Bilateral Task Research Articles

P 052 – Detection of lower extremity asymmetries in slow and dynamic bilateral tasks. Inertial Sensor system vs Optical Motion Capture System

P 052 – Detection of lower extremity asymmetries in slow and dynamic bilateral tasks. Inertial Sensor system vs Optical Motion Capture System

Handedness results from complementary hemispheric dominance, not global hemispheric dominance: evidence from mechanically coupled bilateral movements.

Two contrasting views of handedness can be described as 1) complementary dominance, in which each hemisphere is specialized for different aspects of motor control, and 2) global dominance, in which the hemisphere contralateral to the dominant arm is specialized for all aspects of motor control. The present study sought to determine which motor lateralization hypothesis best predicts motor performance during common bilateral task of stabilizing an object (e.g., bread) with one hand while applying forces to the object (e.g., slicing) using the other hand. We designed an experimental equivalent of this task, performed in a virtual environment with the unseen arms supported by frictionless air-sleds. The hands were connected by a spring, and the task was to maintain the position of one hand while moving the other hand to a target. Thus the reaching hand was required to take account of the spring load to make smooth and accurate trajectories, while the stabilizer hand was required to impede the spring load to keep a constant position. Right-handed subjects performed two task sessions (right-hand reach and left-hand stabilize; left-hand reach and right-hand stabilize) with the order of the sessions counterbalanced between groups. Our results indicate a hand by task-component interaction such that the right hand showed straighter reaching performance whereas the left hand showed more stable holding performance. These findings provide support for the complementary dominance hypothesis and suggest that the specializations of each cerebral hemisphere for impedance and dynamic control mechanisms are expressed during bilateral interactive tasks. NEW & NOTEWORTHY We provide evidence for interlimb differences in bilateral coordination of reaching and stabilizing functions, demonstrating an advantage for the dominant and nondominant arms for distinct features of control. These results provide the first evidence for complementary specializations of each limb-hemisphere system for different aspects of control within the context of a complementary bilateral task.

The sensory origin of the sense of effort is context-dependent.

The origin of the sense of effort has been debated for several decades and there is still no consensus among researchers regarding the underlying neural mechanisms. Some advocate that effort perception mainly arises from an efference copy originating within the brain while others believe that it is predominantly carried by muscle afferent signals. To move the debate forward, we here tested the hypothesis that there is not one but several senses of effort which depend on the way it is evaluated. For this purpose, we used two different psychophysical tests designed to test effort perception in elbow flexors. One was a bilateral isometric force-matching task in which subjects were asked to direct similar amounts of effort toward their two arms, while the other consisted of a unilateral voluntary isometric contraction in which subjects had to rate their perceived effort using a Borg scale. Throughout two distinct experiments, effort perception was evaluated before and following different tendon vibration protocols intended to differentially desensitize muscle spindles and Golgi tendon organs, and to affect the gain between the central effort and muscle contraction intensity. By putting all the results together, we found that spindle afferents played divergent roles across tasks. Namely, while they only acted as modulators of motor pathway excitability during the bilateral task, they clearly intervened as the predominant psychobiological signal of effort perception during the unilateral task. Therefore, the sensory origin of the sense of effort is not central or peripheral. Rather, it is context-dependent.

Knee Extension Strength Asymmetry does not affect Peak Power or Fatigue during the Wingate Test

PURPOSE: Peak and mean power during the Wingate test is associated with knee extensor strength, however it is unknown if knee extensor asymmetry affects this relationship. We hypothesized that increased muscle asymmetry would be associated with decreased peak and mean power during the Wingate test in healthy subjects. METHODS: 206 highly active male subjects (27 ±4 yrs, 84 ±9 kg) completed individual limb isokinetic strength testing on a dynamometer (60°·sec-1), as well as a 30 second Wingate anaerobic test in a seated position. Strength testing included maximal knee extension strength (% Body Weight). Knee extension asymmetry ratio between legs (Aext) was calculated as Aext = Emin/Emax, where Emax = strongest leg, Emin = weakest leg. Subjects were later classified as High Symmetry (HS, Aext > 0.95, n=76), Moderate Symmetry (MS, 0.90 < Aext < 0.95, n=60), Moderate Asymmetry (MA, 0.85 < Aext < 0.90, n=35) or High Asymmetry (HA, Aext < 0.85, n=35). Wingate data (W·kg-1) were analyzed for peak power (Ppeak), mean power (Pmean), as well as power output at 5 second intervals. RESULTS: There were significant differences in Emin (HS > MA, p=0.012; HS > HA, p<0.001; MS > HA, p=0.044) but not Emax between groups. No significant differences in Ppeak (12.89 ±0.68, 12.74 ±0.63, 12.71 ±0.52, 12.87 ±0.79 W·kg-1), Pmean (9.26 ±0.81, 9.05 ±0.82, 9.15 ±0.78, 9.32 ±1.08 W·kg-1) or any other power variables were found between the HS, MS, MA and HA groups respectively (all p>0.055). When all subjects were combined, knee extensor asymmetry (Aext) was not associated with any power variables (all p>0.133). Ppeak and Pmean respectively were positively associated with Emax (r=0.414, p<0.001; r=0.464, p<0.001) and Emin (r=0.397, p<0.001; r=0.420, p<0.001). Although all relationships were significant, the associations between strength variables (Emin and Emax respectively) and power decreased from 5 seconds (r=0.490, p<0.001; r=0.490, p<0.001) to 30 seconds (r=0.265, p<0.001; r=0.331, p<0.001). CONCLUSIONS: Greater knee extensor strength imbalance between legs is not associated with decreased power throughout a 30 second Wingate test. These data suggest that for bilateral tasks in which the legs do not move independently, such as cycling, training focused only on improving strength symmetry between legs may not improve peak power production.

COMPARISON OF CLINICAL FATIGUE PROTOCOLS TO DECREASE SINGLE-LEG FORWARD HOP PERFORMANCE IN HEALTHY INDIVIDUALS

Return to activity decisions after anterior cruciate ligament reconstruction (ACL-R) are limited by functional performance tests often performed in a non-fatigued state. Fatigue can improve test sensitivity, but current methods to induce fatigue are typically bilateral tasks or focus on the quadriceps muscle in isolation. To determine the effects of a two-minute lateral step-down fatigue test compared to a 30-second side-hop test on single-leg forward hop distance in healthy individuals. It was hypothesized that participants would demonstrate decreased hop distance with both tests, but the two-minute lateral step-down fatigue test would result in greater deficits in single-leg forward hop distance. Randomized crossover. Twenty healthy participants (16 females, 4 males; age = 23.7±3.0 years, height = 153.8±36.2 cm; mass = 64.4±12.8 kg; Tegner = 6.8±1.2) were asked to perform single-leg forward hop for distance pre- and post-fatigue. Participants were randomly assigned to one of the two fatigue tests, 30-second side-hop or 2-minute lateral step-down test, during the first visit. They returned within a week and performed the same sequence of tests but underwent whichever fatigue test was not assigned at the prior visit. There was a significant decrease (p < 0.001) in single-leg forward hop distance following the 30-second side-hop test (pre = 134.1±23.7 cm, post = 126.2±24.4 cm) and the two-minute lateral step-down test (pre = 135.0±26.1 cm, post = 122.7±27.4 cm). The decrease in hop distance was significantly greater (p < 0.001) for the two-minute lateral step-down test compared to the 30-second side-hop test. The two-minute lateral step-down test resulted in a greater decrease in hop performance compared to the 30-second side-hop test. The results establish a threshold for expected changes that occur in a healthy population and that can then be compared with an injured athlete population. The two-minute lateral step-down exercise may be an effective method of inducing fatigue to better mimic performance in a sports environment to inform return-to-sport decisions. Level 1b- Therapy.

A longitudinal functional magnetic resonance imaging study of task control circuits and bulimic symptoms over adolescence

Previous cross-sectional findings from adolescents and adults with Bulimia Nervosa (BN) suggest disturbances in fronto-striatal and cingulo-opercular task control circuits that support self-regulatory processes, including the resolution of cognitive conflict. Herein, we used longitudinal data to examine the developmental trajectories of such disturbances and how the functioning of these circuits relates to changes in BN symptoms over adolescence. Thirty-two adolescent females with BN symptoms and 28 healthy control (HC) adolescents participated in the study. Functional magnetic resonance images (fMRI) during performance of a Simon task were acquired at three time points within 2-year intervals over adolescence. From the initial sample, 70% and 30% of the participants completed the second and third time points, respectively. Participants who completed all study time points did not differ from those lost to attrition on baseline demographic characteristics or any outcome measures. Using a region-of-interest approach, growth curve models tested group differences in the trajectory of conflict-related activation in task control circuits over time. Cross-lagged panel models examined transactional relationships between conflict-related activation in the same regions and BN symptoms over time. Growth curve models revealed different trajectories of conflict-related activation in right task control regions across BN and HC adolescents, such that HC but not BN adolescents showed activation decreases over time. These group differences were greatest when including only the BN adolescents whose symptoms remitted over time. Cross-lagged panel models revealed that less frequent bulimic episodes at first follow-up predicted later increases in conflict-related activation in bilateral task control regions. These longitudinal findings suggest overengagement of task control circuits in BN adolescents, especially those most resilient to persistent illness. Such overengagement may compensate for regulatory disturbances, allowing them to regulate eating behaviors over development. Thus, task control circuits may constitute targets for early interventions that enhance self-regulatory control.

Investigating bimanual motor performance on daily bimanual tasks in children with hemiplegic cerebral palsy

Background: Most activities of daily living require the cooperative use of both hands. Children with hemiplegic cerebral palsy (CP) usually have difficulties in bimanual coordination, which would further influence their daily function. However, there was limited research investigating the differences between performance of affected hand and unaffected hand in daily bilateral tasks.

Lateralization of spatial rather than temporal attention underlies the left hemifield advantage in rapid serial visual presentation

In bilateral rapid serial visual presentation (RSVP), the second of two targets, T1 and T2, is better identified in the left visual field (LVF) than in the right visual field (RVF). This LVF advantage may reflect hemispheric asymmetry in temporal attention or/and in spatial orienting of attention. Participants performed two tasks: the “standard” bilateral RSVP task (Exp.1) and its unilateral variant (Exp.1 & 2). In the bilateral task, spatial location was uncertain, thus target identification involved stimulus-driven spatial orienting. In the unilateral task, the targets were presented block-wise in the LVF or RVF only, such that no spatial orienting was needed for target identification. Temporal attention was manipulated in both tasks by varying the T1-T2 lag. The results showed that the LVF advantage disappeared when involvement of stimulus-driven spatial orienting was eliminated, whereas the manipulation of temporal attention had no effect on the asymmetry. In conclusion, the results do not support the hypothesis of hemispheric asymmetry in temporal attention, and provide further evidence that the LVF advantage reflects right hemisphere predominance in stimulus-driven orienting of spatial attention. These conclusions fit evidence that temporal attention is implemented by bilateral parietal areas and spatial attention by the right-lateralized ventral frontoparietal network.

Side-to-side asymmetries in landing mechanics from a drop vertical jump test are not related to asymmetries in knee joint laxity following anterior cruciate ligament reconstruction

PurposeAsymmetries in knee joint biomechanics and increased knee joint laxity in patients following anterior cruciate ligament reconstruction (ACLR) are considered risk factors for re-tear or early onset of osteoarthritis. Nevertheless, the relationship between these factors has not been established. The aim of the study was to compare knee mechanics during landing from a bilateral drop vertical jump in patients following ACLR and control participants and to study the relationship between side-to-side asymmetries in landing mechanics and knee joint laxity.MethodsSeventeen patients following ACLR were evaluated and compared to 28 healthy controls. Knee sagittal and frontal plane kinematics and kinetics were evaluated using three-dimensional motion capture (200 Hz) and two synchronized force platforms (1000 Hz). Static anterior and internal rotation knee laxities were measured for both groups and legs using dedicated arthrometers. Group and leg differences were investigated using a mixed model analysis of variance. The relationship between side-to-side differences in sagittal knee power/energy absorption and knee joint laxities was evaluated using univariate linear regression.ResultsA significant group-by-leg interaction (p = 0.010) was found for knee sagittal plane energy absorption, with patients having 25% lower values in their involved compared to their non-involved leg (1.22 ± 0.39 vs. 1.62 ± 0.40 J kg−1). Furthermore, knee sagittal plane energy absorption was 18% lower at their involved leg compared to controls (p = 0.018). Concomitantly, patients demonstrated a 27% higher anterior laxity of the involved knee compared to the non-involved knee, with an average side-to-side difference of 1.2 mm (p < 0.001). Laxity of the involved knee was also 30% higher than that of controls (p < 0.001) (leg-by-group interaction: p = 0.002). No relationship was found between sagittal plane energy absorption and knee laxity.ConclusionsNine months following surgery, ACLR patients were shown to employ a knee unloading strategy of their involved leg during bilateral landing. However, this strategy was unrelated to their increased anterior knee laxity. Side-to-side asymmetries during simple bilateral landing tasks may put ACLR patients at increased risk of second ACL injury or early-onset osteoarthritis development. Detecting and correcting asymmetric landing strategies is highly relevant in the framework of personalized rehabilitation, which calls for complex biomechanical analyses to be applied in clinical routine.Level of evidenceIII.

The Relationship Between 2-Dimensional Knee-Valgus Angles During Single-Leg Squat, Single-Leg-Land, and Drop-Jump Screening Tests.

Injuries to the anterior cruciate ligament (ACL) and patellofemoral joint (PFJ) are a significant problem in female athletes. A number of screening tasks have been used in the literature to identify those at greatest risk of injury. To date, no study has examined the relationship in 2-dimensional (2D) knee valgus between common screening tasks to determine whether individuals exhibit similar movement patterns across tasks. To establish whether frontal-plane projection angle (FPPA) during the single-leg squat (SLS), single-leg land (SLL), and drop jump (DJ) are related. Cross-sectional study. University laboratory. 52 national-league female football players and 36 national-league female basketball players. 2D FPPA during the SLS, SLL, and DJ screening tasks. Significant correlations were found between tasks. FPPA in the SLS was significantly correlated with SLL (r = .52) and DJ (r = .30), whereas FPPA in the SLL was also significantly correlated to DJ (r = .33). FPPA was significantly greater in the SLS than in the SLL (P < .001) and DJ (P < .001) and in the SLL than in the DJ (P < .001). The results showed that 2D FPPA is correlated across the SLS, SLL, and DJ tasks. However, significantly greater FPPA values in the unilateral tasks suggest that the DJ may not identify risk of injury in sports where primary injury mechanisms are during unilateral loading tasks. Therefore, it is recommended that both unilateral and bilateral tasks be included when screening for ACL and PFJ injury risk.

Swedish–Finnish naval cooperation in the Baltic Sea: motives, prospects and challenges

Recently, Finland and Sweden decided to substantially deepen their defence cooperation and this project involves creating a bilateral standing Naval Task Group (SFNTG). The present article aims at examining the deepening naval cooperation between Finland and Sweden from a regional integration perspective, focusing on its motives, current challenges and future prospects. Driven by perceptions of common challenges and desires for cost-effectiveness, and strengthened by recent successes on sea surveillance and a combined Amphibious Task Unit, the bilateral project has considerable potential to achieve success. To fulfil its objectives, substantial legal changes in both countries are required to allow the use of force on each other’s territorial waters. To cater for the requirement of not conflicting with EU, NORDEFCO or NATO cooperations, the bilateral Task Group must operate according to NATO standards and by using English as the language in command and control. The costs of adjusting the naval units to NATO’s technical requirements are far from negligible and this issue still remains to be solved. If Finland and Sweden manage to incorporate new policies, common structures and common organisational norms among their navies, an even deeper integration, as in Belgium and the Netherlands, are conceivable.

Upper limb kinematics of adults with cerebral palsy on bilateral functional tasks.

Adults with cerebral palsy (CP) often show upper limb impairments which impact their ability to execute activities of daily living (ADLs). Three adults with CP and five healthy adults performed three types of bilateral and unilateral ADLs: drink, pour, and pick and place tasks. An affordable bilateral assessment system (BiAS) was used to measure wrist kinematic trajectories. Four metrics, total completion time, maximum velocity, smoothness, and phase difference, were used to evaluate each functional task. Overall, adults with CP took a longer time than the healthy subjects to complete all unilateral functional tasks with their non-dominant hand. Moreover, while the healthy controls had similar mean velocities in the dominant and non-dominant hands during the bilateral tasks, adults with CP typically exhibited slower mean velocities in the dominant hand during the bilateral tasks than during the unilateral dominant tasks. Similar to existing literature, we found that adults with CP compensated by slowing the dominant arm to match the non-dominant arm in order to complete the tasks, showing the importance of utilizing bilateral training in upper limb rehabilitation treatments.

Does Vertical GRF Asymmetry Reflect Knee Extensor Moment Asymmetry in Squat in Individuals following ACLr?

Individuals following ACL reconstruction (ACLr) adopt a strategy that shifts mechanical demands away from the knee of the surgical limb. Vertical ground reaction forces (vGRF) asymmetry has been used to characterize a shift in demands to the non-surgical limb in bilateral tasks. However, given the potential for both inter- and intra-limb compensations it is possible that vGRF asymmetry does not accurately reflect knee extensor moment (kEXT) asymmetry. PURPOSE: To determine how well between limb symmetry in vGRF predicts between limb symmetry in kEXT during a squat in individuals following ACLr at 2 time points; 3 and 5 months. METHODS: 11 subjects (7 females, 25.3 ± 10.7 yrs) performed bilateral squats to self-selected depths 3 (91± 11.1 days) and 5 months (148.8 ± 9.2 days) post-surgery. 3-D kinematics (250Hz), ground reaction forces (1500 Hz), anthropometrics were used to calculate kEXT moments (inverse dynamics). Symmetry indices (SI) were calculated (surgical/non-surgical limb) for peak vGRFs and kEXT during deceleration; SI<1 indicates smaller kEXT and vGRF in surgical compared to non-surgical limb. Separate linear regression analyses were used to determine how well vRGF symmetry (SIvGRF) predicts knee extensor moment symmetry (SIkext) at 3 and 5 months. RESULTS: On average, SIvGRF and SIkext were .86 ± .11 and .63 ± .18 at 3 months, respectively. At 3 month, SIvGRF predicted of SIkext (r2=.62, p=.004). On average, SIvGRF and SIkext were were .89 ± .070 and .70 ± .12 at 5 months, respectively. At 5 months, SIvGRF did not predict SIkext (p=.28). CONCLUSIONS: The larger asymmetries noted in kEXT versus vGRF indicates that SIvGRF underestimates SIkext. SIvGRF explained 62.4% of the variance in SIkext at 3 months suggesting that the reduction in knee loading is accomplished largely by inter-limb compensations. However, by 5 months post ACLr, reductions kEXT appear to be accomplished through adjustments made within the limb. Together these data suggest that caution should be taken when relating vGRF symmetry to knee loading during bilateral task.

Motor Adaptations to Pain during a Bilateral Plantarflexion Task: Does the Cost of Using the Non-Painful Limb Matter?

During a force-matched bilateral task, when pain is induced in one limb, a shift of load to the non-painful leg is classically observed. This study aimed to test the hypothesis that this adaptation to pain depends on the mechanical efficiency of the non-painful leg. We studied a bilateral plantarflexion task that allowed flexibility in the relative force produced with each leg, but constrained the sum of forces from both legs to match a target. We manipulated the mechanical efficiency of the non-painful leg by imposing scaling factors: 1, 0.75, or 0.25 to decrease mechanical efficiency (Decreased efficiency experiment: 18 participants); and 1, 1.33 or 4 to increase mechanical efficiency (Increased efficiency experiment: 17 participants). Participants performed multiple sets of three submaximal bilateral isometric plantarflexions with each scaling factor during two conditions (Baseline and Pain). Pain was induced by injection of hypertonic saline into the soleus. Force was equally distributed between legs during the Baseline contractions (laterality index was close to 1; Decreased efficiency experiment: 1.16±0.33; Increased efficiency experiment: 1.11±0.32), with no significant effect of Scaling factor. The laterality index was affected by Pain such that the painful leg contributed less than the non-painful leg to the total force (Decreased efficiency experiment: 0.90±0.41, P<0.001; Increased efficiency experiment: 0.75±0.32, P<0.001), regardless of the efficiency (scaling factor) of the non-painful leg. When compared to the force produced during Baseline of the corresponding scaling condition, a decrease in force produced by the painful leg was observed for all conditions, except for scaling 0.25. This decrease in force was correlated with a decrease in drive to the soleus muscle. These data highlight that regardless of the overall mechanical cost, the nervous system appears to prefer to alter force sharing between limbs such that force produced by the painful leg is reduced relative to the non-painful leg.

Effects of functional and analytical strength training on upper-extremity activity after stroke: a randomized controlled trial.

ABSTRACTObjectiveTo investigate the effects of functional strengthening (using functional movements) and analytical strengthening (using repetitive movements) on level of activity and muscular strength gain in patients with chronic hemiparesis after stroke.MethodA randomized, assessor-blinded trial was conducted in a therapist-supervised home rehabilitation program. Twenty-seven patients with chronic stroke were randomly allocated one of two groups: functional strengthening (FS) (n=13) and analytical strengthening (AS) (n=14). Each group received a five-week muscle strengthening protocol (30 minutes per day, three times per week) including functional movements or analytical movements, respectively. Pre-, post-, and ten-month follow-up outcomes included the Upper-Extremity Performance Test (primary outcome), Shoulder and Grip Strength, Active Shoulder Range of Motion (ROM), the Fugl-Meyer Assessment, and the Modified Ashworth Scale (MAS) (secondary outcomes).ResultsThere was significant improvement in the Upper-Extremity Performance Test for the combined unilateral and bilateral task scores in the FS Group (mean difference 2.4; 95% CI=0.14 to 4.6) in the 10-month follow-up. No significant difference was observed between groups in the other outcomes (p>0.05).ConclusionA five-week home-based functional muscle strengthening induced positive results for the upper-extremity level of activity of patients with moderate impairment after chronic stroke.

Kinematic measures of Arm-trunk movements during unilateral and bilateral reaching predict clinically important change in perceived arm use in daily activities after intensive stroke rehabilitation.

BackgroundKinematic analysis has been used to objectively evaluate movement patterns, quality, and strategies during reaching tasks. However, no study has investigated whether kinematic variables during unilateral and bilateral reaching tasks predict a patient’s perceived arm use during activities of daily living (ADL) after an intensive intervention. Therefore, this study investigated whether kinematic measures during unilateral and bilateral reaching tasks before an intervention can predict clinically meaningful improvement in perceived arm use during ADL after intensive poststroke rehabilitation.MethodsThe study was a secondary analysis of 120 subjects with chronic stroke who received 90–120 min of intensive intervention every weekday for 3–4 weeks. Reaching kinematics during unilateral and bilateral tasks and the Motor Activity Log (MAL) were evaluated before and after the intervention.ResultsKinematic variables explained 22 and 11 % of the variance in actual amount of use (AOU) and quality of movement (QOM), respectively, of MAL improvement during unilateral reaching tasks. Kinematic variables also explained 21 and 31 % of the variance in MAL-AOU and MAL-QOM, respectively, during bilateral reaching tasks. Selected kinematic variables, including endpoint variables, trunk involvement, and joint recruitment and interjoint coordination, were significant predictors for improvement in perceived arm use during ADL (P < 0.05).ConclusionsArm–trunk kinematics may be used to predict clinically meaningful improvement in perceived arm use during ADL after intensive rehabilitation. Involvement of interjoint coordination and trunk control variables as predictors in bilateral reaching models indicates that a high level of motor control (i.e., multijoint coordination) and trunk stability may be important in obtaining treatment gains in arm use, especially for bilateral daily activities, in intensive rehabilitation after stroke.

Effects of overhead work configuration on muscle activity during a simulated drilling task

Overhead work is a known catalyst for occupational shoulder injury. Industrial workers must often adopt awkward overhead postures and loading profiles to complete required tasks, potentially elevating injury risk. This research examined the combined influence of multiple overhead working parameters on upper extremity muscular demands for an industrial drilling application.Twenty-two right-handed males completed 24 unilateral and bilateral overhead work exertions stratified by direction (upward, forward), point of force application (15, 30 and 45 cm in front of the body), and whole-body posture (seated, standing).The dependency of electromyographic (EMG) activity on several factors was established. Significant two-way interactions existed between point of force application and direction (p < 0.0001) and direction and whole body posture (p < 0.0001). An average increase in muscular activity of 6.5% maximal voluntary contraction (MVC) occurred for the contralateral limb when the bilateral task was completed, compared to unilateral tasks, with less than a 1% MVC increase for the active limb.These findings assist evidence-based approaches to overhead tasks, specifically in the construction industry. A bilateral task configuration is recommended to reduce glenohumeral stability demands. As well, particularly for tasks with a far reach distance, design tasks to promote a forward directed exertion. The considerable inter-subject variability suggests that fixed heights are not ideal, and should be avoided, and where this is not possible reaches should be reduced.

Biomechanical Effects of Neuromuscular Training in Anterior Cruciate Ligament-Reconstructed Subjects

Objectives:Second anterior cruciate ligament (ACL) injuries occur at a 10-20-fold higher rate than primary injury, and result in significantly poorer outcomes. Targeted neuromuscular training (NMT) alters biomechanics and reduces rates of primary ACL injury, but its effects in an ACL-injured population have not been elucidated. The purpose of this study was to determine the effects of NMT on high-risk biomechanics at the hip and knee in ACL-reconstructed (ACLR) subjects. We hypothesized that trained subjects would demonstrate reduced peak hip rotation and knee abduction motion and moments compared to controls.Methods:13 ACLR subjects (7 males and 6 females, 20.15±7.97 years old) were enrolled and evaluated during drop vertical jump (DVJ), single leg drop (SLD), and crossover drop (COD) tasks using 3D motion analysis prior to and after participation in a 12 session NMT program (Pre: 36.0±18.3 weeks post-operative, Post: 46.6±17.4 weeks post-operative). 13 untrained, ACLR controls (9 males and 4 females, 20.77±6.55 years old) were tested 52.4±2.7 weeks post-operative. Trained subjects participated in a 12 session training program, modified to be safe for patients in the late recovery phase after ACL-injury. The protocol centered around seven separate progressions, each consisting of four phases of increasing difficulty. Each phase consists of a cognitive session, associative session, and autonomous session.1 Discrete variables for hip and knee kinematics and kinetics, and vertical ground reaction force were compared within and between groups. Limb-by-session repeated measures analysis of variance (ANOVA) was used to assess within-subject effects of training. A separate limb-by-group ANOVA was used to compare trained and untrained groups.Results:Frontal plane hip excursion during the COD decreased after training. Trained subjects demonstrated increased knee flexion at initial contact during the DVJ task after training (NMT_Pre: -17.1±6.7 degrees , NMT_Post: -22.5±10.2 degrees; p=0.02). Changes in knee kinematics from pre-to post-NMT are shown in Figure 1. Peak knee flexion within the first 20% of landing increased significantly after NMT (NMT_Pre: -69.2±8.8 degrees, NMT_Post: -74.8±9.2 degrees; p=0.0067) as well as throughout the task (NMT_Pre: -88.2±12.1 degrees, NMT_Post: -95.0±12.5 degrees; p=0.0095). Trained subjects demonstrated significantly greater knee flexion range of motion within the first 20% of the landing phase of DVJ compared to controls (NMT_Post: 52.3±12.8 degrees, CTRL: 45.6±7.7 degrees; p=0.0214). Trained groups demonstrated greater peak knee flexion and flexion ROM compared to controls (p<0.05). Peak hip flexion during the first 20% of DVJ increased from pre- to post-training, but only trended toward differing from controls (p=0.0879).Conclusion:Increased knee flexion angles for both unilateral and bilateral tasks were consistently observed from pre- to post-training. Furthermore, the trained group exhibited significantly greater peak flexion compared to controls during the initial landing phase for most tasks, when ACL injury is most likely to occur. NMT in ACL-reconstructed subjects appeared to primarily affect sagittal plane hip and knee biomechanics.

Effect Of Handedness On Functional Organization Of Bimanual Isometric Handgrip

Summary The aim of this study was to examine force production during maximal isometric handgrip in unilateral (UL) and bilateral (BL) tasks in right- and left-handed subjects. Ten right-handed (RH) and 8 left-handed (LH) young men were studied. The subjects were instructed, after a command, to perform a shot-like handgrip, raising maximal force as fast as possible. Three series were performed as follows: 1) UL - right handgrip; 2) UL - left handgrip; 3) BL handgrip. We measured peak force, time to peak of force and rate of force. The BL/UL ratios for the right (R) and left (L) hand and L/R ratios for the UL and BL tasks were calculated. The L/R ratios for peak force and force rate in RH group ranged across all tasks and conditions from 0.71 to 0.75. They were significantly lower than 1 (p&lt;0.01). These ratios did not differ significantly from 1 for LH subjects (0.98–1.02), indicating the handedness in RH group only. The BL/UL ratios for peak force were 0.89 and 0.89 in RH, suggesting symmetrical bilateral strength deficit. The magnitude of the bilateral deficit in LH group was larger for the dominant (L) hand compared to non dominant (R) hand – 0.93 and 0.97 (p&lt;0.05) respectively, suggesting an asymmetry of bilateral deficit in LH. These ratios for time of force and rate of force indicated bilateral deficit (BD) in the dominant hand of RH group only.

Task-oriented robot-assisted stroke therapy of paretic limb improves control in a unilateral and bilateral functional drink task: a case study.

The purpose of this paper is to evaluate the functional, temporal and spatial effect of a unilateral task-oriented, robot-assisted training on unilateral and bilateral task performance of a drinking task using a real object. Two chronic stroke survivors experienced task-oriented robot assisted therapy, in which the paretic arm was trained using reaching and grasping tasks over 4 weeks. Both subjects experienced improvement in motor control as measured by Fugl-Meyer. The paretic arm was evaluated using movement smoothness (MS) and time to completion (TCT) measures before and after therapy. From the results, we found that the unilateral robotassisted training improved paretic arm control in the unilateral and the bilateral drink task. However, the influence of the non-paretic movement on the temporal and spatial paretic arm control was evident both pre and post therapy suggesting inter-limb coupling aids in the transfer of unilateral improvements in motor control to improvements in bilateral motor control.