Quantifying thigh muscle co-activation during isometric knee extension contractions: within- and between-session reliability.

Muscle co-activation around the knee is important during ambulation and balance. The wide range of methodological approaches for the quantification of co-activation index (CI) makes comparisons across studies and populations difficult. The present study determined within- and between-session reliability of different methodological approaches for the quantification of the CI of the knee extensor and flexor muscles during maximum voluntary isometric contractions (MVICs). Eight healthy volunteers participated in two repeated testing sessions. A series of knee extension MVICs of the dominant leg with concomitant torque and electromyographic (EMG) recordings were captured. CI was calculated utilizing different analytical approaches. Intraclass correlation coefficient (ICC) showed that within-session measures displayed higher reliability (ICC>0.861) and lower variability (Coefficient of variation; CV<21.8%) than between-session measures (ICC<0.645; CV>24.2%). A selection of a 500ms or larger window of RMS EMG activity around the PT delivered more reliable and less variable results than other approaches. Our findings suggest that the CI can provide a reliable measure for comparisons among conditions and is best utilized for within-session experimental designs.

Optimal stimulation parameters to detect deficits in quadriceps voluntary activation.

The purpose of this study was to determine optimal stimulation parameters and calculation methods to estimate quadriceps voluntary activation while minimizing participant discomfort. Twelve healthy adults (8 men and 4 women; mean ± SD, age = 36.8 ± 15.6 years, weight = 76.1 ± 12.9 kg, height = 170.2 ± 8.6 cm). Repeated maximal volitional isometric contractions (MVIC) were performed while imposing 4 stimulation combinations (10 or 2 pulses; 400 or 200 V; and variable or standardized current) with the quadriceps in a relaxed state (resting twitch [RT]) and during an MVIC. Quadriceps activation was quantified by calculating the central activation ratio and the percent activation. Discomfort was quantified using the visual analog scale. When comparing calculation methods between the same stimulation parameters, the central activation ratio calculation method produced quadriceps activation values that were significantly greater (p < 0.009) than those derived using the percent activation calculation method. The doublet pulse stimulus produced less discomfort during the RT (p < 0.04) and MVIC (p < 0.001) when compared with all other combinations using a train of stimuli (10 pulses). Correlations for all estimates of quadriceps activation were strong (r = 0.85-0.99, p < 0.001). A doublet pulse stimulus produced discomfort levels that were over 50% lower than a 10-pulse train of stimuli and correlated well (r > 0.88) with activation levels obtained with a 10-pulse train of stimuli. Therefore, the use of a doublet pulse stimulus provides quadriceps activation information equivalent to other methods while minimizing participant discomfort.

Fibular taping does not influence ankle dorsiflexion range of motion or balance measures in individuals with chronic ankle instability.

OBJECTIVES: To determine the effects of fibular taping on ankle dorsiflexion range of motion (ROM) and dynamic balance in individuals with chronic ankle instability (CAI). DESIGN: Single-blind, randomized crossover. METHODS: Twenty-three individuals (age=23.4 ± 2.5 years, height=171.6 ± 12.4 cm, mass=71.5±13.1 kg) with CAI were allocated to either a fibular taping intervention or sham taping intervention (tape applied without tension) over the course of two visits. Weight-bearing ankle dorsiflexion ROM and components of the Star Excursion Balance Test (SEBT) were measured before and after intervention. RESULTS: There was not a significant change in ankle dorsiflexion ROM when comparing the taping interventions (F1,43=1.03, P=.32), but both interventions resulted in a small increase (F1,43=8.07, P=.007) in dorsiflexion ROM (pre=36.7° ± 6.9°, post=37.7° ± 6.2°). This increase in ROM did not exceed the established minimal detectable change for dorsiflexion ROM. Fibular taping with tension produced an increase (F1,41=5.84, P=.02) (pre=69.0 ± 9.1%, post=70.6±8.6%) in posterolateral reach distance when compared to taping without tension (pre=72.7 ± 11.0%, post=71.4 ± 9.6%), but this increase did not exceed the established minimal detectable change. There was not a significant change in dynamic balance between groups for the anterior (F1,41=2.33, P=.14) and posteromedial (F1,41=.41, P=.53) reach directions. CONCLUSIONS: Although small changes in ankle dorsiflexion ROM and posterolateral reach distances were observed, these changes did not exceed established minimal detectable change values for these measures. These results suggest that the benefits of fibular taping are not related to an increase in ankle dorsiflexion ROM or dynamic balance.

Describing the clinical reasoning process: application of a model of enablement to a pediatric case.

BACKGROUND AND PURPOSE: Clinical reasoning is a core tenet of physical therapy practice leading to optimal patient care. The purpose of this case was to describe the outcomes, subjective experience, and reflective clinical reasoning process for a child with cerebral palsy using the International Classification of Functioning, Disability, and Health (ICF) model. CASE DESCRIPTION: Application of the ICF framework to a 9-year-old boy with spastic triplegic cerebral palsy was utilized to capture the interwoven factors present in this case. Interventions in the pool occurred twice weekly for 1 h over a 10-week period. OUTCOMES: Immediately post and 4 months post-intervention, the child made functional and meaningful gains. The family unit also developed an enjoyment of exercising together. Each individual family member described psychological, emotional, or physical health improvements. DISCUSSION: Reflection using the ICF model as a framework to discuss clinical reasoning can highlight important factors contributing to effective patient management.

Longitudinal gait analysis of a person with a transfemoral amputation using three different prosthetic knee/foot pairs.

Using gait analysis, we documented kinetic and temporospatial changes over a 7-year period in a single healthy individual with a transfemoral amputation walking with three different knees and matched foot components. The knee/foot pairs in chronological order were Four Bar Endolite knee/Endolite Dynamic Response foot; Ossur Total Knee 2000/Pathfinder I foot; and C-Leg knee/IC40 C-walk foot. The design of the suspension and socket were unchanged across the three prostheses. We found an increase in the braking component of A-P ground reaction force on the intact limb while using the C-Leg compared to the other two prosthetic fabrications. There was progressive change across the three component combinations, which included increased step length, increased walking velocity, and decreased double limb support time. The subject ranked the C-Leg system as the most stable. The final gait pattern with the C-Leg was faster, less cautious, and more stable than with the other prosthetic components.

Amplitude- and velocity-dependency of rigidity measured at the wrist in Parkinson's disease.

OBJECTIVE: Quantify the effects of increased amplitude and rate of muscle stretch on parkinsonian rigidity. METHODS: Eighteen subjects with Parkinson's disease participated in this study. Subjects' tested hand was passively displaced through 60° and 90° ranges of wrist flexion and extension at velocities of 50°/s and 280°/s in both treated and untreated conditions. Joint angular position, resistance torque, and surface electromyography (EMG) of the wrist flexors and extensors were recorded. Rigidity was quantified by normalized work scores and normalized angular impulses for flexion and extension, separately. Reflex responses of stretched and shortened muscles were quantified by mean EMG and EMG ratio. A series of ANOVAs was performed to determine the effect of amplitude, velocity and medication on selected variables. RESULTS: Both work scores and angular impulses revealed that the larger displacement amplitude and the higher velocity were associated with significantly greater rigidity, increased EMG ratio and mean EMG of stretched muscles. Dopaminergic medication was not associated with a reduction in rigidity. CONCLUSIONS: Parkinsonian rigidity is modulated by the amplitude and rate of muscle stretch. SIGNIFICANCE: These findings shed light on the biomechanical underpinnings and physiological characteristics of rigidity and may inform clinical rigidity assessment in Parkinson's disease.

Enhancement of parkinsonian rigidity with contralateral hand activation.

OBJECTIVE: Quantify the enhancement of parkinsonian rigidity associated with a contralateral activation maneuver. METHODS: Twelve subjects with PD and eight controls participated in the study protocol. Subjects' tested hand was displaced by a servo-motor throughout wrist flexion and extension motions of 60° without and with a concurrent gripping activation in the contralateral hand, referred to as Passive and Active conditions, respectively. Subjects with PD were tested in both OFF-MED and ON-MED states. Rigidity was quantified by integrating torque with position during both flexion and extension (torque resistance). ANOVA was performed to assess the effect of contralateral activation on rigidity. RESULTS: PD patients had significantly (0.038) enhanced torque resistance in OFF-MED compared to healthy controls and ON-MED. In the Active condition, differences in torque resistance were magnified (p=0.002). Medication substantially reduced differences in torque resistance between controls and PD patients in the Passive and Active conditions. CONCLUSIONS: A contralateral activation maneuver substantially increases rigidity in patients with PD, specifically the OFF-MED state. Rigidity is reduced with the application of dopaminergic medication, even with the presence of a contralateral activation maneuver. SIGNIFICANCE: These data support the use of a contralateral activation maneuver as a tool in the diagnosis of PD.

Differentiation between the contributions of shortening reaction and stretch-induced inhibition to rigidity in Parkinson's disease.

Parkinsonian rigidity is characterized by an increased resistance of a joint to externally imposed motion that remains uniform with changing joint angle. Two candidate mechanisms are proposed for the uniformity of rigidity, involving neural-mediated excitation of shortening muscles, i.e., shortening reaction (SR), or inhibition of stretched muscles, i.e., stretch-induced inhibition (SII). To date, no study has addressed the roles of these two phenomena in rigidity. The purpose of this study was to differentiate these two phenomena, and to quantify the potential contribution of each to wrist joint moment in 17 patients with parkinsonian rigidity, in both Off- and On-medication states. Joint position, torque, and EMGs of selected muscles were collected during externally imposed flexion and extension motions. Moments of shortened and stretched muscles were estimated using a biomechanical model. Slopes of the estimated torque-angle curve were calculated for shortened and stretched muscles, separately. A mixed model ANOVA was performed to compare the contribution between the two mechanisms. During flexion, slopes were significantly (P = 0.003) smaller for SR than for SII, whereas during extension, slopes for SII were significantly (P = 0.003) smaller. Results showed that both SR and SII contributed to rigidity. Which mechanism predominates appeared to be associated with the direction of movement. The findings provide new insights into the biomechanical underpinnings of this common symptom in Parkinson's disease.

Surface muscle pressure as a measure of active and passive behavior of muscles during gait.

While surface electromyography (SEMG) can accurately register electrical activity of muscles during gait, there are no methods to estimate muscular force non-invasively. To better understand the mechanical behavior of muscle, we evaluated surface muscle pressure (SMP) in conjunction with SEMG. Changes in anterior thigh radial pressure during isometric contractions and gait were registered by pressure sensors on the limb. During isometric knee extensions by a single subject, SMP waveforms correlated well with SEMG (r=0.97), and SEMG onsets preceded those of SMP by 35-40 ms. SMP and SEMG signals were simultaneously recorded from the quadriceps of 10 healthy subjects during gait at speeds of 0.4, 0.8, 1.1, 1.4 and 2.2m/s. Muscle activity onset and cessation times were objectively determined for both modalities, and results showed high intra-class correlations. SMP waveforms were highly consistent from stride to stride, while SEMG waveforms varied widely. SEMG waveforms were typically brief, while SMP waveforms tended to be biphasic and outlasted the SEMG by approximately 40% of gait cycle at all speeds. These results are consistent with mechanical models of muscle, and demonstrate the use of SMP to estimate the timing of knee extensor muscle stiffness during gait.

Body weight supported treadmill training at very low treatment frequency for a young adult with incomplete cervical spinal cord injury.

INTRODUCTION: Body weight supported treadmill training (BWSTT) using high treatment frequency has been shown to improve gait after spinal cord injury (SCI). This case report describes the use of BWSTT at a very low treatment frequency. SUBJECT: The subject was a 19 y.o. female with an incomplete C6 SCI, one year post-injury, with multiple gait deficits. INTERVENTION: BWSTT was combined with conventional rehabilitation. Mean treatment frequency was 1.16 days/wk over 28.5 wks. A BWSTT progression algorithm based on observational gait analysis guided progressive changes in support levels, treadmill speed, and session length. OUTCOMES: During the first 3 sessions, the subject tolerated an average of 15.7 minutes of BWSTT with 26% BWS at 0.8 m/s, improving to an average of 28 minutes of BWSTT with 10% BWS at 1.6 m/s in the last 3 sessions. Following 28.5 wks of very low frequency BWSTT, the subject displayed improved kinematics, walking speed, endurance, and distance during overground gait. CONCLUSION: Very low frequency BWSTT combined with conventional treatment improved quality and endurance of walking for a person with incomplete cervical SCI. Further work is needed to evaluate the long-term outcome of very low frequency BWSTT and the interaction of BWSTT with other interventions.

Analysis of interactive effect of stretch reflex and shortening reaction on rigidity in Parkinson's disease.

OBJECTIVE: To examine the correlation between rigidity and interaction of stretch reflex and shortening reaction during passive movements of the wrist and to compare this correlation with that between rigidity and stretch reflex alone. METHODS: Twelve subjects with Parkinson's disease participated in the study in Off-medication and On-medication states. A servomotor imposed wrist flexion and extension within +/-30 degrees at velocities 50 and 280 degrees/s, while joint torque and EMG of the wrist flexors and extensors were recorded. Rigidity was quantified by integrating torque with joint angle, i.e., objective rigidity (OR) score, for extension and flexion, respectively. The interaction between EMG responses was estimated by calculating a ratio of normalized EMG in stretched to shortened muscles for both movements. RESULTS: The OR scores were more strongly correlated with the EMG ratios than with EMG of the stretched muscles alone. The strongest and significant correlation was found between the OR score and EMG ratio during the extension at high velocity in the Off-medication (r=0.792, p=0.002). CONCLUSIONS: Both stretch reflex and shortening reaction are important determinants of rigidity. SIGNIFICANCE: Study findings provide new insight into mechanistic descriptions of rigidity and have implications for development and evaluation of interventions.

Test-retest reliability of the physical performance test for persons with Parkinson disease.

BACKGROUND AND PURPOSE: Reliable measures are needed to document functional status and disease progression for people with Parkinson disease (PD). We, therefore, evaluated the reliability of the Physical Performance Test (PPT) for people with PD. METHODS: Fourteen community-dwelling subjects with PD participated: 8 males, 6 females; modified Hoehn and Yahr Stages 2 and 2.5; mean age 62.4 years (+6.3). The test was administered twice, 1 week apart. The 7-item and 9-item summary scores of the PPT were each compared between sessions using repeated measures analysis of variance (ANOVA). The intraclass correlation coefficient (ICC) and method error (ME) were calculated to further assess reliability. RESULTS: Between sessions, 7- and 9-item summed scores were not statistically different. The range of summed scores fell in the midst of the available score range for both the 7- and 9-item tests suggesting resistance to floor and ceiling effects. The ICCs showed good agreement (7-item = 0.818; 9-item = 0.895) indicating test reliability for this population. Based on the ME, an examiner can expect a 6% variation for the 7-item summary score and a 4% variation for the 9-item score summary between testing sessions. CONCLUSIONS: The 7- and 9-item PPTs were demonstrated to be reliable objective measures in individuals with PD. Simple props and brief administration time (10-15 minutes) make the test practical to use.

Temporospatial and kinematic gait alterations during treadmill walking with body weight suspension.

Our purpose was to analyze the effects of selected levels of body weight support (BWS) on lower extremity kinematics of normal subjects at a predetermined treadmill speed. Seventeen non-disabled volunteers walked on a treadmill at 1.25 ms(-1). Temporospatial and kinematic data were collected while various support levels were applied (Minimal, 10, 30, 50 and 70% BWS). Compared to 10% BWS, significant temporospatial and kinematic changes were induced by 50 and 70% BWS. Fewer differences were induced by 30% BWS compared to 10% BWS. We concluded that gait patterns of unimpaired subjects are significantly changed by 50 and 70% BWS.