Background Neuromuscular electrical stimulation (NMES) is effective in muscle strengthening after orthopedic injury particularly when muscle activation failure is present, but the associated pain can be a barrier. Pain itself can produce a pain inhibitory response called Conditioned Pain Modulation (CPM). CPM is often used in research studies to assess the state of the pain processing system. However, the inhibitory response of CPM could make NMES more tolerable to patients and could improve functional outcomes in people with pain. This study compares the pain-inhibitory effect of NMES compared to volitional contractions and noxious electrical stimulation (NxES). Methods Healthy participants, 18–30 years of age experienced 3 conditions: 10 NMES contractions, 10 bursts of NxES on the patella, and 10 volitional contractions on the right knee. Pressure pain thresholds (PPT) were measured before and after each condition in both knees and the middle finger. Pain was reported on an 11-point VAS. Repeated measures ANOVAs with 2 factors: site and time were performed for each condition followed by post-hoc paired t-tests, with Bonferroni correction. Results Pain ratings were higher in the NxES condition compared to NMES ( p = .000). No differences in PPTs prior to each condition were observed but PPTs were significantly higher in the right and left knees after the NMES contractions ( p = .000, p = .013, respectively) and after the NxES ( p = .006, P -.006, respectively). Pain during NMES and NxES did not correlate with pain inhibition ( p > .05). Self-reported pain sensitivity correlated with pain during NxES. Conclusion NxES and NMES produced higher PPTs in both knees but not in the finger, suggesting that the mechanisms responsible for the reduction in pain are located in the spinal cord and local tissues. Pain reduction was elicited during the NxES and NMES conditions regardless of the self-reported pain ratings. When NMES is used for muscle strengthening significant pain reduction can also occur, which is an unintended benefit of the intervention that could improve functional outcomes in patients.

The purpose of this study was to investigate the influence of sensitivity to sensory input, including pain, on the conditioned pain modulation (CPM) effect of oxious Electrical Stimulation (NxES). Seventeen healthy participants (24.8 (+/- 2) years) were enrolled in this study that was approved by the IRB. Each person participated in a familiarization session, and 2 testing sessions 24 hours apart. Sensory sensitivity was assessed with the Sensory Hypersensitivity Scale, touch and heat/cold detection thresholds. Pain sensitivity was assessed with the Pain Sensitivity Questionnaire, heat/cold pain thresholds, and pressure pain threshold (PPT). Pain modulation was assessed with temporal summation (TS) and CPM involved a test stimulus of PPT and conditioning stimulus was immersion in a cold water bath for 2 min. The NxES: 20 min of electrical stimulation (400 μs pulse duration, 50 pulses/s; 10s on:10s off; intensity was maximum tolerated). The difference between PPT before and after the NxES comprised the treatment effect. Neither Sensitivity to touch or temperature sensations nor pain sensitivity related to the treatment effect of the NxES. A higher the amplitude of pain perception of NxES was associated with greater treatment effect. The NxES was effective in inhibiting pain and reduced the extent of pain facilitation 24 hours after the treatment. CPM was no different after the NxES. The finding suggests that people who are more sensitive to sensations also experience pain inhibition from NxES. The nervous system is not as "reactive" to pain after a treatment of NxES and the lack of change in the CPM after the treatment of NXES suggests that artificially inducing pain inhibition with NXES does not interfere with the normal pain inhibitory function of the nervous system. Thus, any inhibition due to NXES treatment could augment that which is produced by a patient's own nervous system. The purpose of this study was to investigate the influence of sensitivity to sensory input, including pain, on the conditioned pain modulation (CPM) effect of oxious Electrical Stimulation (NxES). Seventeen healthy participants (24.8 (+/- 2) years) were enrolled in this study that was approved by the IRB. Each person participated in a familiarization session, and 2 testing sessions 24 hours apart. Sensory sensitivity was assessed with the Sensory Hypersensitivity Scale, touch and heat/cold detection thresholds. Pain sensitivity was assessed with the Pain Sensitivity Questionnaire, heat/cold pain thresholds, and pressure pain threshold (PPT). Pain modulation was assessed with temporal summation (TS) and CPM involved a test stimulus of PPT and conditioning stimulus was immersion in a cold water bath for 2 min. The NxES: 20 min of electrical stimulation (400 μs pulse duration, 50 pulses/s; 10s on:10s off; intensity was maximum tolerated). The difference between PPT before and after the NxES comprised the treatment effect. Neither Sensitivity to touch or temperature sensations nor pain sensitivity related to the treatment effect of the NxES. A higher the amplitude of pain perception of NxES was associated with greater treatment effect. The NxES was effective in inhibiting pain and reduced the extent of pain facilitation 24 hours after the treatment. CPM was no different after the NxES. The finding suggests that people who are more sensitive to sensations also experience pain inhibition from NxES. The nervous system is not as "reactive" to pain after a treatment of NxES and the lack of change in the CPM after the treatment of NXES suggests that artificially inducing pain inhibition with NXES does not interfere with the normal pain inhibitory function of the nervous system. Thus, any inhibition due to NXES treatment could augment that which is produced by a patient's own nervous system.

Purpose: People with knee osteoarthritis (OA) are often encouraged to maintain strong quadriceps muscles because they are associated with higher function during daily activities. Quadriceps strength is often related to function, but maximum effort is not required for many activities of daily living. Muscle activation across multiple force levels may provide better insight into factors that are important for functional activities. The purpose of this study was to examine the magnitude and consistency of the times to peak force (T2PkF) and half-relaxation times (HalfR) across a range of force outputs in people with knee OA compared to controls. We also sought to relate the T2PkF and HalfR to free (Fr) and fast (Fa) walking speeds (WS), and stair climbing time (SCT). We hypothesized that people with knee OA would have slower mean and greater variability in T2PkF and would have slower walking speeds and stair climbing times. We also hypothesized that faster and more consistent T2PkF would relate to faster walking speeds and stair climbing time. Methods: Twenty-five people (12♀) with knee OA (age 52–81 yrs, mean = 65.3, s = 8.0) and 22 people (11♀) without knee OA (ages 50–78 yrs, mean = 62.7, s = 7.6) were recruited. Subjects sat in a muscle testing chair (Biodex, Shirley, NY) and a force transducer (SM-250, Interface Inc., Scotsdale, AZ, USA) was secured to the lower leg ∼2 cm above the lateral malleolus. Subjects completed maximal voluntary isometric contractions (MVIC) of the quadriceps muscles. Central Activation Ratio (CAR), a measure of the failure of central motor drive, was assessed using the burst superimposition test. Subjects performed a series of rapid isometric force pulses by extending the knee "as fast as possible and then relax immediately" at "small, medium and large" force levels. The T2PkF and HalfR were calculated for each force pulse and the means and standard deviations of all of the force pulses were used as variables for each subject in the analysis. The standard deviation of all of the force pulses was used as a measure of variability. Stair Climbing Time (SCT) was measured as walked up and down a flight of 12 steps as fast as they could comfortably and safely. Free and Fast walking speeds were measured from a reflective marker on the pelvis during 3D motion capture trials that have been reported elsewhere. Results: OA subjects were slower than controls in both walking speeds and in stair climbing time. Mean T2PkF was slower in the OA subjects although it was just outside of the range for statistical significance at p ≤ 0.05. Across all subjects, the T2PkF had a modest negative correlation with FaWS (r = −.291, p = .047); thus the slower the T2PkF the slower the walking speed. Similarly, HalfR correlated with FrWS (r = .329, p = .024) such that slower relaxation times were also related to slower walking speeds. Although the HalfR was no different by group, the OA subjects were less variable in their HalfR than control subjects. Unexpectedly, the HalfR variability correlated with both (FrWS r = .564, p = .000) and FaWS (r = .366, p = .011) demonstrating that more variable the relaxation times related to faster walking speeds. It is possible that the higher variability of HalfR in the control subjects was due to their ability to reach faster relaxation during some of the force pulses. Faster relaxation along with faster time to peak force would likely improve stability in the knee that is subjected to rapid changes in environmental conditions during daily activities. The correlation between T2PkF and CAR (r = −.347, p = .038) demonstrates that people with greater central activation failure also have slower T2PkF in the quadriceps. Conclusions: The speed of muscle contractions and relaxation provide new insights into motor control mechanisms during submaximal quadriceps contractions that relate to daily function in people with knee OA and controls. Further investigation of motor performance over a wide range of force levels is needed to fully understand the importance of these muscle characteristics.Tabled 1Table 1ControlOAp valueFree speed (m/s)1.47 (0.17)1.26 (0.22)0.001Fast speed (m/s)2.06 (0.32)1.79 (0.24)0.002Stair climbing time (s)8.8 (1.8)13.4 (5.1)0.000Avg T2PkF (s)0.143 (0.021)0.155 (0.020)0.058Std Dev of HalfR Time (s)0.081 (0.016)0.069 (0.017)0.018 Open table in a new tab

Adults with stroke have difficulty avoiding obstacles when walking, especially when a time constraint is imposed. The Four Square Step Test (FSST) evaluates dynamic balance by requiring individuals to step over canes in multiple directions while being timed, but many people with stroke are unable to complete it. The purposes of this study were to (1) modify the FSST by replacing the canes with tape so that more persons with stroke could successfully complete the test and (2) examine the reliability and validity of the modified version. Fifty-five subjects completed the Modified FSST (mFSST) by stepping over tape in all four directions while being timed. The mFSST resulted in significantly greater numbers of subjects completing the test than the FSST (39/55 [71%] and 33/55 [60%], respectively) (p < 0.04). The test-retest, intrarater, and interrater reliability of the mFSST were excellent (intraclass correlation coefficient ranges: 0.81-0.99). Construct and concurrent validity of the mFSST were also established. The minimal detectable change was 6.73 s. The mFSST, an ideal measure of dynamic balance, can identify progress in people with stroke in varied settings and can be completed by a wide range of people with stroke in approximately 5 min with the use of minimal equipment (tape, stop watch).

OBJECTIVE:Quadriceps weakness exists in people with knee osteoarthritis (OA), but other muscle factors like rate of force development (RFD) may also be affected by knee OA. The purpose of this study was to determine if people with knee OA have deficits in quadriceps RFD, determine if quadriceps RFD would improve predicting knee joint power absorption and generation during free and fast walking, and determine if RFD would improve predicting functional outcomes.METHODS:26 subjects with knee OA and 23 healthy control subjects performed maximal voluntary isometric strength (MVIC) and RFD measures of the quadriceps. Subjects also underwent a 3-D motion analysis of both self-selected free and self-selected fast walking speeds. Joint kinetics were calculated from inverse dynamics.RESULTS:RFD was not different by group (p = 0.763), however, the OA subjects generated the highest peak RFD at a lower % MVIC (p = 0.008). Controls walked significantly faster at both free and fast walking speeds (p = 0.001, p = 0.029). Knee angles at heel strike and peak knee extension were lower (p = 0.004, p = 0.027) in the OA group. During fast walking knee power generation was higher in controls (p = 0.028). MVIC and force of highest peak RFD predicted KOOS-ADL score in the OA subjects, but only MVIC predicted stair climbing time.CONCLUSIONS:The submaximal force at which peak RFD occurs plays a significant role in knee joint power as well as functional measures in the OA subjects, providing further evidence that factors other than maximal strength are also important in people with knee OA.

Background and Purpose: In rehabilitation, examining how variables change over time can help define the minimal number of training sessions required to produce a desired change. The purpose of this study was to identify the time course of changes in gait biomechanics and walking function in persons with chronic stroke. Methods: Thirteen persons who were more than 6 months poststroke participated in 12 weeks of fast treadmill training combined with plantar- and dorsiflexor muscle functional electrical stimulation (FastFES). All participants completed testing before the start of intervention, after 4, 8, and 12 weeks of FastFES locomotor training. Results: Peak limb paretic propulsion, paretic limb propulsive integral, peak paretic limb knee flexion (P < 0.05 for all), and peak paretic trailing limb angle (P < 0.01) improved from pretraining to 4 weeks but not between 4 and 12 weeks. Self-selected walking speed and 6-minute walk test distance improved from pretraining to 4 weeks and from 4 to 12 weeks (P < 0.01 and P < 0.05, respectively for both). Timed Up & Go test time did not improve between pretraining and 4 weeks, but improved by 12 weeks (P = 0.24 and P < 0.01, respectively). Discussion and Conclusions: The results demonstrate that walking function improves with a different time course compared with gait biomechanics in response to a locomotor training intervention in persons with chronic stroke. Thirty-six training sessions were necessary to achieve an increase in walking speed that exceeded the minimally clinically important difference. These findings should be considered when designing locomotor training interventions after stroke. Video Abstract available (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A63) for more insights from the authors.

Neuromuscular control relies on sensory feedback that influences responses to changing external demands, and the normal response is for movement and muscle activation patterns to adapt to repeated perturbations. People with knee osteoarthritis (OA) are known to have pain, quadriceps weakness, and neuromotor deficits that could affect adaption to external perturbations. The aim of this study was to analyze neuromotor adaptation during walking in people with knee OA (n = 38) and controls (n = 23). Disability, quadriceps strength, joint space width, malalignment, and proprioception were assessed. Kinematic and EMG data were collected during undisturbed walking and during perturbations that caused lateral translation of the foot at initial contact. Knee excursions and EMG magnitudes were analyzed. Subjects with OA walked with less knee motion and higher muscle activation and had greater pain, limitations in function, quadriceps weakness, and malalignment, but no difference was observed in proprioception. Both groups showed increased EMG and decreased knee motion in response to the first perturbation, followed by progressively decreased EMG activity and increased knee motion during midstance over the first five perturbations, but no group differences were observed. Over 30 trials, EMG levels returned to those of normal walking. The results illustrate that people with knee OA respond similarly to healthy individuals when exposed to challenging perturbations during functional weight-bearing activities despite structural, functional, and neuromotor impairments. Mechanisms underlying the adaptive response in people with knee OA need further study.

Objective: People with knee osteoarthritis (OA) are thought to walk with high loads at the knee which are yet to be quantified using modeling techniques that account for subject specific electromyography (EMG) patterns, kinematics and kinetics. The objective was to estimate medial and lateral loading for people with knee OA and controls using an approach that is sensitive to subject specific muscle activation patterns.Methods: Sixteen OA and 12 control (C) subjects walked while kinematic, kinetic and EMG data were collected. Muscle forces were calculated using an EMG-Driven model and loading was calculated by balancing the external moments with internal muscle and contact forces.Results: OA subjects walked slower and had greater laxity, static and dynamic varus alignment, less flexion and greater knee adduction moment (RAM). Loading [normalized to body weight (BW)] was no different between the groups but OA subjects had greater absolute medial load than controls and maintained a greater %total load on the medial compartment. These patterns were associated with body mass, sagittal and frontal plane moments, static alignment and close to significance for dynamic alignment. Lateral compartment unloading during mid-late stance was observed in 50% of OA subjects.Conclusions: Loading for control subjects was similar to data from instrumented prostheses. Knee OA subjects had high medial contact loads in early stance and half of the OA cohort demonstrated lateral compartment lift-off. Results suggest that interventions aimed at reducing BW and dynamic malalignment might be effective in reducing medial compartment loading and establishing normal media-lateral load sharing patterns. (C) 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

6.61), and antibiotics only (5.10) (pϽ0.00000001).GAG assay revealed no significant difference among treatment groups.Discussion: Results of this study show the addition of an adenosine2A agonist to antibiotic therapy diminishes WBC chemotaxis and inflammation in the joint, while not compromising the clearance of intraarticular bacteria.Early bacterial clearance with modulation of the inflammatory response may prevent the long-term arthritic effects of joint sepsis.Results of this study may augment the current treatment regimen and influence the future treatment of septic arthritis and prevent the associated morbidity.

Background People with stroke have reduced walking activity. It is not known whether this deficit is due to a reduction in all aspects of walking activity or only in specific areas. Understanding specific walking activity deficits is necessary for the development of interventions that maximize improvements in activity after stroke. Objective The purpose of this study was to examine walking activity in people poststroke compared with older adults without disability. Design A cross-sectional study was conducted. Methods Fifty-four participants poststroke and 18 older adults without disability wore a step activity monitor for 3 days. The descriptors of walking activity calculated included steps per day (SPD), bouts per day (BPD), steps per bout (SPB), total time walking per day (TTW), percentage of time walking per day (PTW), and frequency of short, medium, and long walking bouts. Results Individuals classified as household and limited community ambulators (n=29) did not differ on any measure and were grouped (HHA-LCA group) for comparison with unlimited community ambulators (UCA group) (n=22) and with older adults without disability (n=14). The SPD, TTW, PTW, and BPD measurements were greatest in older adults and lowest in the HHA-LCA group. Seventy-two percent to 74% of all walking bouts were short, and this finding did not differ across groups. Walking in all categories (short, medium, and long) was lowest in the HHA-LCA group, greater in the UCA group, and greatest in older adults without disability. Limitations Three days of walking activity were captured. Conclusions The specific descriptors of walking activity presented provide insight into walking deficits after stroke that cannot be ascertained by looking at steps per day alone. The deficits that were revealed could be addressed through appropriate exercise prescription, underscoring the need to analyze the structure of walking activity.

It is important to know the magnitude and patterns of joint loading in people with knee osteoarthritis (OA), since altered loads are implicated in onset and progression of the disease. We used an EMG‐driven forward dynamics model to estimate joint loads during walking in a subject with knee OA and a healthy control subject. Kinematic, kinetic, and surface EMG data were used to predict muscle forces using a Hill‐type muscle model. The muscle forces were used to balance the frontal plane moment to obtain medial and lateral condylar loads. Loads were normalized to body weight (BWs) and the mean of three trials taken. The OA subject had greater medial and lower lateral loads compared to the control subject. Seventy‐five to 80% of the total load was borne on the medial compartment in the control subject, compared to 90–95% in the OA subject. In fact, complete lateral unloading occurred during midstance for the OA subject. Loading for the healthy subject was consistent with the data from instrumented knee studies. In the future, the model can be used to analyze the impact of various interventions to reduce the loads on the medial compartment in people with knee OA. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:377–383, 2012

People with knee OA experience pain and the sensation of buckling in their knees that leads to diminished function. Maximum quadriceps force production relates to high function in this group, however, maximum force is rarely used during daily activities. Rate of muscle force development (RFD) is important in maintaining balance and declines with age and disuse, but it is unclear what relationship RFD has with function in people with knee OA. PURPOSE: To examine the relationship between quadriceps RFD and knee function in 3 groups: people with knee OA whose knees were stable (OAS) unstable (OAU) and controls (C). METHODS: Knee joint stiffness and maximum volitional isometric force was measured in 28 people with knee OA (15 OAS and 13 OAU) and 21 C. Functional measures included the KOOS and stair climbing test. The peak instantaneous RFD (RFDi) and average RFD (RFDa) over the interval from 0-200 msec were compared between groups using a one-way ANOVA and post-hoc tests. Pearson's correlation coefficients were used to examine relationships. RESULTS: Significant differences between groups were found in the RFDa (F=5.563, p=.007) and in both relaxed short range and total stiffness (F=4.205, p=.022 and 4.916, p=.012). Post hoc tests revealed that the OAU subjects had higher RFDa and had a higher short range stiffness than controls (p=.006 and p=.021). OAU also had a greater relaxed total stiffness than the OA stable group (p=.010). RFDa correlated negatively with the stair climbing time (r= -0.544, p=.036) in the OAS group. The peak RFDi correlated positively with the KOOS -ADL scores in the OAU group only (r=0.570, p=.042). In the OAU group the peak RFDi and RFDa significantly correlated with the KOOS symptom scores (r=-0.622, p=.023, r=0.606, p=.028) respectively. CONCLUSION: The relationship between RFD and knee function and symptoms in people with knee OA who experience buckling suggests an attempt to stabilize the knee joint. Higher knee joint stiffness in the OAU subjects may allow for these increases in RFD. Accurately assessing and understanding the role of RFD in knee OA may indicate that rehabilitation should involve activities relating to speed in addition to the force of quadriceps contraction. Funded By: NIH P20 RR16458, NIH S10RR022396, ACR REF Health Professional Graduate Student Research Preceptorship

Background Fast treadmill training improves walking speed to a greater extent than training at a self-selected speed after stroke. It is unclear whether fast treadmill walking facilitates a more normal gait pattern after stroke, as has been suggested for treadmill training at self-selected speeds. Given the massed stepping practice that occurs during treadmill training, it is important for therapists to understand how the treadmill speed selected influences the gait pattern that is practiced on the treadmill. Objective The purpose of this study was to characterize the effect of systematic increases in treadmill speed on common gait deviations observed after stroke. Design A repeated-measures design was used. Methods Twenty patients with stroke walked on a treadmill at their self-selected walking speed, their fastest speed, and 2 speeds in between. Using a motion capture system, spatiotemporal gait parameters and kinematic gait compensations were measured. Results Significant improvements in paretic- and nonparetic-limb step length and in single- and double-limb support were found. Asymmetry of these measures improved only for step length. Significant improvements in paretic hip extension, trailing limb position, and knee flexion during swing also were found as speed increased. No increases in circumduction or hip hiking were found with increasing speed. Limitations Caution should be used when generalizing these results to survivors of a stroke with a self-selected walking speed of less than 0.4 m/s. This study did not address changes with speed during overground walking. Conclusions Faster treadmill walking facilitates a more normal walking pattern after stroke, without concomitant increases in common gait compensations, such as circumduction. The improvements in gait deviations were observed with small increases in walking speed.

Purpose:The aim of this study was to develop bioinformatic methods for label-free quantification of proteins identified in the secretome of canine articular cartilage using high throughput tandem mass spectrometry.Methods: Cartilage was obtained from animals euthanized for purposes other than research.Canine cartilage explants were pre-incubated in serum-free DMEM supplemented with 2% penicillin and streptomycin in a CO 2 incubator for 24 hours at 37°C.The explants were then incubated alone (control media), or with recombinant canine IL-1b (10 ng/ml), the non-steroidal anti-inflammatory drug carprofen (Rimadyl, Pfizer Animal Health, 1 mg/ml) or carprofen and IL-1b combined (1 mg/ml and 10 ng/ml respectively).After 5 days in culture, cell-free supernatants were removed and representative samples were selected for proteomic analysis.Mascot was used to analyze the data from each sample, with the Uniprot database, and the results were imported into the Trans-Proteomic Pipeline (TPP).TPP includes both PeptideProphet and ProteinProphet for evaluation of the Mascot assignments.Two label-free spectral counting based quantification software, PepC and APEX, were then used to analyze the output of ProteinProphet.From the APEX results classification models were built, using WEKA, to differentiate between control and IL-1b samples.A number of different classifiers were tested including Naive Bayes, support vector machines, C4.5, IBk and Random Forest and were evaluated using 10-fold cross validation.Results: The label-free quantification methods identified a number of proteins as significantly different between the treatments.In particular matrix metalloproteinase-3 (MMP-3) and thrombospondin-1 (TSP-1) were increased in the IL-1b treated samples when compared to the controls.This supports previously primary experimental data from equine and canine explant models of articular cartilage.Other proteins increased in IL-1b samples included cartilage oligomeric matrix protein (COMP) and triosephosphate isomerase (TPIS).The classification models built using WEKA were able to accurately label the control and IL-1b samples.The Naive Bayes method performed best and correctly assigned all samples to their respective treatments.Classification was also performed on all four treatments, however the similarity between the control and carprofen only treated samples decreased the classification accuracy. Conclusions:The label-free quantification methods for analysis of mass spectrometry data discussed here have been found to be suitable for determining potential biomarkers of OA and for differentiating between control and IL-1b treated samples using machine learning.The methods may now be implemented on larger datasets to support these results and determine any further potential biomarker.The classification method developed may also be used to identify novel biomarkers of OA, as the proteins used in the machine learning models were found in significantly different quantities across the different treatments.

Smart Knee Brace (SKB) is designed to provide controlled perturbations to the human knee during walking. A dynamic model of human walking is then used to evaluate the human applied joint torques to hypothesize how the human neuro-muscular system modulates the joint torques as a response to the perturbations caused on the gait. Our results show that the neuro-muscular response to perturbations can be reasonably well characterized by including the following features in the model: (i) normal gait in the absence of perturbation, (ii) corrective torque at a joint in response to the error at that joint and other joints, (iii) a characteristic time shift in the response. We believe that these parameters can be used to characterize subjects who are more prone to falling under gait perturbations.

Gait dysfunctions are highly prevalent in individuals post-stroke and affect multiple lower extremity joints. Recent evidence suggests that treadmill walking at faster than self-selected speeds can help improve post-stroke gait impairments. Also, the combination of functional electrical stimulation (FES) and treadmill training has emerged as a promising post-stroke gait rehabilitation intervention. However, the differential effects of combining FES with treadmill walking at the fast versus a slower, self-selected speed have not been compared previously. In this study, we compared the immediate effects on gait while post-stroke individuals walked on a treadmill at their self-selected speed without FES (SS), at the SS speed with FES (SS-FES), at the fastest speed they are capable of attaining (FAST), and at the FAST speed with FES (FAST-FES). During SS-FES and FAST-FES, FES was delivered to paretic ankle plantarflexors during terminal stance and to paretic dorsiflexors during swing phase. Our results showed improvements in peak anterior ground reaction force (AGRF) and trailing limb angle during walking at FAST versus SS. FAST-FES versus SS-FES resulted in greater peak AGRF, trailing limb angle, and swing phase knee flexion. FAST-FES resulted in further increase in peak AGRF compared to FAST. We posit that the enhancement of multiple aspects of post-stroke gait during FAST-FES suggest that FAST-FES may have potential as a post-stroke gait rehabilitation intervention.

Altered muscle coordination strategies in persons with knee osteoarthritis (OA) result in an increase in co-contraction of the quadriceps and hamstrings during walking. While this may increase intersegmental joint contact force and expedite disease progression, it is not currently known whether the magnitude of co-contraction increases with a progressive loss of joint space or whether the level of co-contraction is dependent on walking speed. The purposes of this study were to (1) determine if co-contraction increased with OA severity and (2) discern whether differences in co-contraction were a result of altered freely chosen walking speeds or rather an inherent change associated with disease progression. Forty-two subjects with and without knee osteoarthritis were included in the study. Subjects were divided into groups based on disease severity. When walking at a controlled speed of 1.0m/s, subjects with moderate and severe knee OA showed significantly higher co-contraction when compared to a healthy control group. At freely chosen walking speeds only the moderate OA group had significantly higher co-contraction values. Increased walking speed also resulted in a significant increase in co-contraction, regardless of group. The results of this study demonstrate that persons with knee OA develop higher antagonistic muscle activity. This occurs despite differences in freely chosen walking speed. Although subjects with OA had higher co-contraction than the control group, co-contraction may not increase with disease severity.

Background Foot drop is a common gait impairment after stroke. Functional electrical stimulation (FES) of the ankle dorsiflexor muscles during the swing phase of gait can help correct foot drop. Compared with constant-frequency trains (CFTs), which typically are used during FES, novel stimulation patterns called variable-frequency trains (VFTs) have been shown to enhance isometric and nonisometric muscle performance. However, VFTs have never been used for FES during gait. Objective The purpose of this study was to compare knee and ankle kinematics during the swing phase of gait when FES was delivered to the ankle dorsiflexor muscles using VFTs versus CFTs. Design A repeated-measures design was used in this study. Participants Thirteen individuals with hemiparesis following stroke (9 men, 4 women; age=46–72 years) participated in the study. Methods Participants completed 20- to 40-second bouts of walking at their self-selected walking speeds. Three walking conditions were compared: walking without FES, walking with dorsiflexor muscle FES using CFTs, and walking with dorsiflexor FES using VFTs. Results Functional electrical stimulation using both CFTs and VFTs improved ankle dorsiflexion angles during the swing phase of gait compared with walking without FES (X̅±SE=−2.9°±1.2°). Greater ankle dorsiflexion in the swing phase was generated during walking with FES using VFTs (X̅±SE=2.1°±1.5°) versus CFTs (X̅±SE=0.3±1.3°). Surprisingly, dorsiflexor FES resulted in reduced knee flexion during the swing phase and reduced ankle plantar flexion at toe-off. Conclusions The findings suggest that novel FES systems capable of delivering VFTs during gait can produce enhanced correction of foot drop compared with traditional FES systems that deliver CFTs. The results also suggest that the timing of delivery of FES during gait is critical and merits further investigation.