Balance perturbation system to improve balance compensatory responses during walking in old persons
© Shapiro and Melzer; licensee BioMed Central Ltd. 2010
Received: 9 July 2009
Accepted: 15 July 2010
Published: 15 July 2010
Ageing commonly disrupts the balance control and compensatory postural responses that contribute to maintaining balance and preventing falls during perturbation of posture. This can lead to increased risk of falling in old adults (65 years old and over). Therefore, improving compensatory postural responses during walking is one of the goals in fall prevention programs. Training is often used to achieve this goal. Most fall prevention programs are usually directed towards improving voluntary postural control. Since compensatory postural responses triggered by a slip or a trip are not under direct volitional control these exercises are less expected to improve compensatory postural responses due to lack of training specificity. Thus, there is a need to investigate the use balance perturbations during walking to train more effectively compensatory postural reactions during walking.
This paper describes the Balance Measure & Perturbation System (BaMPer System) a system that provides small, controlled and unpredictable perturbations during treadmill walking providing valuable perturbation, which allows training compensatory postural responses during walking which thus hypothesize to improve compensatory postural responses in older adults.
Postural control is the foundation of our ability to move independently. Acute injuries, including traumatic brain and spinal cord injuries, Hip fracture and even death occurring as a result of falls in old adults . In the older adults about one out of three individuals fall at least once a year . Falls are the leading cause of accidental death in the elderly population . The cost has been estimated to be nearly $10 billion for one year [4–6]. Consequently, there is a need to develop new technologies that will improve interventions for reducing falls and increasing quality of life in older adults.
The benefits of exercise with respect to general health, strength, and balance have been long documented in the physical exercise literature [7–16]. However, research studies investigating exercise as a means of falls prevention in older adults have shown controversial results. Several studies show that exercise prevents falls [17–22] and other studies have shown no reduction in falls [23–25]. The controversial results may be the result of the flaw in many balance training programs ignoring a basic principle of physical training, the concept of specificity. The majority of falls occurs during walking  and results from unexpected perturbations. In spite of this, most balance training regimens only include voluntarily controlled exercises [14–25], that do not include perturbation exercises to improve compensatory postural responses during walking, which may improve the ability to prevent falling when a person loses his/her balance.
The postural responses triggered by a slip or a trip are not under direct voluntary control [27–29]. These postural "reflexes", initiated by external postural perturbations, lead to activation of specific recovery strategies. These recovery strategies are not under volitional control and thus the optimal means for training compensatory responses will involve unexpected external perturbation exercises during walking. The Balance Measure and Perturbation System (BaMPer System) described here triggers postural "reflexes" to improve balance responses is designed to supply the patient with an unexpected acceleration during treadmill walking.
Wolfson et al.  were able to demonstrate improvements in balance function in old adults using intensive balance training that included equilibrium control exercises of firm and foam surfaces and/or weight training followed by 6 months of low intensity Tai Chi training. Oddsson et al.  proposed a specific training program that involves use of unpredictable, multi-directional perturbations to evoke stepping responses in elderly persons. Mansfield et al.  used of a perturbation platform that moves suddenly and unpredictably during standing on the platform in one of four directions as part of a balance training program. Rogers et al.  showed that either voluntary or waist-pull-induced step training reduced step initiation time. The above-mentioned studies [30, 32, 33] and perturbation systems previously used in research, train compensatory responses during up-right standing and not during walking, this is not the optimal means for training compensatory responses during walking since it lacks the specificity principle of exercise physiology.
Miziaszek and Krauss  used forwards and backwards perturbations while walking on a motorized treadmill. These were perturbations of center of mass that were randomly applied at the pelvis compared with the base of support perturbations that is applied by the BaMPer System suggested here, both type of perturbation are relevant to 'real-life' postural perturbations and responses. Shimada et al.  used bilateral separated treadmill whereas each of the separated belts where run in a different speed to perturb normal gait. Bhatt and Pai,  exposed elderly subjects to a slip backward balance loss as a training to improve stepping reactions. The unidirectional slip (backwards only) is the major drawback of the system, since the direction of perturbation was expected after several exercises. Thus it seems that this is not the optimal means for training compensatory responses to different directions.
The basic requirements for the BaMPer system are based on Oddson et al. results . Oddson et al. applied perturbation of which the maximal acceleration is 9.81 m/sec^2 and the maximal velocity is 0.7 m/sec. Therefore while designing the BaMPer system we chose the system to be able to apply maximal acceleration of 9.81 m/sec^2, and to reach maximal velocity of 0.8 m/sec. The maximal displacement during perturbation was chosen to be 10 cm to any direction in the horizontal plane in order to simulate bumping into a small obstacle.
List of system's components and their model numbers.
Manufacturer and model number
Main linear slides
Drive unit: AC servomotor
Rockwell Automation MPL-A330P-HJ22AA
Huco flexible coupling p/n 618.104.22.168
Ball drive unit
Supporting bearing unit
linear slide between the nut and the moving frame
ACS SpiiPlus CM-2-BE-MO
The moving platform is mounted on four sliding mechanisms to allow motion in both longitudinal and lateral directions. Each of the four sliding mechanisms is composed of three main linear slides mounted in an H-like shape. Each of the two driving units is composed of an AC servo motor connected through a coupler to a ball screw. The nut of the ball screw is connected through a linear slide to the moving frame. The reason for the additional linear slide between the nut and the frame is that the frame can be moved perpendicularly by the other drive unit. For the drive unit, we used AC servo motors with 1800 W power, maximal speed of 5000 rpm, and peak torque of 11.1 Nm. A flexible coupler transfers the required motion from the motor to the ball drive unit. Position sensing is accomplished by optical encoders mounted on the back side of each motor. Limit switches are mounted on the base stationary part of the system ate the maximal travel distance.
B. Motion Control
C. Software Design and User Interface
The program that serves as the system's user interface is written in Microsoft Visual Basic 2008 and runs on the host PC. The application is a Windows form application and contains four tabs: communication, setting parameters, testing, and run experiment.
Communication tab: The communication tab allows opening and closing the communication port to the ACS controller. It also reminds the operator to check if the safety harness is secured. In addition, it automatically calibrates the travel range of each of the motors and moves the platform into the home position at the center of the working range. This calibration is done by slowly moving the platform until it reaches the limit switches at the maximal travel distance and then setting the position measured by the motors' encoders to be accurately the actual position.
Set Parameters tab: this tab enables changing the minimal and maximal values of the motion profile parameters. It also enables setting the number of perturbations during a single experiment or training series, and the time delay between two consecutive perturbations. For each perturbation to be executed the system will randomly select each parameter within the range specified by the minimal and maximal values.
Testing tab: This tab allows applying a single perturbation in a manually selected direction.
Run Experiment tab: This tab is the most important one, since from here the operators actually starts the training sequence in which a series of perturbations will be applied to the patient. The tab presents several items, first are the start and stop buttons for starting the training or stopping it. Then there is the number of current perturbations within the series (initial value is zero), and the total time left for the current run. The operator can provide a filename for a log file that contains the run parameters. On the right there is a box that will contain a graph of the platform velocity during the perturbation interval. On the bottom there is a table containing all the motion parameters that have been randomly selected for the perturbation executed.
Safety is an extremely important issue since we apply perturbation to an older patient walking and that may cause him or her to fall. During the training the treadmill will continue to run also after platform motion (e.g. perturbation of balance), even though one foot is located on the surrounding surface outside the treadmill. The subject will be instructed to recover from loss of balance due to perturbation by stepping outside the treadmill and than return to walk on the treadmill as fast as he possibly can, which is the most important part of the training regimen. Results of a pilot study show that during lateral perturbations young individuals respond by quick stepping response off the platform to the opposite direction of the perturbation and recovered by stepping back quickly into the treadmill. In anterior posterior platform perturbations young individuals responded by a quick increase (in backward perturbations) or quick decrease (in forward perturbations) of walking speed. Low accelerations did not evoked stepping response however quick movement of the upper body to the opposite side of the perturbation seen to recover movement of the bodies' center of mass. In case the subject fail to recover and falls, safety cables that connect the subject waist to the treadmills control panel will stop the treadmills from its continuous motion. Furthermore, to prevent any injury during loss of balance and fall initiation, the patient is wearing a safety harness that will arrest the fall before the patient's knees touch the ground. Examples of such a safety harness are the Skylotec G-0904 or the PN12 harness. The safety harness is hung from the ceiling by two ropes above the patients. However, for stability reasons the ropes do not hang straight from the ceiling, but in a diagonal such that the distance between the connection points of the two ropes on the ceiling is about 2 m. When the rope is hanged in diagonal it is capable to apply much larger horizontal force in order to keep and stabilize the patient at the center. The treadmill works as an ordinary treadmill and only the therapist controls the speed/stops the treadmill and controls the perturbation displacements/velocity/accelerations ranges. If the subject is unable to 'keep up' with the speed a modifications will be made by the therapists.
Written informed consent was obtained from the patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
The authors wish to acknowledge the contribution of Ayelet Asa, Elad Alfo, Oren Segal and Ofir Gal-or students at the Mechanical Engineering department at Ben-Gurion University that was involved in developing and building the BaMPer system as part of their project.
- Masud T, Morris RO: Epidemiology of falls. Age Ageing 2001, 30: 3-7. 10.1093/ageing/30.3.255View ArticlePubMedGoogle Scholar
- Tinetti ME, Speechley M, Ginter SF: Risk factors for falls among elderly persons living in the community. N Engl J Med 1988,319(26):1701-1707. 10.1056/NEJM198812293192604View ArticlePubMedGoogle Scholar
- Centers for Disease Control and Prevention (CDC): Fatalities and injuries from falls among older adults--United States, 1993-2003 and 2001-2005. MMWR Morb Mortal Wkly Rep 2006,55(45):1221. [http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5545a1.htm]Google Scholar
- Rubenstein LZ, Robbins AS, Josephson KR, Schulman BL, Osterweil D: The value of assessing falls in an elderly population. A randomized clinical trial. Ann Intern Med 1990,113(4):308-316.View ArticlePubMedGoogle Scholar
- Sattin WR: Falls among older persons: A public health perspective. Annu Rev Publ Health 1992, 13: 489-508. 10.1146/annurev.pu.13.050192.002421View ArticleGoogle Scholar
- Province MA, Hadley EC, Hornbrook MC, Lipsitz LA, Miller JP, Mulrow CD, Ory MG, Sattin RW, Tinetti ME, Wolf SL: The effects of exercise on falls in elderly patients. A preplanned meta-analysis of the FICSIT Trials. JAMA 1995,273(17):1341-1347. 10.1001/jama.273.17.1341View ArticlePubMedGoogle Scholar
- Pina IL, Daoud S: Exercise and heart failure. Minerva Cardioangiol 2004,52(6):537-546.PubMedGoogle Scholar
- Ostenson CG, Bavenholm P, Efendic S: Exercise is an effective weapon in the fight against type 2 diabetes. Lakartidningen 2004,101(49):4011-4012. 4014-4015. ReviewPubMedGoogle Scholar
- Audebert H, Haberl RL: Secondary prevention after stroke: healthy life style, oral anticoagulation. MMW Fortschr Med 2003,26:145(Suppl 2):61-64.Google Scholar
- Borjesson M, Dahlof B: Physical activity has a key role in hypertension therapy. Lakartidningen 2005,102(3):123-124. 126, 128-129PubMedGoogle Scholar
- Asikainen TM, Kukkonen-Harjula K, Miilunpalo S: Exercise for health for early postmenopausal women: a systematic review of randomised controlled trials. Sports Med 2004,34(11):753-778. 10.2165/00007256-200434110-00004View ArticlePubMedGoogle Scholar
- Bonnefoy M, Cornu C, Normand S, Boutitie F, Bugnard F, Rahmani A, Lacour JR, Laville M: The effects of exercise and protein-energy supplements on body composition and muscle function in frail elderly individuals: a long-term controlled randomized study. Br J Nutr 2003,89(5):731-739. 10.1079/BJN2003836View ArticlePubMedGoogle Scholar
- Rockwood K, Howlett SE, MacKnight C, Beattie BL, Bergman H, Hebert R, Hogan DB, Wolfson C, McDowell I: Prevalence, attributes, and outcomes of fitness and frailty in community-dwelling older adults: report from the Canadian study of health and aging. J Gerontol A Biol Sci Med Sci 2004,59(12):1310-1317.View ArticlePubMedGoogle Scholar
- Melzer I, Benjuya N, Kaplanski J: Effect of physical training on postural control of elderly. Harefuah 2005,144(12):839-844.PubMedGoogle Scholar
- Hue OA, Seynnes O, Ledrole D, Colson SS, Bernard PL: Effects of a physical activity program on postural stability in older people. Aging Clin Exp Res 2004,16(5):356-362.View ArticlePubMedGoogle Scholar
- Sihvonen SE, Sipilä S, Era PA: Changes in postural balance in frail elderly women during a 4-week visual feedback training: a randomized controlled trial. Gerontology 2004,50(2):87-95. 10.1159/000075559View ArticlePubMedGoogle Scholar
- Gillespie LD, Gillespie WJ, Robertson MC, Lamb SE, Cumming RG, Rowe BH: Interventions for preventing falls in elderly people. Cochrane Database Syst Rev 2001, 3: CD000340.PubMedGoogle Scholar
- Wolf SL, Barnhart HX, Kutner NG, McNeely E, Coogler C, Xu T: Reducing frailty and falls in older persons: an investigation of Tai Chi and computerized balance training. J Am Geriatr Soc 1996, 44: 489-497.View ArticlePubMedGoogle Scholar
- Li FZ, Harmer P, Fisher KJ, McAuley E, Chaumeton N, Eckstrom E, Wilson NL: Tai Chi and fall reductions in older adults: A randomized controlled trial. J Gerontol A Biol Sci Med Sci 2005,60(2):187-194.View ArticlePubMedGoogle Scholar
- Lord SR, Castell S, Corcoran J, Dayhew J, Matters B, Shan A, Williams P: The effect of group exercise on physical functioning and falls in frail older people living in retirement villages: a randomized, controlled trial. J Am Geriatr Soc 2003, 51: 1685-1692. 10.1046/j.1532-5415.2003.51551.xView ArticlePubMedGoogle Scholar
- Means KM, Rodell DE, O'Sullivan PS: Balance, mobility, and falls among community-dwelling elderly persons: effects of a rehabilitation exercise program. Am J Phys Med Rehabil 2005, 84: 238-250. 10.1097/01.PHM.0000151944.22116.5AView ArticlePubMedGoogle Scholar
- Barnett A, Smith B, Lord SR, Williams M, Baumand A: Community-based group exercise improves balance and reduces falls in at-risk older people: a randomized controlled trial. Age Ageing 2003, 32: 407-414. 10.1093/ageing/32.4.407View ArticlePubMedGoogle Scholar
- McMurdo ME, Millar AM, Daly F: A randomized controlled trial of fall prevention strategies in old peoples' homes. Gerontology 2000,46(2):83-87. 10.1159/000022139View ArticlePubMedGoogle Scholar
- Reinsch S, MacRae P, Lachenbruch PA, Tobis J: Attempts to prevent falls and injury: a prospective community study. Gerontologist 1992, 32: 450-456.View ArticlePubMedGoogle Scholar
- Wolf SL, Sattin RW, Kutner M, O'Grady M, Greenspan AI, Gregor RJ: Intense Tai Chi exercise training and fall occurrences in older, transitionally frail adults: a randomized, controlled trial. J Am Geriatr Soc 2003, 51: 1693-1701. 10.1046/j.1532-5415.2003.51552.xView ArticlePubMedGoogle Scholar
- Berg WP, Alessio HM, Mills EM, Tong C: Circumstances and consequences of falls in independent community dwelling older adults. Age Ageing 1997,26(4):261-268. 10.1093/ageing/26.4.261View ArticlePubMedGoogle Scholar
- Nashner LM: Adapting reflexes controlling the human posture. Exp Brain Res 1976, 26: 59-72. 10.1007/BF00235249View ArticlePubMedGoogle Scholar
- Nashner LM: Fixed patterns of rapid postural responses among leg muscles during stance. Exp Brain Res 1977,30(1):13-24. 10.1007/BF00237855View ArticlePubMedGoogle Scholar
- Nashner LM: Balance adjustments of humans perturbed while walking. J Neurophys 1980,44(4):650-663.Google Scholar
- Wolfson L, Whipple R, Derby C, Judge J, King M, Amerman P, Schmidt J, Smyers D: Balance and strength training in older adults: intervention gains and Tai Chi maintenance. J Am Geriatr Soc 1996,44(5):498-506.View ArticlePubMedGoogle Scholar
- Oddsson LIE, Boissy P, Melzer I: How to Improve Gait and Balance Function in Elderly Individuals - Compliance with Principles of Training. Academic Literature Review. European Review of Aging & Physical Activity 2007, 4: 1813-1861.View ArticleGoogle Scholar
- Mansfield A, Peters AL, Liu BA, Maki BE: A perturbation-based balance training program for older adults: study protocol for a randomised controlled trial. BMC Geriatr 2007, 31: 7-12.Google Scholar
- Rogers MW, Johnson ME, Martinez KM, Mille ML, Hedman LD: Step training improves the speed of voluntary step initiation in aging. J Gerontol A Biol Sci Med Sci 2003,58(1):46-51.View ArticlePubMedGoogle Scholar
- Misiaszek JE, Krauss EM: Restricting arm use enhances compensatory reactions of leg muscles during walking. Exp Brain Res 2005, 161: 474-485. 10.1007/s00221-004-2094-8View ArticlePubMedGoogle Scholar
- Shimada H, Obuchi S, Furuna T, Suzuki T: New intervention program for preventing falls among frail elderly people: the effects of perturbed walking exercise using a bilateral separated treadmill. Am J Phys Med Rehabil 2004, 83: 493-499. 10.1097/01.PHM.0000130025.54168.91View ArticlePubMedGoogle Scholar
- Bhatt T, Pai YC: Prevention of slip-related backward balance loss: the effect of session intensity and frequency on long-term retention. Arch Phys Med Rehabil 2009,90(1):34-42. 10.1016/j.apmr.2008.06.021PubMed CentralView ArticlePubMedGoogle Scholar
- Oddsson LIE, Wall C III, McPartland MD, Krebs DE, Tucker CA: Recovery from perturbations during paced walking. Gait and Posture 2004, 19: 24-34. 10.1016/S0966-6362(03)00008-0View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.