Single-leg Movement Research Articles

Stable Rapid Sagittal Walking Control for Bipedal Robot Using Passive Tendon

This paper presents the development, control, and experimental validation of a novel bipedal robot with a passive tendon. The robot, featuring foldable legs, coaxial actuation, and compact folded size, is endowed with a leg configuration with a five-bar mechanism. Based on biological observations of human walking, a passive artificial tendon made of emulsion is fabricated to work in conjunction with a tensioning device, providing adaptive heel touchdown and toe push-off in sync with single-leg movement. The tailored control framework for the bipedal robot is further established with the double-layer architecture. The regulation layer employs the linear inverted pendulum (LIP) model to generate reference trajectory of the center of mass (CoM) with a dead-beat style of parameter adjustment. An inverse-dynamics-based whole-body controller (WBC) is applied to enforce the full-order dynamics of the bipedal robot to reproduce the LIP model’s behavior. We carry out the experiments on the physical prototype to evaluate the walking performance of the developed bipedal robot. The results show that the robot achieves stable walking at the speed of 0.8 m/s (almost twice the leg length/s) and exhibits robustness to external push disturbance.

Active Power Assist with Equivalent Force on Connection for Lower Limb Exoskeleton Robots

Active power-assist lower limb exoskeleton robots aim to enhance wearer assistance while ensuring wearer comfort and simplifying the exoskeleton’s design and control. This study proposes an active assistance method known as Equivalent Force on Connection (EFOC). The EFOC method effectively addresses the limitations encountered in conventional Joint Torque Proportional Compensation (JTPC) approaches. These limitations include the necessity for exoskeleton robot configurations to align with human limb structures for parallel assistance at each lower limb joint, as well as the exoskeleton’s inability to contribute a greater proportion of assistance due to the excessive load on specific skeletal and muscular structures, resulting in wearer discomfort. Furthermore, the effectiveness of the EFOC method is evaluated and validated for assistance during both the stance and swing phases of single-leg movements. Finally, the proposed EFOC method is implemented on a hydraulic-driven lower limb exoskeleton robot to assist wearers in squatting, stepping, and jumping locomotion. The experimental results demonstrate that the proposed EFOC method can effectively achieve the desired assistance effect.

Intersession reliability of quadriceps corticospinal excitability: A functional transcranial magnetic stimulation study

Recording transcranial magnetic stimulation-derived measures during a closed kinetic chain task can serve as a functional technique to assess corticomotor function, which may have implications for activities of daily living or lower extremity injury in physically active individuals. Given the novelty of TMS use in this way, our purpose was to first determine the intersession reliability of quadriceps corticospinal excitability during a single-leg squat. We used a descriptive laboratory study to assess 20 physically active females (22.1 ± 2.5 years, 1.7 ± 0.7 m, 66.3 ± 13.6 kg, Tegner Activity Scale: 5.90 ± 1.12) over a 14-day period. Two-way mixed effects Intraclass Correlation Coefficients (3,1) (ICC) for absolute agreement were used to assess intersession reliability. The active motor threshold (AMT) and normalized motor evoked potential (MEP) amplitudes were assessed in the vastus medialis of each limb. The dominant limb AMTs demonstrated moderate-to-good reliability (ICC = 0.771, 95% CI = 0.51–0.90; p < 0.001). The non-dominant limb AMTs (ICC = 0.364, 95% CI = 0.00–0.68, p = 0.047), dominant limb MEPs (ICC = 0.192, 95% CI = 0.00–0.71; p = 0.340), and non-dominant limb MEPs (ICC = 0.272, 95% CI = 0.00–0.71; p = 0.235) demonstrated poor-to-moderate reliability. These findings may provide insight into corticomotor function during activities requiring weight-bearing, single-leg movement. However, variability in agreement suggests further work is warranted to improve the standardization of this technique prior to incorporating in clinical outcomes research.

Biomechanical Risk Factors of Injury-Related Single-Leg Movements in Male Elite Youth Soccer Players

Altered movement patterns during single-leg movements in soccer increase the risk of lower-extremity non-contact injuries. The identification of biomechanical parameters associated with lower-extremity injuries can enrich knowledge of injury risks and facilitate injury prevention. Fifty-six elite youth soccer players performed a single-leg drop landing task and an unanticipated side-step cutting task. Three-dimensional ankle, knee and hip kinematic and kinetic data were obtained, and non-contact lower-extremity injuries were documented throughout the season. Risk profiling was assessed using a multivariate approach utilising a decision tree model (classification and regression tree method). The decision tree model indicated peak knee frontal plane angle, peak vertical ground reaction force, ankle frontal plane moment and knee transverse plane angle at initial contact (in this hierarchical order) for the single-leg landing task as important biomechanical parameters to discriminate between injured and non-injured players. Hip sagittal plane angle at initial contact, peak ankle transverse plane angle and hip sagittal plane moment (in this hierarchical order) were indicated as risk factors for the unanticipated cutting task. Ankle, knee and hip kinematics, as well as ankle and hip kinetics, during single-leg high-risk movements can provide a good indication of injury risk in elite youth soccer players.

Are Core Stability Tests Related to Single Leg Squat Performance in Active Females?

Core stability (CS) deficits can have a significant impact on lower limb function. The aim of this study was to investigate the relationship between two dynamic core exercise assessments and dynamic knee valgus during single-leg squats. In total, 20 physically active female students participated in this study. The OCTOcore smartphone application assesses CS during two dynamic exercise tests, the partial range single-leg deadlift (SLD) test and the bird-dog (BD) test. A two-dimensional assessment of a single-leg squat test was used to quantify participants’ hip frontal angle (HFASLS) and knee frontal plane projection angle (FPPASLS). Ankle dorsiflexion was evaluated through the weight-bearing dorsiflexion test. The correlational analyses indicated that the HFASLS was significantly related to the partial range single-leg deadlift test (r = 0.314, p < 0.05) and ankle dorsiflexion (r = 0.322, p < 0.05). The results showed a significant difference (p < 0.05) in the CS test between cases categorised as dynamic knee valgus (>10°) and normal (≤10°). The CS deficit may influence the neuromuscular control of the lumbopelvic-hip complex during single-leg movements. The link between CS and kinematic factors related to knee injuries was only observed when CS was measured in the SLD test but not in the BD test.

Functional Movement Quality of Firefighter Recruits: Longitudinal Changes from the Academy to Active-Duty Status.

Approximately half of the injuries experienced by firefighters consist of musculoskeletal injuries (MSKIs). Functional movement quality may be associated with MSKI risk within this tactical athlete population. Previous research indicates that measures of body composition change among firefighter recruits progressing from academy training through active-duty service, but similar changes in functional movement quality have yet to be examined. The purpose of this study was to describe longitudinal changes in functional movement quality of firefighter recruits. Body mass index (BMI), body fat (BF), and Functional Movement Screen (FMS) data were collected from 26 male firefighter recruits at the onset (W1) and completion (W14) of their training academy, and at the completion of their probationary period of active-duty service (W38). After adjusting for changes in BMI and BF across time, significant changes (ps < 0.05) in Composite FMS scores were identified, with significant increases in from W1 to W14 and from W14 to W38, as well as an overall increase from W1 to W38. These results suggest that the development of firefighter-specific skills can decrease the MSKI risk of firefighter recruits by facilitating enhanced functional movement competencies, particularly during tasks that require single-leg movement and core strength and stability.

Dynamic Knee Valgus in Single-Leg Movement Tasks. Potentially Modifiable Factors and Exercise Training Options. A Literature Review.

Dynamic knee valgus (DKV) as an incorrect movement pattern is recognized as a risk factor for lower limb injuries. Therefore, it is important to find the reasons behind this movement to select effective preventive procedures. There is a limited number of publications focusing on specific tasks, separating the double-leg from the single-leg tasks. Test patterns commonly used for DKV assessment, such as single-leg squat (SLS) or single leg landings (SLL), may show different results. The current review presents the modifiable factors of knee valgus in squat and landing single-leg tests in healthy people, as well as exercise training options. The authors used the available literature from PubMed, Scopus, PEDro and clinicaltrials.gov databases, and reviewed physiotherapy journals and books. For the purpose of the review, studies were searched for using 2D or 3D motion analysis methods only in the SLL and SLS tasks among healthy active people. Strengthening and activating gluteal muscles, improving trunk lateral flexion strength, increasing ROM dorsiflexion ankle and midfoot mobility should be taken into account when planning training programs aimed at reducing DKV occurring in SLS. In addition, knee valgus during SLL may occur due to decreased hip abductors, extensors, external rotators strength and higher midfoot mobility. Evidence from several studies supports the addition of biofeedback training exercises to reduce the angles of DKV.

Delineating the age‐related attenuation of vascular function: evidence supporting the efficacy of single passive leg movement.

Passive leg movement (PLM), performed continuously, is a promising clinically relevant assessment of peripheral vascular function which declines with age. To further refine PLM, this study evaluated the efficacy of a single PLM (sPLM) to delineate between young and old healthy males based on vascular function.MethodsTwelve healthy young (26±5 yr) and 12 old (70±7 yr) underwent sPLM: blood flow was assessed by Doppler ultrasound at baseline, during, and for one minute after a single leg movement (range of motion 90°). Blood pressure was continuously recorded by finger photoplethysmography. Factor analysis assessed covariance. If a significant age difference emerged, a cut score was determined by a receiver operator characteristic curve analysis. Data are mean±SD.ResultsAll blood flow and leg vascular conductance measures loaded into one factor (standardized loading ≥ 0.85), indicating the only physiological measure needed was blood flow. Baseline blood flows were similar between groups (p=0.626). Peak increase in blood flow from baseline was significantly attenuated in the old (Young: 717±227, Old: 260±97 ml·min−1, p&lt;0.001; cut score: 485 ml·min−1, sensitivity 1, specificity 1) as was the total sPLM‐induced blood flow, above baseline, for 45 seconds (Young: 155±67, Old: 26±17ml, p&lt;0.001; cut score: 72 ml, sensitivity 1, specificity 1).ConclusionsPLM, a simplified version of PLM, demonstrated strong qualities of a screening test for peripheral vascular function, evidenced by revealing the age‐related reduction in peripheral hyperemic response with clearly delineated cut scores. Indicating, sPLM has strong potential as an accurate screening test for age‐related attenuations in peripheral vascular function.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Altered muscle activation following hamstring injuries

ObjectiveThe purpose of this study was to compare the electromyographic (EMG) activity of gluteal and thigh muscles of sportspeople with a recent hamstring injury with uninjured controls during a weight-bearing...

Movement features and H-reflex modulation. II. Passive rotation, movement velocity and single leg movement

Modulation of soleus H-reflex magnitudes during pedalling, and their approximation when seated with appropriate joint positions and contractile activity was demonstrated in the previous paper. The present study investigated the modulation of H-reflexes during (A) pedalling movement in the absence of contractile activity, (B) different movement velocities and (C) movement of a single limb. Using a customized tandem cycle ergometer, seated subjects with trunk supported relaxed their leg muscles and allowed their legs to be rotated. Their feet were supported on the pedals with the ankle braced. Reflexes were collected at four phases in the movement cycle (with some at 13 phases) and with speeds of 5–60 revolutions per min (cycle times from 12 to 1 s). The results showed that (i) reflex magnitude substantially decreased with limb rotation( P < 0.05). The degree of inhibition was dependent on the phase position. (ii) Increasing speed of passive rotation increased the inhibition at all positions, but was most pronounced near the fullest flexion of hip and knee. When subjects actively pedalled, the relationship between speed and inhibition remained. (iii) When the contralateral leg was moved and the target leg was stationary, crossed projection of reflex inhibition was clear. (iv) The reflex gain measured during active pedalling of one leg was similar to that observed during two legged pedalling. Again, a crossed effect from the contralateral leg could be observed. We conclude that the net influence of discharge from movement-elicited afference is inhibitory on this reflex path and that the reflex modulation during pedalling arises from overlaid sources. From the two papers in this present set of studies, we suggest that tonic inhibition over the whole movement cycle is relieved by overlaid reflex excitation during active pedalling, particularly during the phase when the leg extends. Each component, inhibition and excitation, is multisourced with overlap of effects from peripheral discharge.