Introduction
The rapid aging of the global population presents major challenges to health care and social security systems. Among these, age-related declines in physical function, particularly mobility limitations, adversely affect the quality of life and independence of older adults [1]. To address these challenges, assistive robotic technologies are being developed for various domains, including mobility, transfer, bathing, and communication [2-6]. These systems are anticipated to play a key role in promoting healthy longevity by supporting physical, social, and psychological well-being [7,8].
Fall prevention is a central concern in the context of age-related functional decline, as falls compromise both safety and independence. Approximately one-third of older adults experience at least one fall annually [9,10], and the risk of fall-related injuries increases due to age-associated impairments in musculoskeletal, cardiovascular, visual, vestibular, and proprioceptive functions [11-15]. Beyond physical injury, the fear of falling contributes to a cycle of reduced mobility, decreased activity, and social withdrawal [16,17]. This fear can negatively influence balance control and movement behavior [18], particularly in older adults with physical disabilities, thereby limiting social participation and increasing the risk of future falls [19-21].
To mitigate these risks, various robotic solutions for fall prevention have been proposed. These include “smart robotic walkers” that anticipate movement patterns to provide proactive support [22] and “robotic canes” that adapt to users’ gait characteristics [23-25]. While promising, these systems are often optimized for clinical settings and may be impractical for home use due to space and mobility constraints [26]. Moreover, their potential psychological benefits remain poorly characterized, despite the crucial role of fall-related self-efficacy in fall prevention outcomes.
Recent studies have emphasized the importance of psychological factors in fall prevention. Self-efficacy, as defined by Bandura [27], refers to an individual’s belief in their ability to carry out actions necessary to achieve specific outcomes. Tinetti et al [28] introduced the concept of falls efficacy as a domain-specific form of self-efficacy, meaning the confidence to perform daily activities without falling. Building on this, Powell and Myers [29] developed the Activities-specific Balance Confidence Scale, which assesses confidence in maintaining balance during a range of activities. More recently, Soh et al [30-32] proposed a multidimensional framework for fall efficacy, encompassing 4 distinct domains across the fall continuum: balance confidence (pre-fall), balance recovery confidence (near-fall), safe-landing confidence (fall-landing), and post-fall recovery confidence (post-fall). This expanded model highlights the need for psychological resilience not only to prevent falls but also to manage their occurrence. Clinical findings suggest that such psychological constructs can directly modulate balance control mechanisms, potentially masking or compensating for physical impairments [18]. As such, effective fall prevention strategies should integrate both physical safeguards and psychological reinforcement.
Motor learning theory provides a framework for understanding how to effectively provide such psychological reinforcement. Self-efficacy influences task engagement, and learning is optimized when difficulty appropriately matches ability [27,33]. However, people naturally tend to be conservative, using only a portion of their available stability capacity due to inherent safety mechanisms [34]. This suggests that effective balance training must address both the physical and psychological barriers that limit engagement with appropriately challenging tasks.
The present study focuses on a ceiling-mounted fall impact mitigation robot designed to address both physical and psychological aspects of fall prevention. This suspended system provides continuous support during daily activities in home environments, with almost no limitations on the range of movement. While the system was primarily designed to reduce the physical risk of fall-related injuries, its impact on psychological factors, particularly fall-related self-efficacy, has not been fully elucidated. Specifically, it remains unclear whether the constant presence of such a safety system influences users’ psychological state, and if so, whether this influence translates into measurable changes in motor performance when facing such challenging tasks.
This study aims to examine the effect of the fall impact mitigation robot on psychological reassurance and task performance during dynamic balance challenges. Young healthy adults were selected as participants to establish a baseline understanding of these mechanisms, unconfounded by age-related impairments. We used the functional reach test (FRT), a validated tool for assessing dynamic balance and fall risk across age groups [35]. The FRT was particularly suited to this study, as it provides a quantitative measure of physical reaching ability and reflects the confidence required to perform challenging balance tasks [34]. Participants were asked to perform progressively demanding reaching tasks that exceeded their maximum capacity, either with or without robotic safety support depending on their group assignment. Prior to each attempt, participants were asked the self-efficacy ratings to quantify how perceived safety influences both confidence and motor performance. By investigating this relationship, we aim to elucidate how robotic safety systems modulate human movement behavior, thereby informing the development of comprehensive fall prevention strategies that promote safe, independent living among older adults.
Discussion
Principal Findings
This study investigated the psychological effects of a fall impact mitigation robot, focusing on its influence on self-efficacy and physical performance during balance-challenging tasks. Participants in the experimental group who wore the robot exhibited significantly higher self-efficacy ratings, particularly prior to reaching tasks that exceeded their individualized maximum reach thresholds (Figures 4 and 5). Although survival analysis suggested a trend toward greater task persistence in the experimental group (Figure 6), no statistically significant differences were observed in physical performance metrics, such as FRT scores or COP displacement (Table 1). These findings indicate that the fall impact mitigation robot provided psychological reassurance and enhanced self-efficacy, even in the absence of active robotic assistance.
Implications for Fall Prevention
The observed enhancement in self-efficacy has direct implications for fall prevention strategies. Fear of falling contributes to activity restriction and social withdrawal, which in turn negatively impact balance control and motor behavior [18]. Among older adults, fear of falling is associated with reduced social participation and elevated risk of subsequent falls [19]. Robotic interventions that bolster self-efficacy may help interrupt this deleterious cycle. Existing evidence links higher self-efficacy with increased motivation for activities of daily living and outdoor mobility [16], suggesting that such interventions could support long-term improvements in physical activity and social engagement. However, further longitudinal research is needed to substantiate these potential benefits.
Integration With the Falls Self-Efficacy Framework
To contextualize our findings within current theoretical models, we refer to the framework proposed by Soh et al [32], which delineates falls self-efficacy into 4 domains: balance confidence (pre-fall), balance recovery confidence (near-fall), safe-landing confidence (fall-landing), and post-fall recovery confidence (post-fall). While the fall impact mitigation robot was designed to enhance safe-landing confidence, the observed increase in self-efficacy suggests a broader psychological effect, potentially extending toward balance confidence. This cross-domain influence implies that perceived protection during potential falls may generalize to increased confidence during pre-fall activities, offering a novel direction for fall prevention strategies.
Dissociation Between Psychological and Physical Outcomes
A key observation in this study was the dissociation between psychological and physical outcomes, namely, significant improvements in self-efficacy without parallel changes in FRT or COP displacement. As suggested by Bandura [27], enhancements in self-efficacy typically precede measurable behavioral changes, which may emerge over longer timeframes. The use of healthy young adults likely introduced ceiling effects, limiting the detection of performance-related differences. Moreover, the single-session intervention design may have been insufficient to elicit observable physical adaptations. Longitudinal studies incorporating diverse populations are needed to clarify the temporal relationship between self-efficacy and physical performance.
Insights Into Motor Learning and Human-Robot Interaction
Our findings provide a new perspective on the application of the challenge point framework [33] to balance training. The framework posits that learning is most effective at the edge of a person’s ability. Modulating the level of physical assistance is a common approach to guide learners to this optimal state. Our results, however, demonstrate that psychological safety is a powerful, alternative modulator. The increase in self-efficacy without a change in physical performance indicates that the robot enabled participants to perform closer to their true physical limits, not by making the task easier, but by removing the fear of falling. This suggests a potential model for effective training, where psychological barriers are addressed first to allow a learner to safely engage with their optimal challenge point.
Furthermore, the enhancement of self-efficacy in the mere presence of the robot contributes to the growing body of literature on human-robot interaction. Broadbent et al [7] found that robots can fulfill both physical and psychological roles. Our results support this dual-function hypothesis, demonstrating that robotic presence alone can provide psychological reassurance and influence behavior.
Limitations and Future Directions
Several limitations of this study warrant consideration. First, the small sample size limited statistical power and generalizability. Second, the focus on healthy young adults constrains the applicability of findings to clinical or older populations. Third, only short-term effects were assessed, leaving the long-term psychological and behavioral impacts unexamined. Fourth, the interaction between fear of falling and physical function may differ across age groups, underscoring the need for population-specific studies. Future work should incorporate validated scales aligned with the multifactorial model of falls self-efficacy proposed by Soh et al [32]. Finally, our analysis of motor behavior was restricted to coarse indicators such as COP displacement. Future investigations may benefit from high-resolution, markerless motion capture technologies, already implemented in our Living Lab environment [38], to enable fine-grained analysis of postural and movement strategies associated with robotic safety systems.
Conclusions
These findings demonstrate that a fall impact mitigation robot can enhance self-efficacy via psychological reassurance, even in the absence of active physical assistance. This indicates that psychological support enhances self-efficacy, but that physical assistance is also necessary, highlighting the need for fall prevention strategies that integrate both. The observed enhancement in self-efficacy may promote greater engagement in physical activity and, in turn, contribute to improved functional capacity, a hypothesis that warrants validation through longitudinal investigation.