The research behind the board
Studies on perturbation and reactive balance training: moving the support surface to retrain how the body responds. Select a study to read its abstract.
Perturbation training improves knee kinematics and reduces muscle co-contraction after complete unilateral anterior cruciate ligament rupturePhys Ther. 2005 Aug;85(8):740-9; discussion 750-4.
Background and purpose: Dynamic knee stabilization strategies of people who successfully compensate for the absence of an anterior cruciate ligament (ACL) ("copers") are different from those of people who do not compensate well for the injury ("noncopers"). Early after injury, certain patients ("potential copers") can increase the likelihood of successfully compensating for the injury by participating in 10 sessions of perturbation training. The purpose of this study was to determine how perturbation training alters muscle co-contraction and knee kinematics in potential copers.
Subjects: Seventeen individuals with acute, unilateral ACL rupture who were categorized as potential copers and 17 subjects without injuries who were matched by age, sex, and activity level were recruited for this study.
Methods: Motion analysis and electromyographic data were collected as subjects walked across a stationary or moving platform (horizontal translation) before and after perturbation training.
Results: Before training, potential copers had higher co-contraction indexes and lower peak knee flexion angles than subjects without injuries. After training, potential copers' movement patterns more closely resembled those of subjects without injuries (ie, they showed reduced co-contraction indexes and increased peak knee flexion angles during stance).
Discussion and conclusion: Perturbation training reduced quadriceps femoris-hamstring muscle and quadriceps femoris-gastrocnemius muscle co-contractions and normalized knee kinematics in individuals with ACL rupture who were classified as potential copers. Findings from this study provide evidence for a mechanism by which perturbation training acts as an effective intervention for promoting coordinated muscle activity in a select population of people with ACL rupture.
Find on PubMed →Perturbation-enhanced neuromuscular training alters muscle activity in female athletesKnee Surg Sports Traumatol Arthrosc. 2006 Jan;14(1):60-9. Epub 2005 Jun 4.
Female athletes involved in jumping and cutting sports injure their anterior cruciate ligaments (ACL) 4-6 times more frequently than their male counterparts in comparable sports. Neuromuscular factors, including quadriceps dominance, has been incriminated as contributing to the higher rates of injury in women. Currently, the most effective form of intervention developed to reduce female ACL injury rates has been neuromuscular training.
The purpose of this study was to (1) identify gender based muscle activity patterns during disturbed walking that may contribute to ACL injury, and (2) determine if a novel training program could positively influence patterns among healthy female athletes utilizing a disturbed gait paradigm. Twenty healthy athletes (female=10, male=10) were tested. All subjects participated in five trials during which a platform translated horizontally in a lateral direction at heel contact before and after completing ten sessions of a perturbation training program. Electromyographic (EMG) data from the vastus lateralis, medial and lateral hamstrings, and medial gastrocnemius were collected. Trials were analyzed for the muscle onset, termination of activity, peak amplitude, time to peak amplitude, and integrated EMG activity. Muscle cocontraction, the simultaneous activation of antagonistic muscles (lateral hamstrings-vastus lateralis, and medial gastrocnemius-vastus lateralis), was calculated as indicators of active knee stiffness in preparation for heel strike, during weight acceptance and midstance. Prior to training, women had significantly higher peak quadriceps activity and higher integrated quadriceps activity during midstance than men. Both medial and lateral hamstring integrals during midstance increased from pre to posttraining. Onset times to peak activities for hamstrings and quadriceps were similar before training except for medial hamstring time to peak which occurred after heel strike in most women. Time to peak medial hamstring activity moved from after to just before heel strike after training. Women had higher medial gastrocnemius-vastus lateralis cocontraction indices in the preparatory and weight acceptance phases of gait than men after training.
Prior to training, the athletic women in our sample demonstrated characteristic quadriceps dominance and decreased active knee stiffness when compared to male athletes. Modulation of activity and timing of ACL agonist musculature (hamstrings and gastrocnemius) from before to after training resulted in normal quadriceps-hamstring balance and increased active stiffness. These alterations in ACL agonist muscle activation patterns may reduce the risk of biomechanical strain injury among a high risk population.
Find on PubMed →Gait and step training to reduce falls in Parkinson's diseaseNeuroRehabilitation. 2005;20(3):183-90.
Introduction: Frequent falls and risk of injury are evident in individuals with Parkinson's disease (PD) as the disease progresses. There have been no reports of any interventions that reduce the incidence of falls in PD.
Purpose: Assess the benefit of gait and step perturbation training in individuals with PD.
Design: Randomized, controlled trial.
Setting: Outpatient research, education and clinical center in a tertiary care Veterans Affairs Medical Center.
Outcome measures: Gait parameters, 5-step test, report of falls.
Subjects: Eighteen men with idiopathic PD in stage 2 or 3 of the Hoehn and Yahr staging.
Methods: Subjects were randomly assigned to a trained or control group. They were asked about any falls 2 weeks prior to and after an 8 week period. Gait speed, cadence, and step length were tested on an instrumented walkway. Subjects were timed while stepping onto and back down from an 8.8 cm step for 5 consecutive steps. Gait training consisted of walking on a treadmill at a speed greater than over ground walking speed while walking in 4 directions and while supported in a harness for safety. Step training consisted of suddenly turning the treadmill on and off while the subject stood in the safety harness facing either forwards, backwards, or sideways. Training occurred 1 hour per day, three times per week for 8 weeks. A two-factor (time and group) analysis of variance with repeated measures was used to compare the groups.
Results: Substantial reduction occurred in falls in the trained group, but not in the control group. Gait speed increased in the trained group from 1.28+/-0.33 meters/sec to 1.45+/-0.37 meters/sec, but not in the control group (from 1.26 to 1.27 m/s). The cadence increased for both groups: from 112.8 to 120.3 steps/min for the trained group and 117.7 to 124.3 steps/min for the control group. Stride lengths increased for the trained group, but not the control group. The 5-step test speed increased in the trained group from 0.40+/-0.08 steps/sec to 0.51+/-0.12 steps/sec, and in the control group (0.36+/-0.11 steps/sec to 0.42+/-0.11 steps/sec).
Conclusion: Gait and step perturbation training resulted in a reduction in falls and improvements in gait and dynamic balance. This is a promising approach to reduce falls for patients with PD.
Find on PubMed →A randomized controlled trial of a treadmill training with the perturbation to improve the balance performance in the community dwelling elderly subjects (article in Japanese)Nippon Ronen Igakkai Zasshi. 2004 May;41(3):321-7.
We had developed a gait perturbation system based on a treadmill composed of two separate walking belts. The servomotors in this treadmill are controlled by a personal computer. A falling perturbation can be generated by the sudden and random deceleration of the walking belts. The purpose of this study was to determine, in a cohort of community dwelling elderly subjects, whether our treadmill training with the perturbation would improve balance performance.
The 29 participants aged over 65 years were randomly assigned to receive either perturbed treadmill training or ordinary treadmill training. The single leg standing time with the eyes opened and closed, the functional reach test (FR), the timed up and go test (TUG), the 10 m maximum gait speed and the latency of the bilateral tibialis anterior muscle (LTA) were measured at the pre training period and after the 4-week training period. These indexes were measured again one month after the training period. There were no significant differences between the perturbed training subjects and the ordinary training subjects in these indexes in the pre-training period. Following training period, the perturbed training subjects were improved in FR (mean +/- SD: pre 30.3 +/- 5.0 cm, post 33.5 +/- 5.0 cm, p<.01). TUG (mean +/- SD; pre 5.13 +/- .68 sec, post 4.86 +/- .53 sec, p<.05) and LTA (the perturbed side, mean +/- SD; pre 134 +/- 30 msec, post 116 +/- 22 msec, p<.01, the non-perturbed side, mean SD:pre 132 +/- 35 msec, post 114 +/- 27 msec, p <.05). On the other hand, the ordinary training subjects were improved only in TUG (mean +/- SD; pre 4.93 +/- . 52 sec, post 4.60 +/- .39 sec. p<.01). Additionally, the improvements of the LTA on the perturbed training subjects were retained one month after the training period (the perturbed side, mean +/- SD: pre 134 +/- 30 msec, after 1-month 117 +/- 19 msec, p<.01, the non-perturbed side, mean +/- SD: pre 132 +/- 35 msec, after 1-month 115 +/- 24 msec, p<.05).
The improvements of LTA may represent the improvements of the ability of the stepping reaction which is one of the important factors to avoid the falling. Our treadmill training with perturbation improves the balance performance and may decrease the risk of falling in the community dwelling elderly subjects.
Find on PubMed →New intervention program for preventing falls among frail elderly people: the effects of perturbed walking exercise using a bilateral separated treadmillAm J Phys Med Rehabil. 2004 Jul;83(7):493-9.
Objective: To determine the effects of a perturbed walking exercise using a bilateral separated treadmill in physically disabled elderly. DESIGN: Participants of the study were 32 long-term care facility residents and outpatients aged 66-98 yrs. Participants were randomly assigned to a usual exercise group or to a treadmill exercise group. Perturbed gait exercise on a treadmill continued for 6 mos. Number of falls and time to first fall during a 6-mo period, balance and gait functions, and reaction time were evaluated before and after intervention.
Results: The treadmill exercise group showed significant improvement in balance and reaction time when compared with the usual exercise group. Number of falls in the treadmill exercise group was 21% lower than that in the usual exercise group. However, this difference was not significant. No significant differences were seen in time to first fall.
Conclusions: Gait training with unexpected perturbation seems to have a beneficial impact on physical function in disabled elderly individuals. The results suggest that this program may be used as an exercise intervention to reduce falls in institutional settings.
Find on PubMed →Dynamic knee stability after anterior cruciate ligament ruptureExerc Sport Sci Rev. 2003 Oct;31(4):195-200.
A functional classification scheme has been devised to study knee stabilization strategies after anterior cruciate ligament rupture. A screening examination can determine which patients may be candidates for nonsurgical treatment (potential copers). A rehabilitation program that includes support surface perturbations can improve the potential coper's ability to stabilize the knee. Biomechanical, electromyographic, and clinical data support the classification scheme and perturbation training for improving dynamic knee stability.
Recently, a training program that includes perturbation of support surfaces has been shown to allow most active individuals with ACL injury who pass a screening examination to successfully return to high level activities. The purpose of this study was to identify the effect of this rehabilitation program on involved side muscle activation during walking in subjects with acute ACL rupture and to determine if the activation changes were coincident with improved function. Nine subjects with an acute, unilateral ACL injury or rupture of an ACL graft, who met the screening examination criteria, received ten sessions of rehabilitation that included perturbation training. Motion analysis of five self-paced walking trials were performed before and after training. Electromyographic (EMG) data were collected during stance.
After training during walking, the vastus lateralis (VL) integral of activity increased, and relationships between muscles were significantly altered. During walking, VL activation variables were dependent on lateral hamstrings (LH) and/or the soleus (SOL) activation, while no relationships were found before training.
Function improved after training, and all subjects returned to their pre-injury activities without experiencing instability.
The relationships formed between muscles post-training suggests that perturbation training enhances dynamic knee stability by inducing a well-coordinated strategy among muscles that affect tibial translation.
Find on PubMed →The efficacy of perturbation training in nonoperative anterior cruciate ligament rehabilitation programs for physical active individualsPhys Ther. 2000 Feb;80(2):128-40.
Background and purpose: Treatment techniques involving perturbations of support surfaces may induce compensatory muscle activity that could improve knee stability and increase the likelihood of returning patients to high-level physical activity. The purpose of this study was to determine the efficacy of augmenting standard nonoperative anterior cruciate ligament (ACL) rehabilitation programs with a perturbation training program.
Subjects: Twenty-six patients with acute ACL injury or ruptures of ACL grafts participated in the study. Subjects had to have a unilateral ACL injury, be free of concomitant multiple ligament or meniscal damage requiring surgical repair, and pass a screening examination designed to identify patients who had the potential to return to high-level physical activity with nonoperative treatments. Subjects also had to be regular participants in level I activities (eg, soccer, football, basketball) or level II activities (eg, racquet sports, skiing, construction work).
Methods: Subjects were randomly assigned to either a group that received a standard rehabilitation program (standard group) or a group that received the standard program augmented with a perturbation training program (perturbation group). Treatment outcome was determined from scores on the Knee Outcome Survey's Activities of Daily Living Scale (ADLS) and Sports Activity Scale, a global rating of knee function, scores on a series of single-limb hop tests, measurements of maximum isometric quadriceps femoris muscle force output, and the group frequency of unsuccessful rehabilitation. Unsuccessful rehabilitation was defined as the occurrence of an episode of giving way of the knee or failure to maintain the functional status of a rehabilitation candidate on retesting.
Results: More subjects had unsuccessful rehabilitation in the standard group compared with the perturbation group. There was a within-group x time interaction for the ADLS, global rating of knee function, and crossover hop test scores. These scores decreased from posttraining to the 6-month follow-up for the standard group.
Conclusion and discussion: Although both the standard program and the perturbation training program may allow subjects to return to high-level physical activity, the perturbation training program appears to reduce the risk of continued episodes of giving way of the knee during athletic participation and allows subjects to maintain their functional status for longer periods.
Find on PubMed →Balance perturbation system to improve balance compensatory responses during walking in old personsNeuroeng Rehabil. 2010 Jul 15;7:32.
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..
Find on PubMed →Dynamic posturography in Parkinson's disease: diagnostic utility of the "first trial effect"Neuroscience. 2010 Jun 30;168(2):387-94. Epub 2010 Apr 7.
Previous dynamic posturography studies demonstrated clear abnormalities in balance responses in Parkinson's disease (PD) patients compared to controls at the group level, but its clinical value in the diagnostic process and fall risk estimation in individual patients leaves for improvement.
Therefore, we investigated whether a new approach, focusing on the balance responses to the very first and fully unpractised trial rather than a pooled mean response to a series of balance perturbations, could further improve the diagnostic utility of dynamic posturography.
Following the first trial, subjects were exposed to repeated balance perturbations, which also permitted us to investigate the training responses. Fourteen patients with PD and 18 age-matched controls were enrolled, who received a series of multidirectional postural perturbations, induced by support surface rotations. We measured trunk and upper arm kinematics and electromyographic responses, and evaluated group differences at three levels: the postural response to the very first backward perturbation; pooled first and habituated postural responses; and habituation rates. Analysis of the first trial responses yielded similar results as evaluation of the mean response over trials: forward flexion of the trunk induced by backward perturbations was decreased in patients, accompanied by increased muscle responses present.
Moreover, trunk movement and muscle activity were equally present in both groups-suggesting a preserved training response in PD patients. Early masseter activity in both groups might be indicative of a startle-like component to the balance response. In terms of diagnostic utility, focusing on the first trial response or habituation rate is no better than analysis of pooled responses to a series of perturbations.
The apparently preserved training response in PD patients suggests that balance reactions in PD can be improved by repeated exposure, and this may have implications for future exercise studies.
Find on PubMed →Walking variability during continuous pseudo-random oscillations of the support surface and visual fieldJ Biomech. 2010 May 28;43(8):1470-5. Epub 2010 Mar 26.
Walking on uneven surfaces or while undergoing perturbations has been associated with increased gait variability in both modeling and human studies.
Previous gait research involving continuous perturbations has focused on sinusoidal oscillations, which can result in individuals predicting the perturbation and/or entraining to it. Therefore, we examined the effects of continuous, pseudo-random support surface and visual field oscillations on 12 healthy, young participants.
Participants walked in a virtual reality environment under no perturbation (NOP), anterior-posterior (AP) walking surface and visual oscillation and mediolateral (ML) walking surface and visual oscillation conditions. Participants exhibited shorter (p< or =0.005), wider (p<0.001) and faster (p<0.001) steps relative to NOP during ML perturbations and shorter (p< or =0.005) and wider (p<0.001) steps during AP perturbations. Step length variability and step width variability both increased relative to NOP during all perturbation conditions (p<0.001) but exhibited greater increases for the ML perturbations (p<0.001). Participants exhibited greater trunk position variability and trunk velocity variability in the ML direction than in the AP direction during ML perturbations relative to NOP (p<0.001). Significantly greater variability in the ML direction indicates that to maintain stability, participants needed to exert greater control in the ML direction. This observation is consistent with prior modeling predictions.
The large and consistent responses observed during ML visual and walking surface perturbations suggest potential for application during gait training and patient assessment.
Find on PubMed →Effect of a perturbation-based balance training program on compensatory stepping and grasping reactions in older adultsPhys Ther. 2010 Apr;90(4):476-91. Epub 2010 Feb 18.
Background: Compensatory stepping and grasping reactions are prevalent responses to sudden loss of balance and play a critical role in preventing falls. The ability to execute these reactions effectively is impaired in older adults.
Objective: The purpose of this study was to evaluate a perturbation-based balance training program designed to target specific age-related impairments in compensatory stepping and grasping balance recovery reactions.
Design: This was a double-blind randomized controlled trial.
Setting: The study was conducted at research laboratories in a large urban hospital.
Participants: Thirty community-dwelling older adults (aged 64-80 years) with a recent history of falls or self-reported instability.
Intervention: Participants were randomly assigned to receive either a 6-week perturbation-based (motion platform) balance training program or a 6-week control program involving flexibility and relaxation training.
Measurements: Features of balance reactions targeted by the perturbation-based program were: (1) multi-step reactions, (2) extra lateral steps following anteroposterior perturbations, (3) foot collisions following lateral perturbations, and (4) time to complete grasping reactions. The reactions were evoked during testing by highly unpredictable surface translation and cable pull perturbations, both of which differed from the perturbations used during training.
Results: Compared with the control program, the perturbation-based training led to greater reductions in frequency of multi-step reactions and foot collisions that were statistically significant for surface translations but not cable pulls. The perturbation group also showed significantly greater reduction in handrail contact time compared with the control group for cable pulls and a possible trend in this direction for surface translations.
Limitations: Further work is needed to determine whether a maintenance program is needed to retain the training benefits and to assess whether these benefits reduce fall risk in daily life.
Conclusion: Perturbation-based training shows promise as an effective intervention to improve the ability of older adults to prevent themselves from falling when they lose their balance.
Find on PubMed →Practice-related improvements in posture control differ between young and older adults exposed to continuous, variable amplitude oscillations of the support surfaceExp Brain Res. 2009 Nov;199(2):185-93.
Healthy older adults were repeatedly exposed to continuous, variable amplitude oscillations of the support surface to determine (1) whether age affects the capacity for postural motor learning under continuous perturbation conditions with limited predictability and (2) whether practice leads to modifications in the control strategy used to maintain balance in older adults. During training, a translating platform underwent 45-s trials of constant frequency (0.5 Hz) and seemingly random amplitude oscillations (range ± 2 to 15 cm). The middle 15 s of each trial contained the same sequence of oscillation amplitudes. This repeated middle segment was the same as the repeated segment used in Van Ooteghem et al. (Exp Brain Res 187(4): 603-611, 2008) and was therefore used for analyses. To examine learning, participants performed a retention test following a 24-h delay. Kinematic data were used to derive spatial and temporal measures of whole body centre of mass (COM), trunk, thigh, and shank segment orientation, and ankle and knee angle from performance during the repeated middle segment.
Results showed that with training, older adults maintained the capacity to learn adaptive postural responses in the form of improved temporal control of the COM and minimization of trunk instability a a rate comparable to young adults.
With practice, however older adults maintained a more rigid, 'platform-fixed' control strategy which differed from young adults who shifted towards 'gravity-fixed' control and decreased COM motion. This study provides important insight into the ability of older adults to demonstrate longer-term improvements in postural regulation.
Find on PubMed →Neuromuscular control and ankle instabilityPM R. 2009 Apr;1(4):359-65.
Lateral ankle sprains (LAS) are common injuries in athletics and daily activity. Although most are resolved with conservative treatment, others develop chronic ankle instability (AI)-a condition associated with persistent pain, weakness, and instability-both mechanical (such as ligamentous laxity) and functional (neuromuscular impairment with or without mechanical laxity).
The predominant theory in AI is one of articular deafferentation from the injury, affecting closed-loop (feedback/reflexive) neuromuscular control, but recent research has called that theory into question. A considerable amount of attention has been directed toward understanding the underlying causes of this pathology; however, little is known concerning the neuromuscular mechanisms behind the development of AI. The purpose of this review is to summarize the available literature on neuromuscular control in uninjured individuals and individuals with AI.
Based on available research and reasonable speculation, it seems that open-loop (feedforward/anticipatory) neuromuscular control may be more important for the maintenance of dynamic joint stability than closed-loop control systems that rely primarily on proprioception. Therefore, incorporating perturbation activities into patient rehabilitation schemes may be of some benefit in enhancing these open-loop control mechanisms.
Despite the amount of research conducted in this area, analysis of individuals with AI during dynamic conditions is limited. Future work should aim to evaluate dynamic perturbations in individuals with AI, as well as subjects who have a history of at least one LAS and never experienced recurrent symptoms. These potential findings may help elucidate some compensatory mechanisms, or more appropriate neuromuscular control strategies after an LAS event, thus laying the groundwork for future intervention studies that can attempt to reduce the incidence and severity of acute and chronic lateral ankle injury.
Find on PubMed →Resistance training and neuromuscular performance in seniorsInt J Sports Med. 2009 Sep;30(9):652-7. Epub 2009 Jun 30.
Age-related processes in the neuromuscular and the somatosensory system are responsible for decreases in maximal and explosive force production capacity and deficits in postural control. Thus, the objectives of this study were to investigate the effects of resistance training on strength performance and on postural control in seniors.
Forty healthy seniors (67+/-1 yrs) participated in this study. Subjects were randomly assigned to a resistance training (n=20) and a control group (n=20). Resistance training for the lower extremities lasted for 13 weeks at 80% of the one repetition maximum. Pre and post tests included the measurement of maximal isometric leg extension force with special emphasis on the early part of the force-time-curve and the assessment of static (functional reach test) and dynamic (tandem walk test, platform perturbation) postural control. Resistance training resulted in an enhanced strength performance with increases in explosive force exceeding those in maximal strength. Improved performances in the functional reach and in the tandem walk test were observed.
Resistance training did not have an effect on the compensation of platform perturbations. Increases in strength performance can primarily be explained by an improved neural drive of the agonist muscles. The inconsistent effect of resistance training on postural control may be explained by heterogeneity of testing methodology or by the incapability of isolated resistance training to improve postural control.
Find on PubMed →Effects of a 4-week exercise program on balance using elastic tubing as a perturbation force for individuals with a history of ankle sprainsJ Orthop Sports Phys Ther. 2009 Apr;39(4):246-55.
Study design: Randomized controlled trial with pretraining, posttraining, and follow-up repeated measures.
Objective: To determine the effectiveness of a 4-week elastic resistance exercise program on balance in subjects with and without a history of sprained ankles.
Background: Several researchers have suggested that improving balance may help alleviate the symptoms of functional ankle instability and reduce the rate of recurrent ankle sprains.
Methods and measures: Forty subjects (20 males, 20 females; 20 subjects with chronic ankle instability [CAI], 20 healthy) participated in the study. Ten subjects (5 males, 5 females) from each CAI and healthy group were randomly assigned to either the exercise or control group, resulting in a total of 4 groups. Total travel distance of the center of pressure, monitored using a force platform, was measured before training, after 4 weeks of training, and at a 4-week follow-up.
Results: There were no interactions between gender, ankle sprain history, or training groups. Balance significantly improved in subjects with and without a history of ankle sprains following 4 weeks of elastic resistance exercises. Mean improvement in balance for the exercise group following training, reflected through a decrease in total travel distance, was -11.1 cm (95% confidence interval: -14.0 to -8.2 cm). These improvements in balance were retained 4 weeks after training.
Conclusions: Balance was improved after 4 weeks of elastic resistance exercise in subjects with and without a history of lateral ankle sprains. Balance improvements persisted 4 weeks following the treatment cessation.
Find on PubMed →Perturbation training prior to ACL reconstruction improves gait asymmetries in non-copersJ Orthop Res. 2009 Jun;27(6):724-9.
We investigated whether preoperative perturbation training would help anterior cruciate ligament (ACL) deficient individuals who complain of knee instability ("non-copers") regain quadriceps strength and walk normally after ACL reconstruction. Nineteen non-copers with acute ACL injury were randomly assigned into a perturbation group (PERT) or a strengthening group (STR).
The PERT group received specialized neuromuscular training and progressive quadriceps strength training, whereas the STR group received progressive quadriceps strength training only. We compared quadriceps strength indexes and knee excursions during the mid-stance phase of gait preoperatively to data collected 6 months after ACL reconstruction. Analyses of Variance with repeated measures (time/limb) were conducted to compare quadriceps strength index values over time (time x group) and differences in knee excursions in limbs between groups over time (limb x time x group). If significance was found, post hoc analyses were performed using paired and independent t-tests.
Quadriceps strength indexes before intervention (Pert: 87.2%; Str: 75.8%) improved 6 months after ACL reconstruction in both groups (Pert: 97.1%; Str: 94.4%). Non-copers who received perturbation training preoperatively had no differences in knee excursions between their limbs 6 months after ACL reconstruction (p = 0.14), whereas those who received just strength training continued to have smaller knee excursions during the mid-stance phase of gait (p = 0.007).
Non-copers strength and knee excursions were more symmetrical 6 months postoperatively in the group that received perturbation training and progressive quadriceps strength training than the group who received strength training alone.
Find on PubMed →Dynamic balance training with sensory electrical stimulation in chronic stroke patientsConf Proc IEEE Eng Med Biol Soc. 2006;1:2150-3.
A case study investigating the impact of sensory electrical stimulation during perturbed stance in one chronic stroke patient is presented. A special apparatus called the BalanceTrainer was used. It allows the application of perturbations to neurologically impaired people during standing, while protecting the subject from falling. The subject underwent two different periods of perturbation training, each lasting ten days. During the first period the subject was perturbed in eight different directions. During the second period the subject was also perturbed, but was assisted by sensory electrical stimulation of the soleus, tibialis anterior, tensor fascia latae, and vastus muscles in the impaired leg.
After each period of training an assessment was carried out to measure the forces the subject applied on the ground via two force plates. The subject improved his ability to balance throughout the training, with the largest improvements during the final period when electrical stimulation was used.
Find on PubMed →Postural responses following a rotational support surface perturbation, following knee joint replacement: frontal plane rotationsGait Posture. 2008 Feb;27(2):286-93. Epub 2007 May 17.
Total knee arthroplasty (TKA) is associated with altered sensory and motor functions of the knee which may impair balance control when standing and walking. This study examined the organization of electromyographic and kinematic postural responses to frontal plane support surface rotations, after TKA. Eight TKA patients and nine control participants volunteered. Patients demonstrated changes in onset latency of rectus femoris and gluteus medius, and in amplitude of muscle activity in tibialis anterior, gastrocnemius, rectus femoris, and gluteus medius, for both perturbation directions, and for both the surgical and sound limbs.
Peak knee joint angular velocity was reduced among the patients for both perturbation directions and both the surgical and sound limbs, and patients demonstrated greater peak center of mass displacement. The CNS appears to alter the response to postural perturbation of both lower limbs, based on the reduced capacities of the surgical limb. Impaired detection of the valgus-varus loading of the knee joints may lead to the changes in muscle activity and resultant kinematics.
Clinically, these findings are relevant in understanding that fully recovered TKA patients may continue to demonstrate balance impairments, and that balance training during physical rehabilitation may be advantageous to these patients.
Find on PubMed →A novel approach in objective assessment of functional postural responses during fall-free perturbed standing in clinical environmentTechnol Health Care. 2007;15(3):181-93.
The proposed approach offers few novelties in integration of objective assessment of postural responses when an unexpected perturbation is applied to the standing person into the existing rehabilitation therapy.
The research apparatus was equipped with electrical actuators to provide unexpected perturbations (controllable and repeatable strength and duration) to the standing frame in eight directions during quiet standing in a fall-safe environment. During the perturbations ground reaction forces were recorded under each foot and the motion of center of pressure was derived to extract the postural response indicators in time and space domain. Seven neurologically intact subjects participated in normative set up that was used to develop an algorithm for selective postural response characteristics analysis for each perturbation direction.
The postural responses in two incomplete spinal cord injured persons and hemiparetic stroke patient were investigated and contrasted to the normative responses to test the proposed approach. The outcomes of the investigation showed expected distinctive direction-dependent postural responses characteristic for hemiparetic subjects.
Our observations suggest that the approach may become effective in substantial quantitative multidirectional stabilometric evaluation of functional postural responses, especially when the effectiveness of the balance training rehabilitation program is in need for objective evaluation. Simultaneously the apparatus can be used also for the balance training and therefore become a training and assessment tool for clinical and home environment.
Find on PubMed →Rehabilitation after anterior cruciate ligament reconstruction in the female athleteAthl Train. 1999 Apr;34(2):177-93.
Objective: To discuss the rehabilitation program after anterior cruciate ligament (ACL) reconstruction in the female athlete. In addition, we will discuss 8 unique characteristics identified in the female athlete and specific training drills to address and correct the potentially deleterious effects of these unique characteristics. BACKGROUND: The female athlete appears to be more susceptible to noncontact ACL injuries than the male athlete.
There seem to be many differences between the female and male athlete that may contribute to the increased injury rate in the female athlete. These variations include anatomical and neuromuscular considerations and differences. DESCRIPTION: Based on the unique characteristics of the female athlete and the anatomical and neuromuscular dissimilarities, a specially designed rehabilitation program has been established for the female athlete after ACL surgery. CLINICAL ADVANTAGES:
The rehabilitation drills discussed in this article challenge the neuromuscular system through proprioception, kinesthesia, dynamic joint stability, neuromuscular control, and perturbation training activities. Improving the female athlete's neuromuscular system will, we believe, expedite the injured athlete's recovery after ACL injury or surgery. Although the concepts discussed are part of a postoperative rehabilitation program after ACL surgery, these concepts may also be implemented as a preventive program to assist in reducing the incidence of ACL injuries in the female.
Find on PubMed →Effects of neuromuscular training on the reaction time and electromechanical delay of the peroneus longus muscleArch Phys Med Rehabil. 2006 Mar;87(3):395-401.
Objective: To examine the influence of a 6-week neuromuscular training program on the electromechanical delay and reaction time of the peroneus longus muscle.
Design: A 2 x 2 pre-post factorial design.
Setting: Human performance research center biomechanics laboratory.
Participants: Thirty-six healthy, physically active, college-age subjects were recruited for this study and 26 completed it. There were 5 men and 8 women in the treatment group (mean age +/- standard deviation, 21.9+/-2.1 y; height, 173.7+/-11.1cm; weight, 67.4+/-17.8 kg) and 6 men and 7 women in the control group (age, 21.8+/-2.3 y; height, 173.7+/-11.9 cm; weight, 70.8+/-19.4 kg). Subjects were not currently experiencing any lower-extremity pathology and had no history of injuries requiring treatment to either lower extremity.
Interventions: Subjects in the treatment group completed a 6-week neuromuscular training program involving various therapeutic exercises. Subjects in the control group were asked to continue their normal physical activity during the 6-week period.
Main outcome measures: The electromechanical delay of the peroneus longus was determined by the onset of force contribution after artificial activation, as measured by electromyographic and forceplate data. Reaction time was measured after a perturbation during walking. Data were analyzed using two 2 x 2 analyses of covariance (covariate pretest score). Group (treatment, control) and sex (male, female) were between-subject factors.
Results: Neuromuscular training caused a decrease in reaction time to perturbation during walking compared with controls (F=4.030, P=.029), while there was a trend toward an increase in electromechanical delay (F=4.227, P=.052). There was no significant difference between sexes or the interaction of sex and treatment in either reaction time or electromechanical delay.
Conclusions: The 6-week training program significantly reduced reaction time of the peroneus longus muscle in healthy subjects. Neuromuscular training may have a beneficial effect on improving dynamic restraint during activity.
Find on PubMed →Agility and perturbation training for a physically active individual with knee osteoarthritisPhys Ther. 2002 Apr;82(4):372-82.
Background and purpose: People with knee osteoarthritis (OA) sometimes report episodes of knee instability that limit their activities of daily living. The episodes of instability are similar to those reported by people with knee ligament injuries. The authors believe that modifications of interventions that are used to promote knee stability in individuals with knee ligament injuries can be used to enhance knee stability and function in people with knee OA. The purpose of this case report is to describe the development and implementation of an agility and perturbation training program that was used in conjunction with traditional rehabilitation activities for a patient with knee OA.
Case description: The patient was a 73-year-old woman with a diagnosis of bilateral knee OA. Her chief complaints were knee pain and episodes of partial "giving way" at the knee during walking, stair climbing, and participation in tennis and golf. The patient participated in 12 treatment sessions at a frequency of 2 visits per week. The rehabilitation program consisted of lower-extremity stretching, strengthening and endurance exercises that were supplemented with a variety of walking-based agility training techniques, and perturbation training techniques.
Outcome: At the completion of rehabilitation, the patient was able to walk on level surfaces and stairs and return to playing golf and tennis without episodes of instability and with reduced pain.
Discussion: Supplementing rehabilitation programs for people with knee OA with a modified agility and perturbation training program may assist them in returning to higher levels of physical activity with less pain and instability following rehabilitation. Further research is needed to determine the role of agility and perturbation training in people with knee OA.
Find on PubMed →Rationale for training programs to reduce anterior cruciate ligament injuries in Australian footballJ Orthop Sports Phys Ther. 2001 Nov;31(11):645-54; discussion 66.
This commentary presents the rationale for training programs to reduce the incidence of knee injuries. Our studies have revealed that the external knee loading patterns during sidestep cutting are what put the anterior cruciate ligament at greatest risk for injury. Compared to running, sidestep cutting involves similar levels of knee flexion loading but increased loading in varus-valgus and internal rotation of the knee, and these external loads need to be stabilized or supported by the internal structures of the knee.
People use a generalized hamstrings and quadriceps co-contraction to stabilize these external loads, thereby reducing ligament loading. It is proposed that perturbation of the joint receptors reinforces the use of selective hamstrings and quadriceps co-contraction patterns superimposed on a generalized co-contraction pattern. This is not by immediate ligamento-muscular protective reflex, which is too slow to provide any adequate support, but by enhanced proprioceptive information that may be used in learning.
In contrast, the immediate effect of muscle stretch reflexes would be to reduce co-contraction, a possibly negative outcome for joint stabilization. The effects of different types of training on the control of joint stability are examined.
It is proposed that resistance training may not be appropriate because it enhances muscle stretch reflexes, which may reduce co-contraction, and produces no reductions in voluntary activation times and time to peak torque. However, stability and balance training is thought to suppress muscle stretch reflexes and, in turn, enhance co-contraction. Also, stability and balance training that stimulates the knee joint ligament and capsular receptors may reinforce co-contraction patterns to facilitate greater improvements in joint stabilization.
Stability and balance training and plyometric training produce reductions in voluntary activation times and times to peak torque, which may decrease muscle response times so players are more able to perform rapid and unexpected sports maneuvers.
Training programs that emphasize these neuromuscular mechanisms may enhance protection of the anterior cruciate ligament and reduce the incidence of injury
Find on PubMed →Postural corrections after standardised perturbations of single limb stance: effect of training and orthotic devices in patients with ankle instabilityBr J Sports Med. 1996 Jun;30(2):151-5.
Objective: Soccer players with functional instability of the ankle joint have shown impairment of postural control in single limb stance. The aim of this study was to examine the effect of stance perturbation
Methods: A standardised method for the study of postural corrections after perturbation (Equitest) was used. Female soccer players with and without functional instability were examined.
Results: The subjects showed a relative change from ankle to hip synergy at medially directed translations of the support surface. This impairment was restored after eight weeks of ankle disk training. The effect of a shoe and brace did not exceed the effect of the shoe alone.
Conclusions: Functional instability seems to be related to impaired ability to retain equilibrium in single limb stance by means of ankle corrections. A positive effect of ankle disk training leading to functional restoration was confirmed
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