Introduction
Today, aging is one of the most important issues in all countries. The population of people over 60 is predicted to increase from 900 million in 2015 to 2 billion by 2050 [1]. Falling is a problem that affects one-third of the population over 65 years old; about 50% of seniors over 80 experience falling at least once a year. As a result, they try to reduce their daily physical activities to avoid the risk of falling and its complications [2]. Various complications, including physical injuries (fractures), reduced quality of life, hospitalization, need for long-term care, high medical costs, and even death related to falls, have been mentioned [3, 4].
Normal people try to control the body’s center of mass on a fixed surface to create stability while standing [5]. However, during walking, they experience instability to a small extent. If this instability in older people increases enough, it may cause falling [6].
Various therapeutic approaches are used to reduce the risk of falls and improve stability during walking [5]. Orthotic interventions are one way to control with falls in older people. Some types of interventions, such as medical shoes and insoles (medial or lateral sole wedges), toe grips, arch supports, and technologized shoes, are all used to improve stability in older people [7, 8, 9, 10].
The effect of these interventions on standing stability and walking parameters is still controversial. Abiko et al. investigated spatial and temporal walking parameters in normal and developed insoles with toe grip bar and concluded that although the use of insoles with toe grip bar increased foot muscle activity in static and swing phases of gait, these changes do not have a significant difference on the spatial-temporal parameters of gait [11].
Also, Nakano et al. evaluated the effect of toe grip bar on toe grip strength and body swing rate in older women and concluded that toe grip strength and body sway improved after using this type of insole [10].
Arch support alone in the insole is one of the other effective interventions to improve the balance and motion function of the lower limb [12], which in case of combined use of changes in the insole (metatarsal pad with arch support and heel cup) shows a significant improvement in the balance of older people [13]. Attention to the physical dimensions of the arch support, such as the height of different arches in the insole, is another effective factor in balance, which has a direct effect on the displacement of the center of pressure (decrease in the center of pressure) and the reduction of falls in older people [14].
Another approach to improve balance is the use of modified shoes with insoles. Menz et al. measured these two interventions on the standing balance of older women and observed that high-heel shoes reduce standing stability, while shoes with long collars in the heel and a hard sole improve standing stability in older people [15].
Increasing stability in older people and reducing body sway while standing and walking requires control and improving spatial and temporal parameters. Insoles with toe grip bar alone increase the contact area of the toes with the sole but do not affect the spatial and temporal parameters. The arch support alone reduces the sway of the center of pressure and improves stability. In addition, some shoe changes, such as heel flare, increase support base and improve stability in older people.
A combined intervention can affect the whole foot and apply more stability so that a toe grip bar insole can make the toes flexible. Because it involves the forefoot area, it can be effective in the toe-off phase of gait. The arch support raises the medial longitudinal arch in the middle of the foot, and in addition to increasing static stability, it also plays a role in improving the middle phase of gait. The heel flare in shoes also increases the contact surface of the foot with the ground and increases the base of support, improving stability.
To control and improve balance in each step of the gait cycle, an intervention was considered in the front, middle, and back of the foot. This study investigates the effect of the simultaneous use of arch support, toe grip bar, and heel flare on balance and gait parameters in older people with balance problems.

Materials and Methods 
This study is a quasi-experimental of the before-and-after type, conducted on 15 older people with a history of falling in the past 6 months. Thirteen women and 2 men over 65 years old (mean age: 70±3.94) with a mean body mass index of 69.29±77.3 kg/m2 were included in the study. The exclusion criteria comprised having Parkinson disease, cardiovascular disease or the need for ambulatory assistance, inability to walk, history of neuromuscular and musculoskeletal disorders, peripheral neuropathy, lower limb amputation, and the use of assistive devices while walking. 
First, informed consent was obtained from the subjects. Then, standard shoes made of leather with semi-thick soles were obtained from the medical shoe manufacturing center in Isfahan. A flare was installed under the shoe heel with 1 cm thick of hard rubber and a 20-degree slope in the Orthotic and Prosthetics Center of the Rehabilitation Faculty of Isfahan University of Medical Sciences (Figure 1). On a semi-hard EVA (ethylene vinyl acetate) foam insole, a toe grip bar with a convex structure was installed in the central part of the proximal phalanx of the first to fifth toes. Finally, arch support was applied in the mid-foot area to a 1.75 cm height on the sole (Figure 2). The motion analysis system (frequency 200 Hz) measured walking movements at the musculoskeletal research center once with standard shoes and then in the same session with transformed shoes (heel flare with arch support and toe grip bar). Older people walked in the laboratory environment for 10 minutes to adapt and get used to the shoes before recording and evaluating.
Before the start of testing, 41 markers with a diameter of 14 mm were installed in two limbs at the anterior superior iliac, posterior superior iliac, ankles, sides of the knee joint, posterior heel, acromioclavicular joint, external humerus condyle, styloid process, the radius and head of the first and fifth metatarsals, as well as the spinous process of the seventh cervical vertebra. Also, the 4-marker pad was attached to the anterior-outer surface of the leg and thigh using a stretchable strap.
Static stability was evaluated by force plate (dimensions 50 x 60 cm and frequency 1000 Hz from Kestler Company). In this evaluation, the subject stands for one minute on the power plate while the arms are at the side of the body and looking forward. Then, the dynamic stability of the subject was evaluated by walking at a selected speed of 8 m in the laboratory so that the person’s foot was placed on the force plate by 7 cameras by the motion recording and analysis system (frequency 200 Hz).
The subject walked in the laboratory for 10 minutes before registering and evaluating the device to adapt and get used to the desired shoes. Both tests were performed in static and dynamic conditions, once with the standard shoes and then in the same session with the improved shoes (heel flare with arch support and toe grip bar). Each test was repeated five times. To prevent fatigue, a 5-minute break was taken between each test.
Standing stability was measured with parameters including displacement, velocity, sway, and standard deviation of the center of pressure in medial-lateral and anterior-posterior directions. Stability in walking mode was recorded with walking speed, cadence, step length, and standing phase percentage [16]. Ground reaction force parameters, including vertical forces (Fy), anterior-posterior forces (Fx), and average lateral forces (Fz) were also measured [17].
Statistical analyses were performed by SPSS20 software, with a significance level of P<0.05. All parameters were determined using the Shapiro-Wilk test. Parametric statistical analysis was used to evaluate the difference between mean values. The paired t test was used to determine the difference between parameters related to stability in standing and walking in different phases.

Results
Fifteen (13 women and 2 men) older people were studied. They were all over 65 with an average age of 70±3.94 years, average height of 159±0.09 cm, and average body mass index of 29.69±3.77 kg/m2.
The mean values of center of pressure sway in the medial-lateral direction in the standard shoe and the shoes with heel flare with arch support and toe grip (to check the static stability) were 36.47±12.92 and 44.67±15.36 mm, respectively. No significant difference was observed between the standard and modified shoes in step length, speed, and pressure center movement in the anterior-posterior and medial-lateral planes (Table 1).


Step time and walking speed variables were used to measure dynamic stability. Compared to the standard shoes, the altered shoes caused a significant increase in both step time (P≤0.008) and walking speed (P≤0.003). The mean step times with standard and modified shoes were 1.56±0.18 and 1.46±0.18 seconds, respectively. No significant difference was observed in stride length (P≤0.085) and standing phase percentage (P≤565).
The parameters of the ground reaction force were also evaluated in this study. Intending to create forward force, the FX1 factor increased significantly after using the modified shoes compared to the standard shoes (P≤0.001). On the other hand, the FX2 parameter, the opposing force of the movement, decreased significantly (P≤0.02) after using modified shoes. Factor FY3 decreased significantly (P≤0.000) after using medical insoles and shoes (Table 2).



Discussion
Balance is an important and complex process consisting of receiving information about the body’s position and movements and coordinating movement components to achieve body control while walking and standing. Falling and imbalance are two common problems of old age, which deserve special attention based on biomechanical principles of any significant resistance in balance variables in older people.
Comparing two situations of standard shoes and improved shoes indicates significant balance changes. Therefore, combining interventions following biomechanical principles can be considered a therapeutic approach. The changes and corrections applied in medical shoes and insoles can bring people’s balance and kinematic parameters to a large extent closer to the normal level.
Attention to the changes in temporal and spatial parameters of walking with simple interventions and corrections in the front, middle, and back of the foot, each in the static and dynamic phase of walking, has been effective and can achieve balance and the subsequent reduction in the number of falls in older people, which in the present study is devoted to it.
Walking speed is considered an important parameter in balance, which normally decreases from the beginning of old age onwards [16], and this low speed is a strong predictor and early indicator for adverse outcomes such as falls [17, 18]. In the present study, before the simultaneous use of shoes and medical insoles, the average walking speed was 41.49 m/min, which increased to 45.23 m/min after using shoes with flares and medical insoles. These results show that using shoes with flares and medical insoles can lead to a more symmetrical gait and a stable walking pattern by increasing walking speed and less step time to improve balance [19] and control the displacement of the center of pressure [20, 21]. 
A decrease in step length is observed in most older people who have experienced falling [17]. In a study to change the stride length of older people, insoles with arch support were used, and subsequently, an increase in stride length was seen [22]. However, in this study, the stride length change was not significant; it seems that this difference can be attributed to the decrease in the strength of the plantar flexor muscles of the foot or the flexor muscles of the fingers as a factor in lifting the toes while walking is due to the application of two changes, the  toe grip bar and heel flare, which has reduced the flexibility of the insole and shoe bottom. 
Older people decrease cadence due to speed reduction; among them, older people who experience falling also experience a decrease in cadence while walking [17]. In the present study, in line with the study of Alboim et al., after using modified shoes, we see a significant increase in cadence following an increase in walking speed [23].
Walking stability is closely related to ground reaction force, which changes with age [16]. In the present study, obtaining the peak ground reaction force in three planes showed that the combination of arch support and toe grip bar with shoes with heel flares can affect the ground reaction force parameters.
Factor FX1 is the first peak of anterior-posterior force among the parameters reflecting ground reaction force, which increased significantly after using shoes with flares, a toe grip bar, and arch support. That is, by increasing the speed, the person’s forward movement is facilitated, which indicates an increase in confidence in the balance when moving. Hemti et al., in line with the present study, found that changing the angle of the toes in the insoles can lead to an increase in the first peak of the anterior-posterior force and ultimately increase the step and walking speed [24].
Another parameter of the ground reaction force is the FX2 factor, which, after using shoes with flares and insoles with toe grip bar and arch support, found a significant decrease and made older people experience a better ability to move forward along with increasing walking speed and improving balance.
Another parameter to be evaluated is FY3. It is the vertical force of the push-off peak during the gait cycle in people with less stability. It means either the walking speed is reduced or the function of the muscles responsible for pushing the lower limb forward is reduced. In the present study, when using modified shoes, we see a decrease in this peak, which means that this change reduces the need to compensate for more muscle function in older people and makes walking easier, which indicates an improvement in stability.
One of the important factors in evaluating stability while standing and walking is changes in the center of pressure. In older people who experience falling, the velocity of the center of pressure increases, especially in the anterior-posterior direction [19, 24]. Patton et al. evaluated the impact of insoles on static balance and found that using insoles with arch support increases the speed of the center of pressure and displacement of the center of pressure [25]. On the other hand, Cudejko et al. found that the speed of the center of pressure in both medial-lateral and anterior-posterior directions decreases in wider shoes compared to normal shoes [26]. In the present study, this variable did not increase after using modified shoes, which is a sign of improving static balance. This is because the arch support with the heel flare has given older people’s gait a wide support surface and better balance.
One of the limitations of this study was that most of the subjects were women, and there is a possibility that the balance is different in men compared to women. Another limitation was the short time needed to adapt to changes in shoes and check them immediately and properly. It is suggested that the effect of the modified shoe be carried out over a longer period.

Conclusion
The use of shoes with a heel flare with arch support and a toe grip bar, in addition to increasing balance, will reduce falls and improve the parameters of step time and gait speed to facilitate movements in older people.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the ethics committee of  Isfahan University of Medical Sciences with the ethical code IR.MUI. RESEARCH.REC.1400.062.

Funding
The article was extracted from a master’s thesis, funded by Isfahan University of Medical Sciences (Grant No.: 399988). 

Authors' contributions
Conceptualization and Supervision: Alireza Taheri and Mohammad Taghi Karimi; Methodology and data analysis: Alireza Taheri and Zahra Khajooei; Investigation, writing original draft, and review & editing: All authors; Data collection: Zahra Khajooei; Resources: Alireza Taheri, Mohammad Taghi Karimi, and Zahra Khajooei.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgments
The authors would like to thank the staff and management of the Musculoskeletal Research Center of the Faculty of Rehabilitation Sciences, Isfahan University of Medical Sciences, and all participants for their cooperation and support.


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