Ageing is associated with sensorimotor deficits resulting in muscular weakness, mobility issues, balance disorders and in gait disorders, and this leads to falls and reduced independence in everyday life (1). The sensorimotor system constantly and unconsciously regulates its movements and postural control based on perceived information to achieve postural stability. Numerous research studies have assessed the effect of stochastic resonance (SR) stimulation to the lower extremity on postural regulation and balance performance in sub-populations such as healthy adults (mean age: 23.04 years, ±6.33 years) (2), elderly individuals (mean age: 73.00 years) (3), or individuals with comprised health suffering from Parkinson (4), or multiple sclerosis (5) or stroke (6, 7), SR has been shown in a variety of physiological systems (8–11), in which the presence of noise below the sensory threshold could enhance the response of the system to weak signals (12–14). Collins et al. (12) postulated that SR could be used to elderly individuals with elevated sensory thresholds.

Whole body vibration (WBV) with stochastic resonance (SR) can easily applied. SR-WBV does not lead to exhaustion and blood pressure and lactate levels are low during vibration training (15). SR-WBV could be easily personalized to the individual's level of fitness (16). For example, elderly with low baseline fitness who want to start an exercise program should start with a program that meets their physical capabilities (16). Older people with frailty or pre-frail condition are advised to undergo a “skilling-up” phase before undertaking more traditional forms of training (17). SR-WBV can be used as a training modality for the “skilling-up” phase (16, 18, 19). Compared to traditional balance training, there are indications on how to design a training regime (sets, rest between sets, session per weeks, etc.) and on the other hand the training protocols are characterized by a short duration between 1 and 5 min of intermittent or continuous WBV application (20). There is no need to change clothes or shoes or to shower afterwards, which might be important in the working world or for adults who do not want to waste time on intensive training (2). Eichelberger et al. (21) were able to determine a decrease in accelerations with increasing distance from the vibrating plate due to damping properties of the involved body structures. However, it is known that a prolonged exposure to vibration (e.g., driving, hammering) may lead to musculoskeletal and neurological disorders (22, 23). Systematic reviews and meta-analysis (24–27) have shown that shorter exposure to vibration have a positive effect on muscle strength and postural control if the training regime (e.g., amplitude, duration and frequency of vibration) is correctly dosed.

SR-WBV differs from sinusoidal WBV in that the stimuli are randomized and amplified using noise (25, 28). This results in a generation of action potentials by the suprathreshold stimuli (29). SR-WBV induces an excitatory stimulus to the alpha motoneuron via mono- and polysynaptic pathways and elicits muscle activation in response, resulting in body stabilization (30). SR-WBV can be understood as reactive balance training that simulates a fall situation itself through the application of unpredictable, random, and multidirectional displacements of the stance surface (31). Reactive balance training means that a person has the ability to react to a loss of balance, because reactive balance is a key factor that ultimately determines whether an individual will sustain a fall (32). Reactive balance can be profoundly impaired in older adult populations (32).

In contrast to SR-WBV, sinusoidal WBV are constant. If the stimulus remains the same, the body adapts very quickly and this slows down the impact of growth stimulus (27). Three WBV devices were used in clinical settings: sinusoidal vertical (SV-WBV), sinusoidal side-alternating (SS-WBV), and stochastic resonance (SR-WBV). While the sinusoidal WBV devices uses a single plate for standing, the SR-WBV device uses two plates for standing (24, 33–36). Due to the different physiological mechanisms of impact and use of equipment, this paper focuses on SR-WBV.

Furthermore, study results demonstrated that whole-body vibration training provides more than physiological effects (2, 37). Animals study showed that daily exposure to WBV over five weeks significantly improved cognition in young mice compared to non-vibrated mice (38, 39). Regterschot et al. (37) could determine that passive WBV could improve executive functions in healthy young adults. They postulated that WBV has the potential as a cognition-enhancing therapy. Chan et al. (40) reported that executive functions are a set of cognitive processes that regulate, manage and control other cognitive processes in order to achieve a goal, such as planning, mental flexibility, multi-tasking etc. Research findings described that cognitive decline and falls are linked (41–43) and that cognitive training improve balance and gait (44).

During aging, sensory symptoms such as absent reflexes are clinically relevant. They are not only debilitating but also responsible for changes. This systematic literature review addressed the research question “could SR-WBV positively influence postural control in individuals with balance disability?” using published results.

In summary, the effect of SR-WBV on postural control presents a mixed picture. The statistically significant results from four studies were contrasted with five statistically unsound results. However, the effect size was strengthened by Rogan et al.'s (49) indication of clinical relevance. They were able to demonstrate clinical relevance (2.9 s) for the Expanded Timed Get-up-and-Go (ETGUG) test (51) in frail individuals after SR-WBV training. The SR-WBV group was a median of 3 s faster after the intervention period compared with the baseline measurement (P = 0.043; ES: 0.91). This study result has immediate consequences in terms of treatment recommendation for frail individuals with a postural control deficit of dynamic balance (52). It is known that a normal sensory system is necessary for successful postural control and movement. The central nervous system must accurately assess the position of the body in space and the limbs in relation to each other (proprioception). Postural reflexes must be released efficiently when external perturbations are detected. Maintaining balance must be automatic so that it is not impaired by other tasks. During aging, impairments of the sensorimotor system lead to a loss of postural control and to falls. The process of postural control depends on many sensory signals and neurological pathways and maintaining the quality of these systems at their optimal level is fundamental. SR-WBV could play an important role toward addressing postural control, by involving an interaction of different types of neurophysiological sensors and the adaptation of afferent and efferent signals, the SR-WBV likely serves as an exercise for the sensorimotor system. Tan et al. (53) demonstrated in their systematic review a significant positive benefit on postural control (SMD = 0.61, 95% CI: 0.12 to 1.09, P = 0.01) and muscle activity in tibialis anterior (SMD = 0.46, 95% CI: 0.04 to 0.88, P = 0.03) and gastrocnemius (SMD = 0.68, 95% CI: 0.14 to 1.23, P = 0.01) using sinusoidal whole-body vibration in individuals with a sensorimotor deficit after ankle injury. They concluded that whole body vibration has the potential to improve sensorimotor deficits involving balance, strength, joint position sense, and muscle activity in people with chronic ankle instability. However, Lesinski et al. (54) formulated in their systematic review and meta-analysis article a balance training regime for healthy elderly by a training period of 11–12 weeks, a training frequency of three sessions per week, a total number of 36–40 training sessions, a duration of 31–45 min of a single training session, and a total duration of 91–120 min of balance training per week. Comparing these findings with findings from young healthy adults, it seems plausible that almost the same balance protocols are effective in healthy young and older adults and there seems to be no age effect (54). In this current article, no of the included articles reported this amount of training regimes. Fisher et al. were able to illustrate in their meta-analysis, that long-term WBV (between 4 weeks and 32 weeks) could significantly improve functional balance (Timed-up-Go test: SMD = −0.18; 95% CI: −0.32, −0.04; 10 min walking test SMD = −0.28; 95% CI: −0.56, −0.01). However, no significant changes were found in elderly individuals (tinetti gait scores: SMD = 0.04; 95% CI: −0.23, 0.31, 6 min walking test: SMD = 0.37; 95% CI: −0.03, 0.78).

It is known that muscle strength is a potentially important factor contributing to postural control (61). Large effects of strength training could be determined for static and dynamic balance in elderly individuals, but only a small effect was found for dynamic balance in young adults (62). Son et al. (63) were able to demonstrate that strength training increase muscle strength in ankle musculature and improve one-leg-standing balance compared to control situation. It can be concluded that the intensity of strength training is fundamental not only for increasing muscle strength but also for improving postural balance in elderly participants.

Furthermore, Kingwell described that exercise has the potential to improve cognitive function (64). Explanatory models address the fact that WBV stimulate mechanosensory receptors (e.g., tactile corpuscles). These signals are transmitted to the primary somatosensory cortex. These areas have connection with region in the prefrontal cortex that strongly involved in cognitive processing (37, 65). An indirect pathway involves the limbic system (e.g., amygdala and hippocampus, important areas of learning and memory), which can mediate the effects of sensory correlations on the prefrontal cortex (66). The amygdala has projections to non-thalamic nuclei (e.g., the cholinergic nuclei of the basal forebrain) with diffuse connections to several brain regions (65). It can be speculated that mechanosensory receptor stimulation can increase cognitive function. Furthermore, it has been assumed that improvement in cognitive function depends on increased production of neurotrophins [e.g., brain-derived neurotrophic factor (BDNF)] (67). BDNF is recognized as the most significant neurotrophic growth factor related to neuronal plasticity and has a key role in the differentiation and survival of neurons (68). Studies could demonstrate a close correlation between increased BDNF levels and WBV (69, 70). However, so far it is unclear how mechanical vibrations may influence the expression of BDNF (71).

The loss of balance ability is an important risk factor for falls in elderly individuals. Reactive balance is a crucial part of avoiding and adapting to complex environments that threaten postural stability (72). In German-speaking countries, the balance ability is considered to be a coordinative ability (73). We describe this ability as the aggregate understood to maintain and regain balance, taking into account the necessary personal conditions.

Various types of exercises (e.g., airex pad, tilting board, swinging platforms) are used in treatment settings and summarized with the synonym balance training (74–77). The goal is to optimize balance. It is assumed that balance is a skill, and that balance training improves several balance tasks at the same time (29). However, recent studies indicate that only those balance tasks that are trained can also improve (77, 78). Giboin et al. (32) showed that the group which trained in a single-leg stand on the tilting board and the group that trained in a single-leg stand on the swinging board (Posturomed) improved statistically significantly only in the area in which they trained.

Recently, there have been attempts to move away from the term ability towards the definition of skill (73). Taube (78) explained that balance training does not change the behavior of the spinal reflex per se. It seems rather to improve the ability of finding the right reflex settings for specific conditions of postural control. Thus, balance training improves task-specific reflex modulation. Low et al. (55) postulated, that specific balance exercise could be the only one likely to improve postural balance. Slackline training improves postural balance in young and elderly individuals in a one-leg stance (56, 57). However, the impact of slackline training is limited or negligible for standard static and dynamic bipedal stances (58–60). Paillard (79) explains that specific balance training optimizes postural skills, but it is not known whether these skills improve motor skills in all types of physical activity. He further refers to the fact that additional studies are required to address this question accurately. Grabiner et al. (80) indicates that task-specific perturbation training is superior to traditional balance exercise training in improving reactive balance capacity and thus preventing falls. Kim et al. (72) performed a network meta-analysis to specify which exercise method is most effective to improve reactive balance in elderly individuals. They analyzed data of 39 RCTs including 1,388 elderly individuals receiving balance training with reactive components (perturbations training) demonstrated the most amount of improvement in reactive training, followed by power training and gait training. SR-WBV is power training. SR-WBV has the potential to improve race of force development after four weeks SR-WBV training in elderly individuals (48). In relation to gait, SR-WBV can be used as skilling up in elderly not able to perform standard gait training. It is known that SR-WBV could significantly improve gait in older adults (19, 47, 49). In the case of a reactive balance, the better the gait, the sooner gait training can be started.

The observed heterogeneity in the individual studies' study quality and findings impede a clear-cut answer to the research question. Furthermore, the study design of the pilot study does not allow a clear conclusion on efficacy because the primary aim of the pilot study is not to assess an exact intervention effect size, but rather to determine the sample sizes and evaluate feasibility of the study protocol (81–83).

We found a heterogeneous situation on effects for balance according to SR-WBV. One study showed clinical relevance for ETGUG. Two studies examined the skill in reactive balance. Since balance is a skill and SR-WBV trains reactive balance, future studies should focus on the parameter reactive balance.