Contribution of non-extensor muscles of the leg to maximal-effort countermovement jumping

BACKGROUND: The purpose of this study was to determine the effects of non-extensor muscles of the leg (i.e., muscles whose primary function is not leg extension) on the kinematics and kinetics of human maximal-effort countermovement jumping. Although it is difficult to address this type of question through experimental procedures, the methodology of computer simulation can be a powerful tool. METHODS: A skeletal model that has nine rigid body segments and twenty degrees of freedom was developed. Two sets of muscle models were attached to this skeletal model: all (most of) major muscles in the leg ("All Muscles" model) and major extensor muscles in the leg (i.e., muscles whose primary function is leg extension; "Extensors Only" model). Neural activation input signal was represented by a series of step functions with a step duration of 0.05 s. Simulations were started from an identical upright standing posture. The optimal pattern of the activation input signal was searched through extensive random-search numerical optimization with a goal of maximizing the height reached by the mass centre of the body after jumping up. RESULTS: The simulated kinematics was almost two-dimensional, suggesting the validity of two-dimensional analyses when evaluating net mechanical outputs around the joints using inverse dynamics. A greater jumping height was obtained for the "All Muscles" model (0.386 m) than for the "Extensors Only" model (0.301 m). For the "All Muscles" model, flexor muscles developed force in the beginning of the countermovement. For the "All Muscles" model, the sum of the work outputs from non-extensor muscles was 47.0 J, which was 13% of the total amount (359.9 J). The quantitative distribution of the work outputs from individual muscles was markedly different between these two models. CONCLUSION: It was suggested that the contribution of non-extensor muscles in maximal-effort countermovement jumping is substantial. The use of a computer simulation model that includes non-extensor muscles seems to be more desirable for the assessment of muscular outputs during jumping

A Planning Algorithm for Dynamic Motions

Motions such as flips and jumps are challenging to animate and to perform in real life. The difficulty arises from the dynamic nature of the movements and the precise timing required for their successful execution. This paper presents a decision-tree search algorithm for planning the control for these types of motion. Several types of results are presented, including cartwheels, flips and hops for a two-link gymnastic `acrobot'. It is also shown that the same search algorithm is effective at a macroscopic scale for planning dynamic motions across rugged terrain. Animations: http://www.dgp.utoronto.ca/people/van/ani.html 1 Introduction Creating realistic movement for animated objects is a difficult task, one which remains difficult even if a physical simulation is used. Controlling a simulated gymnast involves solving the same problem that the real gymnast faces in executing a sequence of manoevres. Of particular interest to us are unstable, dynamic motions which must typically rely o..

Fabrication of the mini multi-function pepper machine

Pepper is one of the most significant agricultural products in Sarawak, Malaysia currently in the fifth largest pepper producer in the world after Vietnam, India, Brazil and Indonesia. Black pepper and white pepper both come from the same plant, but they are prepared differently. Black pepper is made by cooking dried unripe fruit, meanwhile white pepper is made by cooking and drying the ripe seeds. The production contributes to the aspects of economy and plantation rate of the state. However, the process of pepper through manual work is time consuming and a tough process which requires commitment and hard labor from the farmers. Therefore, the objective of this research is to fabricate the Mini Multi-Function Pepper Machine for small or medium enterprise by reducing the time of drying process. This fabrication machine consists of all the procedures involved in the production of white pepper, which are soaking, heating, drying and grinding process. Through the operation observed, this machine was able to undergo production in 208 to 300 minutes for 300g of white pepper, in comparison to the traditional way that needs approximately 1 to 4 weeks to undergo one production batch of white pepper

Multibody Optimisations: From Kinematic Constraints to Knee Contact Forces and Ligament Forces. In : Biomechanics of Anthropomorphic Systems

Musculoskeletal models are widely used in biomechanics today to better understand muscle and joint function. Musculo-tendon forces as well as joint contact forces and ligament forces can be estimated within an inverse dynamics computational framework. Using a musculoskeletal model of the lower limb, this chapter presents the different optimisations required to drive the model with experimental data and to compute these forces and their interactions. In these optimisations, the development of anatomical constraints representing, for example, the medial and lateral tibiofemoral contacts or the cruciate ligaments is crucial both to inverse kinematics and to inverse dynamics. Some emblematic results are presented for knee contact forces and ligament forces during gait, illustrating the couplings between joint degrees of freedom and the interactions between forces acting both in muscles and in joints