Abstract
Highlights
Non-slip soles significantly improved balance and reduced falls in older women compared to regular soles.
PVC soles showed the highest effectiveness in maintaining balance among different sole types tested.
PU soles were most effective in reducing fear of falling, with a high improvement compared to other materials.
EVA soles demonstrated the best results in improving timed up-and-go (TUG) test performance.
Participants reported higher satisfaction and comfort with PU and EVA soles compared to PVC soles.
Introduction
The global population of older adults is projected to reach 2 billion by 2050 (Jellema et al., 2019). This stage of life is marked by significant changes that can increase vulnerability (Pahlevanian et al., 2020; Shaw et al., 2019), including a heightened risk of falls and balance issues (Peeters et al., 2007). Falls are a major concern for older adults, with research indicating that approximately 30% experience at least one fall per year (Cudejko et al., 2020a, 2020b; Hatton & Rome, 2019), and 20% of falls resulting in significant consequences (Kim & Lockhart, 2020; Otis et al., 2016). Factors that cause falls are classified into two categories (Golmakani et al., 2014; Li, n.d.): internal factors (Bustamante-Troncoso et al., 2020) and external factors (Dadashi et al., 2014; Kelsey et al., 2010).
Another important factor is the fear of falling (FoF; Moreira et al., 2017), which can reflect a realistic assessment of reduced functional abilities that leads to appropriate cautious behavior to prevent falling (Hewston & Deshpande, 2018; Osoba et al., 2019). According to research (Park et al., 2021), the foot plays a crucial role in performing daily activities. Wearing appropriate shoes is a key measure to prevent falls (Jellema et al., 2019; Menz et al., 2006), as footwear can impact walking style (Mann et al., 2015), protect the feet from hazards (Jessup, 2007), and provide support between the feet and the ground (Barwick et al., 2019a, 2019b).
Shoes are composed of the heel, inside, and sole (Cudejko et al., 2020). The sole and heel are particularly important for maintaining balance, as they can provide subsensory mechanical noise signals to the feet (Hatton et al., 2013). The risk of falling is influenced by the characteristics of shoes (Park et al., 2021). One crucial aspect of shoe design is the height, geometry, and material of the sole, as very high or low heels can decrease balance and increase the risk of falling (Kim & Lockhart, 2020). For older individuals, the optimal heel size for shoes is between 1.5 to 2.5 cm, as this range has been shown to reduce the risk of falling (Davis et al., 2016; Kelsey et al., 2010).
In particular, shoes with high or narrow heels, soft midsoles, and a lack of stabilization are considered harmful (Menz et al., 2017). Research suggests that falling poses a greater risk of injury than slipping, particularly during winter months (Bagheri et al., 2021). It has been demonstrated that shoes with textured soles and soft plastic materials are more appropriate for older adults (Hatton et al., 2013), as they can alter the secretion of mechanical receptors and spatiotemporal firing patterns of sensory afferents in the feet (Hatton et al., 2013).
These shoes can increase sensitivity to changes in foot mechanical events during standing and walking by enhancing tactile and proprioceptive sensory inputs (de Morais Barbosa et al., 2018; Kelsey et al., 2010). Softer soles in shoes tend to improve balance by accommodating the foot position, while stiffer soles provide greater postural stability by placing the foot in a more neutral position (Losa Iglesias et al., 2012; Qu, 2015). The geometry and shape of the sole also play a significant role in balance, with the sole’s geometry affecting the distance between the toes (Thies et al., 2015). Recent studies have highlighted the role of footwear design in improving balance and preventing falls among older adults. For instance, Menz et al. (2017) evaluated prototype balance-enhancing footwear and found that although such shoes could improve gait parameters such as step width and sway, user acceptability remained a concern due to issues related to comfort and esthetics. Likewise, Cudejko et al. (2020) demonstrated that minimal footwear could enhance postural stability and functional mobility (including Timed Up and Go performance) compared to conventional or barefoot conditions in older adults. In a comprehensive review, Menant et al. (2008) identified several critical features of safer footwear for seniors, such as low heel height, firm slip-resistant soles, high collars, and beveled edges, all of which contribute to reduced fall risk. These findings underscore the need to integrate biomechanical efficacy with wearer acceptability in designing and evaluating footwear interventions for older populations (Cudejko et al., 2020; Menant et al., 2008a, 2008b; Menz et al., 2017).
Rome et al. (2011) showed that walking shoes with appropriate features reduce heel and forefoot side pressure and increase midfoot pressure compared to wearing their shoes. These findings help health professionals deal with the challenges of wearing shoes, especially those challenges affecting women (Barwick et al., 2019). Considering that there are three types of soles in the Iranian market as anti-slip soles, namely PU soles, EVA soles, and PVC soles, in this study, the material, geometry, and size of these soles were discussed to determine the best type of non-slip soles for older women.
Materials and Methods
Study Design and Participants
This is a parallel controlled trial study in the population of older women with permanent membership of Farzngan Daily Caring Foundation (FDCF) in Shiraz city, Southern Iran, in the second half of 2022. Using PASS sampling software version 15.0.13 (2023, NCSS Statistical Software, Kaysville, Utah, USA), upon Thies et al.’s (2015) study as aligned study in its objectives and with 15% dropout about 32 older women over 60 years old were chosen (alpha error = 0.01 and effect size = 0.367). The appropriate effect size (37%) indicates to the suitable of sample size in this research as well. However, it should be noted that the small sample size (n = 8 per group) substantially limits the statistical power and increases the risk of Type II error, particularly when comparing across three intervention groups and a control group. Inclusion criteria for participation included has no any musculoskeletal disorders, do not use assistive devices for walking, being permanent membership in FDCF, willingness to participate, do not experience a falling during the past year, receiving an score between 14 and 28 in fear of fall upon FES-I short version, normal cognitive function according to the MoCA test (as a rapid screening instrument for mild cognitive dysfunction), verbal communication ability, and a normal TUG score. Participants were excluded from the study if they experienced stressful events such as the death of relatives, demonstrated an unwillingness to continue cooperation, or developed musculoskeletal problems that interfered with walking during the study. Using Efron’s random allocation method with equal blocks in PASS software (2023), the samples were divided into four groups with eight participants in each group. The randomization sequence was computer-generated by an independent statistician, and allocation concealment was achieved using sealed, opaque, and sequentially numbered envelopes. The study did not implement stratified randomization. Neither participants nor outcome assessors were blinded to group assignments, which may increase the risk of performance and detection biases, particularly for subjective outcomes such as fear of falling and comfort. The membership code of older individuals in the foundation was used as the basis for sampling. The selected people were checked according to the entry criteria, and if they did not meet the entry criteria, the next person from the list was selected. All participants completed a written informed consent form. The interviews and questionnaires are performed from April 4, 2023, to April 11, 2023 (first phase) and from August 13, 2023, to August 20, 2023 (second phase) in the FDCF.
Data Collection
After being informed about the research objectives and methods the older female subjects provided written consent. Two questionnaires were then conducted. Participants completed a demographic survey consisting of 29 questions on age, sex, education level, marital status, having children, housing status, employment status, monthly income, illness, and types of diseases. Additionally, a validated questionnaire was used to measure FoF among older adults in 2022. This was the Iranian shortened version of FES-I 7-items, each of which is scored on a 4-point Likert scale (from “Never” (1) to “Always” (4)). A score of 28 indicated high FoF, while a score of 7 indicated no FoF. The 3-TUG dynamic balance test and 4-BERG static balance test were performed for both intervention and control groups. The questionnaires were collected 1 week before the start of the intervention and 1 week after the 3-month intervention, which took place from March 23, 2023, to June 6, 2023.
Intervention Procedure
The intervention and control groups participated in separate briefing sessions at the start of the study. These sessions lasted 60 min and included lectures, educational video clips, and practical demonstrations to familiarize participants with the study objectives, the importance of footwear in fall prevention, and the correct use of the provided shoes. At the end of the session, participants were given shoes with different types of soles (PU, PVC, EVA) based on their assigned group.
Participants were instructed to wear the provided shoes daily for 3 months while performing their routine activities. To ensure compliance, daily usage was monitored through two methods:
1. Phone calls: Participants received regular phone calls to confirm adherence and address any concerns or issues related to the shoes.
2. Home visits: Researchers visited participants’ homes at the end of each week to visually inspect the shoes and document their condition and usage patterns. Throughout the 3-month follow-up period, participants were encouraged to provide ongoing feedback about their experiences, including comfort, stability, and any challenges faced while wearing the shoes. This feedback was collected during phone calls and home visits to ensure continuous engagement and accurate data collection. At the end of the study period, participants were asked to complete the same set of questionnaires they had filled out at baseline. These questionnaires assessed variables such as fear of falling (FoF), balance performance, and frequency of falls. The post-intervention responses were compared with baseline data to evaluate the impact of the anti-slip soles on the measured outcomes.
Statistical Analysis
The data of the first and second stages were normal according to the Shapiro-Wilk and D-Agostino tests. The validity of the questionnaires was higher than 0.75 using McDonnell’s Omega, and the intraclass correlation coefficient (ICC) was higher than .78. To determine the difference between the groups and before and after the intervention, independent and paired t-tests were performed. The intervention effect was primarily assessed using Cohen’s d and partial eta squared, which are standard and interpretable indices. To control for the potential inflation of Type I error due to multiple comparisons, Bonferroni correction was applied. The data were analyzed with the help of SPSS software (version 28; SPSS Inc, 2018) and Magnusson web software (Magnusson, 2022), with a significance level set at less than .05.
Ethical Consideration
The ethics code of this study was issued by the Shiraz University of Medical Sciences under the number IR.SUMS.SCHEANUT. REC.1401.009 on March 21, 2022, and the international trial code under the number IRCT20180514039648N3 from the Iranian Registry of Clinical Trials (IRCT) on May 25, 2022. The study was carried out following Declaration of Helsinki (DoH, 7th ed.) and CONSORT guidelines (Ext.) as well.
Results
In this research, 32 older adults were investigated. The mean age of years was 69.72 (SD = 6.78), which showed no significant difference in the age of the two groups based on the ANOVA test. The Supplemental Table 1 showed a significant difference between experiment and control groups in terms of demographic variables, such as having chronic diseases, duration of diseases, taking certain drugs, living alone, marital status, level of education, health status, etc. there was not (see Supplemental Table 1).
In this parallel controlled trial study, the data in the table shows that there was no significant difference between the intervention and control groups in terms of the Berg Balance Scale (BBS; p = .314) based on the significance level. All sample members met the entry criteria, which included a certain score from the BBS test. However, after 3 months of intervention, the data revealed a significant difference in the BBS between the intervention and control groups due to the use of non-slip shoe soles (p = .073, Cohen’s d = 1.40, 95% CI [0.91, 1.89]; partial η² = 0.205), indicating that non-slip shoe soles have a significant effect on the BBS. To reduce the risk of Type I error resulting from multiple comparisons, the Bonferroni correction was applied. Additionally, ANOVA findings in Table 1 demonstrate a significant difference even among the intervention groups, specifically for the ranking of cumin seeds, which is highly important.
One-Way ANOVA Analysis of Variance Results for BBS Before and After Using Anti-Slip Shoes.
The subjective sense of comfort/satisfaction reported by participants was collected using non-standardized interviews; future studies should consider visual analog scales (VAS) or Likert-based standardized tools. The intervention’s effectiveness in improving balance was highest for PVC anti-slip soles, with Cohen’s d = 1.40 (95% CI [0.84, 1.96]), indicating large effect size.
According to Table 2, there was no significant difference between the intervention and control groups in terms of the BBS (p = .107) at the beginning of the study. All participants had a certain score on the FoF test according to the entry criteria. However, after 3 months of using non-slip shoe soles, a significant difference was observed between the intervention and control groups in terms of FoF (p = .006, Cohen’s d = 1.43, 95% CI [0.97, 1.89]; partial η² = 0.539), indicating that the soles were effective in reducing FoF.
One-Way ANOVA Analysis Results for the Fear of Falling Variable Before and After Using Anti-Slip Shoes.
Again, Bonferroni correction was applied across multiple outcome measures to control for the inflation of Type I error.
According to Table 3, the significance level indicated no significant difference between the intervention and control groups in terms of reducing the number of falls (p = .099) at the beginning of the study. All participants had experienced at least one fall according to the entry criteria. However, after 3 months of using anti-slip shoe soles, a significant difference was observed between the intervention and control groups in terms of the frequency of falls (p = .000, Cohen’s d = 1.61, 95% CI [1.07, 2.14]; partial η² = 0.472), as shown in the table. This suggests that the soles have a positive effect in reducing the frequency of falls.
One-Way ANOVA Variance Analysis Results Table for the Variable of Fall Frequency Before and After Using Anti-Slip Shoes.
According to Table 4, there was no significant difference between the intervention and control groups in terms of TUG balance (p = .332) at the beginning of the study. However, after 3 months of using anti-slip shoe soles, a significant difference was observed between the intervention and control groups in terms of TUG balance (p = .001, Cohen’s d = 1.31, 95% CI [0.85, 1.78]; partial η² = 0.467), as shown in the table. This suggests that the soles have a significant effect on improving the TUG balance.
One-Way ANOVA Analysis Results for TUG Variable Before and After Using Anti-Slip Shoes.
The effect coefficient of the intervention including omega square (0.336) and partial eta square (0.467) shows that after the intervention, anti-slip soles have a positive effect of 33.6% in improving TUG in older adults. A pair was also used. The results showed that with the help of Cohen’s d-effect coefficient (1.31) and Glass’s delta (1.09), EVA anti-slip soles could have the highest percentage of effectiveness (131%) in improving TUG in older adults (p < .05). Also, Cohen’s U3 coefficient evaluated the effectiveness of the intervention regarding this variable, which showed that this intervention was very favorable with a score of 99.9%.
Discussion
The study aim was to evaluate if the anti-slip soles available in the market reduce the frequency of falls, lower the fear of falling (FoF), and have a positive impact on balance in older adults in Shiraz city. The results were consistent with recent literature and demonstrated that anti-slip soles significantly affect these variables. The material density of the three types of soles used in the study by Sipaut et al. (2017) was measured in different environments, and it was found that the density relationship of the soles was as follows: PU < EVA < PVC. Soles with lower density are lighter and more comfortable (Sipaut et al., 2017). Menz et al. (2017) reported that the coefficient of friction and sole shape significantly impacts slipperiness.
Older adults’ fall risk increases during transitional movements while age-related declines in sensory function may reduce balance ability (Amiez et al., 2021). Accordingly, Takahashi et al. (2006) found that higher Timed Up and Go (TUG) scores (commonly used balance tests for older adults) were associated with falls. The use of non-slip soles improves the balance of older people and makes walking easier while reducing the risk of falling. Additionally, comparing the soles with each other, the EVA sole provided the most balancing function for forward and backward movement in older adults. Then, PU and PVC soles were the most effective for balancing walking and general mobility. Menant et al. (2008) recommended a heel height of 2.5 cm for older individuals to avoid negative effects (Menant et al., 2008; Roman de Mettelinge et al., 2015). In a separate study, Zhang (2015) found that runners who wore shoes with the best breathability and PU insoles had a 4% increase in their average speed compared to those who wore EVA or PVC soles.
An informed choice of footwear can optimize a person’s mobility. In the current study, the Berg Balance Scale (BBS-9) was used to evaluate the dynamic and static balance of older individuals, proving that most participants performed weaker in these tasks before the intervention but showed relative improvement, especially in one-leg balance, after the intervention. Consistent with this, Amiez et al. (2021) reported that the use of balance shoes enhances the balance of individuals with closed eyes on both legs, and a majority of users reported feeling more secure and stable.
Whereas FoF can result in reduced engagement in daily activities (Zhang, 2015), this study found that older people who used non-slip shoes experienced significantly less FoF, which led to an increase in their confidence when shopping and walking. The PU sole had the highest score, followed by the EVA sole and finally the PVC sole in terms of this variable. The pairwise comparison of all groups using Cohen’s F-square test showed that the TUG test had the highest effect coefficient on the balance variable, while the Berg test had the lowest effect coefficient. In general, the effectiveness of any intervention can first be assessed with the help of the TUG balance test. In sequential comparisons between the intervention groups, Cohen’s f-square effect coefficient was the highest in older people with PU soles, especially compared to those with PVC soles in three study variables, and also compared to EVA soles in the variable of fall frequency.
The frequency of falls was the final variable examined in this study. The use of soles had a positive impact on several participants who had previously experienced falls, and no falls were reported during the study period. However, due to the relatively short duration of the intervention (3 months), the long-term sustainability of these positive outcomes, including behavioral adaptation and durability of anti-slip function, remains unclear and should be addressed in future longitudinal studies. Based on previous research and the study’s data, participants who used PU and EVA soles reported higher satisfaction levels and better balance and comfort compared to the other group. In contrast, those who used PVC soles reported feeling slightly dry and slippery due to the rubber material. This study’s findings were similar to those of Healy and Ahmad, who also investigated the impact of different soles on balance and comfort. However, their study found that participants preferred the PU sole over the EVA sole for comfort and balance (Ahmad et al., 2012; Healy et al., 2012).
It should also be noted that all participants in this study were older Iranian women residing in Shiraz, a city with semi-desert and mountainous climate conditions. This homogeneity in gender, ethnicity, and environmental context limits the generalizability of the findings to broader populations, especially males, non-Iranians, or those living in different climatic or urban environments.
The current study highlights the importance of shoe sole selection for older women, as it can affect their performance on the FoF, TUG, and BBS tests. Wearing shoes with non-slip soles during a short familiarization period (in this study, 3 months) is necessary to optimize the resulting effects. Additionally, most participants reported positive effects of shoes with non-slip soles compared to their previous shoes. Therefore, the tested anti-slip soles can serve as a viable solution to enhance the safety of older adults and prevent falls. Based on the feedback of the participants and previous research, it was determined that PU soles are the most comfortable and slip-resistant, followed by EVA soles and PVC soles. Therefore, it is recommended that older individuals wear shoes with these types of soles, particularly when walking, to reduce the risk of falls.
Conclusion
The results confirmed that the use of non-slip soles in shoes significantly improved balance, walking ability, and fall prevention among older women with low-risk factors for falls. Knowledge of the benefits of non-slip soles and its dissemination to healthcare professionals and geriatric nurses could easily influence seniors’ choice of footwear and further prevent falls, reduce FoF and improve balance in a cost-effective way. However, the intervention period was limited to 3 months, which may not allow for a full assessment of the long-term durability of effects or behavioral adaptation. Additionally, the lack of blinding in the study design—both for participants and assessors—could have introduced performance or detection bias, particularly in subjective outcomes such as fear of falling and satisfaction.
The sample exclusively consisted of older Iranian women living in a semi-desert, mountainous climate, which limits the generalizability of the findings to other genders, age groups, cultures, or geographical settings. Therefore, future studies should investigate the psychological and functional benefits of footwear interventions among older men and in diverse environmental contexts. Limited financial resources at the university also restricted the sample size. Increasing the sample size would improve the reliability of the results. Future research should employ larger, more diverse samples and adopt longer follow-up periods to better understand the sustainability and broader applicability of anti-slip footwear interventions.
Supplemental Material
sj-docx-1-ggm-10.1177_30495334251358528 – Supplemental material for Effectiveness of Shoes With Non-Slip Insole on Balance, Fear of Falling, and Fall Prevention Among Older Women: A Parallel RCT
Supplemental material, sj-docx-1-ggm-10.1177_30495334251358528 for Effectiveness of Shoes With Non-Slip Insole on Balance, Fear of Falling, and Fall Prevention Among Older Women: A Parallel RCT by Sahar Norouzi, Aleksandra Błachnio, Bahareh Zeynalzadeh Ghoochani, Abdolrahim Asadollahi and Mohammad Hossein Kaveh in Sage Open Aging
Footnotes
Acknowledgements
Our warm thanks go to the Research & Technology Deputy Dean of Shiraz University of Medical Sciences, Director of Farzanegan Daily Caring Foundation (FDCF), and The Middle East Longevity Institute in Abyad Medical Centre, as well as Iranian older people who are permanent member of FDCF for their patience and participation in our study.
Ethical Considerations
The ethics code of this study was issued by the Shiraz University of Medical Sciences under the number IR.SUMS.SCHEANUT.REC.1401.009 on March 21, 2022, and the international trial code under the number IRCT20180514039648N3 from the Iranian Registry of Clinical Trials (IRCT) on May 25, 2022. The study was carried out following the 2013 Helsinki Convention and CONSORT guidelines (2009) as well.
Author Contributions
MHK & BZG have assisted in the conceptualization and design of the study, oversaw data collection; ZN has collected the data, and did data file preparation and screening; AB has written the discussion section and drafted the first version of the manuscript. AA have interpreted data, analyzed it, and extracted the results. All authors read and approved the final manuscript.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.
Artificial Intelligence (AI) in Publication
No artificial intelligence tools were used during the entire process of conducting and publishing the present study. However, in the current manuscript, the AI tool QWEN version 2.5 Max was utilized for literary editing, grammatical corrections, and adherence to English language conventions.
Declaration of Generative AI and AI-Assisted Technologies in the Writing Process
During the preparation of this work the author(s) have not used any generative AI and AI-assisted technologies.
Trial Registration
The ethics code of this study was issued by the Shiraz University of Medical Sciences under the number IR.SUMS.SCHEANUT.REC.1401.009 on March 21, 2022, and the international trial code under the number IRCT20180514039648N3 from the Iranian Registry of Clinical Trials (IRCT) on May 25, 2022.
Level of Evidence
Level I, randomized controlled trial.
Supplemental Material
Supplemental material for this article is available online.
MeSH Terms
Accidental Falls/prevention & control
Aged, 80 and over
Checklist
Chronic Disease
Female
Humans
Independent Living
Mental Recall
Middle Aged
Musculoskeletal Equilibrium
Osteoporosis/physiopathology
Pediatric Obesity/psychology
Perception
Postural Balance
Postural Balance/physiology
Posture Balance
Posture Equilibrium
Self-Efficacy
Self-Report
Falling
Non-Slip
Older Adults
Berg Balance Scale
FES-I
TUG
References
Supplementary Material
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