Robust and energy-efficient bipedal locomotion in robotics is still a challenging topic. In order to address issues in this field, we can take inspiration from nature, by studying human locomotion. The Spring-Loaded Inverted Pendulum (SLIP) model has shown to be a good model for this purpose. However, the human musculoskeletal system enables us to actively modulate leg stiffness, for example wh...

Understanding leg and joint stiffness adjustment during maximum hopping may provide important information for developing more effective training methods. It has been reported that ankle stiffness has major influence on stable spring-mass dynamics during submaximal hopping, and that knee stiffness is a major determinant for hopping performance during maximal hopping task. Furthermore, there are ...

Biomechanical studies suggest that animals’ abilities to tune their effective leg compliance in response to changing terrain conditions plays an important role in their agile, robust locomotion. However, despite growing interest in leg compliance within the robotics literature, little experimental work has been reported on tunable passive leg compliance in running machines. In this paper we pre...

This study investigated differences in knee extensor/flexor electromyography (EMG), leg loading rate, and leg stiffness in older and younger men during stair descent. Sixteen older men (mean +/- standard deviation [SD] = 72 +/- 4.5 years) and sixteen younger men (mean +/- SD = 21.2 +/- 0.5 years) were recruited. The EMG signals were recorded from the rectus femoris and the biceps femoris, while...

BACKGROUND Running and hopping involve moving in a bouncing fashion during which the limbs behave as springs. The ability to alter the stiffness of these leg springs is essential to maintaining an efficient gait. Since the plantar surface of the foot is the only part of the body to encounter the ground during bipedal locomotion, it would seem logical that some aspect of the neurological functio...

This study investigated relationships between 10 m sprint acceleration, step kinematics (step length and frequency, contact and flight time), and leg muscle performance (power, stiffness, strength). Twenty-eight field sport athletes completed 10 m sprints that were timed and filmed. Velocity and step kinematics were measured for the 0-5, 5-10, and 0-10 m intervals to assess acceleration. Leg po...

As an alternative to walking and running, humans are able to skip. However, adult humans avoid it. This fact seems to be related to the higher energetic costs associated with skipping. Still, children, some birds, lemurs and lizards use skipping gaits during daily locomotion. We combined experimental data on humans with numerical simulations to test whether stability and robustness motivate thi...

BACKGROUND Anterior cruciate ligament (ACL) injuries often occur during landing, with female athletes at higher injury risk than male athletes. Interestingly, female dancers have lower ACL injury rates than do female athletes in general. HYPOTHESIS Female dancers will have earlier and greater lower extremity muscle activity and higher sagittal knee joint and leg stiffness than will female bas...

During bouncing gaits such as hopping and running, leg muscles generate force to enable elastic energy storage and return primarily from tendons and, thus, demand metabolic energy. In an effort to reduce metabolic demand, we designed two elastic leg exoskeletons that act in parallel with the wearer's legs; one exoskeleton consisted of a multiple leaf (MLE) and the other of a single leaf (SLE) s...

Analysis of human running has revealed that the motion of the human leg can be modeled by a compression spring because the joints of the leg behave like a torsion spring in the stance phase. In this paper, we describe the development of a joint mechanism that mimics the elastic characteristics of the joints of the stance leg. The knee was equipped with a mechanism comprising two laminated leaf ...