Abstract
BACKGROUND:
Step symmetry is an important feature of human gait and is often regarded as a key index of healthy individuals’ walking. This study evaluated the effects of height, white cane technique, and cane tip on symmetrical gait in blind individuals.
MATERIALS AND METHODS:
Twenty blind and ten sighted subjects, aged 15–38 years, participated in this study. The harmonic ratio (HR) and improved HR (iHR) were measured by trunk accelerometer as gait symmetry index in three axes: anteroposterior (AP), vertical, and mediolateral of the body. These parameters were measured in the sighted group in open-eye conditions and in the blind group in five experimental conditions with different two heights (standard and long), two tips (pencil and roller), and two techniques (two-point touch and constant contact) of white cane when they walked in the 6-m path.
RESULTS:
There was a significant difference between HR and iHR of the blind and sighted group, which indicates a significant reduction of symmetry loss in the blind group. Among the five different conditions studied in the group of blind people, an increase was observed in the HR and the iHR on the AP axis during the application of a standard cane with a roller tip, which indicated an increase in symmetry.
CONCLUSION:
Based on the results, a long cane with a pencil tip and a standard cane with a roller tip in the constant contact technique can increase step symmetry.
Keywords: Blind individuals, ergonomics, harmonic ratio, improved harmonic ratio, step symmetry
Introduction
Gait, as a basic skill and a repetitive and continuous pattern, is the most important daily motor activity of human beings.[1] Consequently, the improvement of this basic human skill is a common goal in rehabilitation interventions.[2] Understanding the complexities and subtleties of human gait and step symmetry has always attracted researchers’ interest in this field of study.[3]
Step symmetry is an important feature of human gait and is often regarded as a key index of healthy individuals’ walking in both clinical and research settings.[4,5] This index is usually defined as functional coordination between left and right body parts during gait and reflects step-to-step symmetry in one stride.[4,6]
Studies show that an increase in asymmetry is associated with higher energy consumption and risk of falls, as well as lower balance, quality of life, and level of physical activity.[7,8] In rehabilitation interventions, the quantification of asymmetry is an important issue that should be measured using valid and reliable tools.[3,4] Among the indicators used to determine step symmetry, the harmonic ratio (HR) and the improved HR (iHR) have been introduced as appropriate indicators in recent years due to their applicability.[4,5] These indices are based on trunk acceleration data in the anteroposterior (AP), vertical (VT), mediolateral (ML) axes, and Fourier frequency analysis.[4,5] Studies have also confirmed the relationship between HR from the trunk accelerometer and the rate of falls.[4,9]
Due to the importance of vision in walking, and considering the fact that 80% of the information in the motion control system is communicated through vision, blind and visually impaired people often experience changes in their gait patterns.[10,11] Mostly, these changes can restrict movement and physical activity and increase the possibility of falling or related injuries.[12,13]
According to the World Health Organization, falls are the second leading cause of death in unintentional accidents, with about 10,000 deaths/year (80% of fall incidents occur in developing countries).[14] Several causes have been identified for fall incidents, among which poor vision is a leading one.[13] Studies show that the risk of falls in blind and partially sighted populations is 1.9 times more, compared to people with normal vision, which can be attributed to the nonaccommodating environment on one hand and the lack of visual cues on the other.[15]
To walk, blind people or those with severe visual impairment need assistive devices.[16] The white cane is still one of the most common means of mobility assistance despite the new emerging methods and tools.[17] Therefore, improving the conditions of the white cane, especially from an ergonomics view, can help to reduce accidents and the rate of falls and increase a person’s independence.[18,19]
The white cane consists of three parts: grip handle, shaft, and tip.[20] Typically, the handle and the tip of the cane are made of rubber or plastic materials and the body part is made of hard and lightweight metal, such as aluminum.[20] The shaft and tip are the essential parts of the cane due to the importance of height adjustment and constant contact with the ground, respectively.[17,20] In various studies, these two factors along with cane techniques have been studied as ergonomic factors, especially in the detection of obstacles.[20,21]
Some studies have examined the effect of cane height in the detection of obstacles in canes with standard height (VT distance from the ground up to 5 cm above the xiphoid appendix) and long height (which is 10%–20% higher than the standard cane).[17,22] Currently, more than ten tips of white canes with different dimensions and materials are commercially available, among which canes with pencil and roller tips are the most common.[19,20]
The two-point touch and the constant contact techniques are the two most common and basic cane techniques adopted by blind people.[21,23] While there are many similarities between these two techniques, it should be noted that when using the two-point touch technique, the cane tip rises from the ground and rotates to the opposite side between each contact on the surface, while in constant contact technique, the cane tip is in continuous contact with the ground and moves from side to side like a broom.[21]
Most studies conducted on white canes have only investigated the effect of cane characteristics such as height, weight, and cane techniques on the detection of obstacles, while fewer studies have addressed the ergonomics aspects of the canes and their impacts on the blind person’s gait and balance.[19,20,24] The results of a study by Santos et al. showed that using a cane changed the walking pattern of visually-impaired people.[24] Subtle changes in the ankle during a cane-assisted walk indicate better exertion of force and easier walk, compared to a nonassisted walk (without a cane). These types of assessments can be important for improving motor training and rehabilitation strategies.[24] Therefore, identification of the variables that affect blind people’s gait can help researchers find solutions to prevent and reduce movement problems caused by blindness in daily and professional life.
Considering the results of studies on the effect of the white cane in walking and based on what is mentioned in the introduction, no ergonomics studies have been conducted to date to assess the effectiveness of white cane on the step symmetry of blind people. Therefore, the present study was carried out to assess the effects of height, cane technique, and cane tip type on symmetrical gait in blind people and comparing the step symmetry in sighted people with the step symmetry of blind people.
Materials and Methods
Study participants
This study was conducted on 20 blind people in the case group and 10 sighted people in the control group. The congenital blind individuals, in the age range of 15–40 years, whose blindness was approved by the Iranian Welfare Organization and had no other disabilities other than visual impairment were included in the study.
Participants were also required to have at least a 3-month history of white cane use. Participants with a history of surgery or injury to the lower limbs and spine and those who were unwilling to participate were excluded from the study. All participants signed a written consent form after they were informed about the study objectives and testing process.
Calculation of harmonic ratio and improved harmonic ratio variables
Harmonic ratio
The HR is used to examine changes in gait patterns and, in particular, step-to-step asymmetry. In gait research, the HR index is usually derived from a trunk accelerometer on the AP, VT, and ML axes. The acceleration pattern of AP and VT axes in a gait is biphasic by nature due to the right and left steps.[4]
It should be noted that even and odd harmonics represent the biphasic symmetry of the acceleration signal and the deviation from symmetry, respectively. In the ML direction, due to its monophasic nature, odd harmonics indicate greater symmetry and even harmonics indicate deviation from symmetry.[4]
The harmonics resulting from Fourier analysis of each step were used to calculate the HR of walking. To calculate the HR for the AP and VT directions, the sum of the amplitudes of the even harmonics is divided by the sum of the amplitudes of the odd harmonics, and vice versa in the ML direction as follows: [4]
Improved harmonic ratio
Recently, Pasciuto et al. introduced what they defined as the iHR.[5] This measure has been suggested to overcome some drawbacks of traditional HR, due to simpler interpretation and less variability.[5]
The iHR is calculated by dividing the squares of even harmonics (on the AP and VT axes) or the odd harmonics (on the ML axis) by the sum of the squares of the even and odd harmonics multiplied by 100.[5] Therefore, this index indicates symmetry in a range from total asymmetry (zero) to total symmetry (100), and its interpretation is easier to understand compared to HR.[5]
Data collection
Anthropometric and demographic characteristics of the participants including height, weight, and grip strength of both hands were measured and recorded. Afterward, participants were asked to walk in the laboratory to get acquainted with the environment.
The gait analysis setup in the present study consisted of a three-axis accelerometer (ADXL345) hosted by an AVR microcontroller. The data were locally sampled by the microcontroller at 100 Hz and were stored on a memory card. The accelerometer was secured by a belt along the AP, VT, and ML axes as close to the gravity center of the body, around the third and fourth lumbar vertebrae.
The participants walked a straightforward 6-m path covered with tactile paving for three times. Those with uninterrupted walking, correct use of a white cane, and the least deviation from the set path were selected as acceptable cases. The subjects were asked to attend the laboratory with any comfortable shoes except sandals and high heels and walk at a voluntary and uniform speed.
Subjects in the control group walked through the 6-m path nonstop at a voluntary speed while looking directly at a fixed point on the wall to prevent deviation from the normal course of movement.
In the group of blind people, participants moved in five conditions as follows:
Long cane with two-point touch techniques and pencil tip, long cane with constant contact techniques and pencil tip, standard cane with two-point touch techniques and pencil tip, standard cane with constant contact techniques and pencil tip, and standard cane with constant contact techniques and roller tip. The sets of experimental conditions were presented in random order to counterbalance the order effects and carryover. Before the test, the cane height was adjusted according to the measurements.
Data processing
Signal processing was performed using Matlab (Mathworks Inc., USA). Each step was identified as the time interval from an initial contact event to determine the next event on the other side, and the steps were distinguished according to previous studies [Figure 1].[25]
Figure 1.
Schematic representation of gait asymmetry assessment: The three-axis accelerometer and a recorded signal along AP (AP, blue line), VT (VT, red line), and ML (ML, yellow line) in sighted (a) and blind (b) group. AP: Anteroposterior, VT: Vertical, ML: Mediolateral
Accelerometer data were filtered using a two-way Butterworth filter with a cutting frequency of 30 Hz was used. HR and iHR were calculated separately for each step and then the average of each three to five steps was obtained.
Statistical analysis
Descriptive and analytical analyses of data were carried out using SPSS software (SPSS, Chicago, IL, USA). Kolmogorov–Smirnov test and independent t-test were used to assess the normality of the data and compare the normal distribution of data between the two groups, respectively.
The Chi-square test and independent t-test were used to compare qualitative variables between the two study groups. Repeated measurements analysis of variance was then used to examine and compare the two cane techniques (two-point touch and the constant contact techniques), two cane heights (standard and long), and two cane tips (pencil and roller tips) as well as their interaction. The independent samples t-test was also used to compare different walking conditions of blind and sighted individuals in open eyes condition. The level of significance in this study was set at 0.05.
This study was approved by the Ethics Committee of Shiraz University of Medical Sciences and the authors report no declaration of interest.
Results
The demographics and characteristics of the participants in the two groups of sighted and blind individuals are presented in Table 1. There was no significant difference between the demographic characteristics of the participants in the two study groups which made the comparison between the two groups feasible. The mean history of white cane use in the group of blind participants was 7 years and the average use of white cane per day was 56 min.
Table 1.
Subject characteristics in sighted and blind groups
| Variables | Sighted person (n=10), n (%) | Blind person (n=20), n (%) | P |
|---|---|---|---|
| Age (years) | 28.1±7.17 | 25.55±5.48 | 0.28* |
| Height (cm) | 163.10±7.83 | 165±9.55 | 0.59* |
| Weight (kg) | 56.90±9.27 | 58.45±11.67 | 0.71* |
| BMI (kg/m2) | 21.24±2.46 | 21±3.49 | 0.91* |
| Grip strength (right hand) (kg) | 31.30±12.90 | 29.07±7.11 | 0.54* |
| Grip strength (left hand) (kg) | 28.82±9.93 | 28.32±8.20 | 0.88* |
| Sex (female) | 6 (60) | 8 (40) | 0.30† |
| Marital status (single) | 7 (70) | 16 (80) | 0.54† |
| Level of education | |||
| Diploma and lower | 2 (20) | 9 (45) | 0.40† |
| BSc | 6 (60) | 8 (40) | |
| MS and PhD | 2 (20) | 3 (15) | |
| Dominant hand | |||
| Right | 8 (80) | 16 (80) | 0.98† |
| Left | 2 (20) | 4 (20) |
*P values were calculated using independent t-test or †Chi-square tests. Values are means±SD or percentages. SD: Standard deviation, BMI: Body mass index
Table 2 presents the mean and standard deviation of HR and iHR variables in the sighted group and five experimental conditions in the blind group in the analysis of 20 harmonics on three axes (AP, VT, and ML). Significant differences between HR and iHR in diverse test conditions for blind individuals are shown in Figure 2. Among different conditions investigated in the blind group, an increase was observed in the HR and the iHR on the AP axis during the use of a standard cane with a roller tip. On the ML axis, significant differences in the HR were observed only between the two conditions of long TP and long CP. No significant differences were observed between different conditions on the VT axis.
Table 2.
Mean and standard deviation of the mean values of the harmonic ratio and improved harmonic ratio indices for 20 harmonic and 3 strides, along the three axes in blind and sighted group
| Conditions | HR-AP | HR-VT | HR-ML | iHR-AP | iHR-VT | iHR-ML |
|---|---|---|---|---|---|---|
| Blind group (n=20) | ||||||
| Long TP | 1.36±0.23 | 1.60±0.60 | 1.42±0.30 | 67.84±8.44 | 68.17±15.38 | 67.43±11.7 |
| Long CP | 1.43±0.35 | 1.58±0.46 | 1.81±0.47 | 68.81±10.27 | 70.39±9.65 | 75.86±9.63 |
| Standard TP | 1.45±0.29 | 1.62±0.41 | 1.57±0.30 | 69.33±10.03 | 69.54±9.79 | 70.42±11.36 |
| Standard CP | 1.35±0.36 | 1.43±0.34 | 1.57±0.35 | 63.31±13.16 | 67.48±10.45 | 71.97±11.61 |
| Standard CM | 1.67±0.30 | 1.63±0.40 | 1.69±0.32 | 73.71±8.42 | 72.70±11.03 | 75.17±8.92 |
| Sighted group (n=10) | ||||||
| Walking | 2.22±0.46 | 2.72±0.50 | 1.92±0.41 | 83.47±7.72 | 87.23±7.64 | 77.96±8.34 |
Long TP: Long cane with two-point touch techniques and pencil tip, Long CP: Long cane with constant contact techniques and pencil tip, Standard TP: Standard cane with two-point touch techniques and pencil tip, Standard CP: Standard cane with constant contact techniques and pencil tip, Standard CM: Standard cane with constant contact techniques and roller tip. HR: Harmonic ratio, AP: Anteroposterior, VT: Vertical, ML: Mediolateral, iHR: Improved HR
Figure 2.
LongTP: long cane with TPT and pencil tip, LongCP: Long cane with CCT and pencil tip, StandardTP: Standard cane with TPT and pencil tip, StandardCP: Standard cane with CCT and pencil tip, StandardCM: Standard cane with CCT and roller tip. *Significant difference (P < 0.05) by ANOVA. ANOVA: Analysis of variance. ** Significant difference (P < 0.001) by ANOVA. TPT: Two-point touch techniques, CCT: Constant contact techniques, ANOVA: Analysis of variance
Table 3 compares the different conditions of using a cane in blind and sighted individuals. The difference between HR and iHR in the medial axis when blind people used a long cane with a pencil tip and a standard cane with a roller tip in the constant contact technique is the lowest when compared to sighted people
Table 3.
Comparison of gait outcome measures between walking of sighted individuals with open eyes and walking of blind people with five different cane conditions; Mean Difference (95% CI)
| Cane conditions | HR-AP | HR-VT | HR-ML | iHR-AP | iHR-VT | iHR-ML |
|---|---|---|---|---|---|---|
| Long TP | -0.85** (-1.11,-0.59) | -1.12** (-1.57,-0.66) | -0.51** (-0.78,-0.24) | -15.63** (-22.15,-9.10) | 19.06** (-29.68,-8.43) | 10.52* (-19.05,-0.92) |
| Long CP | -0.78** (-1.10,-0.47) | -1.13** (-1.51,-0.75) | -0.11 (-0.48,-0.24) | -14.66** (-22.22,-7.10) | -16.84** (-24.02,-9.66) | 2.09 (-9.42,5.23) |
| Standard TP | -0.76** (-1.05,-0.47) | -1.09** (-1.48,-0.70) | -0.35* (-0.62,-0.08) | -14.14** (-21.56,-6.72) | -17.69** (-24.95,-10.42) | -7.53* (-15.85,0.78) |
| Standard CP | -0.86** (-1.18,-0.54) | -1.28** (-1.60,-0.97) | -0.35* (-0.65,-0.06) | -20.16** (-29.44,-10.88) | -19.75** (-27.40,-12.10) | -5.99 (-14.45,2.47) |
| Standard CM | -0.54** (-0.84,-0.25) | -1.08** (-1.43,-0.74) | -0.23 (-0.51,0.04) | -9.76** (-16.27,-3.24) | -14.53** (-22.52,-6.54) | -2.78 (-9.72,4.14) |
LongTP: long cane with two-point touch techniques and pencil tip, LongCP: long cane with constant contact techniques and pencil tip, StandardTP: standard cane with two-point touch techniques and pencil tip, StandardCP: standard cane with constant contact techniques and pencil tip, StandardCM: standard cane with constant contact techniques and roller tip. *P<0.05. **P<0.001
Discussion
This study was carried out to examine the effects of height, tip, and technique of white cane on the step symmetry of blind individuals and compare the step symmetry of sighted and blind subjects.
Among the five different conditions studied in the group of blind people [Figure 2], an increase was observed in the HR and the iHR on the AP axis during the application of a standard cane with a roller tip, which indicated an increase in the symmetry in mentioned conditions. No significant differences were observed between different conditions on the VT axis. However, on the ML axis, significant differences in the HR were observed only between the two conditions of long TP and long CP. Therefore, the use of a long cane with a pencil tip increased the step symmetry compared to the other conditions in the constant contact technique.
Our results were in line with the results of studies conducted on the detection of obstacles, indicating that the use of the constant contact technique and a roller tip led to more effective detection of obstacles compared to the two-point touch technique with a fixed cane tip.[20,21] Although the present study did not tell us why the constant contact technique was better than the two-point touch technique in increasing symmetry, a reason could be due to a better perception of the path in the constant contact technique.
A few studies that have examined cane length have addressed in different fields. Bongers et al. showed that increasing the length of the cane increased drop-off, while Kim et al. pointed out that the obstacle detection rate with the extended-length cane was not significantly different from that with the standard-length cane.[17,22] Researchers also found a significant relationship between cane height, employment, and income. Visually impaired people who used a long cane above the chin were employed and had higher incomes.[18]
The comparison between the different conditions of using a cane in blind individuals and normal steps of sighted individuals in this study showed that using a standard cane with a roller tip and using a long cane with a pencil tip in the constant contact technique lead to similar step symmetry to those of a sighted person on the ML axis.
In other conditions, there was a significant difference between HR and iHR of the blind and sighted group, which indicates a significant reduction of symmetry loss in the blind group.
Majlesi and Farahpour investigated the symmetry index in step parameters and compared the left and right legs in both blind and sighted people. They observed no significant differences between the two study groups.[10]
Based on the obtained results in this study, it seems that the use of standard canes with roller tips and constant contact techniques can increase step symmetry.
Study limitations
Regarding the limitations of the present study, one can refer to the sampling and the impossibility of random selection of samples. Moreover, the study was conducted to control interfering factors in laboratory conditions. This might have affected the obtained results, as well.
Conclusion
Blindness leads to a decrease in step symmetry. Nevertheless, given the important role of the white cane in the independent living of blind people, improvement of the cane characteristics, such as height, tip, and adoption of an appropriate cane technique, can enhance step symmetry and reduce the risk of falls. Based on the results, a long cane with a pencil tip and a standard cane with a roller tip in the constant contact technique lead to similar step symmetry to those of a sighted person on the ML axis.
Recommendations
Other than the structural conditions of the white cane and its effect on step symmetry, further studies are recommended to examine other influential variables, such as the type of pavement, environmental conditions (e.g., unfamiliar and noisy environments), and their effects on symmetry and other kinematic and kinetic walking parameters. It is also suggested that this study be carried out on individuals with severe visual impairment.
Financial support and sponsorship
This study was financially supported by Shiraz University of Medical Sciences based on contract number 98-01-04-20362.
Conflicts of interest
There are no conflicts of interest.
Acknowledgments
This article has been extracted from the Ph. D. dissertation of Zeinab Rasouli, an Ergonomics student at Shiraz University of Medical Sciences in Iran. The authors would like to thank all the people who participated in this study, as well as the officials in the Shiraz Institute for the Blind and Entrepreneurs for their valuable cooperation.
References
- 1.Kharb A, Saini V, Jain Y, Dhiman S. A review of gait cycle and its parameters. IJCEM Int J Comput Eng Manage. 2011;13:78–83. [Google Scholar]
- 2.Hisano G, Hashizume S, Kobayashi T, Major MJ, Nakashima M, Hobara H. Unilateral above-knee amputees achieve symmetric mediolateral ground reaction impulse in walking using an asymmetric gait strategy. J Biomech. 2021;115:110201. doi: 10.1016/j.jbiomech.2020.110201. [DOI] [PubMed] [Google Scholar]
- 3.Viteckova S, Kutilek P, Svoboda Z, Krupicka R, Kauler J, Szabo Z. Gait symmetry measures:A review of current and prospective methods. Biomed Signal Process Control. 2018;42:89–100. [Google Scholar]
- 4.Bellanca JL, Lowry KA, Vanswearingen JM, Brach JS, Redfern MS. Harmonic ratios:A quantification of step to step symmetry. J Biomech. 2013;46:828–31. doi: 10.1016/j.jbiomech.2012.12.008. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Pasciuto I, Bergamini E, Iosa M, Vannozzi G, Cappozzo A. Overcoming the limitations of the Harmonic Ratio for the reliable assessment of gait symmetry. J Biomech. 2017;53:84–9. doi: 10.1016/j.jbiomech.2017.01.005. [DOI] [PubMed] [Google Scholar]
- 6.Hsiao-Wecksler ET, Polk JD, Rosengren KS, Sosnoff JJ, Hong S. A review of new analytic techniques for quantifying symmetry in locomotion. Symmetry. 2010;2:1135–55. [Google Scholar]
- 7.Awad LN, Palmer JA, Pohlig RT, Binder-Macleod SA, Reisman DS. Walking speed and step length asymmetry modify the energy cost of walking after stroke. Neurorehabil Neural Repair. 2015;29:416–23. doi: 10.1177/1545968314552528. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Park S, Liu C, Sánchez N, Tilson JK, Mulroy SJ, Finley JM. Using biofeedback to reduce step length asymmetry impairs dynamic balance in people poststroke. Neurorehabil Neural Repair. 2021;35:738–49. doi: 10.1177/15459683211019346. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Patel M, Pavic A, Goodwin VA. Wearable inertial sensors to measure gait and posture characteristic differences in older adult fallers and non-fallers:A scoping review. Gait Posture. 2020;76:110–21. doi: 10.1016/j.gaitpost.2019.10.039. [DOI] [PubMed] [Google Scholar]
- 10.Majlesi M, Farahpour N. Kinematic and spatio-temporal characteristics of gait in blind individuals. J Res Rehabil Sci. 2015;11:292–9. [Google Scholar]
- 11.Hallemans A, Ortibus E, Truijen S, Meire F. Development of independent locomotion in children with a severe visual impairment. Res Dev Disabil. 2011;32:2069–74. doi: 10.1016/j.ridd.2011.08.017. [DOI] [PubMed] [Google Scholar]
- 12.Reed-Jones RJ, Solis GR, Lawson KA, Loya AM, Cude-Islas D, Berger CS. Vision and falls:A multidisciplinary review of the contributions of visual impairment to falls among older adults. Maturitas. 2013;75:22–8. doi: 10.1016/j.maturitas.2013.01.019. [DOI] [PubMed] [Google Scholar]
- 13.Montana CL, Bhorade AM. Glaucoma and quality of life:Fall and driving risk. Curr Opin Ophthalmol. 2018;29:135–40. doi: 10.1097/ICU.0000000000000455. [DOI] [PubMed] [Google Scholar]
- 14.World Health Organization. FALLS. 2021. [[Last updated on 2021 Apr 26]]. https://www.who.int/news-room/fact-sheets/detail/falls#:~:text=Falls%20are%20the%20 second%20leading,greatest%20number%20of%20fatal%20falls.
- 15.Legood R, Scuffham P, Cryer C. Are we blind to injuries in the visually impaired?A review of the literature. Inj Prev. 2002;8:155–60. doi: 10.1136/ip.8.2.155. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Shen J, Chen Y, Sawada H. A wearable assistive device for blind pedestrians using real-time object detection and tactile presentation. Sensors. 2022;22:4537. doi: 10.3390/s22124537. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Kim DS, Emerson RW, Naghshineh K. Effect of cane length and swing arc width on drop-off and obstacle detection with the long cane. Br J Vis Impair. 2017;35:217–31. doi: 10.1177/0264619617700936. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Bell EC, Mino NM. Blind and visually impaired adult rehabilitation and employment survey:Final results. J Blind Innov Res. 2013;3:1–35. [Google Scholar]
- 19.Kim DS, Emerson RW. Obstacle detection with the long cane:Effect of cane tip design and technique modification on performance. J Vis Impair Blind. 2018;112:435–46. [PMC free article] [PubMed] [Google Scholar]
- 20.Kim DS, Emerson RS, Curtis AB. Ergonomic factors related to drop-off detection with the long cane:Effects of cane tips and techniques. Hum Factors. 2010;52:456–65. doi: 10.1177/0018720810374196. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Kim DS, Emerson RW, Curtis A. Drop-off detection with the long cane:Effects of different cane techniques on performance. J Vis Impair Blind. 2009;103:519–30. [PMC free article] [PubMed] [Google Scholar]
- 22.Bongers RM, Schellingerhout R, Van Grinsven R, Smitsman AW. Variables of the touch technique that influence the safety of cane walkers. J Vis Impair Blind. 2002;96:516–31. [Google Scholar]
- 23.Tai NC, Jiang PH, Liou JJ, editors. Development of a Smart Cane to Utilize Ultrasonic Sensing to Extend the Detection Range of Cane Techniques. 2019 8th International Conference on Innovation, Communication and Engineering (ICICE) IEEE. 2019 [Google Scholar]
- 24.Santos D, Abrantes JM, Lewis P, Macedo AF. Influence of the use of cane on the gait cycle of individuals who are blind. Br J Vis Impair. 2018;36:251–61. [Google Scholar]
- 25.Zijlstra W, Hof AL. Assessment of spatio-temporal gait parameters from trunk accelerations during human walking. Gait Posture. 2003;18:1–10. doi: 10.1016/s0966-6362(02)00190-x. [DOI] [PubMed] [Google Scholar]