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OPINION article

Front. Psychol., 09 November 2022
Sec. Psychology for Clinical Settings

Falls efficacy: The self-efficacy concept for falls prevention and management

  • 1Health and Social Sciences Cluster, Singapore Institute of Technology, Singapore, Singapore
  • 2Centre for Health, Activity and Rehabilitation Research, Queen Margaret University, Musselburgh, United Kingdom

Introduction

Falls efficacy has been keenly studied in older people since the introduction of the Falls Efficacy Scale. The seminal paper “Falls efficacy as a measure of fear of falling” has received over 2,500 citations since 1990 (Tinetti et al., 1990). The presence of newer versions of falls efficacy-related scales, either modified from the ancestral version or constructed afresh, suggests that many researchers and clinicians are interested in investigating the meaningful impact of falls efficacy (Soh et al., 2021a). Ultimately, endeavors aiming to empower older people to prevent and manage falls need a clear understanding of falls efficacy. Some articles featured in the Frontiers have demonstrated these efforts, such as presenting the mediating role of falls efficacy between fatigue and falls risk (He et al., 2022) and the role of a falls risk-reduction program on falls efficacy (Cho et al., 2014). Given the advances in research on falls efficacy, have we adequately understood this self-efficacy concept and have the most appropriate measure applied for the construct of interest?

Literature has reported several challenges in understanding falls efficacy since the 2000s. Two systematic reviews reported significant difficulties in deciphering whether the measures of falls efficacy were measuring falls efficacy, balance confidence or fear of falling (Jorstad et al., 2005; Moore and Ellis, 2008). Various researchers have attempted to clarify the falls efficacy concept. Hadjistavropoulos et al. (2011) presented key research findings to advocate that falls efficacy and balance confidence are equivalent and interchangeable. However, Hughes et al. (2015) drew on the theoretical origins of falls efficacy, balance confidence and outcome expectancy to recommend that researchers clarify the different constructs. Recently, Soh et al. (2021b) posited that falls efficacy and balance confidence are dissimilar and that falls efficacy encompasses four domains surrounding falls (i.e., pre-fall, near-fall, fall-landing, and completed-fall). Elucidating falls efficacy as a broader set of perceived capabilities would advocate a complete approach to helping older people overcome falls and falling.

This commentary aims to update the understanding of falls efficacy by revisiting Bandura's self-efficacy theory and then offering a contemporary interpretation. The commentary highlights some selected measures to suggest that appropriate measures should be applied in research surrounding falls efficacy.

Theoretical origin

Falls efficacy is rooted in Bandura's self-efficacy theory (Tinetti et al., 1990). Self-efficacy is the belief in personal capabilities to organize and execute the sources of action required to manage prospective situations (Bandura, 1997). As a cognitive mechanism, self-efficacy mediates between thoughts/emotions and actions (Bandura, 1986). The theory of self-efficacy postulates that perceived capability (i.e., level of confidence), other than the person's true capability, can influence behavior (Bandura, 1997). It is noteworthy to recognize that the efficacy belief system is a differentiated set of self-beliefs linked to distinct realms of functioning (Bandura, 2006). A fuller understanding of falls efficacy will provide more strategies to help individuals deal with falls and overcome concerning issues (i.e., fear of falling and fear-related activities-avoidance behavior).

Evolution of the concept

Falls efficacy was first introduced to rationalize a novel scale, the Falls Efficacy Scale, to measure fear of falling (Tinetti et al., 1990). There were a few reasons. First, the theoretical framework of the scale would be grounded in Bandura's self-efficacy concept (Bandura, 1986). Second, fear could be purportedly determined through a continuous scale. Third, fear would be dissociated from psychiatric connotations. However, a follow-up study by the developers reported that the Falls Efficacy Scale should remain an efficacy measure rather than a fear measure because older people who were reportedly efficacious also feared falling (Tinetti et al., 1994).

Falls efficacy was then associated with the perceived ability to perform various activities steadily (balance confidence) (Hadjistavropoulos et al., 2011). Falls efficacy (i.e., balance confidence) was shown to improve by interventions, such as Tai Chi (Chewning et al., 2020), but not for those that improve performances of reactive balance (Kurz et al., 2016) or safe falling (Arkkukangas et al., 2020). These interventions might have improved other perceived self-efficacy to overcome falls, such as balance recovery confidence and safe-landing confidence. However, their effectiveness remains inconclusive due to the measures' limitations. Balance confidence measures aim to determine the perceived ability to perform activities steadily rather than to recover the balance from perturbations or fall safely on the floor (Soh et al., 2021a).

Falls efficacy has recently been posited to encompass four different types of self-efficacy surrounding falls: balance confidence, balance recovery confidence, safe-landing confidence, and post-fall recovery confidence (Soh et al., 2021b). Balance confidence relates to the perceived self-efficacy of performing activities without losing balance (Powell and Myers, 1995). Balance recovery confidence refers to the perceived ability to recover balance and arrest a fall in response to perturbations that can occur in everyday activities (Soh et al., 2022b). Balance recovery confidence differs from balance confidence, given that balance confidence focuses on the perceived capability to perform activities steadily, such as climbing up or down stairs. In contrast, balance recovery confidence refers to the perceived reactive balance recovery reactions, such as grabbing onto a handrail or taking a few steps to recover balance in response to a trip or a slip. Safe-landing confidence refers to the self-efficacy of falling safely onto the ground by minimizing landing injuries (Moon and Sosnoff, 2017). Fall recovery confidence refers to the self-efficacy to recover from falls, such as getting up or getting help (Hofmeyer et al., 2002). The concept was substantiated based on a review paper investigating the methodological quality of content developed for different falls efficacy-related measurement instruments (Soh et al., 2021a).

Measurement instruments of falls efficacy

Measures of falls efficacy can be categorized into two broad types: single-domain and multi-domain. Single-domain measures that focus on one domain of falls efficacy rely on a well-defined conceptual analysis of the specific domain (De Vet et al., 2011). In contrast, multi-domain measures that encompass more than one domain of falls efficacy aim to reveal a general sense of personal efficacy to produce certain attainment (Bandura, 2006), that is, to overcome falls threat. However, a significant number of existing falls efficacy measures lack high quality evidence in their content development and validity based on a systematic review (Soh et al., 2021a) that applied the COSMIN methodology (COSMIN., 2021). Nevertheless, some of the measures commonly used in falls practice (APTA Geriatrics., 2021) that potentially fit into the current understanding of falls efficacy are presented in Table 1.

TABLE 1
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Table 1. A list of potential measurement instruments for balance confidence, balance recovery confidence, fall recovery confidence, and falls efficacy based on a systematic review conducted by Soh et al. (2021a).

Discussion

The concept of falls efficacy has evolved. Translating new insights of falls efficacy into practice promotes new and novel approaches to help older people overcome the threat of falls. In highlighting the different perceived self-efficacies, researchers and clinicians should select the most appropriate measures when studying the impact of different interventions on the construct of interest (McKenna et al., 2019). For example, exercise interventions, such as Pilates (Roller et al., 2018; Aibar-Almazan et al., 2019), Tai Chi (Okuyan and Bilgili, 2017; Chewning et al., 2020), Otago exercises (Johnson et al., 2021) and Fall Management Exercise programme (FaME) (Iliffe et al., 2015), being more holistic, could consider using multi-domain measures. Skill training interventions, such as Chinese martial arts training (Ma et al., 2019), perturbation training (Kurz et al., 2016; Lurie et al., 2020), Judo4Balance (Arkkukangas et al., 2020), and backward chain training (Leonhardt et al., 2020), being more focused strategies, could benefit from using single-domain measures for the targeted constructs.

Past research has primarily focused on balance confidence as an outcome (Soh et al., 2022a). A review of falls efficacy-related studies found that 90% employed either the Falls Efficacy Scale or the Activities-specific Balance Confidence Scale. Through these measures, the effect on balance recovery confidence, safe-landing confidence, and fall recovery confidence remains unclear. Single-domain measures should be appropriately used. However, completing several self-reported questionnaires can be burdensome. Multi-domain measures, such as the Perceived Ability to Prevent and Manage Fall Risks Scale (Yoshikawa and Smith, 2019), could be considered to obtain a general sense of perceived self-efficacy in preventing and managing falls. It is, however, imperative that these measures are used cautiously. Unlike the FES and ABC scale, these measures have not been rigorously validated. There is an urgent need for validation studies to critically evaluate falls efficacy-related measures and present their measurement properties.

Researchers and clinicians who want to measure fear of falling should use measures such as the Falls Efficacy Scale-International (FES-I) (Yardley et al., 2005), short FES-I (Kempen et al., 2008), Fear of Falling Questionnaire (Bower et al., 2015), and Fear of Falling Avoidance Behavior Questionnaire (Landers et al., 2011). Unlike self-efficacy instruments, these fear of falling measures were constructed to determine concerns about falling. These measures potentially capture multiple expectancies, such as perceived consequences arising from a fall, perceptual control, and their judgement of capability to act in the given scenarios (Lach, 2006). Falls efficacy measures should be complementarily used with the fear of falling measures. A fuller picture of the different psychological factors is essential in predicting falls and determining performance (Hadjistavropoulos and Delbaere, 2021). Thoughtful employment of an enduring self-efficacy concept in falls research and clinical work will help advance novel interventions to address the person's self-development and behavioral adaptation and changes.

In conclusion, falls efficacy can be viewed as a perceived ability to prevent and manage falls. Embracing this interpretation provides a broader paradigm toward helping older adults be more resilient against falls. Applying appropriate measures for the perceived capability in preventing and managing falls is imperative to clarify the targeted construct.

Author contributions

The author confirms being the sole contributor of this work and has approved it for publication.

Acknowledgments

The Balance Recovery Confidence Scale was developed as part of the author's PhD studies under the tutelage of Dr Judith Lane, Dr Chee-Wee Tan, and Prof Nigel Gleeson. The author was awarded a PhD Scholarship by the Singapore Institute of Technology.

Conflict of interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher's note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Author disclaimer

The opinions given in this article are those of the author and do not necessarily represent the official position of Queen Margaret University and Singapore Institute of Technology.

References

Aibar-Almazan, A., Martinez-Amat, A., Cruz-Diaz, D., De la Torre-Cruz, M. J, Jimenez-Garcia, J. D, Zagalaz-Anula, N., et al. (2019). Effects of Pilates on fall risk factors in community-dwelling elderly women: A randomized, controlled trial. EJSS. 19, 1386–94. doi: 10.1080/17461391.2019.1595739

PubMed Abstract | CrossRef Full Text | Google Scholar

APTA Geriatrics. (2021). Outcome Measure Toolkit for Geriatric Fall/Balance Assessment. Available online at: https://www.aptageriatrics.org/special-interest-groups/balance-falls/Outcome-Measure-Toolkit/Outcome%20Measures%20Toolkit%202020.pdf (accessed on October 15, 2022).

Arkkukangas, M., Baathe, K. S., Hamilton, J., Ekholm, A., and Tonkonogi, M. (2020). Feasibility of a novel Judo4Balance—fall preventive exercise programme targeting community-dwelling older adults. JFSF. 5, 47–52. doi: 10.22540/JFSF-05-047

PubMed Abstract | CrossRef Full Text | Google Scholar

Bandura, A. (1986). Social Foundations of Thought and Action: A Social Cognitive Theory. Englewood Cliffs, NJ: Prentice Hall.

Bandura, A. (1997). Self-Efficacy: The Exercise of Control. New York: W.H. Freeman and Company.

Google Scholar

Bandura, A. (2006). “Guide for constructing self-efficacy scales,” in Self-Efficacy Beliefs of Adolescents, T. Urdan and F. Pajares (eds). Connecticut: Information Age Publishing. p. 307–337.

Google Scholar

Bower, E. S., Wetherell, J. L., Merz, C. C., Petkus, A. J., Malcarne, V. L., Lenze, E. J. A., et al. (2015). A new measure of fear of falling: Psychometric properties of the fear of falling questionnaire revised (FFQ-R). Int. Psychogeriatr. 27, 1121–33. doi: 10.1017/S1041610214001434

PubMed Abstract | CrossRef Full Text | Google Scholar

Chewning, B., Hallisy, K. M., Mahoney, J. E., Wilson, D., Sangasubana, N., Gangnon, R., et al. (2020). Disseminating Tai Chi in the community: Promoting home practice and improving balance. Gerontologist. 60, 765–75. doi: 10.1093/geront/gnz006

PubMed Abstract | CrossRef Full Text | Google Scholar

Cho, J., Smith, M. L., Ahn, S., Kim, K., Appiah, B., Ory, M. G., et al. (2014). Effects of an evidence-based falls risk-reduction program on physical activity and falls efficacy among oldest-old adults. Front. Public. Health. 2, 182. doi: 10.3389/fpubh.2014.00182

PubMed Abstract | CrossRef Full Text | Google Scholar

COSMIN. (2021). COSMIN Helps you Select the Most Suitable Outcome Measurement Instruments. Available online at: https://www.cosmin.nl (accessed on October 15, 2022).

Google Scholar

De Vet, H. C. W., Terwee, C. B., Mokkink, L. B., and Knol, D. L. (2011). Measurement in Medicine. Cambridge: Cambridge University Press.

Google Scholar

Hadjistavropoulos, T., and Delbaere, K. (2021). “The psychology of fall risk: Fear, anxiety, depression, and balance confidence,” in S. R. Lord, C. Sherrington, V. Naganathan (eds) Falls in Older People: Risk Factors, Strategies for Prevention and Implications for Practice. Cambridge, UK: Cambridge University Press. P. 160–171.

PubMed Abstract | Google Scholar

Hadjistavropoulos, T., Delbaere, K., and Fitzgerald, T. D. (2011). Reconceptualizing the role of fear of falling and balance confidence in fall risk. J. Aging. Health. 23, 3–23. doi: 10.1177/0898264310378039

PubMed Abstract | CrossRef Full Text | Google Scholar

He, Y., Zhang, H., Song, M., Wu, H., and Pi, H. (2022). Association between fatigue and falls risk among the elderly aged over 75 years in China: The chain mediating role of falls efficacy and lower limb function. Front. Public. Health. 10, 850533. doi: 10.3389/fpubh.2022.850533

PubMed Abstract | CrossRef Full Text | Google Scholar

Hofmeyer, M. R., Alexander, N. B., Medell, J. L., Koreishi, A., and Nyquist, L. V. (2002). Floor-rise strategy training in older adults. J. Am. Geriatr. Soc. 50, 1702–6. doi: 10.1046/j.1532-5415.2002.50463.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Hughes, C. C., Kneebone, I. I., Jones, F., and Brady, B. (2015). A theoretical and empirical review of psychological factors associated with falls-related psychological concerns in community-dwelling older people. Int. Psychogeriatr. 27, 1071–87. doi: 10.1017/S1041610214002701

PubMed Abstract | CrossRef Full Text | Google Scholar

Iliffe, S., Kendrick, D., Morris, R., Griffin, M., Haworth, D., Carpenter, H., et al. (2015). Promoting physical activity in older people in general practice: ProAct65+ cluster randomized controlled trial. Br. J. Gen. Pract. 65, e731–8. doi: 10.3399/bjgp15X687361

PubMed Abstract | CrossRef Full Text | Google Scholar

Johnson, S. T., Anens, E., Johansson, A. C., and Hellstrom, K. (2021). The Otago exercise program with or without motivational interviewing for community-dwelling older adults: A 12-month follow-up of a randomized, controlled trial. J. Appl. Gerontol. 40, 289–99. doi: 10.1177/0733464820902652

PubMed Abstract | CrossRef Full Text | Google Scholar

Jorstad, E. C., Hauer, K., Becker, C., and Lamb, S. E. (2005). Measuring the psychological outcomes of falling: A systematic review. J. Am. Geriatr. Soc. 53, 501–10. doi: 10.1111/j.1532-5415.2005.53172.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Kempen, G. I., Yardley, L., van Haastregt, J. C., Zijlstra, G. A., Beyer, N., Hauer, K., et al. (2008). The short FES-I: A shortened version of the falls efficacy scale-international to assess fear of falling. Age Ageing 37, 45–50. doi: 10.1093/ageing/afm157

PubMed Abstract | CrossRef Full Text | Google Scholar

Kurz, I., Gimmon, Y., Shapiro, A., Debi, R., Snir, Y., Melzer, I., et al. (2016). Unexpected perturbations training improves balance control and voluntary stepping times in older adults - a double blind randomized control trial. BMC. Geriatr. 16, 58. doi: 10.1186/s12877-016-0223-4

PubMed Abstract | CrossRef Full Text | Google Scholar

Lach, H. W. (2006). Self-efficacy and fear of falling: In search of complete theory. J. Am. Geriatr. Soc. 54, 381–2. doi: 10.1111/j.1532-5415.2005.00592_11_1.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Landers, M. R., Durand, C., Powell, D. S., Dibble, L. E., and Young, D. L. (2011). Development of a scale to assess avoidance behavior due to a fear of falling: The fear of falling avoidance behavior questionnaire. Phys. Ther. 91, 1253–65. doi: 10.2522/ptj.20100304

PubMed Abstract | CrossRef Full Text | Google Scholar

Leonhardt, R., Becker, C., Gross, M., and Mikolaizak, A. S. (2020). Impact of the backward chaining method on physical and psychological outcome measures in older adults at risk of falling: A systematic review. Aging. Clin. Exp. Res. 32, 985–97. doi: 10.1007/s40520-019-01459-1

PubMed Abstract | CrossRef Full Text | Google Scholar

Lurie, J. D., Zagaria, A. B., Ellis, L., Pidgeon, D., Gill-Body, K. M., Burke, C., et al. (2020). Surface perturbation training to prevent falls in older adults: A highly pragmatic, randomized controlled trial. Phys. Ther. 100, 1153–62. doi: 10.1093/ptj/pzaa023

PubMed Abstract | CrossRef Full Text | Google Scholar

Ma, A. W. W., Wang, H. K., Chen, D. R., Chen, Y. M., Chak, Y. T. C., Chan, J. W. Y., et al. (2019). Chinese martial art training failed to improve balance or inhibit falls in older adults. Percept. Mot. Skills. 126, 389–409. doi: 10.1177/0031512518824945

PubMed Abstract | CrossRef Full Text | Google Scholar

McKenna, S. P., Heaney, A., and Wilburn, J. (2019). Measurement of patient-reported outcomes. 2: Are current measures failing us? J. Med. Econ. 22, 523–30. doi: 10.1080/13696998.2018.1560304

PubMed Abstract | CrossRef Full Text | Google Scholar

Moon, Y., and Sosnoff, J. J. (2017). Safe landing strategies during a fall: Systematic review and meta-analysis. Arch. Phys. Med. Rehabil. 98, 783–94. doi: 10.1016/j.apmr.2016.08.460

PubMed Abstract | CrossRef Full Text | Google Scholar

Moore, D. S., and Ellis, R. (2008). Measurement of fall-related psychological constructs among independent-living older adults: A review of the research literature. Aging. Ment. Health. 12, 684–99. doi: 10.1080/13607860802148855

PubMed Abstract | CrossRef Full Text | Google Scholar

Okuyan, C. B., and Bilgili, N. (2017). Effect of Tai Chi Chuan on fear of falling, balance and physical self-perception in elderly: A randomized controlled trial. Turk. Geriatri. Derg. 20, 232–41. doi: 10.1111/ppc.12684

PubMed Abstract | CrossRef Full Text | Google Scholar

Powell, L. E., and Myers, A. M. (1995). The Activities-specific Balance Confidence (ABC) scale. J. Gerontol. A. Biol. Sci. Med. Sci. 50A:M28-M34. doi: 10.1093/gerona/50A.1.M28

PubMed Abstract | CrossRef Full Text | Google Scholar

Prinsen, C. A. C., Mokkink, L. B., Bouter, L. M., Alonso, J., Patrick, D. L., Vet, D. e., et al. (2018). HCW, et al. COSMIN guideline for systematic reviews of patient-reported outcome measures. Qual. Life. Res. 27, 1147–57. doi: 10.1007/s11136-018-1798-3

PubMed Abstract | CrossRef Full Text | Google Scholar

Roller, M., Kachingwe, A., Beling, J., Ickes, D. M., Cabot, A., Shrier, G., et al. (2018). Pilates reformer exercises for fall risk reduction in older adults: A randomized controlled trial. J. Body. Mov. Ther. 2, 983–98. doi: 10.1016/j.jbmt.2017.09.004

PubMed Abstract | CrossRef Full Text | Google Scholar

Soh, S. L. H., Lane, J., Lim, A. Y. H., Mujtaba, M. S., and Tan, C. W. (2022a). Interventions and measurement instruments used for falls efficacy in community-dwelling older adults: A systematic review. JFSF. 7, 151–64. doi: 10.22540/JFSF-07-151

PubMed Abstract | CrossRef Full Text | Google Scholar

Soh, S. L. H., Lane, J., Xu, T., Gleeson, N., and Tan, C. W. (2021a). Falls efficacy instruments for community-dwelling older adults: A COSMIN-based systematic review. BMC. Geriatr. 21, 1–10. doi: 10.1186/s12877-020-01960-7

PubMed Abstract | CrossRef Full Text | Google Scholar

Soh, S. L. H., Tan, C. W., Thomas, J. I., Tan, G., Xu, T., Ng, Y. L., et al. (2021b). Falls efficacy: Extending the understanding of self-efficacy in older adults towards managing falls. JFSF. 6, 131–8. doi: 10.22540/JFSF-06-131

PubMed Abstract | CrossRef Full Text | Google Scholar

Soh, S. L. H., Tan, C. W., Xu, T., Yeh, T. T., Rahman, F. A., Soon, B., et al. (2022b). The balance recovery confidence (BRC) scale. Physiother. Theory Pract. 1–12. doi: 10.1080/09593985.2022.2135420. [Epub ahead of print].

PubMed Abstract | CrossRef Full Text | Google Scholar

Tinetti, M. E., de Leon, C. F. M., Doucette, J. T., and Baker, D. I. (1994). Fear of falling and fall-related efficacy in relationship to functioning among community-living elders. J. Gerontol. A. Biol. Sci. 49, M140–M7. doi: 10.1093/geronj/49.3.M140

PubMed Abstract | CrossRef Full Text | Google Scholar

Tinetti, M. E., Richman, D., and Powell, L. (1990). Falls efficacy as a measure of fear of falling. J. Gerontol. B. Psychol. Sci. Soc. Sci. 45, 239–43. doi: 10.1093/geronj/45.6.P239

PubMed Abstract | CrossRef Full Text | Google Scholar

Yardley, L., Beyer, N., Hauer, K., Kempen, G., Piot-Ziegler, C., Todd, C., et al. (2005). Development and initial validation of the Falls Efficacy Scale-International (FES-I). Age Ageing 34, 614–9. doi: 10.1093/ageing/afi196

PubMed Abstract | CrossRef Full Text | Google Scholar

Yoshikawa, A., and Smith, M. L. (2019). Mediating role of fall-related efficacy in a fall prevention program. Am. J. Health. Behav. 43, 393–405. doi: 10.5993/AJHB.43.2.15

PubMed Abstract | CrossRef Full Text | Google Scholar

Keywords: falls efficacy, self-efficacy, older people, falls prevention, falls management, balance confidence, fear of falling, balance recovery confidence

Citation: Soh SLH (2022) Falls efficacy: The self-efficacy concept for falls prevention and management. Front. Psychol. 13:1011285. doi: 10.3389/fpsyg.2022.1011285

Received: 04 August 2022; Accepted: 24 October 2022;
Published: 09 November 2022.

Edited by:

Andrew Mark Williams, Florida Institute for Human and Machine Cognition, United States

Reviewed by:

Anne-Marie Hill, University of Western Australia, Australia
Andrés Soto-Varela, Complejo Hospitalario Universitario de Santiago, Spain

Copyright © 2022 Soh. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Shawn Leng-Hsien Soh, shawn.soh@singaporetech.edu.sg

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.