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Publications Related to ActiveStep®

Below is a list of abstracts of published research that are related to the principals upon which ActiveStep is based and research that used either the actual ActiveStep or systems and protocols that are functionally similar.  The references are arranged in the following categories, from the most recent to the oldest for convenience:  

Efficacy of task specific training to reduce fall risk

Trunk kinematics and fall risk of older adults: translating biomechanical results to the clinic.
Grabiner MD, Donovan S, Bareither ML, Marone JR, Hamstra-Wright K, Gatts S, Troy KL.

Department of Movement Sciences, University of Illinois at Chicago, 808 S. Wood Street Room 690B, CME 690 M/C 994, Chicago, IL 60612, USA.

This paper reviews some of our experiences over nearly 15 years of trying to determine modifiable factors that contribute to the high incidence of fall by older adults. As part of our approach, we have subjected healthy young and older adults to very large postural disturbances during locomotion, in the form of trips and slips, to which rapid compensatory responses have been necessary to avoid falling. For both trips and slips, the ability to limit trunk motion has consistently discriminated older adults who fall from both younger adults and older adults who have been able to avoid falling. We have shown that the ability to limit trunk motion can be rapidly acquired, or learned, by older adults as a result of task-specific training. The learned motor skill has demonstrated short-term retention and has been shown to effectively decrease fall-risk due to trips. Collectively, we believe the works strongly suggests that the traditional exercise-based fall-prevention and whole-body, task-specific training can synergize to reduce falls and fall-related injury in older adults.

Electromyogr Kinesiol. 2008 Apr;18(2):197-204. Epub 2007 Sep 7


Mechanisms of failed recovery following postural perturbations on a motorized treadmill mimic those associated with an actual forward trip
Tammy M. Owings , Michael J. Pavol, Mark D. Grabiner

Objective. To examine the recovery strategies employed during a treadmill acceleration task, to determine if mechanisms that contributed to failed recoveries on a motorized treadmill are the same general biomechanical mechanisms that contributed to falls from a trip, and to determine if failed recovery responses could be modified to allow for successful recoveries on subsequent trials.

Design. A motorized treadmill was used to induce postural perturbations in healthy older adults.

Background. Previously, we induced trips in older adults to identify the mechanisms of failed recovery. However, inducing trips is not a clinically practical test for identifying older adults who are predisposed to falling.

Methods. Safety-harnessed older adults stood on a treadmill that was accelerated from 0 to 0.89 m/s to impose a postural perturbation. Recoveries were classified as successful (n=42) or failed (n=23). Selected biomechanical variables were calculated using motion analysis methods.

Results. Initial failed recoveries had slower reaction times, shorter step lengths, and greater trunk flexion angles and velocities. Subjects who failed on the initial attempt modified their recovery strategy to successfully recover. The biomechanics of these recoveries resembled those used by subjects who successfully recovered on their initial attempt.

Conclusions. The biomechanical mechanisms involved with a failed treadmill recovery mimic those responsible for failed recoveries from an induced trip. Subjects who failed on their initial recovery response made modifications allowing successful recoveries on subsequent attempts.
Relevance  This protocol may be useful as a testing and rehabilitation tool for fall recovery.

ClinBioMech: Volume 16, Issue 9, Pages 813-819 (November 2001)


Repeated-slip training: an emerging paradigm for prevention of slip-related falls among older adults.
Pai YC, Bhatt TS

Department of Physical Therapy, University of Illinois at Chicago, 1919 W Taylor St, Room 426 (M/C 898), Chicago, IL 60612, USA.

Falls frequently cause injury-related hospitalization or death among older adults. This article reviews a new conceptual framework on dynamic stability and weight support in reducing the risk for falls resulting from a forward slip, based on the principles of motor control and learning, in the context of adaptation and longer-term retention induced by repeated-slip training. Although an unexpected slip is severely destabilizing, a recovery step often is adequate for regaining stability, regardless of age. Consequently, poor weight support (quantified by reduction in hip height), rather than instability, is the major determinant of slip-related fall risk. Promisingly, a single session of repeated-slip training can enhance neuromechanical control of dynamic stability and weight support to prevent falls, which can be retained for several months or longer. These principles provide the theoretical basis for establishing task-specific adaptive training that facilitates the development of protective strategies to reduce falls among older adults.

Phys Ther. 2007 Nov;87(11):1478-91. Epub 2007 Aug 21.
Comment in:  Phys Ther. 2007 Nov;87(11):1491-3; author reply 1493-4.


Practicing recovery from a simulated trip improves recovery kinematics after an actual trip.
Bieryla KA, Madigan ML, Nussbaum MA.
Department of Mechanical Engineering, Virginia Tech, USA.

The goal of this study was to determine if practicing recovery from a simulated trip improved the ability of older adults to recover from an actual trip. Twelve healthy older adults ranging in age from 63 to 83 years were randomly assigned to either a control or an experimental group. Each group performed one trip before and one trip after an intervention. The experimental group received trip recovery training on a modified treadmill while the control group walked on a treadmill for 15 min. Compared to the control group, the experimental group showed greater reduction in maximum trunk angle (p=0.027) and time to maximum trunk angle (p=0.043), as well as increased minimum hip height (p=0.020). Although the results showed beneficial effects of trip recovery training on actual trip recovery, future studies should explore the ability to retain improvements over extended periods.

Gait Posture. 2007 Jul;26(2):208-13. Epub 2006 Oct 13


Young and older adults exhibit proactive and reactive adaptations to repeated slip exposure.
Pavol MJ, Runtz EF, Pai YC.
Department of Exercise and Sport Science, Oregon State University, Corvallis, USA.

BACKGROUND: A previous study found that, with repeated exposure to slipping during a sit-to-stand task, fall incidence decreased at a similar exponential rate in young and older adults. This study investigated the adaptations responsible for this decrease.

METHODS: Slips were induced, using bilateral low-friction platforms, during a sit-to-stand in 60 young and 41 older healthy safety-harnessed adults. Participants underwent 5 slips, then a 6th slip (reslip) after 3-4 nonslipping trials. Between-trial adjustments in body center of mass state at seat-off were examined and correlated to the likelihoods of falling and stepping. Changes in reactive response between the first slip and reslip were investigated.

RESULTS: With repeated slipping, both young and older adults adjusted to increase their center of mass anterior position and forward velocity at seat-off (p <.001), contributing to decreased fall incidence and changes in step incidence and direction (p <.001). These proactive adjustments predicted fall incidence well in later trials, but underpredicted fall incidence upon the first slip by 9%-21%, suggesting that reactive response deficiencies also initially contributed to falls by both age groups. Ten participants who initially fell without stepping adapted by stepping to recover upon the reslip. Thirty-six participants who stepped backward initially and upon the reslip altered their nonstepping limb reactive response to reduce hip vertical descent during the step (p <.001).

CONCLUSIONS: Young and older adults rapidly learned to avoid falling through similar proactive and reactive adaptations that persisted in the short term. Both proactive and reactive adaptations should be targeted in interventions to reduce older adult fall incidence.

J Gerontol A Biol Sci Med Sci. 2004 May;59(5):494-502


Age influences the outcome of a slipping perturbation during initial but not repeated exposures.
Pavol MJ, Runtz EF, Edwards BJ, Pai YC.
Department of Physical Therapy,University of Illinois at Chicago, 60612, USA.

BACKGROUND: Fall incidence in older adults might be reduced through learning to better recover from or adjust to perturbations. Extents of age-related declines and limitations in the ability to recover are not well established, however.

METHODS: Slips were induced, using bilateral low-friction platforms, during a sit-to-stand task in 60 young and 41 older, healthy, safety-harnessed adults. Subjects underwent five slips, a block of nonslipping trials, then two reexposures to the slip. The first slip was novel and unexpected. Age-group and trial effects on fall incidence (evidenced by excessive hip descent) and on the direction of the initial protective step were examined.

RESULTS: More older than young adults fell upon the first slip (73% vs 28%; p <.001). With repeated exposure, fall incidence decreased at similar exponential rates in both age groups. All but one subject eventually learned to slip without falling, and two-thirds of fallers fell only once. Repeat fallers fell without stepping in 63% of falls. Upon later slip reexposure, more older than young adults fell (20% vs 2%), but fewer falls occurred than did originally (p =.001). Likelihoods of forward and backward stepping during successful recovery changed with repeated slip exposure and upon reexposure, but did not differ between age groups.

CONCLUSIONS: Older adults are more likely to fall upon initial, unexpected perturbation exposure, but, upon repeated exposure, healthy young and older adults rapidly learn to avoid falling at a similar rate. Healthy older adults appear fully capable of learning to better recover from or adjust to a perturbation through repeated exposure.

J Gerontol A Biol Sci Med Sci. 2002 Aug; 57(8):M496-503.


Can fall-related hip fractures be prevented by characterizing the biomechanical mechanisms of failed recovery?
Grabiner MD, Pavol MJ, Owings TM.
School of Kinesiology, University of Illinois at Chicago, 60608, USA.

Unintentional injuries are the seventh leading cause of death in adults ages 65 and older, and the greatest number of these deaths results from fall-related injuries. In addition to the startling mortality, the morbidity associated with fall-related injuries, particularly hip fractures, has become a research imperative. This article reviews a series of studies that was undertaken to determine the biomechanical reasons that older adults are unable to recover from very large postural perturbations that are applied during locomotion that, if not corrected, can lead to a fall. Our protocol involves causing older adults to trip unexpectedly while walking normally in the laboratory. The results from this series of experiments were used to design an experiment that characterized the biomechanical similarities between recovery biomechanics after an induced trip and those following a large postural perturbation delivered by a motorized treadmill. Collectively, we have been able to document different recovery strategies and categories of falls by older adults following an induced trip; the biomechanical causes of these falls by older adults; and the very rapid motor adaptations that occur with repeated exposure to large perturbations that may be protective against falls from tripping and, therefore, reduce the substantial fall-related morbidity and mortality in older adults.

Endocrine. 2002 Feb;17(1):15-20.


Ability of older adults to rapidly learn new responses that influence fall risk

Practicing recovery from a simulated trip improves recovery kinematics after an actual trip.
Bieryla KA, Madigan ML, Nussbaum MA.
Department of Mechanical Engineering, Virginia Tech, USA.

The goal of this study was to determine if practicing recovery from a simulated trip improved the ability of older adults to recover from an actual trip. Twelve healthy older adults ranging in age from 63 to 83 years were randomly assigned to either a control or an experimental group. Each group performed one trip before and one trip after an intervention. The experimental group received trip recovery training on a modified treadmill while the control group walked on a treadmill for 15 min. Compared to the control group, the experimental group showed greater reduction in maximum trunk angle (p=0.027) and time to maximum trunk angle (p=0.043), as well as increased minimum hip height (p=0.020). Although the results showed beneficial effects of trip recovery training on actual trip recovery, future studies should explore the ability to retain improvements over extended periods.

Gait Posture. 2007 Jul;26(2):208-13. Epub 2006 Oct 13


Young and older adults exhibit proactive and reactive adaptations to repeated slip exposure.
Pavol MJ, Runtz EF, Pai YC.
Department of Exercise and Sport Science, Oregon State University, Corvallis, USA.

BACKGROUND: A previous study found that, with repeated exposure to slipping during a sit-to-stand task, fall incidence decreased at a similar exponential rate in young and older adults. This study investigated the adaptations responsible for this decrease.

METHODS: Slips were induced, using bilateral low-friction platforms, during a sit-to-stand in 60 young and 41 older healthy safety-harnessed adults. Participants underwent 5 slips, then a 6th slip (reslip) after 3-4 nonslipping trials. Between-trial adjustments in body center of mass state at seat-off were examined and correlated to the likelihoods of falling and stepping. Changes in reactive response between the first slip and reslip were investigated.

RESULTS: With repeated slipping, both young and older adults adjusted to increase their center of mass anterior position and forward velocity at seat-off (p <.001), contributing to decreased fall incidence and changes in step incidence and direction (p <.001). These proactive adjustments predicted fall incidence well in later trials, but underpredicted fall incidence upon the first slip by 9%-21%, suggesting that reactive response deficiencies also initially contributed to falls by both age groups. Ten participants who initially fell without stepping adapted by stepping to recover upon the reslip. Thirty-six participants who stepped backward initially and upon the reslip altered their nonstepping limb reactive response to reduce hip vertical descent during the step (p <.001).

CONCLUSIONS: Young and older adults rapidly learned to avoid falling through similar proactive and reactive adaptations that persisted in the short term. Both proactive and reactive adaptations should be targeted in interventions to reduce older adult fall incidence.

J Gerontol A Biol Sci Med Sci. 2004 May;59(5):494-502


Age influences the outcome of a slipping perturbation during initial but not repeated exposures.
Pavol MJ, Runtz EF, Edwards BJ, Pai YC.
Department of Physical Therapy, University of Illinois at Chicago, 60612, USA.

BACKGROUND: Fall incidence in older adults might be reduced through learning to better recover from or adjust to perturbations. Extents of age-related declines and limitations in the ability to recover are not well established, however.

METHODS: Slips were induced, using bilateral low-friction platforms, during a sit-to-stand task in 60 young and 41 older, healthy, safety-harnessed adults. Subjects underwent five slips, a block of nonslipping trials, then two reexposures to the slip. The first slip was novel and unexpected. Age-group and trial effects on fall incidence (evidenced by excessive hip descent) and on the direction of the initial protective step were examined.

RESULTS: More older than young adults fell upon the first slip (73% vs 28%; p <.001). With repeated exposure, fall incidence decreased at similar exponential rates in both age groups. All but one subject eventually learned to slip without falling, and two-thirds of fallers fell only once. Repeat fallers fell without stepping in 63% of falls. Upon later slip reexposure, more older than young adults fell (20% vs 2%), but fewer falls occurred than did originally (p =.001). Likelihoods of forward and backward stepping during successful recovery changed with repeated slip exposure and upon reexposure, but did not differ between age groups.

CONCLUSIONS: Older adults are more likely to fall upon initial, unexpected perturbation exposure, but, upon repeated exposure, healthy young and older adults rapidly learn to avoid falling at a similar rate. Healthy older adults appear fully capable of learning to better recover from or adjust to a perturbation through repeated exposure.

J Gerontol A Biol Sci Med Sci. 2002 Aug; 57(8):M496-503.
Comment in:  J Gerontol A Biol Sci Med Sci. 2002 Aug;57(8):M492-5.


Research that identifies individuals as more or less likely to fall from observations of imbalance response kinematics

Control of rapid limb movements for balance recovery: age-related changes and implications for fall prevention.
Maki BE, McIlroy WE.
Department of Surgery and Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.

BACKGROUND: balancing reactions that involve rapid stepping or reaching movements are critical for preventing falls. These compensatory reactions are much more rapid than volitional limb movements and can be very effective in decelerating the centre-of-mass motion induced by sudden unpredictable balance perturbation; however, age-related deterioration in the neural, sensory and/or musculoskeletal systems may impede the ability to execute these reactions effectively.

OBJECTIVE: this paper summarises recent research regarding age-related changes in compensatory stepping and reaching reactions and the practical implications of these findings for fall prevention programmes.

RESULTS: even healthy older adults experience pronounced difficulties. For stepping reactions, the main problems pertain to control of lateral stability--arresting the lateral body motion that occurs during forward and backward steps, and controlling lateral foot movement so as to avoid collision with the stance limb during lateral steps. Older adults appear to be more reliant on arm reactions than young adults but are less able to execute reach-to-grasp reactions rapidly.

CONCLUSIONS: it is important for clinicians to assess compensatory stepping and reaching, in order to identify individuals who are at risk of falling and to pinpoint specific control problems to target for balance or strength training or other intervention. More effective use of stepping and reaching reactions can be promoted through improved design and appropriate use of sensory aids, mobility aids, footwear, handrails and grab-bars. It is particularly important to address the problems associated with the control of lateral stability because it is the lateral falls that are most likely to result in hip fracture.

 Age Ageing. 2006 Sep;35 Suppl 2:ii12-ii18


Diminished stepping responses lead to a fall following a novel slip induced during a sit-to-stand.
Pavol MJ, Runtz EF, Pai YC.
Department of Exercise and Sport Science, Oregon State University, Corvallis, OR 97331, USA.

While neuromotor responses associated with successfully restoring balance have been widely characterized, little is known of how responses employed to regain balance fail. We identified biomechanical factors that characterized the unsuccessful recovery responses to a novel perturbation. An unexpected forward slip was induced, using a low-friction platform, just after seat-off of a sit-to-stand in 41 young subjects. Kinematic variables describing the recovery responses were compared between fallers and those who recovered; "falls" into the fall-arrest system were identified based on center of mass (COM) descent. Twelve "single-step" falls, four "multi-step" falls, and 11 recoveries resulted. Single-step fallers exhibited a more posterior COM at slip onset, support (nonstepping) limb collapse resulting in hip vertical descent, and a shortened protective step backward. A factor analysis indicated that six common factors explained 88% of the variance in 22 kinematic variables describing the slip and recovery response. Single-step falls were associated with two factors, one related to initial or imposed instability and one to the reactive response. The former factor indicated that step length and COM position at step touchdown were related to COM position at slip onset. Support limb collapse comprised the latter factor. Multi-step fallers, by appearance, exhibited a shortened initial backward step that was ineffective at enabling balance recovery. As a whole, the results indicated that unsuccessful recovery was associated with a diminished stepping response. Fallers may have inadequately scaled an appropriate reflexive stepping response or might, inappropriately, have reflexively attempted to recover without stepping.

Gait Posture. 2004 Oct;20(2):154-62


Can fall-related hip fractures be prevented by characterizing the biomechanical mechanisms of failed recovery?
Grabiner MD, Pavol MJ, Owings TM.
School of Kinesiology, University of Illinois at Chicago, 60608, USA.

Unintentional injuries are the seventh leading cause of death in adults ages 65 and older, and the greatest number of these deaths results from fall-related injuries. In addition to the startling mortality, the morbidity associated with fall-related injuries, particularly hip fractures, has become a research imperative. This article reviews a series of studies that was undertaken to determine the biomechanical reasons that older adults are unable to recover from very large postural perturbations that are applied during locomotion that, if not corrected, can lead to a fall. Our protocol involves causing older adults to trip unexpectedly while walking normally in the laboratory. The results from this series of experiments were used to design an experiment that characterized the biomechanical similarities between recovery biomechanics after an induced trip and those following a large postural perturbation delivered by a motorized treadmill. Collectively, we have been able to document different recovery strategies and categories of falls by older adults following an induced trip; the biomechanical causes of these falls by older adults; and the very rapid motor adaptations that occur with repeated exposure to large perturbations that may be protective against falls from tripping and, therefore, reduce the substantial fall-related morbidity and mortality in older adults.
Endocrine. 2002 Feb;17(1):15-20.


Gait characteristics as risk factors for falling from trips induced in older adults.
Pavol MJ, Owings TM, Foley KT, Grabiner MD.
Biomedical Engineering Center, The Ohio State University, Columbus, USA.

BACKGROUND: Falls are a significant source of morbidity and mortality in older adults, with up to 53% of these falls due to tripping. To aid in preventing trip-related falls, the factors that increase an individual's risk of falling following a trip must be identified. This study investigated whether an older adult's gait influences their risk of failing following a trip.

METHODS: Trips were induced during gait in 79 healthy, safety-harnessed, community-dwelling older adults using a concealed, mechanical obstacle. Associations between selected gait kinematic characteristics, recorded during normal walking, and the likelihood of falling following the trip were determined using logistic regression.

RESULTS: Older adults who walked faster, took more rapid steps, or took longer steps relative to their body height had a significantly increased likelihood of falling following the trip. Step width, average trunk flexion during gait, and the phase of gait in which the trip occurred did not affect the likelihood of falling. A multivariable logistic regression model correctly classified 89.8% of trip outcomes based on two gait characteristics: step time and step length. As predicted from their gait characteristics, the subjects, as a group, had a low likelihood of falling following a trip, but selected individuals had a high likelihood of falling.

CONCLUSIONS: The incidence of trip-related falls in healthy older adults is determined primarily by the frequency of tripping and not the ability to recover from a trip. Older adults can reduce their likelihood of falling following a trip by not hurrying while walking.

J Gerontol A Biol Sci Med Sci. 1999 Nov;54(11):M583-90.


Inefficient postural responses to unexpected slips during walking in older adults.
Tang PF, Woollacott MH.
Department of Exercise and Movement Science and Institute of Neuroscience, University of Oregon, USA.

BACKGROUND: Slips account for a high percentage of falls and subsequent injuries in community-dwelling older adults but not in young adults. This phenomenon suggests that although active and healthy older adults preserve a mobility level comparable to that of young adults, these older adults may have difficulty generating efficient reactive postural responses when they slip. This study tested the hypothesis that active and healthy older adults use a less effective reactive balance strategy than young adults when experiencing an unexpected forward slip occurring at heel strike during walking. This less effective balance strategy would be manifested by slower and smaller postural responses, altered temporal and spatial organization of the postural responses, and greater upper trunk instability after the slip.

METHODS: Thirty-three young adults (age range=19-34 yrs, mean=25+/-4 yrs) and 32 community-dwelling older adults (age range=70-87 yrs, mean=74+/-14 yrs) participated. Subjects walked across a movable forceplate which simulated a forward slip at heel strike. Surface electromyography was recorded from bilateral leg, thigh, hip, and trunk muscles. Kinematic data were collected from the right (perturbed) side of the body.

RESULTS: Although the predominant postural muscles and the activation sequence of these muscles were similar between the two age groups, the postural responses of older adults were of longer onset latencies, smaller magnitudes, and longer burst durations compared to young adults. Older adults also showed a longer coactivation duration for the ankle, knee, and trunk agonist/antagonist pairs on the perturbed side and for the knee agonist/antagonist pair on the nonperturbed side. Behaviorally, older adults became less stable after the slips. This was manifested by a higher incidence of being tripped (21 trials in older vs 5 trials in young adults) and a greater trunk hyperextension with respect to young adults. Large arm elevation was frequently used by older adults to assist in maintaining trunk stability. In an attempt to quickly reestablish the base of support after the slips, older adults had an earlier contralateral foot strike and shortened stride length.

CONCLUSION: The combination of slower onset and smaller magnitude of postural responses to slips in older adults resulted in an inefficient balance strategy. Older adults needed secondary compensatory adjustments, including a lengthened response duration and the use of the arms, to fully regain balance and prevent a fall. The shorter stride length and earlier contralateral foot strike following the slip indicate use of a more conservative balance strategy in older adults.

J Gerontol A Biol Sci Med Sci. 1998 Nov;53(6):M471-80.


Kinematics of recovery from a stumble.
Grabiner MD, Koh TJ, Lundin TM, Jahnigen DW.
Department of Biomedical Engineering, Cleveland Clinic Foundation, Ohio.

BACKGROUND. Injuries most frequently related to accidents in elderly persons are falls during locomotion and stair ascent and descent. Although numerous risk factors have been related to falling behavior, effective strategies to predict and prevent falls have not evolved. The rationale underlying this study was that systematic experimental and analytical investigation of the effects of perturbations during locomotion and the subsequent requisites for recovery could lead to the development of clinically relevant evaluation(s) capable of identifying a predisposition to falling. The present study is the first biomechanical investigation of recovery from an anteriorly directed stumble.

METHODS. Seven healthy, young males participated in this study. While the subjects walked along a walkway in the laboratory, stumbles were unexpectedly induced using a mechanical obstacle. Videotape records of these trials were analyzed and selected sagittal plane kinematics extracted.

RESULTS. The perturbation caused an increase in the maximum trunk flexion angle from 4.3 degrees (control) to 18.3 degrees (p = .057), and this change was significantly associated with preperturbation walking velocity (p = .036). The maximum hip and knee flexion angles increased from 26 to 47 degrees (p = .039) and from 60 to 89 degrees (p = .009), respectively. The increases in maximum hip flexion velocity (79%) and maximum knee extension velocity (36%) were not significant.

CONCLUSIONS. Identification of the principal elements of control during perturbed locomotion can contribute to understanding the relationship between specific age-related performance deficits and some types of falling behavior. The results suggest that recovery from a stumble is dependent upon lower extremity muscular power and the ability to restore control of the flexing trunk.

J Gerontol. 1993 May;48(3):M97-102.


Research that contradicts some commonly held concepts about fall risk and interventions

Kenosha County falls prevention study: a randomized, controlled trial of an intermediate-intensity, community-based multifactorial falls intervention.
Mahoney JE, Shea TA, Przybelski R, Jaros L, Gangnon R, Cech S, Schwalbe A.
Department of Medicine, Section of Geriatrics, School of Medicine and Public Health, University of Wisconsin Madison, Madison, Wisconsin, USA.

OBJECTIVES: To decrease the rate of falls in high-risk community-dwelling older adults.

DESIGN: Randomized, controlled trial.

SETTING: Community-based.

PARTICIPANTS: Three hundred forty-nine adults aged 65 and older with two falls in the previous year or one fall in the previous 2 years with injury or balance problems.

INTERVENTION: Subjects received two in-home visits from a trained nurse or physical therapist who assessed falls risk factors using an algorithm. The intervention consisted of recommendations to the subject and their primary physician, referrals to physical therapy and other providers, 11 monthly telephone calls, and a balance exercise plan. Control subjects received a home safety assessment.

MEASUREMENTS: The primary outcome was rate of falls per year in the community. Secondary outcomes included all-cause hospitalizations and nursing home admissions per year.

RESULTS: There was no difference in rate of falls between the intervention and control groups (rate ratio (RR)=0.81, P=.27). Nursing home days were fewer in the intervention group (10.3 vs 20.5 days, P=.04). Intervention subjects with a Mini-Mental State Examination (MMSE) score of 27 or less had a lower rate of falls (RR=0.55; P=.05) and, if they lived with someone, had fewer hospitalizations (RR=0.44, P=.05), nursing home admissions (RR=0.15, P=.003), and nursing home days (7.5 vs 58.2, P=.008).

CONCLUSION: This multifactorial intervention did not decrease falls in at-risk community-living adults but did decrease nursing home utilization. There was evidence of efficacy in the subgroup who had an MMSE score of 27 or less and lived with a caregiver, but validation is required.

J Am Geriatr Soc. 2007 Apr;55(4):489-98


Lower extremity strength plays only a small role in determining the maximum recoverable lean angle in older adults.
Grabiner MD, Owings TM, Pavol MJ.
Department of Movement Sciences, University of Illinois at Chicago, 808 S. Wood St., Room 690B, CME 690 M/C 994, Chicago, IL 60612, USA.

BACKGROUND: The purpose of this study was to determine the extent to which measures of lower extremity strength and power contribute to the ability of older men and women to restore postural equilibrium using a single-step recovery following a large postural disturbance.

METHODS: The postural disturbance, which has been used as a surrogate for forward-directed falls, involved a sudden release from a forward-leaning angle. The ability to recover using a single step was evaluated as the maximum recoverable lean angle for 56 healthy older women and men. Maximum voluntary isometric and isokinetic strength was measured for ankle plantarflexion and dorsiflexion, knee flexion and extension, and hip flexion and extension. Discriminant analysis was used to determine the strength measures that best classified participants as members of the highest (n = 14) or lowest (n = 14) quartiles of maximum recoverable lean angle. Those variables were subsequently entered into a regression analysis to characterize the relationship between strength and maximum recoverable lean angle for the entire participant sample.

RESULTS: Maximum isokinetic dorsiflexion strength at 90 degrees /s satisfied the criteria of the stepwise discriminant analysis, and correctly classified 82.1% of the participants in the highest or lowest quartiles of maximum recoverable lean angle. The multiple regression procedure, performed on all participants (n = 56) revealed a significant quadratic relationship between maximum isokinetic dorsiflexion strength at 90 degrees /s and maximum recoverable lean angle (R2 = 0.295; p <.001).

CONCLUSIONS: Lower extremity strength makes a small, but significant contribution to maximum recoverable lean angle. However, because 70% of the shared variability remained unaccounted for, it is suggested that other performance factors, such as coordination, may be of greater importance to performance of this time-critical motor task.

J Gerontol A Biol Sci Med Sci. 2005 Nov;60(11):1447-50


Influence of lower extremity strength of healthy older adults on the outcome of an induced trip.
Pavol MJ, Owings TM, Foley KT, Grabiner MD.
Department of Biomedical Engineering, Lerner Research Institute, The Cleveland Clinic Foundation, Ohio, USA. /p>

OBJECTIVES: To determine whether decreased lower extremity strength contributes to trip-related falls in older adults.

DESIGN: A cross-sectional sample of older adults were safety-harnessed and tripped while walking using a concealed, mechanical obstacle. Lower extremity strength was compared between trip outcome groups.

SETTING: A biomechanics research laboratory.

PARTICIPANTS: Seventy-nine healthy, community-dwelling adults aged 65 and older (50 women).

MEASUREMENTS: Ankle, knee, and hip flexion and extension strength were measured isometrically and isokinetically. Measured strengths were subjected to a factor analysis. Strength factor scores were compared between those who recovered from the trip and those who fell by three previously identified mechanisms: during-step, after-step, and elevating-response falls.

RESULTS: Seven common factors, one associated with each direction of exertion at each joint and one with the time rate of moment increase, explained 88% of the variance in measured strength. The during-step (n=5) fallers were significantly stronger in the ankle extension (plantarflexion), knee flexion, overall extension, and total strength factors than those who successfully recovered using a similar, lowering strategy (n=26). The elevating-response faller (n=1) was stronger in the plantarflexion and overall extension factors than most of those who recovered using a similar, elevating strategy (n=11). Two of three after-step fallers were among the weakest subjects tested.

CONCLUSION: Weak older adults and the strongest older adults may be at greater risk of falling from a trip, although by different mechanisms. High strength may increase the likelihood of a during-step or elevating-response fall; decreased strength may increase the likelihood of an after-step fall.

J Am Geriatr Soc. 2002 Feb;50(2):256-62


Measures of postural stability are not predictors of recovery from large postural disturbances in healthy older adults.
Owings TM, Pavol MJ, Foley KT, Grabiner MD.
Department of Biomedical Engineering, The Lerner Research Institute, The Cleveland Clinic Foundation, Ohio 44195, USA.

OBJECTIVES: To determine, in healthy older adults, the relationship between postural steadiness, stability limits, and the ability to recover balance from three postural disturbances requiring anteriorly directed stepping responses.

DESIGN: Analysis of multiple motor tasks in a cross-sectional sample of healthy older adults.

SETTING: A biomechanics research laboratory.

PARTICIPANTS: Fifty women and 29 men aged 65 or older, all healthy, living in the community, participated in this study. Subjects were examined by a geriatrician to identify the presence of exclusionary factors.

MEASUREMENTS: Anterior-posterior and medial-lateral excursion distances of the center of pressure during quiet standing (postural steadiness), static leaning (static stability limits), and dynamic swaying (dynamic stability limits) were determined from ground reaction forces measured by a strain gauge forceplate. Within the same group of subjects, the maximum angle of forward lean from which a subject could recover with a single step, the ability to recover balance in response to an accelerated support surface, and the ability to recover balance after being tripped were determined.

RESULTS: Recovery from the three types of postural disturbances were found to be statistically independent. The 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. The average medial-lateral center of pressure speed during the postural steadiness test was significantly slower for those who failed to recover after tripping than for the subjects who recovered successfully. However, a logistic regression model failed to achieve statistical significance, suggesting that the difference may not be functionally important. The anterior-posterior static stability limits were significantly larger for subjects who recovered successfully than for those who failed to recover during the accelerated support surface test. Although logistic regression suggested that a reduced anterior-posterior stability limit represents a risk factor for failure to recover during this task, only nine of 28 failures could be properly classified, thus diminishing the functional importance of this finding.

CONCLUSIONS: Because recovery following postural disturbances could not generally be predicted from measures of postural stability, these findings suggest that these measures of postural stability are of limited utility in identifying potential anteriorly directed fallers in healthy older adults.

J Am Geriatr Soc. 2000 Jan;48(1):42-50. Links


Measures of paraspinal muscle performance do not predict initial trunk kinematics after tripping.
Grabiner MD, Feuerbach JW, Jahnigen DW.
Department of Biomedical Engineering, W63, The Cleveland Clinic Foundation, OH 44106, USA.

The ability to limit the trunk flexion associated with an anteriorly directed trip is a determinant of successful recovery of recovering postural stability and is subservient to rapidly detecting and correcting the imposed trunk flexion in the available time. This experiment tested the hypothesis that subjects demonstrating greater eccentric trunk/hip extension strength, faster voluntary reaction times, shorter automatic response latencies, and larger automatic activation amplitudes of the paraspinal muscles, would demonstrate less trunk flexion following a trip. An isokinetic protocol was used to obtain measures of trunk extension strength, response latencies, and activation amplitudes. Motion analysis methods were used to quantify trunk kinematics during the positioning phase of recovery following an induced trip. Statistically significant and functionally meaningful relationships between eccentric strength of the trunk/hip extensors, voluntary-reaction time, automatic reaction time, activation amplitudes and trunk kinematics failed to emerge. Thus, although automatic and voluntary paraspinal muscle responses have the potential to limit trunk flexion during the positioning phase of recovery, the task may be achieved through intersegmental factors or other muscular sources such as the gluteus maximus and hamstrings.

J Biomech. 1996 Jun;29(6):735-44.