Introduction
Over the past few decades, the population of elderly people has been increasing. The aging process is associated with many physiological and biological changes. Improper distribution of forces and plantar pressure in the elderly cause abnormal movement and accumulation of stress in some areas, damage to foot tissue and muscles, and a wide range of abnormalities such as pain, calluses, wounds due to dry skin, and connective tissue, which can ultimately reduce mobility in the elderly and affect their quality of life (QoL) and independence. The purpose of this study is to investigate and evaluate the distribution of force and plantar pressure in the elderly to maintain the independence of the elderly and prevent possible injuries. Considering the use of rocker shoes in clinical and research settings to determine the plantar pressure distribution, conducting a study in this field and knowing the forces on the soles has a significant role in evaluating many pathological conditions and providing a suitable treatment plan for the elderly. Therefore, the present study aims to investigate the effect of toe rocker shoes with an angle of 10 and 15 degrees on the plantar pressure, force and contact surface of healthy older adults.
Methods
In this clinical trial study, 35 healthy older adults aged 60 years and older were selected using a convenience sampling method. They had no any deformity in the lower limb, no orthopedic and neurological diseases, with foot posture score of 0-6 using the foot posture index, and pain in the front of the foot with a score of 0-1 due to the reduction of the medial longitudinal arch and transverse arch, and the ability to walk without an assistance device. Exclusion criteria were learning disability and lack of consciousness, difficulty in maintaining balance, presence of weak muscles in feet and lower limbs with a score 3 or lower. Based on the information obtained from 15 people for the main study variable (maximum plantar pressure), the sample size was estimated to be 26, at 95% confidence interval and considering an 80% test power. During the study, 35 older people were evaluated. The weight of the participants was measured using a clinical scale, and their height was measured using a tape measure. The distance traveled by each participant in the test was also measured by a meter.
Three types of shoes were used, including control shoes, shoes with a 10-degree toe rocker angle, and shoes with a 15-degree toe rocker angle. For this purpose, standard shoes were prepared with a strong, wide and high toe rocker and their back was strong, short and below the ankle. To avoid the effect of the type of shoes, the shoes of all the participants were of the same type, and all the tests were performed in the same conditions and in a specific place with sufficient light. Ethylene vinyl acetate rubber was used to prepare the toe rockers. The rocker apex was at a 65% of the shoe length.
To perform the tests, the examiner first gave the necessary training to the participants. Participants were allowed to withdraw from the study at any time. The participant was asked to walk the eight-meter route three times at a desired speed and paused for 5 seconds between each attempt. There was a 5-minute rest between the tests for each section. Speed was recorded according to the time it took to travel a certain distance. Pedar system was used to measure the maximum plantar pressure in eight anatomical regions while walking. In each test, the data from the first and last three steps and the data while turning were removed. During the tests, the speed change in the range of +10% and -10% was acceptable, and then the data was recorded. Shapiro-Wilk test was used to check the normal distribution of the obtained data. Due to the normality of the distribution, repeated measures analysis of variance was used for data analysis in SPSS software, version 16.
Results
Of 35 participants, 15 (42.8%) were male and 20 (57.2%) were female. Their mean age, body height and body mass index (BMI) are given in Table 1.


The result of analysis of variance showed the distribution of plantar pressure (P>0.05), force (P>0.05) and contact surface (P>0.05) in the eight anatomical areas of the sole of the foot when using shoes with toe rocker angles of 10 and 15 did not have a statistically significant difference compared to the control shoe (without rocker).
Discussion
The use of shoes with toe rockers with angles of 10 and 15 degrees does not have a negative effect on the plantar pressure distribution, force and contact surface of the elderly. This study supports prescribing these shoes without fear of changing the plantar pressure distribution and causing pain and ulcers in the elderly. The elderly can also take advantage of other long-term benefits of rocker shoes and take a step towards dynamic aging. The current study was conducted at a short period due to time constraints, hence, the long-term effect of the rocker shoes was investigated; the results for the long-term effects of these shoes may be different.

Ethical Considerations
Compliance with ethical guidelines
All ethical principles were considered in this study. Informed consent was obtained from all participants. They were assured of the confidentiality of their information and were free to leave the study at any time.

Funding
This study was not funded by any organizations.

Authors' contributions
The authors had equal contribution to the preparation of this article.

Conflicts of interest
The authors declare no conflict of interest.

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