Abstract
[Purpose] This study aimed to compare the direction-specific kinematic characteristics of stepping movements in the Four Square Step Test among community-dwelling older adults who fell and those who did not, using an optical motion capture device. In addition, specific elements of fall risk were identified based on the kinematic characteristics of stepping movements. [Participants and Methods] We enrolled 74 individuals aged ≥65 years who visited community centers in this study. The participants were interviewed to determine their fall history in the past year and divided into two groups: fallers and non-fallers. An optical motion capture device was used to assess the stepping parameters (step length, step speed, and toe clearance). [Results] The step length of both lower extremities in the right direction and the step speed of both lower extremities in the forward direction, the right lower extremity in the backward direction, and the left lower extremity in the right direction were significantly shorter and slower in the faller group, respectively. [Conclusion] The step length and speed in each direction may be important kinematic indicators for estimating the likelihood of falls in community-dwelling older adults.
Keywords: Fall risk screening, Four Square Step Test, Optical motion capture system
INTRODUCTION
Currently, approximately 30% of community-dwelling older adults aged ≥65 years fall within a given year1), and this number is increasing each year. Trauma and fractures resulting from falls have a significant impact on physical function and are serious social problems that can lead to fear of falling, decreased activity, and, in the long term, functional decline and death2,3,4,5).
As people age, the percentage of falls occurring indoors increases, mainly in living rooms, bedrooms, and entrances6). Falls are caused by tripping, slipping, or loss of balance while walking or starting to walk7). Approximately 40% of falls are reported to be forward or backward and 30% are sideways or concurrent7).
Since injuries such as spinal compression fractures and femoral neck fractures are observed in falls to the side or back, it is necessary to prevent injuries from falling forward and from falling to the side or back7). Many people fall home by tripping over steps or cords; therefore, it is important to take appropriate measures to prevent falls8).
The Timed Up and Go Test (TUG)9), Berg Balance Scale10), and Four Square Step Test (FSST)11) are commonly used to assess gait and balance to screen for fall risk. Among these fall risk screening tests, the FSST, which involves placing a T-shaped cane or other object in a crisscross pattern, performing rapid stepping movements in each direction, and assessing stepping over obstacles while considering obstacle avoidance, is considered to have high sensitivity and specificity for fall risk screening.
Step speed, step length, and toe clearance by the directions tend to decrease in the stepping movements of the older adults and the fallers while walking and stepping over obstacles12,13,14,15,16,17,18,19).
From this perspective, the FSST, which measures the time taken to take a step while stepping over an obstacle as fast as possible in the forward-backward and left-right directions, is considered highly valid as a fall risk-screening test from a task-oriented perspective.
However, in previous studies on the FSST, the total time required was measured, but no further specific kinematic characteristics of the stepping movements in the front-back and left-right directions have been reported.
Therefore, we thought it would be possible to identify specific kinematic characteristics of fall risk by quantitatively analyzing the total time required for the FSST and the kinematic characteristics of the stepping movements by direction and comparing them between the faller and non-faller groups.
The purpose of this study was to clarify the direction-specific kinematic characteristics during FSST stepping movements between faller and non-faller groups in community-dwelling older adults using an optical motion capture device and to identify specific elements of fall risk based on the kinematic characteristics of stepping movements.
PARTICIPANTS AND METHODS
Seventy-four older adults community center users (aged ≥65 years) were enrolled in the study after providing an information session and written informed consent. Participants included 57 females and 17 males with a mean age of 77.6 ± 5.9 years.
The inclusion criterion was the ability to walk independently. The exclusion criteria included severe cerebrovascular, cardiovascular, or musculoskeletal disease; high risk of falls due to Parkinson’s disease or stroke; or inability to walk independently. In addition, those who could not complete the measurements due to significant hearing or visual impairment, severe cognitive impairment, or participation in a regular fall prevention class or study in the previous 12 months were excluded.
Based on Gibson’s definition of falls20), participants with a history of unintentional landing on the ground, floor, or a lower flat surface without external force from another person or loss of consciousness within the past year were categorized into the faller group (n=27; 5 males, 22 females), and participants with no history of falls were defined as the non-faller group (n=47; 12 males, 35 females).
This study was approved by the Medical Ethics Committee of Shinshu University School of Medicine (Approval No. 5298) and conformed to the Declaration of Helsinki.
First, the participants were interviewed to determine whether they had a history of falls in the past year. Furthermore, the participants were interviewed about the locations of the falls.
Next, the total time required for the FSST twice using 3 cm high sticks arranged in a cross pattern and a stopwatch. The total time required for the FSST was measured by dividing the compartment into four sections with sticks arranged in a cross pattern, as described in a previous study11), and moving back and forth over the sticks as quickly as possible. Starting from the lower-left compartment, the participants made one clockwise turn, followed by one counterclockwise turn, and the total time required by one evaluator to return to the starting point was measured using a stopwatch. The teaching method was as follows: “Please perform the steps as quickly as possible without touching the sticks. Please land both feet in their respective compartments and keep the body facing forward as far as possible”. After explaining the procedure, the participants practiced only two times, and the measurements were obtained two times using a shorter time as the data11). If participants lost balance, became disoriented, or had their feet touch the sticks during the test, the measurements were repeated. The evaluator was positioned close to the participants and attempted to be immediately available to help them in cases of loss of balance. During FSST measurement, markers were attached to the first metatarsal heads of the participants’ left and right lower extremities, and the kinematic parameters of the stepping movements (step length, step speed, and toe clearance) were analyzed using optical motion capture (OptiTrack V120:Trio, NaturalPoint, Inc., Corvallis, OR, USA)21).
The kinematic parameters of the stepping movements were analyzed using Kissei Comtec software (KineAnalyzer, KISSEI COMTEC Co., Ltd., Nagano, Japan). For the data analyses of the stepping movements of the FSST, the results with no noise or missing data and the shortest total time were selected.
To perform the TUG test, participants were timed with a stopwatch while rising from a chair, walking at a comfortable and safe pace to a cone 3 m away, turning and walking back to the chair, and sitting down again9). The evaluator was positioned close to the participants and attempted to be immediately available to help them in cases of loss of balance.
The Mini-Cog is a brief cognitive screening test scored on immediate and delayed recall of three words and clock drawing22). Each correct delayed recall of the three words was worth one point, and each correct clock drawing was worth two points, with a maximum score of five points. Participants with Mini-Cog scores of three points or less are suspected of dementia.
The fall risk score23) was assessed using the portable Falls Risk Index (FRI) checklist, which consists of five questions, including fall history and gait speed in relation to falls. Participants were considered at a high risk of falls if they scored 7 or higher.
The Falls Efficacy Scale-International (FES-I)24) is a self-report questionnaire comprising 16 items rated on a 4-point scale to determine how much attention is usually paid to avoid falls. The total score of all items was used to determine the fear or concern about falling, with a minimum score of 16 and a maximum score of 64.
The normality of the data for the kinematic parameters of the stepping movements of the FSST was analyzed using the Shapiro–Wilk test before comparing the parameters of the faller and non-faller groups. Differences in the parameters were then compared using the t-test for normally distributed data and the Mann–Whitney U test for non-normally distributed data. The χ2 test was used to compare the differences between the sexes in the faller and non-faller groups.
Differences between the groups were considered statistically significant at a p-value of 0.05. For exploratory studies, all p-values reported for comparisons of kinematic characteristics of stepping movements by left/right and direction were uncorrected p-values25). All statistical analyses were performed using the IBM SPSS Statistics version 29 (IBM Corporation, Armonk, NY, USA).
RESULTS
The characteristics of the participants in the faller and non-faller groups are summarized in Table 1. No significant differences were observed in participant characteristics between both groups. The locations of the falls in the faller group are summarized in Table 2. Eleven falls occurred indoors, and 13 falls occurred outdoors, with more falls occurring outdoors. Three participants could not recall the location of their falls. Of all the people who fell, 10 were injured by the fall. Three people required conservative treatment for ligament damage or fractures, but the other people who fell had only minor injuries such as bruises or abrasions, and there were no serious disabilities.
Table 1. Characteristics between both groups.
| Non-faller group (n=47) | Faller group (n=27) | |
| Age [years]a | 77.6 ± 5.9 (76.0) | 77.8 ± 5.4 (77.0) |
| Sex [n males, n females]b | 12, 35 | 5, 22 |
| Height [cm]a | 155.2 ± 7.9 (155.0) | 154.8 ± 7.8 (152.0) |
| Weight [kg]c | 54.3 ± 8.2 (54.0) | 55.4 ± 9.5 (52.0) |
Data are expressed as mean ± standard deviation (median).
a: Mann–Whitney’s U test, b: χ2 test, c: t-test.
Table 2. Location of fall between both groups.
| All faller (n=27), n (%) | |
| Indoor of faller | 11 (41%) |
| Living room | 2 (7%) |
| Bedroom | 2 (7%) |
| Entrance | 1 (3%) |
| Stairs | 2 (7%) |
| Hallway | 2 (7%) |
| Bathroom | 2 (7%) |
| Outdoor of faller | 13 (48%) |
| Home garden | 4 (15%) |
| Car park | 3 (11%) |
| Sidewalk | 6 (22%) |
| Cannot recall | 3 (11%) |
When comparing the Questionnaires and the TUG results between both groups, the FES-I and FRI scores were significantly higher in the faller group than in the non-faller group (Table 3). No significant differences were noted in Mini-Cog and TUG test results between both groups.
Table 3. Comparison of the questionnaire and the TUG between both groups.
| Non-faller group | Faller group | |
| Mini-cog [point]a | 4.6 ± 0.7 (5.0) | 4.7 ± 0.5 (5.0) |
| Fall risk index [point]a | 2.9 ± 2.6 (2.0) | 8.0 ± 2.0 (9.0)*** |
| Falls Efficacy Scale-International (FES-I) [point]a | 26.6 ± 5.3 (25.0) | 33.7 ± 11.6 (30.0)* |
| Timed Up & Go Test (TUG) [s]a | 7.5 ± 1.9 (7.4) | 8.0 ± 2.2 (7.7) |
Data are expressed as mean ± standard deviation (median).
a: Mann–Whitney’s U test. *p<0.05, ***p<0.001.
No significant differences exist in the total time required for the FSST between both groups (Table 4).
Table 4. Comparison of FSST and kinematic specificity by both lower extremities in four directions between both groups.
| Non-faller group | Faller group | |
| Four square step test (FSST) [s]a | 7.6 ± 1.2 (7.8) | 8.4 ± 1.7 (7.9) |
| Step length | ||
| Forward step in the right lower extremity [cm]b | 47.3 ± 4.2 (47.0) | 45.6 ± 3.7 (44.8) |
| Forward step in the left lower extremity [cm]b | 45.9 ± 4.5 (45.8) | 45.1 ± 4.2 (44.1) |
| Right step in the right lower extremity [cm]b | 42.2 ± 3.9 (42.1) | 40.6 ± 4.1 (40.0)* |
| Right step in the left lower extremity [cm]b | 42.0 ± 3.7 (42.2) | 39.9 ± 3.9 (40.0)** |
| Backward step in the right lower extremity [cm]b | 46.2 ± 4.3 (45.9) | 44.3 ± 4.7 (44.4) |
| Backward step in the left lower extremity [cm]b | 46.0 ± 4.4 (46.4) | 44.3 ± 5.0 (43.9) |
| Left step in the right lower extremity [cm]b | 43.7 ± 4.0 (43.9) | 43.9 ± 3.7 (43.9) |
| Left step in the left lower extremity [cm]b | 43.7 ± 3.8 (43.9) | 43.5 ± 3.4 (43.5) |
| Step speed | ||
| Forward step in the right lower extremity [m/s]b | 1.1 ± 0.2 (1.1) | 0.9 ± 0.2 (0.9)* |
| Forward step in the left lower extremity [m/s]b | 1.1 ± 0.2 (1.1) | 1.0 ± 0.2 (1.0)* |
| Right step in the right lower extremity [m/s]b | 1.0 ± 0.2 (0.9) | 0.9 ± 0.2 (0.8) |
| Right step in the left lower extremity [m/s]b | 1.0 ± 0.2 (1.0) | 0.9 ± 0.2 (0.9)* |
| Backward step in right lower extremity [m/s]b | 1.0 ± 0.2 (1.0) | 0.9 ± 0.3 (0.9)* |
| Backward step in left lower extremity [m/s]b | 1.1 ± 0.2 (1.1) | 1.0 ± 0.2 (1.0) |
| Left step in right lower extremity [m/s]b | 1.1 ± 0.2 (1.1) | 1.0 ± 0.2 (1.0) |
| Left step in left lower extremity [m/s]b | 1.1 ± 0.2 (1.0) | 1.0 ± 0.2 (0.9) |
| Toe clearance | ||
| Forward step in right lower extremity [cm]b | 13.0 ± 2.0 (12.5) | 13.0 ± 2.4 (12.8) |
| Forward step in left lower extremity [cm]b | 13.0 ± 1.9 (12.6) | 12.9 ± 2.1 (12.8) |
| Right step in right lower extremity [cm]b | 12.6 ± 2.0 (12.0) | 12.8 ± 2.1 (12.6) |
| Right step in left lower extremity [cm]b | 12.4 ± 1.8 (12.0) | 12.6 ± 1.9 (12.2) |
| Backward step in right lower extremity [cm]b | 14.5 ± 2.9 (14.2) | 13.9 ± 2.9 (13.6) |
| Backward step in left lower extremity [cm]b | 14.1 ± 2.6 (14.0) | 13.7 ± 2.6 (13.5) |
| Left step in right lower extremity [cm]b | 12.2 ± 1.9 (12.2) | 12.4 ± 2.2 (12.4) |
| Left step in left lower extremity [cm]b | 12.4 ± 2.0 (12.5) | 12.6 ± 2.1 (12.6) |
Data are expressed as mean ± standard deviation (median).
a: t-test, b: Mann–Whitney’s U test. *p<0.05, **p<0.01 (uncorrected p-values).
For the purpose of this exloratory analysis, all p-values reported are uncorrected p-values.
When comparing the mean values of the kinematic characteristics of the right and left lower extremities in both groups, the faller group had a significantly shorter step length in the right direction for both lower extremities than the non-faller group. Step speed was significantly slower in the faller group than in the non-faller group for both lower extremities in the forward direction, the right lower extremity in the backward direction, and the left lower extremity in the right direction. No significant difference was observed in toe clearance between both groups (Table 4).
DISCUSSION
In this study, the Mini-Cog to screen for cognitive impairment in participants according to the exclusion criteria, but no significant difference was found between both groups.
Previous studies have reported that older adults with regular exercise habits have a lower risk of dementia26). As many of the participants in this study were active older adults who were able to attend the community center to maintain their health and had regular exercise habits, it is thought that both the faller and non-faller groups had a low risk of dementia and maintained their cognitive function.
This study compared the kinematic characteristics of the stepping movements of the FSST in faller and non-faller groups of community-dwelling older adults using an optical motion capture system and revealed direction-specific kinematic characteristics.
The results showed that there was no significant difference in the TUG test and the time required for the FSST between the groups.
Previous studies on fall risk screening have shown that the TUG test and total time required for the FSST are slower in faller groups than in non-faller groups; however, this study showed a different result. This discrepancy between the results of the previous study and the current study may be because the faller group in this study included a mix of active individuals who fell while playing active sports or walking outdoors and frail individuals who slipped and lost their balance and fell indoors, as shown in Table 2. Therefore, it is important to analyze the causes of falls in the future by stratifying the faller groups according to the cause of the falls.
The main finding of this study was that the faller group had a significantly shorter step length in the right direction for both the lower extremities than that in the non-faller group. Previous studies on step tasks involving obstacle stepping have shown that the step lengths of older adults and fallers are shorter, suggesting that it is challenging for them to control their lateral stability27,28,29).
Based on the results of these previous studies, the reduction in step length in the right direction when stepping over obstacles in the faller group in this study may have been influenced by a decline in the ability to control lateral stability in the right direction.
Step speed in the faller group was significantly slower than that in the non-faller group in the forward, backward, and right directions. Previous research on the kinematic characteristics of stepping movements has shown that the step speeds of older adults and people who have fallen are slow12, 14,15,16,17).
Previous research on step speed has suggested that a decline in neurological factors related to the preparation and initiation of stepping movements, as well as a decline in lower extremity muscle strength and balance function, affects step speed16).
Referring to these previous studies, it was thought that the decline in both neurological and biomechanical factors, such as muscle strength, was affected by a decrease in the step speed of the faller group.
However, in this study, we did not measure indicators of neural factors, such as electroencephalography and electromyography (EMG), or indicators of biomechanical factors, such as EMG or ground reaction force; therefore, these points are considered issues for the future.
Furthermore, the dominant lower extremity of all participants was the right lower extremity. The non-dominant lower extremity of the fallers was less supported when stepping over an obstacle than that of the non-fallers, and it is thought that this may have led to a decrease in the lateral step length and speed.
In this study, there was no significant difference in toe clearance between faller and non-faller groups. Previous research on toe clearance has reported that older adults at risk of falling have lower toe clearance than those at low risk of falling15, 18, 19).
The difference between the results of this study and those of previous studies was thought to be because the stepping movements required to avoid obstacles were different, as obstacles 5–25 cm in height were used in previous studies, whereas obstacles of 3 cm in height were used in this study.
This study has certain limitations. First, all the participants in this study can walk outdoors to participate in community center events, making it difficult to adapt the results to a more frail population with difficulty walking outdoors.
Second, this study used optical motion capture to measure step length, speed, and clearance, making it difficult to perform similar measurements in facilities without such equipment. Therefore, one of the limitations of this study is that the methodology used cannot be generalized to facilities that do not have such measuring equipment.
Third, the FSST is difficult for older adults with impaired balance and may cause floor effects, as it is required to assess the ability to make quick movements when changing posture or avoiding obstacles30).
Fourth, this study used multiple secondary outcome measures, and no adjustment for multiple comparisons was made.
In conclusion, the kinematic characteristics of step length and step speed during the FSST, as measured by optical motion capture, may be specific fall factors that distinguish between the faller and non-faller groups in community-dwelling older adults. The results of this study suggest that to prevent falls among community-dwelling older adults, it is necessary to implement training that improves step length and speed in stepping movements, such as FSST, which involves stepping over low obstacles.
Funding
This study was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science [Grant Number JP22K11445]. The funders had no role in the design, conduct, analysis, interpretation of the data, or writing of the manuscript.
Conflict of interest
The authors declare no conflict of interest.
Acknowledgments
I would like to express my sincere gratitude to the Welfare Policy Division of Matsumoto City, and all the coordinators of the Matsumoto City Welfare Plaza, for their cooperation in this research.
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