In the literature, it is well established that subjects are able to jump higher in a countermovement jump (CMJ) than in a squat jump (SJ). The purpose of this study was to estimate the relative contribution of the time available for force development and the storage and reutilization of elas

Why is countermovement jump height greater than squat jump height

Adaptive gaits of humans were produced as a result of emergent properties of a model based on the neurophysiology of the central pattern generator and the biomechanics of the human musculoskeletal system. We previously proposed a neuromusculoskeletal model for human locomotion, in which movements emerged as a stable limit cycle that was generated through the global entrainment among the neural system, composed of neural oscillators, the musculoskeletal system, and the environment. In the present study, we investigated the adaptability of this model under various types of environmental and task constraints. Using a computer simulation, it was found that walking movements were robust against mechanical perturbations, loads with a mass, and uneven terrain. Moreover, the speed of walking could be controlled by a single parameter which tonically drove the neural oscillators, and the step cycle could be entrained by a rhythmic input to the neural oscillators.

A model of the neuro-musculo-skeletal system for human locomotion

Biomechanics and muscle coordination of human walking. Part I: introduction to concepts, power transfer, dynamics and simulations.

A three-dimensional model of the human body is used to simulate a maximal vertical jump. The body is modeled as a 10-segment, 23 degree-of-freedom (dof), mechanical linkage, actuated by 54 muscles. Six generalized coordinates describe the position and orientation of the pelvis relative to the ground; the remaining nine segments branch in an open chain from the pelvis. The head, arms, and torso (HAT) are modeled as a single rigid body. The HAT articulates with the pelvis via a 3 dof ball-and-socket joint. Each hip is modeled as a 3 dof ball-and-socket joint, and each knee is modeled as a 1 dof hinge joint. Each foot is represented by a hindfoot and toes segment. The hindfoot articulates with the shank via a 2 dof universal joint, and the toes articulate with the hindfoot via a 1 dof hinge joint. Interaction of the feet with the ground is modeled using a series of spring-damper units placed under the sole of each foot. The path of each muscle is represented by either a series of straight lines or a combination of straight lines and space curves. Each actuator is modeled as a three-element, Hill-type muscle in series with tendon. A first-order process is assumed to model muscle excitation-contraction dynamics. Dynamic optimization theory is used to calculate the pattern of muscle excitations that produces a maximal vertical jump. Quantitative comparisons between model and experiment indicate that the model reproduces the kinematic, kinetic, and muscle-coordination patterns evident when humans jump to their maximum achievable heights.

A Dynamic Optimization Solution for Vertical Jumping in Three Dimensions.

▪ Abstract Recent interest in using modeling and simulation to study movement is driven by the belief that this approach can provide insight into how the nervous system and muscles interact to produce coordinated motion of the body parts. With the computational resources available today, large-scale models of the body can be used to produce realistic simulations of movement that are an order of magnitude more complex than those produced just 10 years ago. This chapter reviews how the structure of the neuromusculoskeletal system is commonly represented in a multijoint model of movement, how modeling may be combined with optimization theory to simulate the dynamics of a motor task, and how model output can be analyzed to describe and explain muscle function. Some results obtained from simulations of jumping, pedaling, and walking are also reviewed to illustrate the approach.

Computer modeling and simulation of human movement.

Explosive movements such as throwing, kicking, and jumping are characterized by high velocity and short movement time. Due to the fact that latencies of neural feedback loops are long in comparison to movement times, correction of deviations cannot be achieved on the basis of neural feedback. In other words, the control signals must be largely preprogrammed. Furthermore, in many explosive movements the skeletal system is mechanically analogous to an inverted pendulum; in such a system, disturbances tend to be amplified as time proceeds. It is difficult to understand how an inverted-pendulum-like system can be controlled on the basis of some form of open loop control (albeit during a finite period of time only). To investigate if actuator properties, specifically the force-length-velocity relationship of muscle, reduce the control problem associated with explosive movement tasks such as human vertical jumping, a direct dynamics modeling and simulation approach was adopted. In order to identify the role of muscle properties, two types of open loop control signals were applied: STIM(t), representing the stimulation of muscles, and MOM(t), representing net joint moments. In case of STIM control, muscle properties influence the joint moments exerted on the skeleton; in case of MOM control, these moments are directly prescribed. By applying perturbations and comparing the deviations from a reference movement for both types of control, the reduction of the effect of disturbances due to muscle properties was calculated. It was found that the system is very sensitive to perturbations in case of MOM control; the sensitivity to perturbations is markedly less in case of STIM control. It was concluded that muscle properties constitute a peripheral feedback system that has the advantage of zero time delay. This feedback system reduces the effect of perturbations during human vertical jumping to such a degree that when perturbations are not too large, the task may be performed successfully without any adaptation of the muscle stimulation pattern.

https://rd.springer.com/content/pdf/10.1007%2FBF00198959.pdf

The contribution of muscle properties in the control of explosive movements

The influence of the biarticularity of the gastrocnemius muscle on vertical-jumping achievement

In textbooks on the anatomy of the musculo-skeletal system, both muscles crossing only one joint (mono-articular muscles) and muscles crossing more than one joint (multi-articular muscles) are classified according to the location of their line of action relative to joint axes of rotation (e.g. Williams and Warwick, 1980). For instance, the line of action of the mono-articular vastus medialis passes anterior to the flexion/extension axis of the knee joint, and therefore the muscle is classified as a knee extensor. Similarly, the bi-articular gastrocnemius is classified as a knee flexor and ankle plantar flexor. As such, the gastrocnemius is considered to be an antagonist of the vasti at the knee joint.

The Unique Action of Bi-Articular Muscles in Leg Extensions

The effect of tendon on muscle force in dynamic isometric contractions: a simulation study.

According to the equilibrium point theory, the control of posture and movement involves the setting of equilibrium joint positions (EP) and the independent modulation of stiffness. One model of EP control, the α-model, posits that stable EPs and stiffness are set open-loop, i.e. without the aid of feedback. The purpose of the present study was to explore for the elbow joint the range over which stable EPs can be set open-loop and to investigate the effect of co-contraction on intrinsic low-frequency elbow joint stiffness (K ilf). For this purpose, a model of the upper and lower arm was constructed, equipped with Hill-type muscles. At a constant neural input, the isometric force of the contractile element of the muscles depended on both the myofilamentary overlap and the effect of sarcomere length on the sensitivity of myofilaments to [Ca2+] (LDCS). The musculoskeletal model, for which the parameters were chosen carefully on the basis of physiological literature, captured the salient isometric properties of the muscles spanning the elbow joint. It was found that stable open-loop EPs could be achieved over the whole range of motion of the elbow joint and that K ilf, which ranged from 18 to 42 N m·rad−1, could be independently controlled. In the model, LDCS contributed substantially to K ilf (up to 25 N m·rad−1) and caused K ilf to peak at a sub-maximal level of co-contraction.

/pdf/a-model-of-open-loop-control-of-equilibrium-position-and-2nmlaqaopf.pdf

Arthur J. van Soest

Papers

The contribution of muscle properties in the control of explosive movements

The influence of the biarticularity of the gastrocnemius muscle on vertical-jumping achievement

The Unique Action of Bi-Articular Muscles in Leg Extensions

The effect of tendon on muscle force in dynamic isometric contractions: a simulation study.

A model of open-loop control of equilibrium position and stiffness of the human elbow joint