Fall-related injuries in adults over the age of 65 pose an important public health issue especially with an increasing number of older adults living in retirement homes and nursing homes. Safety floors have been developed as an intervention to reduce the risk of these injuries. However, their effects on balance control reactions had never been tested during certain activities of daily living in retirement home dwellers. This research investigated how balance reactions are affected by the mechanical properties of safety flooring in older adults. The safety flooring showed minimal impact on the balance reactions while retaining force attenuation properties. There were two studies as part of this thesis. The purpose of the first study was to determine whether the Nintendo Wii Balance Board (WBB) can be used as an appropriate substitution for a force plate when measuring balance reactions during common tests used to assess balance in older adults. Specifically, I characterized the technical specifications of the WBB and compared them to those of the force plate, showing that the two devices yielded similar responses during balance measures of quiet stance. The second study investigated the effect of two traditional floors and three safety flooring systems on balance control mechanisms (based on changes in underfoot centre of pressure) during sit-to-stand and quiet stance tasks in retirement home-dwellers. The results of this study provided evidence supporting the potential for safety floors to reduce fall-related injury risk without impairing balance and mobility of users. Additional research may want to assess WBB performance during dynamic tasks involving shear forces. The results from this study supports prospective clinical investigations of pilot installations of safety flooring in retirement and nursing home settings to evaluate their real life effects on fall related injuries.

PURPOSE. To determine the influence of cataractous and refractive blur on postural stability and limb-load asymmetry (LLA) and to establish how postural stability changes with the spatial frequency and contrast of the visual stimulus. METHODS. Thirteen elderly subjects (mean age, 70.76 ± 4.14 [SD] years) with no history of falls and normal vision were recruited. Postural stability was determined as the root mean square [RMS] of the center of pressure (COP) signal in the anterior¿posterior (A-P) and medial¿lateral directions and LLA was determined as the ratio of the average body weight placed on the more-loaded limb to the less-loaded limb, recorded during a 30-second period. Data were collected under normal standing conditions and with somatosensory system input disrupted. Measurements were repeated with four visual targets with high (8 cyc/deg) or low (2 cyc/deg) spatial frequency and high (Weber contrast, 95%) or low (Weber contrast, 25%) contrast. Postural stability was measured under conditions of binocular refractive blur of 0, 1, 2, 4, and 8 D and with cataract simulation. The data were analyzed in a population-averaged linear model. RESULTS. The cataract simulation caused significant increases in postural instability equivalent to that caused by 8-D blur conditions, and its effect was greater when the input from the somatosensory system was disrupted. High spatial frequency targets increased postural instability. Refractive blur, cataract simulation, or eye closure had no effect on LLA. CONCLUSIONS. Findings indicate that cataractous and refractive blur increase postural instability, and show why the elderly, many of whom have poor vision along with musculoskeletal and central nervous system degeneration, are at greater risk of falling. Findings also highlight that changes in contrast sensitivity rather than resolution changes are responsible for increasing postural instability. Providing low spatial frequency information in certain environments may be useful in maintaining postural stability. Correcting visual impairment caused by uncorrected refractive error and cataracts could be a useful intervention strategy to help prevent falls and fall-related injuries in the elderly.

Fall-related injuries in adults over the age of 65 pose an important public health issue especially with an increasing number of older adults living in retirement homes and nursing homes. Safety floors have been developed as an intervention to reduce the risk of these injuries. However, their effects on balance control reactions had never been tested during certain activities of daily living in retirement home dwellers. This research investigated how balance reactions are affected by the mechanical properties of safety flooring in older adults. The safety flooring showed minimal impact on the balance reactions while retaining force attenuation properties. There were two studies as part of this thesis. The purpose of the first study was to determine whether the Nintendo Wii Balance Board (WBB) can be used as an appropriate substitution for a force plate when measuring balance reactions during common tests used to assess balance in older adults. Specifically, I characterized the technical specifications of the WBB and compared them to those of the force plate, showing that the two devices yielded similar responses during balance measures of quiet stance. The second study investigated the effect of two traditional floors and three safety flooring systems on balance control mechanisms (based on changes in underfoot centre of pressure) during sit-to-stand and quiet stance tasks in retirement home-dwellers. The results of this study provided evidence supporting the potential for safety floors to reduce fall-related injury risk without impairing balance and mobility of users. Additional research may want to assess WBB performance during dynamic tasks involving shear forces. The results from this study supports prospective clinical investigations of pilot installations of safety flooring in retirement and nursing home settings to evaluate their real life effects on fall related injuries.

Fall-related injuries are common problems in elderly care in particular. These can cause brain damage and hip fractures, which in many cases can be serious. To reduce or mitigate the damage, various safety measures have been developed. One of them concerns a change in the surroundings, more specifically, the floor. At KTH within the Division of Neuronic Engineering, research has been done on how the impact of the case can be minimized and a shock absorbing floor (SAF) was developed. Diving problems with this type of flooring are that heavy medical beds sink into the floor, which means increased rolling resistance and thus long-term damage to both the floor and the medical staff. The aim of this thesis was to investigate how much rolling resistance can be minimized by building a downscaled hovering device based on hovercraft technology. The purpose was to enable the device to possibly be mounted under hospital beds and create a lifting force. To evaluate the performance, force measurements were performed on KTH SAF with different weights and with the use of a dynamometer. The results showed that the device reduced rolling resistance by up to 57.4% with additional weight. Four axial fans were used together with manual control of the speed of each fan. The selected components were made taking into account, in particular, cost, weight and dimensions and can thus also be limiting factors for this thesis. For future work, effective soundproofing is needed for this solution to be possible to be implemented in a hospital environment. Furthermore, studies needs to be carried out for a full-scale prototype to confirm that an equally large reduction in rolling resistance can be achieved.

The overall goal of my research was to advance our understanding of the potential for novel compliant flooring systems to reduce the risk for fall-related injuries in older adults, including fall-related traumatic brain injury (TBI). This entailed an assessment of how these floors affect the competing demands of fall-related TBI – impact severity attenuation in concert with minimal concomitant impairments to balance control and postural stability. Two studies are included as part of this thesis. The first study used a mechanical drop tower to assess the effects of four traditional flooring systems and six novel compliant flooring conditions on the impact dynamics of a surrogate headform during the impact phase of simulated ‘worst- case’ head impacts. The second study entailed an assessment of the effect of two traditional and three novel compliant floors on the initial phase of the compensatory balance reactions of older adult men and women living in a residential-care facility environment following an externally induced perturbation using a tether-release paradigm. Overall, this thesis demonstrates that novel compliant floors substantially attenuate the forces and accelerations applied to the head during simulated worst- case impacts when compared to traditional flooring surfaces such as vinyl and carpet with underpadding. These benefits are achieved without compromising indices of balance control, supported by the finding that parameters characterizing early compensatory balance reactions were unaffected by the novel compliant floors tested. This work supports the introduction of pilot installations of novel compliant flooring systems into environments with high incidences of falls to test their effectiveness at reducing fall-related injuries in clinical settings.

The overall goal of my research was to advance our understanding of the potential for novel compliant flooring systems to reduce the risk for fall-related injuries in older adults, including fall-related traumatic brain injury (TBI). This entailed an assessment of how these floors affect the competing demands of fall-related TBI – impact severity attenuation in concert with minimal concomitant impairments to balance control and postural stability. Two studies are included as part of this thesis. The first study used a mechanical drop tower to assess the effects of four traditional flooring systems and six novel compliant flooring conditions on the impact dynamics of a surrogate headform during the impact phase of simulated ‘worst- case’ head impacts. The second study entailed an assessment of the effect of two traditional and three novel compliant floors on the initial phase of the compensatory balance reactions of older adult men and women living in a residential-care facility environment following an externally induced perturbation using a tether-release paradigm. Overall, this thesis demonstrates that novel compliant floors substantially attenuate the forces and accelerations applied to the head during simulated worst- case impacts when compared to traditional flooring surfaces such as vinyl and carpet with underpadding. These benefits are achieved without compromising indices of balance control, supported by the finding that parameters characterizing early compensatory balance reactions were unaffected by the novel compliant floors tested. This work supports the introduction of pilot installations of novel compliant flooring systems into environments with high incidences of falls to test their effectiveness at reducing fall-related injuries in clinical settings.

As falls and fall-related injuries are a major cause of injuries, the purpose of this study was to investigate whether, and to what extent, the stage combat fall technique training could reduce the impact forces of falls from standing. Twenty-six healthy young adults (14 males and 12 females) participated in our study, and were randomly assigned to either a training group or non-training (control) group. Both groups completed a pre-intervention and a post-intervention fall testing session, separated by two weeks, in which they performed naturalistic falls. The training group performed identical pre-intervention fall testing as the control group, and was then required to receive four 1-hour training sessions in the course of two weeks, led by a certified stage combat fall technique training instructor. The training group then completed a post-intervention fall testing session where they performed naturalistic falls and also falls using the fall technique they learned. Falls were induced in both forward and backward directions using a tether-release protocol. Differences between control and training groups at pre-training, and group differences in the change in dependent measures with training, were examined using Mann-Whitney U tests. The results showed that, following stage-combat fall training, the training group exhibited 32% and 35% reduction in median impact forces for forward and backward falls respectively, while the control group exhibited 5% and 2% reductions (p = 0.002 and <0.001). In addition, the training group showed shorter backward fall duration as well as longer impact time, larger impulse, and longer or larger center-of-pressure based measures for both directions of falling than the control group. However, training was not associated with reduced impact force during the naturalistic falls of the training group. To our knowledge, this was the first study to investigate the stage combat fall technique training and demonstrate its effectiveness as an intervention to reduce impact forces of falls, thereby exploring the potential to reduce the number of fall-related injuries. While these falls were induced from standing, whether these results would transfer to an unanticipated fall while walking due to a slip/trip remain to be explored. / Master of Science / As falls and fall-related injuries are a major cause of injuries, the purpose of this study was to investigate whether, and to what extent, the stage combat fall technique training could reduce the impact forces of falls from standing. Twenty-six healthy young adults (14 males and 12 females) participated in our study, and were randomly assigned to either a training group or non-training (control) group. Both groups completed a pre-intervention and a post-intervention fall testing session, separated by two weeks, in which they performed naturalistic falls. The training group was required to receive four 1-hour training sessions in the two-week intervention period, led by a certified stage combat fall technique training instructor. The training group then completed a post-intervention fall testing session where they performed naturalistic falls and also falls using the fall technique they learned. The results showed that, following stage-combat fall training, the training group exhibited nearly a 1/3rd reduction in impact forces for both forward and backward falls, while the control group only exhibited 5% and 2% reductions respectively. Our analysis also showed that the training group achieved this reduction in impact force by increasing the impact time and spreading out their bodies more, to distribute the impact over a larger area. To our knowledge, this was the first study to investigate the stage combat fall technique training and demonstrate its effectiveness as an intervention to reduce impact forces of falls, thereby exploring the potential to reduce the number of fall-related injuries.

Abstract: Background: In Parkinson’s disease, postural instability and falls are of particular socioeconomic relevance. Although effective fall prevention and the prophylaxis of fall-related injuries depend on low-threshold symptom monitoring, validated instruments are lacking. Objectives: To develop a self-report questionnaire for the assessment of falls, near falls, fear of falling, fallrelated injuries, and causes of falls for patients with Parkinson’s disease (PwPD). - Methods: A pool of potential items was generated from a literature review and by discussion in an expert panel. The first version of the Dresden Fall Questionnaire (DREFAQ) was tested in a group of German-speaking movement disorder specialists as well as PwPD. The resulting 5-item questionnaire was assessed in a validation cohort of 36 PwPD who documented fall events and near-fall events in a calendar for 3 months and completed the DREFAQ at the end of the study. The questionnaire was subsequently used in a separate cohort of 46 PwPD to determine test–retest reliability and confirm the factor structure. - Results: The DREFAQ showed good internal consistency (Cronbach’s α = 0.84) and good test–retest reliability (intraclass correlation coefficient, 0.76; 95% confidence interval, 0.60–0.86). The total DREFAQ score showed good concurrent validity with fall events (Spearman’s ρ = 0.82) and near-fall events (Spearman’s ρ = 0.78) as determined by fall and near-fall diaries. Factor analysis revealed a 2-factor structure composed of near falls with fear of falling and severe falls with injuries. - Conclusions: The DREFAQ is a reliable and valid 5-item questionnaire for determining the incidence of falls, near falls, fear of falling, fall-related injuries, and causes of falls in PwPD.