scholarly journals Performance analysis of unpowered lower limb exoskeleton during sit down and stand up

Robotica ◽  
2021 ◽  
pp. 1-19
Author(s):  
Yongfeng Wang ◽  
Guoru Zhao ◽  
Yanan Diao ◽  
YU Feng ◽  
Guanglin Li
Keyword(s):  
Lower Limb ◽  
Theoretical Basis ◽  
Metabolic Cost ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Motion Model ◽  
Storage Element ◽  
Lower Limb Exoskeleton ◽  
Long Head ◽  
Motion Characteristics

ABSTRACT Conventional unpowered lower limb exoskeleton paid little attention to the metabolic cost of body during sit down (SD)/stand up (SU). The SD motion model and the motion characteristics of lower extremity are analyzed; then, a novel unpowered lower limb exoskeleton is proposed, and the contribution degree of muscles and stiffness of joints are used for determining the location and stiffness of energy storage element. The metabolic cost of relevant muscles in joints of the left leg is obtained based on Opensim software. The results show that metabolic cost of the gracilis, rectus femoris (RF), and long head of the biceps femoris decreased about 13%, 9%, and 68%, respectively. The total metabolic cost of body decreased about 14% during SD. However, the metabolic cost of the gracilis, RF, and long/short head of the biceps femoris increased about 22%, 33%, 208%, and 46%, respectively. And the metabolic cost of sartorius reduces about 39%, the total metabolic cost of body increased about 25.6% during SU, under the exoskeleton conditions. The results of this study can provide a theoretical basis for the optimal design of unpowered lower limb exoskeleton.

scholarly journals Modeling and Simulation of an Unpowered Lower Extremity Exoskeleton Based on Gait Energy

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Yongfeng Wang ◽  
Xiangzhan Kong ◽  
Jing Yang ◽  
Guanglin Li ◽  
Guoru Zhao
Keyword(s):  
Lower Extremity ◽  
High Efficiency ◽  
Metabolic Cost ◽  
Rectus Femoris ◽  
Eccentric Contraction ◽  
Human Motion ◽  
Motion Model ◽  
Tensor Fascia Lata ◽  
Lower Limb Exoskeleton ◽  
Positive Work

Aiming at the problem of how to store/release gait energy with high efficiency for the conventional unpowered lower extremity exoskeletons, an unpowered lower-limb exoskeleton is proposed. In the current study, the human motion model is established, and the change rule and recovery/utilization mechanism of gait energy are illustrated. The stiffness and metabolic cost of relevant muscles in lower extremity joints are obtained based on OpenSim software. The results show that stiffness of muscle is increased when muscle concentric contraction generates positive work, but it is reverse when muscle eccentric contraction generates negative work. Besides, metabolic cost of the soleus, gastrocnemius, and tibialis anterior decreased about 31.5%, 34.7%, and 40%, respectively. Metabolic cost of the rectus femoris, tensor fascia lata, and sartorius decreased about 36.3%, 7%, and 5%, respectively, and the total metabolic cost of body decreased about 15.5%, under the exoskeleton conditions. The results of this study can provide a theoretical basis for the optimal design of unpowered lower extremity exoskeleton.

Develop a Flexible Regenerative Exoskeleton to Assist Walking

2018 ◽  
Author(s):  
Longhan Xie ◽  
Xiaodong Li
Keyword(s):  
Kinetic Energy ◽  
Human Body ◽  
Lower Limb ◽  
Metabolic Cost ◽  
Lower Limbs ◽  
Metabolic Energy ◽  
Lower Limb Exoskeleton ◽  
Negative Work ◽  
Lower Limb Muscles ◽  
Assisting Device

During walking, human lower limbs accelerate and decelerate alternately, during which period the human body does positive and negative work, respectively. Muscles provide power to all motions and cost metabolic energy both in accelerating and decelerating the lower limbs. In this work, the lower-limb biomechanics of walking was analyzed and it revealed that if the negative work performed during deceleration can be harnessed using some assisting device to then assist the acceleration movement of the lower limb, the total metabolic cost of the human body during walking can be reduced. A flexible lower-limb exoskeleton was then proposed; it is worn in parallel to the lower limbs to assist human walking without consuming external power. The flexible exoskeleton consists of elastic and damping components that are similar to physiological structure of a human lower limb. When worn on the lower limb, the exoskeleton can partly replace the function of the lower limb muscles and scavenge kinetic energy during lower limb deceleration to assist the acceleration movement. Besides, the generator in the exoskeleton, serving as a damping component, can harvest kinetic energy to produce electricity. A prototype of the flexible exoskeleton was developed, and experiments were carried out to validate the analysis. The experiments showed that the exoskeleton could reduce the metabolic cost by 3.12% at the walking speed of 4.5 km/h.

A NOVEL CABLE-PULLEY UNDERACTUATED LOWER LIMB EXOSKELETON FOR HUMAN LOAD-CARRYING WALKING

2017 ◽  
Vol 17 (07) ◽  
pp. 1740042
Author(s):  
YANG LIU ◽  
YONGSHENG GAO ◽  
YANHE ZHU
Keyword(s):  
Lower Limb ◽  
Evaluation Method ◽  
Joint Angle ◽  
Metabolic Cost ◽  
Human Motion ◽  
Control Effect ◽  
Effective Power ◽  
Lower Limb Exoskeleton ◽  
Load Carrying ◽  
Power Assistance

Wearable lower limb exoskeleton has comprehensive applications such as load-carrying augmentation, walking assistance, and rehabilitation training by using many active actuators in the joints to reduce the metabolic cost generally. The traditional fully actuated exoskeleton is bulky and requires large energy consumption, and the passive exoskeleton is difficult to provide effective power assistance. To achieve both small number of actuators and good assisting performance, this paper proposes a cable-pulley underactuated principle-based lower limb exoskeleton. The exoskeleton dynamics was modeled and the human-exoskeleton hybrid model was analyzed via ADAMS and LifeMOD to provide an evaluation method for power assistance. By exploiting the control strategy and utilizing the synergies of torque and power assistance, the hip joint and the knee joint can be actuated by a single cable simultaneously. Moreover, the human-exoskeleton co-simulation method was utilized to verify the assisting performance and control effect. In this simulation, the upper toque peak and power required by human are obviously reduced by power assistance and the joint angle curves without exoskeleton are in accordance with the joint angle curves with exoskeleton almost. In conclusion, the designed exoskeleton is compatible with human motion and feasible to provide effective power assistance in load-carrying walking.

scholarly journals The Effect of Step Width on Muscle Contributions to Body Mass Center Acceleration During the First Stance of Sprinting

2021 ◽  
Vol 9 ◽  
Author(s):  
Ruoli Wang ◽  
Laura Martín de Azcárate ◽  
Paul Sandamas ◽  
Anton Arndt ◽  
Elena M. Gutierrez-Farewik
Keyword(s):  
Lower Limb ◽  
Sagittal Plane ◽  
Center Of Mass ◽  
Gluteus Maximus ◽  
Rectus Femoris ◽  
Gluteus Medius ◽  
Biceps Femoris ◽  
The Body ◽  
Step Width ◽  
Acceleration Analysis

BackgroundAt the beginning of a sprint, the acceleration of the body center of mass (COM) is driven mostly forward and vertically in order to move from an initial crouched position to a more forward-leaning position. Individual muscle contributions to COM accelerations have not been previously studied in a sprint with induced acceleration analysis, nor have muscle contributions to the mediolateral COM accelerations received much attention. This study aimed to analyze major lower-limb muscle contributions to the body COM in the three global planes during the first step of a sprint start. We also investigated the influence of step width on muscle contributions in both naturally wide sprint starts (natural trials) and in sprint starts in which the step width was restricted (narrow trials).MethodMotion data from four competitive sprinters (2 male and 2 female) were collected in their natural sprint style and in trials with a restricted step width. An induced acceleration analysis was performed to study the contribution from eight major lower limb muscles (soleus, gastrocnemius, rectus femoris, vasti, gluteus maximus, gluteus medius, biceps femoris, and adductors) to acceleration of the body COM.ResultsIn natural trials, soleus was the main contributor to forward (propulsion) and vertical (support) COM acceleration and the three vasti (vastus intermedius, lateralis and medialis) were the main contributors to medial COM acceleration. In the narrow trials, soleus was still the major contributor to COM propulsion, though its contribution was considerably decreased. Likewise, the three vasti were still the main contributors to support and to medial COM acceleration, though their contribution was lower than in the natural trials. Overall, most muscle contributions to COM acceleration in the sagittal plane were reduced. At the joint level, muscles contributed overall more to COM support than to propulsion in the first step of sprinting. In the narrow trials, reduced COM propulsion and particularly support were observed compared to the natural trials.ConclusionThe natural wide steps provide a preferable body configuration to propel and support the COM in the sprint starts. No advantage in muscular contributions to support or propel the COM was found in narrower step widths.

scholarly journals Aging Affects Lower Limb Joint Moments and Muscle Responses to a Split-Belt Treadmill Perturbation

2021 ◽  
Vol 3 ◽  
Author(s):  
Dongyual Yoo ◽  
Junmo An ◽  
Kap-Ho Seo ◽  
Beom-Chan Lee
Keyword(s):  
Older Adults ◽  
Lower Limb ◽  
Recovery Period ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Young Group ◽  
Joint Moments ◽  
Age Related ◽  
Muscle Responses ◽  
Perturbation Period

Age-related changes cause more fall-related injuries and impede the recoveries by older adults compared to younger adults. This study assessed the lower limb joint moments and muscle responses to split-belt treadmill perturbations in two groups (14 healthy young group [23.36 ± 2.90 years] and 14 healthy older group [70.93 ± 4.36 years]) who performed two trials of unexpected split-belt treadmill perturbations while walking on a programmable split-belt treadmill. A motion capture system quantified the lower limb joint moments, and a wireless electromyography system recorded the lower limb muscle responses. The compensatory limb's (i.e., the tripped limb's contralateral side) joint moments and muscle responses were computed during the pre-perturbation period (the five gait cycles before the onset of a split-belt treadmill perturbation) and the recovery period (from the split-belt treadmill perturbation to the baseline gait relying on the ground reaction forces' profile). Joint moments were assessed by maximum joint moments, and muscle responses were quantified by the normalization (%) and co-contraction index (CCI). Joint moments and muscle responses of the compensatory limb during the recovery period were significantly higher for the YG than the OG, and joint moments (e.g., knee flexion and extension and hip flexion moments) and muscle responses during the recovery period were higher compared to the pre-perturbation period for both groups. For CCI, the older group showed significantly higher co-contraction for biceps femoris/rectus femoris muscles than the young group during the recovery period. For both groups, co-contraction for biceps femoris/rectus femoris muscles was higher during the pre-perturbation period than the recovery period. The study confirmed that older adults compensated for muscle weakness by using lower joint moments and muscle activations and increasing muscle co-contractions to recover balance after split-belt treadmill perturbations. A better understanding of the recovery mechanisms of older adults who train on fall-inducing systems could improve therapeutic regimens.

An Anthropometrically Parameterized Assistive Lower-limb Exoskeleton

2021 ◽  
Author(s):  
Curt Laubscher ◽  
Ryan Farris ◽  
Antonie van den Bogert ◽  
Jerzy T. Sawicki
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Vastus Lateralis ◽  
Mechanical Energy ◽  
Biceps Femoris ◽  
Knee Joints ◽  
Lower Limb Exoskeleton ◽  
Hip Abduction ◽  
The Subject ◽  
Muscle Activations

Abstract This paper presents a newly developed lower-limb exoskeleton tested for walking assistance. The novel exoskeleton design methodology uses additive manufacturing and a parametrized model based on user anthropometrics to give a person-specific custom fit. The process is applied to average children and a healthy adult, and a prototype device is fabricated for the adult to validate the feasibility of the approach. The developed prototype actuates the hip and knee joints without restricting hip abduction-adduction motion. To test usability of the device and evaluate walking assistance, user torque, mechanical energy generated, and muscle activation are analyzed in an assisted condition where the subject walks on a level treadmill with the exoskeleton powered. This is compared to an unassisted condition with the exoskeleton unpowered and a baseline condition with the subject not wearing the exoskeleton. Comparing assisted to baseline conditions, torque magnitudes increased at the hip and knee, mechanical energy generated increased at the hip but decreased at the knee, and muscle activations decreased in the Biceps Femoris and increased in the Vastus Lateralis. The presented preliminary results are inconclusive on whether the newly developed exoskeleton can assist in walking though show promise for basic usability of the device.

Different Muscle-Recruitment Strategies Among Elite Breaststrokers

2015 ◽  
Vol 10 (8) ◽  
pp. 1061-1065 ◽  
Author(s):  
Brice Guignard ◽  
Bjørn H. Olstad ◽  
David Simbaña Escobar ◽  
Jessy Lauer ◽  
Per-Ludvik Kjendlie ◽  
...  
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Sagittal Plane ◽  
National Level ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Recovery Phase ◽  
Elite Group ◽  
Flexion Extension ◽  
High Level

Purpose:To investigate electromyographical (EMG) profiles characterizing the lower-limb flexion-extension in an aquatic environment in high-level breaststrokers.Methods:The 2-dimensional breaststroke kick of 1 international- and 2 national-level female swimmers was analyzed during 2 maximal 25-m swims. The activities of biceps femoris, rectus femoris, gastrocnemius, and tibialis anterior were recorded.Results:The breaststroke kick was divided in 3 phases, according to the movements performed in the sagittal plane: push phase (PP) covering 27% of the total kick duration, glide phase (GP) 41%, and recovery phase (RP) 32%. Intrasubject reproducibility of the EMG and kinematics was observed from 1 stroke cycle to another. In addition, important intersubject kinematic reproducibility was noted, whereas muscle activities discriminated the subjects: The explosive Pp was characterized by important muscle-activation peaks. During the recovery, muscles were likewise solicited for swimmers 1 (S1) and 2 (S2), while the lowest activities were observed during GP for S2 and swimmer 3 (S3), but not for S1, who maintained major muscle solicitations.Conclusions:The main muscle activities were observed during PP to perform powerful lower-limb extension. The most-skilled swimmer (S1) was the only 1 to solicit her muscles during GP to actively reach better streamlining. Important activation peaks during RP correspond to the limbs acting against water drag. Such differences in EMG strategies among an elite group highlight the importance of considering the muscle parameters used to effectively control the intensity of activation among the phases for a more efficient breaststroke kick.

Acute Effects of Different Stretching Techniques on Lower Limb Kinematics, Kinetics and Muscle Activities during Vertical Jump

2019 ◽  
Vol 40 ◽  
pp. 1-15
Author(s):  
Zi Xiang Gao ◽  
Yang Song ◽  
Pei Min Yu ◽  
Yan Zhang ◽  
Shu Dong Li
Keyword(s):  
Internal Rotation ◽  
Lower Limb ◽  
Vertical Jump ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Acute Effects ◽  
Warm Up ◽  
Gastrocnemius Medialis ◽  
Limb Kinematics ◽  
Lower Limb Kinematics

The purpose of this study was to examine the acute effects of different stretching techniques on performance and lower limb kinematics, kinetics and muscle activities during vertical jump in female aerobics athletes. 10 female college aerobics athletes participated in this study. Three-dimensional kinematic and kinetic data, as well as electromyography of rectus femoris, biceps femoris and gastrocnemius medialis were collected using Vicon motion analysis system, Kistler force plate and Wireless surface electromyographic system respectively during the test. No significant differences in jump height had been determined among these 3 warm-up methods. Hip peak flexion and internal rotation angles decreased significantly after BSM and peak adduction angle decreased significantly after SSM and BSM during landing. Knee peak flexion and internal rotation angles increased significantly after SSM and BSM during take-off. Also, BSM showed significantly greater peak flexion compared with SSM. Ankle peak plantarflexion angle increased significantly after BSM. In addition, BSM showed significantly greater improvement in the variation range than SSM except for the ankle int-external rotation. Existence of no significant differences in the peak value of vertical ground reaction force during take-off and landing phase had been determined among these 3 warm-up methods, and muscle activities of rectus femoris, biceps femoris and gastrocnemius medialis were likewise not significantly different. The results of this study suggest that it would be suitable for female aerobics athletes to perform ballistic stretching in warm-up in order to improve flexibility without decreasing the following vertical jumping event and may also reduce the risk of ankle sprain injury.

scholarly journals Biarticular muscles are most responsive to upper-body pitch perturbations in human standing

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Christian Schumacher ◽  
Andrew Berry ◽  
Daniel Lemus ◽  
Christian Rode ◽  
André Seyfarth ◽  
...  
Keyword(s):  
Muscular Activity ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Upper Body ◽  
Leg Muscles ◽  
Thigh Muscles ◽  
Biarticular Muscles ◽  
Upper Body Posture ◽  
Efficient Gait ◽  
Long Head

Abstract Balancing the upper body is pivotal for upright and efficient gait. While models have identified potentially useful characteristics of biarticular thigh muscles for postural control of the upper body, experimental evidence for their specific role is lacking. Based on theoretical findings, we hypothesised that biarticular muscle activity would increase strongly in response to upper-body perturbations. To test this hypothesis, we used a novel Angular Momentum Perturbator (AMP) that, in contrast to existing methods, perturbs the upper-body posture with only minimal effect on Centre of Mass (CoM) excursions. The impulse-like AMP torques applied to the trunk of subjects resulted in upper-body pitch deflections of up to 17° with only small CoM excursions below 2 cm. Biarticular thigh muscles (biceps femoris long head and rectus femoris) showed the strongest increase in muscular activity (mid- and long-latency reflexes, starting 100 ms after perturbation onset) of all eight measured leg muscles which highlights the importance of biarticular muscles for restoring upper-body balance. These insights could be used for improving technological aids like rehabilitation or assistive devices, and the effectiveness of physical training for fall prevention e.g. for elderly people.

The Effect of Saddle Position on Maximal Power Output and Moment Generating Capacity of Lower Limb Muscles during Isokinetic Cycling

2011 ◽  
Vol 27 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Jeroen Vrints ◽  
Erwin Koninckx ◽  
Marc Van Leemputte ◽  
Ilse Jonkers
Keyword(s):  
Power Output ◽  
Lower Limb ◽  
Mechanical Performance ◽  
Knee Kinematics ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Leg Length ◽  
Maximal Power ◽  
Maximal Power Output ◽  
Generating Capacity

Saddle position affects mechanical variables during submaximal cycling, but little is known about its effect on mechanical performance during maximal cycling. Therefore, this study relates saddle position to experimentally obtained maximal power output and theoretically calculated moment generating capacity of hip, knee and ankle muscles during isokinetic cycling. Ten subjects performed maximal cycling efforts (5 s at 100 rpm) at different saddle positions varying ± 2 cm around the in literature suggested optimal saddle position (109% of inner leg length), during which crank torque and maximal power output were determined. In a subgroup of 5 subjects, lower limb kinematics were additionally recorded during submaximal cycling at the different saddle positions. A decrease in maximal power output was found for lower saddle positions. Recorded changes in knee kinematics resulted in a decrease in moment generating capacity of biceps femoris, rectus femoris and vastus intermedius at the knee. No differences in muscle moment generating capacity were found at hip and ankle. Based on these results we conclude that lower saddle positions are less optimal to generate maximal power output, as it mainly affects knee joint kinematics, compromising mechanical performance of major muscle groups acting at the knee.

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