The shifting of the torsion axis of the foot during the stance phase of lateral cutting movements

The highly dynamic legged jumping motion is a challenging research topic because of the lack of established control schemes that handle over-constrained control objectives well in the stance phase, which are coupled and affect each other, and control robot’s posture in the flight phase, in which the robot is underactuated owing to the foot leaving the ground. This paper introduces an approach of realizing the cyclic vertical jumping motion of a planar simplified legged robot that formulates the jump problem within a quadratic-programming (QP)-based framework. Unlike prior works, which have added different weights in front of control tasks to express the relative hierarchy of tasks, in our framework, the hierarchical quadratic programming (HQP) control strategy is used to guarantee the strict prioritization of the center of mass (CoM) in the stance phase while split dynamic equations are incorporated into the unified quadratic-programming framework to restrict the robot’s posture to be near a desired constant value in the flight phase. The controller is tested in two simulation environments with and without the flight phase controller, the results validate the flight phase controller, with the HQP controller having a maximum error of the CoM in the x direction and y direction of 0.47 and 0.82 cm and thus enabling the strict prioritization of the CoM.

Download Full-text

Ankle Muscle Activations during Different Foot-Strike Patterns in Running

Sensors ◽

10.3390/s21103422 ◽

2021 ◽

Vol 21 (10) ◽

pp. 3422

Author(s):

Jian-Zhi Lin ◽

Wen-Yu Chiu ◽

Wei-Hsun Tai ◽

Yu-Xiang Hong ◽

Chung-Yu Chen

Keyword(s):

Muscle Activity ◽

Muscle Activation ◽

Stance Phase ◽

Inertial Sensors ◽

Plantar Flexion ◽

Intraclass Correlation ◽

Biceps Femoris ◽

Ankle Muscle ◽

Foot Strike ◽

Muscle Activations

This study analysed the landing performance and muscle activity of athletes in forefoot strike (FFS) and rearfoot strike (RFS) patterns. Ten male college participants were asked to perform two foot strikes patterns, each at a running speed of 6 km/h. Three inertial sensors and five EMG sensors as well as one 24 G accelerometer were synchronised to acquire joint kinematics parameters as well as muscle activation, respectively. In both the FFS and RFS patterns, according to the intraclass correlation coefficient, excellent reliability was found for landing performance and muscle activation. Paired t tests indicated significantly higher ankle plantar flexion in the FFS pattern. Moreover, biceps femoris (BF) and gastrocnemius medialis (GM) activation increased in the pre-stance phase of the FFS compared with that of RFS. The FFS pattern had significantly decreased tibialis anterior (TA) muscle activity compared with the RFS pattern during the pre-stance phase. The results demonstrated that the ankle strategy focused on controlling the foot strike pattern. The influence of the FFS pattern on muscle activity likely indicates that an athlete can increase both BF and GM muscles activity. Altered landing strategy in cases of FFS pattern may contribute both to the running efficiency and muscle activation of the lower extremity. Therefore, neuromuscular training and education are required to enable activation in dynamic running tasks.

Download Full-text

IMU-Based Effects Assessment of the Use of Foot Orthoses in the Stance Phase during Running and Asymmetry between Extremities

Sensors ◽

10.3390/s21093277 ◽

2021 ◽

Vol 21 (9) ◽

pp. 3277

Author(s):

Juan Luis Florenciano Restoy ◽

Jordi Solé-Casals ◽

Xantal Borràs-Boix

Keyword(s):

Contact Time ◽

Stance Phase ◽

Inertial Sensors ◽

Sagittal Plane ◽

Plantar Flexion ◽

Foot Orthoses ◽

Foot Kinematics ◽

Running Injuries ◽

The Right ◽

Movement Differences

The objectives of this study were to determine the amplitude of movement differences and asymmetries between feet during the stance phase and to evaluate the effects of foot orthoses (FOs) on foot kinematics in the stance phase during running. In total, 40 males were recruited (age: 43.0 ± 13.8 years, weight: 72.0 ± 5.5 kg, height: 175.5 ± 7.0 cm). Participants ran on a running treadmill at 2.5 m/s using their own footwear, with and without the FOs. Two inertial sensors fixed on the instep of each of the participant’s footwear were used. Amplitude of movement along each axis, contact time and number of steps were considered in the analysis. The results indicate that the movement in the sagittal plane is symmetric, but that it is not in the frontal and transverse planes. The right foot displayed more degrees of movement amplitude than the left foot although these differences are only significant in the abduction case. When FOs are used, a decrease in amplitude of movement in the three axes is observed, except for the dorsi-plantar flexion in the left foot and both feet combined. The contact time and the total step time show a significant increase when FOs are used, but the number of steps is not altered, suggesting that FOs do not interfere in running technique. The reduction in the amplitude of movement would indicate that FOs could be used as a preventive tool. The FOs do not influence the asymmetry of the amplitude of movement observed between feet, and this risk factor is maintained. IMU devices are useful tools to detect risk factors related to running injuries. With its use, even more personalized FOs could be manufactured.

Download Full-text

Effects of Tendon Release Surgery on Inter-Limb Leg Stiffness Control in Children with Spastic Diplegic Cerebral Palsy during Gait

Applied Sciences ◽

10.3390/app11104562 ◽

2021 ◽

Vol 11 (10) ◽

pp. 4562

Author(s):

Chien-Chung Kuo ◽

Hsing-Po Huang ◽

Hsuan-Yu Lu ◽

Tsan-Yang Chen ◽

Ting-Ming Wang ◽

...

Keyword(s):

Cerebral Palsy ◽

Stance Phase ◽

Reaction Force ◽

Bilateral Symmetry ◽

Healthy Controls ◽

Leg Stiffness ◽

Characteristic Features ◽

Total Leg ◽

Analysis System ◽

Single Limb Support

Impaired motor control and musculotendon tightness in the lower extremities are characteristic features of patients with diplegic cerebral palsy (CP). Tendon release surgery (TRS) helps improve joint and leg stiffness, but the effects of TRS on inter-limb coordination in terms of the total leg stiffness, and the bilateral symmetry in leg stiffness during gait, remain unknown. Ten children with spastic diplegic CP scheduled for TRS and ten healthy controls participated in this study. The inter-limb sharing of total leg stiffness during double-limb support phase and bilateral leg stiffness symmetry during stance phase of gait were calculated using the kinematic and ground reaction force data measured by a motion analysis system. Before TRS, the patients with diplegic CP walked with a decreased share of total leg stiffness during weight-acceptance (p < 0.05) and with increased bilateral leg stiffness asymmetry during single-limb support and weight-transfer during gait (p < 0.05) when compared to healthy controls. After TRS, the bilateral leg stiffness asymmetry was significantly reduced in the CP group, especially in the terminal stance phase, with inter-limb sharing of total leg stiffness becoming similar to that in controls (p > 0.05). The surgery seemed to improve the lower limb control and increased the bilateral limb symmetry during gait.

Download Full-text

Novel active magnetorheological knee prosthesis presents low energy consumption during ground walking

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x20983923 ◽

2021 ◽

pp. 1045389X2098392

Author(s):

Rafhael Milanezi de Andrade ◽

Jordana Simões Ribeiro Martins ◽

Marcos Pinotti ◽

Antônio Bento Filho ◽

Claysson Bruno Santos Vimieiro

Keyword(s):

Energy Consumption ◽

Stance Phase ◽

Gait Cycle ◽

Dynamic Models ◽

Knee Prosthesis ◽

Regenerative Braking ◽

Harmonic Drive ◽

Low Energy Consumption ◽

Energetic Expenditure ◽

Over Ground Walking

This study analyses the energy consumption of an active magnetorheological knee (AMRK) actuator that was designed for transfemoral prostheses. The system was developed as an operational motor unit (MU), which consists of an EC motor, a harmonic drive and a magnetorheological (MR) clutch, that operates in parallel with an MR brake. The dynamic models of the MR brake and MU were used to simulate the system’s energetic expenditure during over-ground walking under three different working conditions: using the complete AMRK; using just its motor-reducer, to operate as a common active knee prosthesis (CAKP), and using just the MR brake, to operate as a common semi-active knee prosthesis (CSAKP). The results are used to compare the MR devices power consumptions with that of the motor-reducer. As previously hypothesized, to use the MR brake in the swing phase is more energetically efficient than using the motor-reducer to drive the joint. Even if using the motor-reducer in regenerative braking mode during the stance phase, the differences in power consumption among the systems are remarkable. The AMRK expended 16.3 J during a gait cycle, which was 1.6 times less than the energy expenditure of the CAKP (26.6 J), whereas the CSAKP required just 6.0 J.

Download Full-text