Standardization of vestibular stimulation through rocking chair in elderly population

The present study was undertaken to standardize the vestibular stimulation applied through the usage of the rocking chair in elderly population. A total of 50 elderly male and female participants were part of the study after obtaining the written informed consent. Rocking chair used for the application of vestibular stimulation was specially designed for the study. The rocking chair speci ically designed for this study was equipped with four different frequencies that is 15 cycles/ min, 30 cycles/min, 45 cycles/min and 60 cycles/min. As the selection of ideal speed is subjective, the participants were subjected to all the speeds. The speed was adjusted as per their comfort level and was scored on a likert scale. Other physiological parameters, like pulse rate and blood pressure, weremeasured. Pulse rate and blood pressurewas decreased and remained within normal limits in step-2 in both male and female participants. Majority of the participants reported that they were comfortable in step-2 that is the frequency of 30 cycles/min and duration of 30 minutes. The study standardized the frequency and duration of vestibular stimulation through the rocking chair in the elderly for the irst time. Further, detailed studies are recommended to support the bene icial effects of rocking at this particular frequency in the elderly population.


INTRODUCTION
Vestibular system is having immense importance in the functioning of our body. It has a wide variety of functions other than the maintenance of balance and equilibrium. Vestibular system is connected with different brain areas extensively to regulate various body mechanisms (Saisailesh and Mukkadan, 2019). Earlier studies reported that vestibular stimulation in a controlled manner can relieve stress in young adults (Saisailesh et al., 2014). Similar observation was also reported in pre-hypertensive women (Archana et al., 2018). It was reported that vestibular stimulation may be effective in the management of metabolic disorders like diabetes. This may be due to vagal stimulation and simultaneous inhibition of the sympathetic system (Mukkadan et al., 2015). A recent study has observed the immediate effect of vestibular stimulation on blood pressure and reported that there is a decrease in the blood pressure followed by the vestibular stimulation (Brinda et al., 2019). Both spatial and verbal Step -1  15  15  Step-2  30  30  Step-3  45  45 Step-4 60 60 memory showed improvement followed by linear vestibular stimulation in both the genders (Bashetti et al., 2018). There are different types of vestibular stimulation for humans and animals. Our daily activities like swimming, jogging, running etc. also stimulate the vestibular system, but the stimulation may not be ideal. The fact to be kept in mind is that only ideal vestibular stimulation can elicit the effective control mechanisms. Overstimulation is dangerous as it is associated with adverse effects and under stimulation may cause no effects. Hence, any type of vestibular stimulation should be standardized for that particular population to obtain data for ideal stimulation. The present study was undertaken to standardize the vestibular stimulation through the rocking chair in the elderly population.

MATERIALS AND METHODS
The present study was an observational study, approved by the institutional human ethical committee of SIMATS, Chennai, Tamil Nadu, India.
(002/04/2018/IEC/SMCH). A total of 50 elderly male and female participants were part of the study after obtaining the written informed consent. Willing participants within the age group of 60-75 years were included in the study. Participants with any ear diseases, migraine, cerebrovascular disease, any serious systemic illness and undergoing any treatment or therapy were excluded from the study.

Rocking chair
Rocking chair was specially designed for the study. Details of the make of the chair were mentioned in our earlier article (Rani et al., 2019).

Method of standardization
The rocking chair which was designed for this study is equipped with four different frequencies that are 15 cycles/ min, 30 cycles/min, 45 cycles/min and 60 cycles/min. As the selection of ideal speed is subjective, the participants were subjected to all the speeds according to their comfort level, noted on a Likert scale. All the participants were subjected to four steps as per their comfort and the recording of the physiological outcome measures were per-formed before the stimulation and after each step as given in Table 1.

Outcome measures
The physiological outcome measures assessed were systolic blood pressure, diastolic blood pressure and pulse rate. All the parameters were recorded between 10 to 11 am to minimize diurnal variation.

Recording of blood pressure
Blood pressure was measured in the right arm in the sitting position by diamond digital blood pressure monitor-fully automatic M60, manufactured by Industrial Electronic and allied products as per the standard guidelines according to AHA 2017 criteria. For estimation of the individual's BP level, 3 readings were taken and the lowest value obtained was used (American Heart Association, 2017). Pulse rate was recorded by using Pulse Oximeter using a standard method.

Comfort levels
The participants were instructed to show the ingers representing their comfort levels during the rocking, as mentioned in Table 2.

Data analysis
Data was analyzed using SPSS 20.0 version. One way ANOVA was applied to analyze the quantitative data and percentages were reported for the qualitative data. Probability value less than 0.05 was considered as signi icant.

RESULTS
Pulse rate was decreased and remained within normal limits in step-2. The f -ratio value is 2.09797. The p-value is .101798. The result is not signi icant at p< .05. Systolic blood pressure was decreased and remained within normal limits in step-2. The f -ratio value is 11.48808. The p-value is < .00001. The result is signi icant at p< .05. Diastolic blood pressure was decreased and remained within normal limits in step-2. The f -ratio value is 8.3546. The p-value is .000032. The result is signi icant at p< .05. The values obtained in step -1 and step -3 are not signi icant from the values obtained before vestibular stimulation applied through rocking (Table 3). In females, pulse rate was decreased and remained within normal limits in step-2. The f -ratio value is 1.01392. The p-value is .389546. The result is not signi icant at p< .05. In females, systolic blood pressure was decreased and remained within normal limits in step-2. The f -ratio value is 3.86492. The pvalue is .011385. The result is signi icant at p< .05. In females, diastolic blood pressure was decreased and remained within normal limits in step-2. The fratio value is 3.09388. The p-value is .03003. The result is signi icant at p< .05. The values obtained in step -1 and step -3 are not signi icant from the values obtained before vestibular stimulation applied through rocking (Table 4).
In males, pulse rate was decreased and remained within normal limits in step-2. The f -ratio value is 1.2208. The p-value is .307278. The result is not signi icant at p< .05. In males, systolic blood pressure was decreased and remained within normal limits in step-2. The f -ratio value is 9.78523. The p-value is .000013. The result is signi icant at p< .05. In males, diastolic blood pressure was decreased and remained within normal limits in step-2. The fratio value is 5.23525. The p-value is .002317. The result is signi icant at p< .05. The values obtained in step -1 and step -3 are not signi icant from the values obtained before vestibular stimulation applied through rocking (Table 5).
Majority of the participants have reported step -2 was comfortable compared to step -1 and step-3.
Step-2 has a frequency of 30 cycles/min and a duration of 30 minutes. The details of step 1, 2 and 3 are given in Figures 1, 2 and 3.

DISCUSSION
Balance dif iculties increase with the increase in age. As age increases, the treatment regimen has to be planned very carefully. There is a need for simple and affordable management method for postural problems. The present study was undertaken to standardize the vestibular stimulation through rocking chair in elderly population. Three different frequencies were applied in the study through the chair offers four different frequencies. The reason is most of the participants were not at all comfortable at the frequency of 60 cycles per minute. Out of the three frequencies that we have applied, the frequency of 30 cycles per minute for 30 minutes was highly effective as the physiological parameters were decreased and remained within the normal limits. Hence, the same can be administered for further study.
Earlier studies reported that the exercises which stimulate the vestibular system are very effective in the maintenance of postural stability (Goothy et al., 2019). Another study reported that electrical stim- Step-1 (n=50) Step-2 (n=50) Step-3  Step-1 (n=28) Step-2 (n=28) Step-3  Step-1 (n=22) Step-2 (n=22) Step-3 Data is expressed as mean ±SD. *P< 0.01 ulation of the vestibular system that is stochastic stimulation is effective in the management of problems associated with balance and equilibrium (Piccolo et al., 2020). To the knowledge of authors, this is the irst study to standardize the vestibular stimulation for the elderly through rocking.

CONCLUSIONS
The study standardized the frequency and duration of vestibular stimulation through the rocking chair in the elderly for the irst time. The study recommends further detailed studies to support the bene icial effects of rocking at this particular frequency in the elderly.