Falls are the leading cause of non-fatal injuries and death by injury in the United States, accounting for approximately 48 percent to 75 percent of all unintentional injuries reported for adults 65 years and older,¹ with hip fracture incidence expected to rise due to the growth in the older population.²

Most falls occur in or just outside the home,³ resulting in persistent strength and mobility deficits contributing to declines in balance, limiting capacity for independent function, and further increasing risk of recurrent injury.⁴

Current tests are less successful in explaining falls in active aging adults than in those who are described as frail.⁵ Timed mobility performance measures may not adequately challenge systems to detect problems essential in fall risk situations in individuals not exhibiting existing balance deficits or outwardly displaying observable limitations.^6,7 The inability of certain balance and timed mobility performance measures to explain falls is due in part to intrinsic ceiling effects, compromised sensitivity associated with a lack of variability in maximum performance scores, as well as their lack of responsiveness to falls in active community-dwelling aging adults.^5,8,9

New assessment tools are needed for an active aging population. Such tools should contain more challenging performance-based measures,⁵ including situations requiring reactive balance and perturbations.¹⁰ Following a perturbation that might cause a fall, one must recover balance using a feet-in-place postural strategy response, or a protective compensatory step.¹¹

Perturbation assessment and treatment paradigms have gained recent attention.^9,12-15 The use of a predictable perturbation assessment paradigm is supported by studies concluding that predictability and prior knowledge of magnitude and direction of perturbation forces do not alter EMG latency of lower extremity motor responses and have no effect on automatic postural responses.^16,17 A valid, reliable, practical, safe and clinically feasible predictable perturbation method (ICC = 0.94, ROC AUC = 0.992, sensitivity = 93 percent, specificity = 96.6 percent) has been described.¹⁸

Predictable Scaling

Individuals without neurologic impairments proportionately scale to the magnitude of their automatic postural responses to the magnitude of their disequilibrium.¹⁹ 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.¹⁹

Responses: Proactive and Reactive

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.¹⁹ Proactive adaptations can be highly effective when the direction of a perturbation is foreseeable.¹⁹ When perturbations are less

Louis DePasquale, PT, MA, practices exercises in postural control with a patient.

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. Proactive adaptation to movement stability represents a first line of defense against falling, whereas reactive responses represent a second line of defense.²⁰ Both anticipatory and reactive mechanisms are regularly employed to control balance during gait, centrally organized, and modulated based upon available sensory information, biomechanical constraints, support surface conditions and behavioral goals and learning.¹² 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.¹² Reactive postural control can be used to modify movements already in progress and can be either automatic (reflexive) trip, or volitional in the case of a self-initiated correction of foot placement.¹²

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.¹⁴ A feasible stability region (FSR) exists between forward and backward loss of balance thresholds.¹⁴ 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.¹⁴

Plasticity

Neuromuscular protective mechanisms against falls can be developed or enhanced with appropriate adaptive training. With repeated exposure to perturbations, a newly acquired, predominantly predictive form of adaptive control emerges, with a decreased reliance on feedback corrective mechanisms for recovery.¹⁴

Retention

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 an increase in the strength of existing synapses in the cortical and sub-cortical structures (basal ganglia, cerebellum) for tasks involving voluntary movements.¹⁴

A highly threatening environment would be sufficient to induce long-term retention of acquired motor behavior.¹⁴ Emerging evidence supports applying perturbations as a form of motor training, with long-term effects on postural stability for prevention of loss of balance and falls.¹⁴ Older adults can rapidly develop adaptive skills for fall prevention in a similar manner as young adults.¹⁴

The RIPPS Method

Based upon a recent study,¹⁸ The Spring Scale Test (SST): A Reliable and Valid Tool for Explaining Fall History, a clinically practical, predictable perturbation method exists. Predicated on repeated incremental predictable perturbations in standing (RIPPS), the RIPPS method is a first-attempt, single-failure protocol to quantify forward and rear direction stepping limits.¹⁸ Beginning at 1-pound waist-pull force, rounds of loading and unloading are increased by one additional pound to the limits of postural stability determined by RIPPS performance criteria, identifying forward and rear directional stepping limits, quantified as percent of total body weight (TBW%).¹⁸ The use of TBW% to quantify perturbation force is well established.^10-15,18

Instrumentation and Setup

Perturbation forces are quantified by a pocket-sized linear spring scale strain gauge calibrated in 1-pound increments, affixed to a 5-inch wide padded waist belt secured around the client's waist and connected to the examiner via a 4-foot length safety tether strap.¹⁸ Perturbations are administered with the examiner positioned in close proximity to the client, standing approximately three feet from a compliant support surface. Anterior direction limit testing (rear stepping) is performed with the examiner facing the client, while posterior direction limit testing (forward stepping) is performed with the client's back toward the examiner.18

RIPPS Perturbation Method

Loading waist-pull forces are administered in a predictable, gradual, accommodative fashion. Clients are continuously instructed to resist loading forces to their maximum limit and are reminded of the RIPPS performance criteria.¹⁸

Unloading occurs at each round of progressive 1-pound incremental accommodated loading force. Unloading is administered in a quasi-random fashion within a 5-count window, at the discretion of the examiner. Clients are continuously reminded of the RIPPS unloading performance criteria.¹⁸

Performance Criteria

RIPPS loading forces must be accompanied by a foot-flat or heel-sole contact with floor postural response, defined as accommodation. RIPPS unloading postural responses must not exceed a 3-step response.¹⁸

RIPPS end points. A RIPPS end point occurs when either a loading or unloading RIPPS performance criterion is not achieved at a given round of waist-pull force value.

RIPPS directional limit score. A RIPPS TBW percent directional limit score is obtained for both the anterior and posterior directions. A directional limit force value is derived from the round previous to the directional end point force (failure) round. The directional limit TBW percent score is calculated by dividing the spring scale measured force in pounds by the client's body weight.¹⁸

RIPPS TBW percent performance measure. The lower of the two-directional limit TBW percent scores is the RIPPS TBW percent performance measure of clinical significance.¹⁸

RIPPS clinical applications. The RIPPS 10 percent TBW performance value is highly discriminant to fall status, providing clinicians with a highly sensitive and specific fall risk screening tool¹⁸ capable of ID deficits that otherwise would be missed in the active community-living older adult.

The RIPPS 10 percent TBW value should be considered a minimal threshold performance value consistent with known non-fallers over the age of 65 with a mean 12.3 percent TBW,¹⁸ suggesting a functional stepping "reserve" exists and could be attainable and should be a clinical treatment outcome particularly in the 80-to-89 age group, which represented the largest sample subgroup in the SST study.

Despite the RIPPS predictable design, reactive postural responses are typical, dominating anticipatory postural responses in those individuals with compromised balance evidenced by apprehension, excessive loading hip strategy, multiple steps in response to unloading, and excessive upper extremity responses. Ceiling effects rarely occur using the RIPPS method of assessment.

Induced Stepping Treatment Paradigm

Induced stepping has been associated with greater skill retention.¹⁴ The RIPPS method offers a safe option for induced step training for individuals 65 years of age and older. RIPPS induced step training would involve blocks of repeated rounds of loading and unloading at progressive waist-pull forces.

Anecdotal evidence suggests that sustained percent TBW values equal to or greater than 10 percent over a two-week period for three consecutive treatment sessions could suggest retention of a newly acquired stepping skill.

Manipulation of anticipatory and reactive responses is possible by variations in perturbation loading/unloading force intervals. Non-stepping training options as well as lateral perturbation methods are possible.

The goal of RIPPS is to introduce percent of total body weight (TBW percent) as a practical balance measure for fall risk assessment and treatment purposes. Research supports the reliability and discriminant validity of the RIPPS 10 percent TBW performance value for explaining fall history in active, independent community-living older adults.¹⁸

References are available at www.advanceweb.com/pt under the Resources tab.

Louis DePasquale has worked as a geriatric clinical specialist and consultant for more than 30 years. Currently he is affiliated full-time with the Francis Schervier/Bon Secours Long-Term Home Health Program and is an independent clinical consultant with Elderserve Home Health program/Hebrew Home at Riverdale. DePasquale has published articles in various journals and is a recipient of the Robert Salant award for outstanding abstract. He has developed an innovative balance assessment tool based on years of clinical research, the RIPPS Balance Method. These research results can be viewed at www.rippsmethod.com.