Balance related performance measures represent the fundamental foundation of physical therapy clinical pay for performance documentation and evidence-based practice. Current clinical balance assessment tools may not be balance domain specific, unable to challenge systems responsible for preventing a fall from occurring. The following studies raise questions and challenge current fall risk identification scales and balance assessment performance measures. Do clinical performance measures measure up, and does current practice reflect existing evidence?
A functional balance test (POMA, BBS) does not necessarily coincide with the individual’s ability to deal with external balance threats ( Neuls, et al, Usefulness of the Berg Balance Scale to Predict falls in the Elderly, Jl Ger. Phys. Ther: 2011;(34).) It may be that the BBS does not test the domains of balance required to prevent or successfully recover from a fall, which may indicate that a more sensitive measure of balance, including larger components of reactive and dynamic balance is necessary. The level of ability of reactive balance control in the elderly thus needs to be sufficiently addressed before interventions can be developed. (Lin,Woolacott; Association Between Sensori-Motor Function and Functional and Reactive Balance Control in the Elderly, Age and Aging: 2005:34). Decreased Berg Balance Scale sores did not predict increased frequency of falls. (Bogle, Thornbahn, Norton; Use of Berg Balance Test to Predict Falls in Elderly Persons Phys Ther 1996;76(6). The BBS is able to identify disease in community living older adults.(Brotherton, Are Measures Employed in the Assessment of Balance Useful for detecting differences Among Groups That Vary by Age and Disease? JGPT: 28 2005.) The Tinetti POMA demonstrated poor responsiveness to fall status. Lin et al; Psychometric Comparisons of the TUGT and One-Leg Stand, Functional Reach and Tinetti Balance Measures in Community Dwelling Older People, J. Amer Geriatr Soc; 2004). The usefulness of the POMA scales for predicting future falls is severely limited. (Faber MJ, Clinimetric Properties of the Performance Oriented Mobility Assessment: Phys Ther; 2006: 86 (7). Proactive and reactive adaptations should be targeted in interventions to decrease fall incidence in older adults. (Pavol, Runtz, Pai, Young and Older Adults Exhibit Proactive and Reactive adaptations to repeated slip Exposure: 2004; J Gerontol A Biol Sci Med Sci ).
Measures of postural stability are not predictors of recovery from large postural disturbances in healthy older adults. Excursion distances of the center of pressure (COP), medio-lateral and antero-posterior during quiet standing (postural steadiness), static leaning (static stability limits), and dynamic swaying (dynamic stability limits) were determined from ground reaction forces via force plate. Postural steadiness and the stability limit variables were only weakly correlated. Postural steadiness and stability limits were not related to the maximum recoverable angle of lean. Recovery following postural disturbances could not generally be predicted from measures of postural stability. Measures of postural stability are of limited utility in identifying potential anteriorly directed fallers in healthy older adults. (Owings, Pavol; Measures of Postural Stability Are Not Predictors of Recovery From Large Postural Disturbances in Healthy Older Adults; Jl Am Ger Soc 2000:48(1). ) Postural steadiness during quiet stance is not predictive of ability to recover balance with the ankle strategy. Measures of postural steadiness during quiet stance were acquired, (amplitude, velocity and frequency of center of pressure movement) when standing with eyes open or closed on a rigid or compliant surface. Ankle strategy was measured upon release of a forward leaning position to assess recovery of balance. Reaction time and peak torque did not correlate with any steadiness variables. (Mackey, Robinovitch, Postural Steadiness During Quiet Stance Does Not Associate with the Ability to Recover Balance in Older Women; Clin Biomech: 2005 July). Functional reach does not differentiate fallers from non-fallers. (Wallman;Comparison of Elderly Non fallers and Fallers on Performance Measures; J Gerontol A Bio Sci Med Sci; 2001:56 (9).. The functional reach is a weak measure of stability limits. Jonsson , Does the Functional Reach Test Reflect stability of limits in Elderly People? Jl of Rehab Med 2003:35 (11) ). Functional reach does not measure dynamic balance. Healthy elders and impaired individuals with vestibular dysfunction attained the same functional reach distance. (Wernick, Robinson, Krebs; Functional Reach: Does it Really measure Dynamic Balance: Arch Phys Med and Rehab; 1999; 80(3).
The ABC 6 balance scale is a more useful balance confidence assessment tool compared to the ABC 16 for community- living adults. (Schepens; The Short Version of the Activities-Specific Balance Confidence Scale: Its Validity, Reliability and Relationship to Balance Impairment and falls in Older Adults; Archives of Gerontology and Geriatrics: 2009 July). Caution is recommended when interpreting ABC scores of community living seniors. More confident seniors are not necessarily more active and less confident seniors do not necessarily restrict their activity. (Cavanaugh, JGPT: 29 abstract).
Several studies have challenged the usefulness of the timed get up and go test (TUGT). The TUGT with or without cognitive task, did not predict falls in community living older women. (Valliant, J et al: Prediction of falls With Performance on Timed up and Go and One-Leg Balance tests and additional Cognitive tasks; Ann Readapt Med Phys 2006 49 (1). The TUGT demonstrated poor responsiveness to fall status. (Lin et al; Psychometric Comparisons of the Timed Up and Go , One-Leg Stand, Functional Reach and Tinetti Balance Measures in Community Dwelling Older People; J Amer Geriatr Soc 2004 ,52 (8). The TUGT is not suitable for older high functioning adults. (Boulgarides,L, Use of Clinical and Impairment Based Tests to Predict Falls by Community Dwelling P
Older Adults; Phys Ther 2003 83 (4). Even in retrospective design, hardly any association was found between the TUGT and fall risk. The TUGT may not be used as a test of fall risk in an ambulatory elderly population. (Thrane, The Association Between the Timed Get Up and Go Test and Fall Risk; BMC Geriatr 2007 7:1). Lower TUGT scores do not translate to fewer retrospective reports of falls. The TUGT is not discriminant to known fall status. (Arnold, The History of Falls and the Association of the TUGT to Falls and Near Falls in Older Adults with Osteo- Arthritis; 2007 BMC Geriatr: 7:17).
Tai Chi has gained recent popularity as a balance improvement and fall prevention intervention. The results of a randomized clinical trial on the effects of a Tai Chi fall prevention in community-living older people with a high risk of falling in the Netherlands showed no beneficial effects on falls and secondary outcomes (e.g. balance, fear of falling). Logghe IH et al, Explaining the Ineffectiveness of a Tai Chi Fall Prevention Training for Community-Living Older People: A Process Evaluation Alongside a Randomized Clinical Trial (RCT);Arch Gerontol Geriatr 2010 June). Tai Chi has the potential to reduce falls or risk of falls in the elderly, provided they are relatively young and non-frail. (OK for wellness programs, but does not reflect typical patient populations) (Low S et al; A Systematic Review of the Effectiveness of Tai Chi on Fall Reduction Among the Elderly: Arch Gerontol Geriatr; 2009:48(3). There is insufficient evidence to conclude whether Tai Chi is effective in fall prevention, decreasing fear of falling and improving balance in people over age 50 years. Nine trials (2203 participants) were included in the analysis.( Logghe IH, et al; The Effects of Tai Chi on Fall Prevention, Fear of Falling and Balance in Older people: A Meta-analysis. Prev Med:2010 51(3-4).
Physical impairments such as muscle strength may not be sufficient to predict changes in this ability either. (Schlicht,Effect of Intense Strength Training on Standing Balance and Walking Speed, and Sit-to Stand performance in Older Adults Jl Gerontol A Biol Sci Med Sci:2001).
Researchers may need to test situations in which people are required to elicit reactive balance in response to externally imposed perturbations.( Harris,Eng; Relationship of Balance and Mobility to Fall Incidence in People With Chronic Stroke, Phys Ther 2005:85(2).
Balance and Perturbations: Neurophysiologic Foundations
Individuals without neurologic impairments proportionately scale to the magnitude of their automatic postural responses to the magnitude of their disequilibrium. This scaling is based on both the direct sensory characteristics, such as the initial speed of the perturbation and anticipatory mechanisms based on prediction of displacement characteristics, such as the estimated displacement amplitude. The nervous system must rely on predictive mechanisms based on prior experience. Scaling is a component of predictable perturbation testing.
Responses: Proactive and Reactive
Proactive and reactive adaptations each have an important role in fall prevention. Reactive adaptations can reduce the likelihood that a balance loss will lead to a fall, whereas proactive adaptations can eliminate the occurrence of a balance loss entirely. Proactive adaptations can be highly effective when the direction of a perturbation is foreseeable and can lead to desirable movement patterns that allow balance to be maintained under both perturbed and unperturbed conditions. When perturbations are less certain, reactive responses may play the dominant role in avoiding a fall. It may thus be argued that both proactive and reactive adaptations should be targeted in interventions to reduce fall incidence in older adults. Motor learning from prior outcomes is similar in young and older adults. (Pavol, Runtz, Pai, Young and Older Adults Exhibit Proactive and Reactive Adaptations to Repeated Slip Exposure; Jl of Gerontology: 2004 59a(5). Proactive adaptation to movement stability represents a first line of defense against falling, whereas reactive responses represent a second line of defense; both are important. Adaptive feed-forward control of stability is based on a continuously updated internal model of COG thus appears to be used by old and young alike. Evidence suggests that the effective size of the feasible stability region decreases with older age, and with the magnitude of the adaptive changes in feed-forward control. (Pai, Wening, Runtz,Pavol, Role of Feed-forward Control of Movement Stability in Reducing Slip-Related Balance Loss and Falls Among Older Adults; J. Neurophysiol:2003:90). Both anticipatory and reactive mechanisms are regularly employed to control balance during gait, centrally organized patterns of muscle activity, and modulated based upon available sensory information, biomechanical constraints, support surface conditions and behavioral goals and learning. Anticipatory mechanisms are based on a feed-forward movement plan utilized in predictable, well- learned situations, whereas reactive mechanisms are generated by the use of sensorimotor feedback utilized in unpredictable situations. Reactive postural control can be used to modify movements already in progress and can be either automatic (reflexive) trip, or volitional in the case or a self-initiated correction of foot placement. Vision is a key sensory feedback input for reactive control.(Tseng, Stanhope, Morton, Impaired Reactive Stepping adjustments in Older Adults; Jl Gerontolol A Biol Sci Med Sci:2009:64a;(7).)
Feasible Stability Region
With repeated perturbations affecting posture, the CNS likely builds new, or updates existing internal representations to improve its feed-forward control, while decreasing a person’s reliance on feedback corrective mechanisms for recovery. The relationship between a standing person’s center of mass (COM) and base of support (BOS) defines the stability limits that outlines a “stability region”. The BOS consists of the outline area of each foot in contact with the ground and the area between the feet in bipedal stance. An age- related increase in body sway often is cited as an indication of a decline in stability, and has been associated with falling among older adults. No conclusive evidence however, indicates that people who sway with greater amplitude are less likely to recover balance after perturbation. Because most falls occur during locomotion, body sway evaluated during quiet standing may not be the most appropriate indicator of stability during activities of daily living. A feasible stability region (FSR) exists between forward and backward loss of balance thresholds. Balance loss occurs when a large-scale perturbation displaces the COM state outside the FSR exceeding in place ankle and hip strategies resulting in a compensatory step and establishing a new BOS. Unperturbed locomotion is a series of controlled volitional forward falling constantly requiring forward stepping.(Pai, Bhatt, Repeated Slip Training: An Emerging Paradigm for Fall Prevention of Slip-Related Falls Among Older Adults, 2007: Phys Ther:89(11).)
Neuromuscular protective mechanisms against falls can be developed or enhanced with appropriate adaptive training. With repeated exposure to perturbation, a newly acquired, predominantly predictive form of adaptive control emerges. Such control exhibits feed- forward behavior by responding to perturbation in a predefined way that improves performance by modifying present and future motor commands, relying on stored information from previous experience. The CNS builds, refines or updates an internal representation of the potential threats that may occur in the external environment. Without actual experience and adaptive modification of movement, explicit knowledge of pending perturbation may not be sufficient fro humans to exhibit appropriate behavior. With repeated perturbations affecting posture, the CNS builds new or updates existing internal representations to increase its feed-forward control while decreasing reliance on feedback corrective mechanisms for successful recovery. (Pai, Bhatt, Repeated Slip Training: An Emerging Paradigm for Prevention of Slip-Related Falls Among Older Adults, 2007: Phys Ther: 87(11).
Retention within the CNS usually is considered a function of long-term changes that occur within the neural circuitry, a consequence of the process of consolidation or stabilization of long- term memory. This process accompanies the formation of new synapses, synthesis of new protein and increase in the strength of existing synapses. These changes occur in the cortical and sub-cortical structures (basal ganglia, cerebellum) for tasks involving voluntary movements. The presence of an aftereffect of repeated perturbations has been well established. The retention of adaptive behavior may be conditioned by the penalties imposed upon an inappropriate response by the CNS and increased potential of injury. A highly threatening environment would be sufficient to induce long-term retention of acquired motor behavior. Emerging evidence supports applying perturbations mimicking real-life situations as a form of motor training, with long-term effects on postural stability for prevention of loss of balance and falls. Older adults can rapidly develop adaptive skills for fall prevention in a similar manner as young adults. (Pai, Bhatt, Phys Ther: 2007).
The primary benefit of perturbation-based training is a reduction in movement time, rather than time required to detect instability and initiate the response. (Mansfield, Peters Maki, Effect of a Perturbation-Based Balance training Program on Compensatory Stepping and Grasping Reactions in Older adults: A Randomized Control Trial: 2010; Phys Ther 90 (4).
A domain specific, reliable and valid repeated, incremental, predictable, perturbation in standing (RIPPS), clinical balance assessment tool, highly discriminant to fall history, has been reported; (DePasquale, Toscano, The Spring Scale Test (SST): A Reliable and Valid Tool for Explaining Fall History; Jl Geriatr Phys Ther; 2009:32(4). The SST employs repeated incremental predictable perturbations in standing (RIPPS) to assess non-stepping and stepping response limits in both the anterior and posterior directions. The RIPPS clinical performance measure is percent of total body weight (TBW %) in accordance with the RIPPS performance criteria. In addition to balance assessment, RIPPS has treatment applications appropriate for the older adult.
Louis DePasquale PT, MA
Latest posts by Louis DePasquale PT, MA (see all)
- Association Of Protective Stepping With Fall History - November 17, 2016
- Fall Prevention: Current Perspectives, Tools with Evidence - April 1, 2014
- Performance Measures: Does Performance Really Measure Up? - April 1, 2014
- Predictable Perturbations: An Innovative Clinical Perspective - September 30, 2008