Single-limb Stance Research Articles

Predictors of static balance in ambulatory persons with multiple sclerosis.

People with multiple sclerosis (MS) experience a high rate of falls and have decreased static and dynamic balance. The purpose of this study was to determine best predictors of static standing balance, as measured by a single limb stance (SLS) timed test, in ambulatory persons with MS (PwMS) from among commonly used medical and rehabilitation clinical tests. Ambulatory PwMS participated in a single test session. Medical exam data gathered included the Function System (FS) neurologic exam and Expanded Disability Status Score (EDSS). A variety of commonly administered rehabilitation clinical tests addressing static balance, dynamic balance, gait endurance, functional lower extremity strength, abdominal and respiratory muscle strength were completed. Descriptive statistics, Pearson product moment correlations, and forward step-wise linear regressions were calculated. Twenty-eight ambulatory PwMS completed this study. Mean age was 54.74 years. Mean SLS score was 14.6 s. Pyramidal, sensory, bowel/bladder, and visual FS scores and the EDSS were significantly correlated with SLS. Maximal step length scores were significantly correlated with SLS at P less than 0.05 and the Functional Stair Test (FST) and 6-min walk test were correlated with SLS at P less than 0.10. Medical exam data EDSS and FS sensory explain 72.1% of the variance in SLS scores. Rehabilitation exam data FS sensory and FST explain 68.8% of the variance. The FS sensory, EDSS, and FST together explain 73.3% of the variance.

Pilates vs. Balance Training in Healthy Community-Dwelling Seniors: a 3-arm, Randomized Controlled Trial.

The study examined effects of traditional balance vs. mat-based Pilates training on balance and trunk strength in healthy community dwellers. Forty-eight seniors were either stratified to a balance training group (BAL, n=16, 69.1 (SD 5.8) y), Pilates training group (PIL, n=17, 70.8 (6.5) y) or control group (CON, n=15, 69.2 (6.1) y). BAL performed traditional balance training, while PIL conducted mat-based Pilates-exercises (8 weeks, 2 sessions/week 66 min each). Balance performance (single limb stance and perturbed kneeling, Y-Balance test), dynamic and isometric trunk flexion and extension were assessed during pre- and post-testing. According to the magnitude-based inference approach, substantial positive effects in favor of BAL compared to CON were found for the Y-balance score (right leg, effect size (d)=0.68; left leg, d=0.56), trunk extension (d=0.68) and single leg stance (right leg, d=0.61; left leg, d=0.38). Dynamic (d=0.32) and isometric (d=0.15) trunk flexion revealed unclear effects. For the Y-balance score (right leg, d=0.48, left leg, d=0.75) and single leg stance (right leg, +d=0.61%; left leg, d=0.67), interestingly, BAL substantially exceeded PIL. PIL vs. CON revealed unclear effects for most parameters (0.05

Pilates vs. Balance Training in Health Community-Dwelling Seniors: a 3-arm, Randomized Controlled Trial.

The study examined effects of traditional balance vs. mat-based Pilates training on balance and trunk strength in healthy community dwellers. Forty-eight seniors were either stratified to a balance training group (BAL, n=16, 69.1 (SD 5.8) y), Pilates training group (PIL, n=17, 70.8 (6.5) y) or control group (CON, n=15, 69.2 (6.1) y). BAL performed traditional balance training, while PIL conducted mat-based Pilates-exercises (8 weeks, 2 sessions/week 66 min each). Balance performance (single limb stance and perturbed kneeling, Y-Balance test), dynamic and isometric trunk flexion and extension were assessed during pre- and post-testing. According to the magnitude-based inference approach, substantial positive effects in favor of BAL compared to CON were found for the Y-balance score (right leg, effect size (d)=0.68; left leg, d=0.56), trunk extension (d=0.68) and single leg stance (right leg, d=0.61; left leg, d=0.38). Dynamic (d=0.32) and isometric (d=0.15) trunk flexion revealed unclear effects. For the Y-balance score (right leg, d=0.48, left leg, d=0.75) and single leg stance (right leg, +d=0.61%; left leg, d=0.67), interestingly, BAL substantially exceeded PIL. PIL vs. CON revealed unclear effects for most parameters (0.05<d<0.36). Mat-based Pilates training did not cause relevant adaptations in trunk strength and balance performance, whereas balance training substantially improved balance and trunk strength.

Stress and stability of plate-screw fixation and screw fixation in the treatment of Schatzker type IV medial tibial plateau fracture: a comparative finite element study.

PurposeThe purpose of this study is to compare the stress and stability of plate-screw fixation and screw fixation in the treatment of Schatzker type IV medial tibial plateau fracture.MethodsA three-dimensional (3D) finite element model of the medial tibial plateau fracture (Schatzker type IV fracture) was created. An axial force of 2500 N with a distribution of 60 % to the medial compartment was applied to simulate the axial compressive load on an adult knee during single-limb stance. The equivalent von Mises stress, displacement of the model relative to the distal tibia, and displacement of the implants were used as the output measures.ResultsThe mean stress value of the plate-screw fixation system was 18.78 MPa, which was significantly (P < 0.001) smaller than that of the screw fixation system. The maximal value of displacement (sum) in the plate-screw fixation system was 2.46 mm, which was lower than that in the screw fixation system (3.91 mm). The peak stress value of the triangular fragment in the plate-screw fixation system model was 42.04 MPa, which was higher than that in the screw fixation model (24.18 MPa). But the mean stress of the triangular fractured fragment in the screw fixation model was significantly higher in terms of equivalent von Mises stress (EVMS), x-axis, and z-axis (P < 0.001).ConclusionsThis study demonstrated that the load transmission mechanism between plate-screw fixation system and screw fixation system was different and the stability provided by the plate-screw fixation system was superior to the screw fixation system.

Lower Limb Interjoint Postural Coordination One Year after First-Time Lateral Ankle Sprain.

Longitudinal analyses of participants with a history of lateral ankle sprain are lacking. This investigation combined measures of lower limb interjoint coordination and stabilometry to evaluate static unipedal stance with the eyes open (condition 1) and closed (condition 2) in a group of participants with chronic ankle instability (CAI) compared to lateral ankle sprain "copers" (both recruited 12 months after sustaining an acute first-time lateral ankle sprain) and a group of noninjured controls. Twenty-eight participants with CAI, 42 lateral ankle sprain "copers," and 20 noninjured controls completed three 20-s single-limb stance trials in conditions 1 and 2. An adjusted coefficient of multiple determination statistic was used to compare stance limb three-dimensional kinematic data for similarity to establish patterns of interjoint coordination. The fractal dimension of the stance limb center of pressure path was also calculated. Between-group analyses revealed that participants with CAI displayed notable increases in ankle-hip linked coordination compared with both lateral ankle sprain "copers" (-0.52 (1.05) vs 0.28 (0.9), P = 0.007) and controls (-0.52 (1.05) vs 0.63 (0.64), P = 0.006) in condition 1 and compared with controls only (0.62 (1.92) vs 0.1 (1.0) P = 0.002) in condition 2. Participants with CAI also exhibited a decrease in the fractal dimension of the center-of-pressure path during condition 2 compared with both controls and lateral ankle sprain "copers." Participants with CAI present with a hip-dominant strategy of eyes-open and eyes-closed static unipedal stance. This coincided with reduced complexity of the stance limb center of pressure path in the eyes-closed condition.

EFFECTIVENESS OF ICE PACK VERSUS COLD WATER IMMERSION ON STATIC AND DYNAMIC BALANCE IN ANKLE SPRAIN

Results: The static balance for both the groups showed a decrease number of errors in tandem stance and double limb stance after ice pack application, Whereas there is no difference found in single limb stance. Dynamic balance increased in ice pack application compared to ice water immersion. Conclusion: Results after 10 days showed marked variation suggesting better improvements in both static and dynamic balance by ice pack application than cold water immersion for ankle sprain athletes.

Patellar taping alters knee kinematics during step descent in individuals with a meniscal injury: An exploratory study

BackgroundMeniscus lesions are common musculoskeletal knee injuries which often lead to pain, limitation and compensations during functional tasks, such as descending stairs. This study investigated the effect of patellar taping with tension and without tension on three-dimensional (3D) kinematics of the knee during a slow step descent task in patients with meniscal lesions. MethodsTen patients diagnosed with a meniscal lesion, confirmed by magnetic resonance imaging, underwent five, step descent movements at slow speed under three different conditions: 1) no taping; 2) tension-free taping; and 3) patellar taping with medial tension. 3D kinematic data were recorded from the injured knee using an eight-camera infrared Vicon motion analysis system. Maximum and minimum angle values and total range of motion (maximum/minimum value) in three movement planes during single-limb stance were compared using a repeated measure ANOVA. FindingsResults showed a significant increase in the maximum and minimum angle value in the sagittal plane (mean differences=2.4° and 4.2°, respectively) and a decrease in the transverse plane (−6.3° and −2.2°, respectively) for the patellar taping condition compared to the no taping condition. A decreased rotational angle range when comparing the patellar taping to the no taping (−4.1°) and tension-free taping (−3.1°) conditions was also observed. These changes remained significant when pain was considered as a covariate in the analysis. The tension applied to the patellar tape played a role in controlling the sagittal and transverse plane step-down movement among patients in our study. InterpretationThese results support the use of patellar taping with a medially oriented tension to help to reduce the transversal plane movement of the knee in this population and they bring new light to the taping effect.

Biomechanical demands of the 2-step transitional gait cycles linking level gait and stair descent gait in older women

Stair descent is an inherently complex form of locomotion posing a high falls risk for older adults, specifically when negotiating the transitional gait cycles linking level gait and descent. The aim of this study was to enhance our understanding of the biomechanical demands by comparing the demands of these transitions. Lower limb kinematics and kinetics of the 2-step transitions linking level and descent gait at the top (level-to-descent) and the bottom (descent-to-level) of the staircase were quantified in 36 older women with no falls history. Despite undergoing the same vertical displacement (2-steps), the following significant (p<.05) differences were observed during the top transition compared to the bottom transition: reduced step velocity; reduced hip extension and increased ankle dorsiflexion (late stance/pre-swing); reduced ground reaction forces, larger knee extensor moments and powers (absorption; late stance); reduced ankle plantarflexor moments (early and late stance) and increased ankle powers (mid-stance). Top transition biomechanics were similar to those reported previously for continuous descent. Kinetic differences at the knee and ankle signify the contrasting and prominent functions of controlled lowering during the top transition and forward continuance during the bottom transition. The varying musculoskeletal demands encountered during each functional sub-task should be addressed in falls prevention programmes with elderly populations where the greatest clinical impact may be achieved. Knee extensor eccentric power through flexion exercises would facilitate a smooth transition at the top and improving ankle plantarflexion strength during single and double limb stance activities would ease the transition into level gait following continuous descent.

Gait analysis in Down syndrome pediatric patients using a sheet‐type gait analyzer: Pilot study

Children with Down syndrome (DS), who are likely to suffer from a large number of musculoskeletal problems, tend to have a unique pattern of walking in clinical settings. Despite such apparent uniqueness, few studies have empirically investigated gait development pattern in DS children, especially at an earlier age. We therefore conducted gait analysis in young DS children who are prescribed insoles, to explore how their gait patterns develop, using the gait parameters identified by Sutherland et al. as determinants of gait maturity of typical children. Participants consisted of 63 DS children (31 boys) aged 1-6 years (mean, 4 years 1 month) with a diagnosis of flat feet who were prescribed orthotic insoles. A 2.4 m sheet-type gait analyzer was used to analyze gait pattern. We measured the following variables: walking velocity (cm/min), cadence (steps/min), step length (cm), and single-limb stance phase ratio (%), and examined their relationship with age on regression analysis. Walking velocity and step length were significantly and positively related to age. Cadence was also significantly, but negatively associated with age. In contrast, SLS phase ratio did not have a statistically significant relationship with age. Down syndrome children have unique gait development patterns. Although walking velocity, cadence, and step length were found to develop with age, as in typical children, SLS phase ratio did not change with age in DS children. Further studies with a larger sample are necessary to replicate these findings.

Effects of constrained arm swing on vertical center of mass displacement during walking

The purpose of this study was to determine the effects of constraining arm swing on the vertical displacement of the body's center of mass (COM) during treadmill walking and examine several common gait variables that may account for or mask differences in the body's COM motion with and without arm swing. Participants included 20 healthy individuals (10 male, 10 female; age: 27.8±6.8 years). The body's COM displacement, first and second peak vertical ground reaction forces (VGRFs), and lowest VGRF during mid-stance, peak summed bilateral VGRF, lower extremity sagittal joint angles, stride length, and foot contact time were measured with and without arm swing during walking at 1.34m/s. The body's COM displacement was greater with the arms constrained (arm swing: 4.1±1.2cm, arm constrained: 4.9±1.2cm, p<0.001). Ground reaction force data indicated that the COM displacement increased in both double limb and single limb stance. However, kinematic patterns visually appeared similar between conditions. Shortened stride length and foot contact time also were observed, although these do not seem to account for the increased COM displacement. However, a change in arm COM acceleration might have contributed to the difference. These findings indicate that a change in arm swing causes differences in vertical COM displacement, which could increase energy expenditure.

Degradation of postural control with aging.

Aging negatively impacts the ability to maintain postural stability due to degraded control systems. The entropic half-life, a non-linear variable that quantifies the transition of sample entropy with increasing time scales, quantifies the time that elapses before old positional information no longer influences, or is no longer related to, the control mechanisms that regulate the movement at the current center of pressure location. The entropic half-life provides a more representative and comprehendible way of detecting changes in complexity using measurement units of time. The purpose of this study was to determine the effects of aging on the magnitude and temporal structure of the center of pressure movement during quiet single-limb stance. Center of pressure data of 24 older and 24 younger subjects were analyzed. The complexity of the temporal structure of the center of pressure signal was quantified by calculating the entropic half-life of the center of pressure in the medio-lateral and anterior-posterior directions. The magnitude of movement was quantified using excursion of the center of pressure in the medio-lateral and anterior-posterior directions, the path length, and the 95% ellipse area of the center of pressure. The older subjects demonstrated a significantly shorter entropic half-life for the center of pressure in the anterior-posterior direction (p < 0.001), longer excursions of the center of pressure in the medio-lateral (p < 0.001) and anterior-posterior (p = 0.001) directions, increased center of pressure path lengths (p < 0.001), and increased 95% ellipse areas of the center of pressure (p < 0.001). The results from this study showed that even though older subjects demonstrated more frequent postural adjustments (shorter entropic half-life), this did not help to reduce the magnitude of movement of their center of pressure during quiet stance, thus indicating an impaired peripheral and/or central neuromuscular control mechanism.

The influence of thermoplastic thoraco lumbo sacral orthoses on standing balance in subjects with idiopathic scoliosis.

Idiopathic scoliosis patients have postural equilibrium problems. The objective of this study was to assess postural control in subjects with idiopathic scoliosis following a 4-month intervention in an unbraced position. Quasi-experimental. Eight healthy girls and eight girls with idiopathic scoliosis took part. A Kistler force platform was used with a frequency of 100 Hz for recording data. The center of pressure was recorded in different positions out of brace for scoliosis and healthy subjects. Test conditions were single limb and double limb stance, with eyes open and closed, and foam and rigid surfaces. The data reflected a weak balance of idiopathic scoliosis subjects compared to healthy subjects. After 1 and 4 months of wearing the brace, center of pressure and center of gravity sway increased in the majority of the tests, although there were no significant differences in any of the test conditions (p > 0.05). While the center of pressure sway in medio-lateral direction decreased after 4 months of wearing a brace, in other variables center of pressure and center of gravity sway increased. Idiopathic scoliosis patients have weak balance in comparison to healthy subjects. In addition, following a period of 4 months of wearing a brace, balance parameters in the scoliosis subjects did not improve. The results show that we need more follow-up of orthoses wearing in idiopathic scoliosis subjects and suggest more studies at least 1-year follow-up to identify the efficiency of brace wear on balance. Scoliosis can alter postural stability and balance performance during quiet standing. Spinal deformity can alter a subject's ability to compensate for postural changes and cause gait deviations. This study investigated balance differences between the healthy and idiopathic scoliosis patients and the results of thoraco lumbo sacral orthosis brace wear. It might provide some new insight into the conservative treatment of idiopathic scoliosis patients for clinicians and researchers.

중재방법에 따른 엄지발가락 가쪽휨증 환자의 발바닥 압력분포에 미치는 영향

Purpose: The purpose of this study was to investigate the foot pressure of subjects with hallux valgus following conservative management. Methods: The subjects (20 females) were divided into 2 groups; Hallux valgus group (10) and Control group (10) who could evaluate questionnaire & weight bearing X-ray. All the participants were evaluated distribution of foot pressure by Zebris FDM-S system with conservative management (taping therapy and hallux valgus device) during single-limb stance. Results: The Hallux valgus group (HVG) was significantly different than Control group (CG) in hallux valgus angle(p<0.05). The Hallux valgus group with Foot Device (HVG-FD), Hallux valgus group with Taping (HVG-Tp) and Hallux valgus group with Foot device and Taping (HVG-FD&Tp) was not significantly different than CG in hallux valgus angle (p<0.05). The HVG was not significantly different than CG in forefoot (p1, p2, p3), significantly different than CG in rearfoot (p7) about foot pressure during single-limb stance (p<0.05). The HVG-FO and HVG-FO and TP was significantly different than HVG in forefoot (p1, p2, p3), on significantly different than HVG in rearfoot (p7) about foot pressure during single-limb stance (p<0.05). There was significantly correlation HVG-FO and HVG-FO & TP in forefoot (p1, p2, p3) was negative correlation (p<0.05) and in rearfoot (p7) was positive correlation (p<0.05). Conclusion: This study showed that hallux valgus were effected hallux valgus angle and foot pressure by various treatment methods during single-limb stance. Further study is needed to measure various age and work with hallux valgus for clinical application.

Biomechanical and Clinical Correlates of Stance-Phase Knee Flexion in Persons With Spastic Cerebral Palsy

ObjectiveTo identify biomechanical and clinical parameters that influence knee flexion (KF) angle at initial contact (IC) and during single limb stance phase of gait in children with spastic cerebral palsy (CP) who walk with flexed-knee gait. DesignRetrospective analysis of gait kinematics and clinical data collected from 2010-2013. SettingMotion & Gait Analysis Laboratory at Lucile Packard Children's Hospital, Stanford, CA. ParticipantsGait analysis data from persons with spastic CP (Gross Motor Function Classification System [GMFCS] I-III) who had no prior surgery were analyzed. Participants exhibiting KF ≥20° at IC were included; the more-involved limb was analyzed. MethodsOutcome measures were analyzed with respect to clinical findings, including passive range of motion, Selective Motor Control Assessment for the Lower Extremity (SCALE), gait kinematics, and musculoskeletal models of muscle-tendon lengths during gait. Main Outcome MeasuresKF at IC (KFIC) and minimum KF during single-limb support (KFSLS) were investigated. ResultsThirty-four participants met the inclusion criteria, and their data were analyzed (20 males and 14 females, mean age 10.1 years, range 5-20 years). Mean KFIC was 34.4 ± 8.4 degrees and correlated with lower SCALE score (ρ = –0.530, P = .004), later peak KF during swing (ρ = 0.614, P < .001), and shorter maximal muscle length of the semimembranosus (ρ = –0.359, P = .037). Mean KFSLS was 18.7 ± 14.9 and correlated to KF contracture (ρ = 0.605, P < .001) and shorter maximal muscle length of the semimembranosus (ρ = –0.572, P < .001) and medial gastrocnemius (ρ = –0.386, P = .024). GMFCS correlated more strongly to KFIC (ρ = 0.502, P = .002) than to KFSLS (ρ = 0.371, P = .031). Linear regression found that both the SCALE score (P = .001) and delayed timing of peak KF during swing (P = .001) independently predicted KFIC. KF contracture (P = .026) and maximal length of the semimembranosus (P = .043) independently predicted KFSLS. ConclusionCorrelates of KFIC differed from those for KFSLS and suggest that impaired selective motor control and later timing of swing-phase KF influence knee position at IC, whereas KF contracture and muscle lengths influence minimal KF in single-limb support, findings with important treatment implications.

The impact of previous knee injury on force plate and field-based measures of balance

BackgroundIndividuals with post-traumatic osteoarthritis demonstrate increased sway during quiet stance. The prospective association between balance and disease onset is unknown. Improved understanding of balance in the period between joint injury and disease onset could inform secondary prevention strategies to prevent or delay the disease. This study examines the association between youth sport-related knee injury and balance, 3–10years post-injury. MethodsParticipants included 50 individuals (ages 15–26years) with a sport-related intra-articular knee injury sustained 3–10years previously and 50 uninjured age-, sex- and sport-matched controls. Force-plate measures during single-limb stance (center-of-pressure 95% ellipse-area, path length, excursion, entropic half-life) and field-based balance scores (triple single-leg hop, star-excursion, unipedal dynamic balance) were collected. Descriptive statistics (mean within-pair difference; 95% confidence intervals) were used to compare groups. Linear regression (adjusted for injury history) was used to assess the relationship between ellipse-area and field-based scores. FindingsInjured participants on average demonstrated greater medio-lateral excursion [mean within-pair difference (95% confidence interval); 2.8mm (1.0, 4.5)], more regular medio-lateral position [10ms (2, 18)], and shorter triple single-leg hop distances [−30.9% (−8.1, −53.7)] than controls, while no between group differences existed for the remaining outcomes. After taking into consideration injury history, triple single leg hop scores demonstrated a linear association with ellipse area (β=0.52, 95% confidence interval 0.01, 1.01). InterpretationOn average the injured participants adjusted their position less frequently and demonstrated a larger magnitude of movement during single-limb stance compared to controls. These findings support the evaluation of balance outcomes in the period between knee injury and post-traumatic osteoarthritis onset.

Analysis of medial deviation of center of pressure after initial heel contact in forefoot varus.

After initial heel contact, the rearfoot everts and causes medial deviation of the center of pressure (CoP). Although rearfoot angle in single-limb stance has been associated with forefoot varus (FV)≥8°, medial CoP deviation has not. After 12 participants with FV<8° (neutral group) and 11 participants with FV≥8° (FV group) stepped one heel initially onto an array of pressure sensors parallel to its Y coordinate axis, when the CoP of array deviated most medially, the X coordinate of the CoP of each row was calculated to find the most medial CoP of the row. Starting since the row with the most medial CoP just began to have the same sensors with pressures >0kPa as when it had the most medial CoP, the medial deviations of the CoP of the array, the most medial CoP of the row, and its relative position in the row (CoP%), were compared between neutral and FV groups. The medial deviations of the most medial CoP of the row (1.1±0.6 vs. 1.6±0.3mm, p=0.049) and CoP% (2.9±1.4 vs. 4.2±1.1%, p=0.023) were significantly different between neutral and FV groups, whereas that of the CoP of the array (1.1±0.6 vs. 1.4±0.6mm, p=0.36) was not. The most medial CoP of the row and CoP% detected increased medial CoP deviation in FV≥8°, and may be applied to other clinical conditions where rearfoot angle and CoP of the array after initial heel contact cannot detect significant differences.

Single-limb Stance Increases Cortical Excitability To The Lower-leg Muscles In Able-bodied Adults

Postural control is a crucial component required for maintenance of joint stability. Recent evidence has linked alterations in the cortex with sensations of instability as quantified through motor evoked potentials (MEPs) from transcranial magnetic stimulation. However, no studies have quantified the effect of single-limb stance on cortical excitability of the lower-leg muscles. PURPOSE: To determine how single-limb stance on stable and unstable surfaces alters cortical excitability to the tibialis anterior (TA), peroneus longus (PL), and soleus (SOL) muscles. METHODS: MEPs were elicited over the primary motor cortex of 15 able-bodied individuals (22.4±3.6yrs; 174.1±12.9cm; 71.4±21.7kg) under 4 conditions: seated and relaxed (REL); seated and facilitated (FAC); single-limb standing on a stable surface (STA); and single-limb standing on an unstable surface (UNS, Biodex Stability System Level 12). Peak-to-peak MEP’s (%max) were measured at stimulus intensities equal to 90, 110, and 150 percent of TA resting motor threshold (RMT). A 4x3x3 ANOVA compared conditions, intensities, and muscles. RESULTS: A significant 3-way interaction effect was observed (F=1.91, p=0.03). Generally, standing trials increased excitability at all intensities compared to seated trials, while FAC was typically greater than REL. At 90% RMT, only PL excitability increased greatly in the UNS condition. At 110% RMT, greatest increases in UNS trials were observed for the TA (REL=0.02±0.01; FAC=0.08±0.02; STA=0.09±0.03; UNS=0.13±0.04, p<0.05) & SOL (REL=0.017±0.01; FAC=0.03±0.01; STA=0.07±0.02; UNS=0.10±0.03, p<0.05) muscles. At 150% RMT, no differences were observed between standing and unstable conditions. CONCLUSION: Cortical excitability to the lower-leg muscles increases with single-limb stance on stable & unstable surfaces. Increases from STA to UNS were observed across all muscles; however, these appear to be stimulus-dependent indicating altered modulation of excitability across muscles. Further research might investigate how injury affects the cortical modulation of single-limb stance.

Those with Unilateral Chronic Ankle Instability have Impaired Unilateral Single Limb Balance and Self-Reported Function

Chronic ankle instability (CAI) is a common sequela of an ankle sprain. Single limb balance impairments have been reported in those with CAI, but it is unclear whether these deficits are found on only the self-reported more dysfunctional limb or if they are bilateral. PURPOSE: To determine whether single limb balance deficits exist when comparing the self-reported CAI limb to the healthy limb in subjects with unilateral CAI. METHODS: 26 subjects with self-reported unilateral CAI participated. Each participant completed the Foot and Ankle Ability Measure Sport Scale (FAAMS). A score of <80% on the FAAMS was considered as an ankle with CAI. All subjects performed 3, 10-second trials of single limb stance with eyes open on a force plate and 3, 20-second trials of single limb balance on a firm surface (SLBT) with eyes closed. From the force plate, time-to-boundary was calculated in the mediolateral (TTBML) and anteroposterior (TTBAP) directions. TTB estimates the amount of time a person has to make a postural correction to prevent balance loss. Dependent variables included the FAAMS score (%), TTBAP and TTBML (s), and mean errors committed during the SLBT. Paired t-tests were used to compare the dependent variables between limbs (self-reported CAI vs. healthy limb) for all comparisons. Alpha was set a priori at p<0.05 for all analyses. RESULTS: The CAI limb (64.2±11.7%) had lower FAAMS scores than the healthy limb (98.1±5.6%, p<0.001). TTBML (CAI: 1.8±0.7s, Healthy: 2.1s, p<0.001) and TTBAP (CAI: 4.9±1.4, Healthy: 5.8±1.9s, p<0.001) were lower on the CAI limb. The CAI limb (CAI: 2.49±1.55) also had more SLBT errors than the healthy limb (1.77±1.48, p=0.006) CONCLUSION: Those with unilateral CAI reported significantly more disability when performing sport-related activities on the CAI limb relative to the healthy limb. These individuals, while balancing on the CAI limb, had significantly less time to make postural corrections in both the ML and AP directions with eyes open. Similarly, these individuals also made more errors on an eyes closed clinical balance test on the CAI limb. Based on these results, less time to make postural corrections with eyes open and more errors with eyes closed may be contributing factors for the reported CAI limb disability. This project was supported by: NIAMS 1R03AR061561.

Different ankle muscle coordination patterns and co-activation during quiet stance between young adults and seniors do not change after a bout of high intensity training

BackgroundAvailable evidence suggests that young adults and seniors use different strategies to adjust for increasing body sway during quiet standing. Altered antagonist muscle co-activation and different ankle muscle coordination patterns may account for this finding. Consequently, we aimed at addressing whether aging leads to changes in neuromuscular coordination patterns as well as co-activation during quiet stance. We additionally investigated whether a bout of high intensity interval training additionally alters these patterns.MethodsTwenty healthy seniors (age: 70 ± 4 y) and twenty young adults (age: 27 ± 3 y) were enrolled in the present study. In between the testing procedures, four consecutive high-intensity intervals of 4 min duration at a target exercise intensity of 90 to 95% HRmax were completed on a treadmill. The total center of pressure (COP) path length displacement served as standing balance performance outcome. In order to assess ankle muscle coordination patterns, amplitude ratios (AR) were calculated for each muscle (e.g. tibialis anterior (TA) [%] = (TA × 100)/(gastrocnemius medialis (GM) + soleus (SOL) + peroneus longus (PL) + TA). The co-activation was calculated for the SOL and TA muscles computing the co-activation index (CAI = 2 × TA/TA + SOL).ResultsSeniors showed an inverted ankle muscle coordination pattern during single limb stance with eyes open (SLEO), compared to young adults (rest: GM, S: 15 ± 8% vs Y: 24 ± 9%; p = 0.03; SOL, S: 27 ± 14% vs Y: 37 ± 18%; p = 0.009; TA, S: 31 ± 13% vs Y: 13 ± 7%; p = 0.003). These patterns did not change after a high-intensity training session. A moderate correlation between amplitude ratios of the TA-contribution and postural sway was observed for seniors during SLEO (r = 0.61). Ankle co-activation was twofold elevated in seniors compared to young adults during SLEO (p < 0.001). These findings were also not affected by high intensity training.ConclusionIncreased ankle co-activation in the anterior-posterior plane and inverted ankle muscle coordination pattern merely occurred during single-leg stance. Seniors with decreased postural control showed higher TA contributions during SLEO. These neuromuscular changes are not affected by acute intermittent high intensity aerobic exercise.

Effect of an eccentrically biased hamstring strengthening home program on knee flexor strength and the length-tension relationship.

The purposes of this study were to document relative activation intensities of the hamstrings and gluteus maximus during 4 eccentric hamstring strengthening exercises and to assess the effects of a short-term strengthening program comprised of these exercises on knee flexor strength and the length-tension relationship. Twelve healthy subjects participated in this study. Electromyographic (EMG) activities from the biceps femoris, semitendinosus, and gluteus maximus were recorded as subjects performed (a) standing hip extension with elastic resistance, (b) trunk flexion in single limb stance (diver), (c) standing split (glider), and (d) supine sliding bridge (slider). Baseline isometric knee flexor strength was measured at 90, 70, 50, and 30° of flexion at the knee with the subject seated and the hip flexed to 50° from horizontal. After completing the 4-week training program, strength tests were repeated. Repeated-measures analysis of variance were used to compare EMG activity between muscles and to assess angle-specific strength improvements. Hamstring activity exceeded gluteus maximus activity for resisted hip extension, glider, and slider exercises (p < 0.001) but not for the diver (p = 0.087). Hamstring activation was greatest during the slider and resisted hip extension and lowest during the glider and the diver. Knee flexor strength improved by 9.0% (p = 0.005) but was not angle specific (training by angle p = 0.874). The short-term home training program effectively targeted the hamstrings and resulted in strength gains that were similar at short and long muscle lengths. These data demonstrate that hamstring strength can be improved using eccentrically biased unilateral exercises without the use of weights or other equipments.