Therefore, the aim of this review was to attempt to gain a better understanding of how acute and short-term vibration exercise may impact on warm-up, flexibility and sprint speed. The importance of warming up for sporting performance has been well documented and vibration exercise has the capability to be included or used as a standalone warm-up modality to increase intramuscular temperature at a faster rate compared to other conventional warm-up modalities. However, vibration exercise does not provide any additional neurogenic benefits compared to conventional dynamic and passive warm-up interventions. Vibration exercise appears to be a safe modality that does not produce any adverse affects causing injury or harm and could be used during interval and substitution breaks, as it would incur a low metabolic cost and be time-efficient compared to conventional warm-up modalities. Acute or short-term vibration exercise can enhance flexibility and range of motion without having a detrimental effect on muscle power, however it is less clear which mechanisms may be responsible for this enhancement. It appears that vibration exercise is not capable of improving sprint speed performance; this could be due to the complex and dynamic nature of sprinting where the purported increase in muscle power from vibration exercise is probably lost on repeated actions of high force generation. Vibration exercise is a safe modality that produces no adverse side effects for injury or harm. It has the time-efficient capability of providing coaches, trainers, and exercise specialists with an alternative modality that can be implemented for warm-up and flexibility either in isolation or in conjunction with other conventional training methods.

Spectral properties of H-reflex recordings after an acute bout of whole-body vibration

Although research supports the use of whole-body vibration (WBV) to improve neuromuscular performance, the mechanisms for these improvements remain unclear. The purpose of this study was to identify the effect of WBV on the spectral properties of electrically evoked H-reflex recordings in the soleus (SOL) muscle. The H-reflex recordings were measured in the SOL muscle of 20 participants before and after a bout of WBV. The H-reflexes were evoked every 15 seconds for 150 seconds after WBV. A wavelet procedure was used to extract spectral data, which were then quantified with a principle components analysis. Resultant principle component scores were used for statistical analysis. The analysis extracted 1 principle component associated with the intensity of the myoelectric spectra and 1 principle component associated with the frequency. The scores of the principle component that were related to the myoelectric intensity were smaller at 30 and 60 milliseconds after WBV than before WBV. The WBV transiently decreased the intensity of myoelectric spectra during electrically evoked contractions, but it did not influence the frequency of the spectra. The decrease in intensity likely indicates a smaller electrically evoked muscle twitch response, whereas the lack of change in frequency would indicate a similar recruitment pattern of motor units before and after WBV.

Limb segment vibration modulates spinal reflex excitability and muscle mRNA expression after spinal cord injury

OBJECTIVE

We investigated the effect of various doses of vertical oscillation (vibration) on soleus H-reflex amplitude and post-activation depression in individuals with and without SCI. We also explored the acute effect of short-term limb vibration on skeletal muscle mRNA expression of genes associated with spinal plasticity.

METHODS

Six healthy adults and five chronic complete SCI subjects received vibratory stimulation of their tibia over three different gravitational accelerations (0.3g, 0.6g, and 1.2g) at a fixed frequency (30Hz). Soleus H-reflexes were measured before, during, and after vibration. Two additional chronic complete SCI subjects had soleus muscle biopsies 3h following a single bout of vibration.

RESULTS

H-reflex amplitude was depressed over 83% in both groups during vibration. This vibratory-induced inhibition lasted over 2min in the control group, but not in the SCI group. Post-activation depression was modulated during the long-lasting vibratory inhibition. A single bout of mechanical oscillation altered mRNA expression from selected genes associated with synaptic plasticity.

CONCLUSIONS

Vibration of the lower leg inhibits the H-reflex amplitude, influences post-activation depression, and alters skeletal muscle mRNA expression of genes associated with synaptic plasticity.

SIGNIFICANCE

Limb segment vibration may offer a long term method to reduce spinal reflex excitability after SCI.

The potential neural mechanisms of acute indirect vibration

There is strong evidence to suggest that acute indirect vibration acts on muscle to enhance force, power, flexibility, balance and proprioception suggesting neural enhancement. Nevertheless, the neural mechanism(s) of vibration and its potentiating effect have received little attention. One proposal suggests that spinal reflexes enhance muscle contraction through a reflex activity known as tonic vibration stretch reflex (TVR), which increases muscle activation. However, TVR is based on direct, brief, and high frequency vibration (>100 Hz) which differs to indirect vibration, which is applied to the whole body or body parts at lower vibration frequency (5-45 Hz). Likewise, muscle tuning and neuromuscular aspects are other candidate mechanisms used to explain the vibration phenomenon. But there is much debate in terms of identifying which neural mechanism(s) are responsible for acute vibration; due to a number of studies using various vibration testing protocols. These protocols include: different methods of application, vibration variables, training duration, exercise types and a range of population groups. Therefore, the neural mechanism of acute vibration remain equivocal, but spinal reflexes, muscle tuning and neuromuscular aspects are all viable factors that may contribute in different ways to increasing muscular performance. Additional research is encouraged to determine which neural mechanism(s) and their contributions are responsible for acute vibration. Testing variables and vibration applications need to be standardised before reaching a consensus on which neural mechanism(s) occur during and post-vibration. Key pointsThere is strong evidence to suggest that acute indirect vibration acts on muscle to enhance force, power, flexibility, balance and proprioception, but little attention has been given to the neural mechanism(s) of acute indirect vibration.Current findings suggest that acute vibration exposure may cause a neural response, but there is little consensus on identifying which neural mechanism(s) are specifically responsible. This is due to a number of studies using various vibration testing protocols (i.e.varying frequencies, amplitudes, durations, and methods of application).Spinal reflexes, muscle tuning and neuromuscular aspects and central motor command are all viable neuromechanical factors that may contribute at different stages to transiently increasing muscular performance.Additional research is encouraged to determine when (pre, during and post) the different neural mechanism(s) respond to direct and indirect vibration stimuli.

Immediate effects of 2 different whole-body vibration frequencies on muscle peak torque and stiffness

OBJECTIVE

To examine the immediate effects of 2 vibration protocols with different vibration frequencies that yielded the same maximum acceleration (106.75ms(-2)) on muscle peak torque and stiffness of knee extensor and flexor.

DESIGN

Randomized crossover study with repeated measures.

SETTING

Laboratory setting.

PARTICIPANTS

Recreationally active male adults (N=10).

INTERVENTION

Participants performed 10 bouts of 60-second static half squats intermitted with a 60-second rest period between bouts on a platform with no vibration (control) and a vibration frequency of 26Hz or 40Hz.

MAIN OUTCOME MEASURES

Concentric and eccentric peak torques of knee extensor and flexor were examined within 5 minutes before and after vibration by isokinetic test. Young's modulus as an index of tissue stiffness was determined at quadriceps and hamstring pre- and postvibration by using an ultrasound indentation method.

RESULTS

The 2-way repeated-measures analysis of variance indicated a significant interaction effect between vibration and vibration frequency for knee extensor concentric peak torque (P=.003). The vibration-induced changes of knee extensor concentric peak torque in vibration frequency of 26Hz (14.5Nm) and 40Hz (12.0Nm) were found to be significantly greater than that in controls (-29.4Nm) (P<.05). The change in eccentric peak torque of knee flexor after vibration tended to be greater in 26Hz of vibration frequency when compared with controls (26Hz of vibration frequency vs controls: 13.9±7.1 vs -11.4±5.3Nm, P=.08). No statistically significant differences were obtained in tissue stiffness in the quadriceps and hamstring with any of the conditions.

CONCLUSIONS

Our data suggest that whole-body vibration at a frequency of 26Hz and 40Hz preclude the decline in concentric peak torque of knee extensor observed after 10 bouts of 60 seconds of static half squats. A change in muscle mechanical stiffness property as induced by whole-body vibration is not supported by our data.