Feasibility and effects applying stochastic resonance whole-body vibration on untrained elderly: A randomized crossover pilot study

Background
Aging is associated with loss of balance and activity in daily life. It impacts postural control and increases the risk of falls. The current study was conducted to determine the feasibility and long-term impact of stochastic resonance whole-body vibration (SR-WBV) on static and dynamic balance and reaction time among elderly individuals.

Methods
A randomized crossover pilot study with blinding of the participants. Twenty elderly were divided into group A (SR-WBV 5 Hz, Noise 4/SR-WBV 1 Hz, Noise 1) or group B (SR-WBV 1 Hz, Noise 1/SR-WBV 5 Hz, Noise 1). Feasibility outcomes included recruitment, compliance and safety. Secondary outcomes were Semi-Tandem Stand (STS), Functional Reach Test (FRT), Expanded Timed Get Up-and-Go (ETGUG), walking under single (ST) & dual task (DT) conditions, hand and foot reaction time (RTH/RTF). Puri and Sen Rank-Order L Statistics were used to analyse carry-over effects. To analyse SR-WBV effects Wilcoxon signed-ranked tests were used.

Results
With good recruitment rate (55%) and compliance (attrition 15%; adherence 85%) rates the intervention was deemed feasible. Three participants dropped out, two due to knee pain and one for personal reasons. ETGUG 0 to 2 m (p = 0.143; ES: 0.36) and ETGUG total time (p = 0.097; ES: 0.40) showed medium effect sizes.

Conclusions
Stochastic resonance training is feasible in untrained elderly resulting in good recruitment and compliance. Low volume SR-WBV exercises over 12 training sessions with 5 Hz, Noise 4 seems a sufficient stimulus to improve ETGUG total time. The stimulation did not elicit changes in other outcomes.

Trial registration
This trial has been registered at the U.S. National Institutes of Health under ClinicalTrials.gov: NCT01045746.