Biomechanical Analysis and Visualization

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Hello. My name's James Shippen of BoB Biomechanics. I'd like to give the presentation entitled Biomechanical analysis and visualization. My background is in engineering analysis within the automotive and aerospace industries, and also, in academia. But then I started to analyze something that's much more interesting.

As you'll all know, MATLAB is a well established mathematical modeling environment with many tools to simulate lots of different scenarios, from aerospace products, to financial markets, and much more in between. However, MATLAB does have one significant hole in its modeling domain, and often, that's the most important component of any system. MATLAB does not contain a model of the human body. BoB Biomechanics has plugged this gap by developing Biomechanics of Bodies, or BoB. BoB's a musculoskeletal model of the human body, which can be analyzed in isolation or interacting with other MATLAB models.

The benefits of using a BoB model include being able to model the complete system which incorporates an actual person within it, thus saving time and money in research or development product. BoB extends the envelope of MATLAB's labs engineering analysis capabilities to integrate engineering and biological components. With a person in the model, what if questions can be asked and answered much more rapidly. This might replace some of the stages in prototype development projects. There could be circumstances where being able to model a person will reduce the need to put people in hazardous situations, like climbing a tree.

BoB has been developed completely within the MATLAB environment. Its development has been widely published in academic journals and presented at international conferences. BoB is deployed as a stand alone package using the MATLAB deployment tool and can be used without the need for a MATLAB license.

But BoB is also deployed as P-code so it can run within the MATLAB environment and share data with MATLAB. Additionally, users can write their own bespoke end code to interact with BoB. BoB has been accredited by the MathWorks Connections program.

BoB provides objective, quantitative information on the movement of the body. Biometrics can be output that include trajectories, velocities, velocity vectors, accelerations, distances, and angles. BoB can also calculate the forces acting on and within the body together with the torques and contact forces at all of the joints. BoB can also calculate the energy and power expenditure of the whole body or on a muscle by muscle basis. All of this information can be output to data files, plotted as graphs, or displayed as objects in the BoB workspace.

Applications of BoB include, but are not limited to, academic research, product development, sporting performance and optimization, health care, ergonomics, injury reduction and prevention, or anywhere that the motion of people and the loads generated within the body are of interest. We've got some examples of real-life applications of BoB later in this presentation.

BoB makes extensive use of graphics-- of MATLAB's graphics capabilities. BoB doesn't use any external graphical software or hardware from any third party organization. Nevertheless, BoB can display the skeleton and 600 color-coded muscles together with ancillary equipment, synchronized graphs, output from biomechanical analysis, all in real-time. Also, users can even insert their own graphics into BoB using touch objects.

BoB also contains an interactive three-dimensional viewer which the user can use to manipulate the view of the BoB workspace. The view can be rotated in any direction. It can also be translated across the screen in any direction.

The user can zoom in and out on the subject. Additionally, they can display any biomechanical metrics. For example, the trajectory of the left foot is shown in this illustration.

BoB is a musculoskeletal model, hence, BoB contains a model of the human skeleton. Major body segments are connected with constraint equations which represent the movement of the corresponding joints. The dimensions and inertia properties of all of the body segments can be edited by the user.

BoB also contains a model of the human locomotor muscles. By default, there are over 600 locomotor muscles within the BoB model. These muscles can wrap around the underlying skeleton and any deeper muscles. Additionally, BoB has got a muscle editor so the user can add, modify, and delete any muscles that are required.

One way to animate BoB is simply to list the joint angles as functions of time. This is quite useful for simple applications, for example, as what might be used in teaching biomechanics, but it's very limited in terms of its real-world applications.

For more realistic applications, BoB can take in motion data, for example, from optical tracking systems. This is a system where small reflective markers are attached all over the body, as shown in this illustration by the little white spheres. The subject is then surrounded by a large number of cameras and the information from these cameras is combined to reconstruct a full three-dimensional movement pattern. This is the kind of technology that's used for generating animated movies or for producing video games.

BoB can also use motion data from inertial measurement unit systems. This is a system where MEMS, accelerometers, gyroscopes, and magnetometers are attached to the body to measure the three-dimensional motion. In this illustration, the sensors are shown as these 17 little orange boxes attached to the body. If you're using an [INAUDIBLE] system you can actually stream the motion in real-time into BoB.

BoB can calculate and output many biomechanical metrics. Perhaps the most basic of BoB's tools is to visualize and interrogate the motion of the subject. This slide shows the trajectories of the hands during cricket bowling as red and yellow lines. The motion is also displayed in the form of multiple position instances spaced at equal times throughout the trial.

BoB can also display the range of motion of any joint in any direction. In this animation, the colored slice of the disk at the joint displays the range of motion of that joint. Also, the color coding from red to green shows the proportion of time the joint spends at each individual angle. BoB can analyze and display just a part of the body if the whole body isn't of interest. For example, in this animation, only the right leg segments, joints, and muscles are shown.

The force that occurs between the feet and the ground is often important in a biomechanical analysis. Ideally, this would be measured by force plates which are mounted into the ground, but often, this is impractical. For example, covering a whole football pitch just couldn't be done with force plates, or they might not simply be available. In these situations, BoB can calculate the ground reaction forces in terms of their magnitude, direction, and the force division between each of the feet. The output from this calculation is shown in this slide as the little yellow arrows that are appearing at the feet.

BoB uses inverse dynamics to calculate the torques generated at all of the joints of the body. This slide shows the torques that are generated at the right shoulder and in the lumbar region of the spine. The total magnitude is illustrated by the size of the circular arrows, and the direction of the torque is indicated by the arrow wrapping around the torque's axis. You'll also notice that moving the force at the hand also changes the calculated ground reaction force at the feet, as shown by the yellow arrows.

The purpose of muscles is to generate torques at the joints to enable a posture or movement. However, in the body, there are many more muscles than there are torques to generate. It is, therefore, a redundant system, and therefore, there's no unique solution to the muscle force distribution problem.

To calculate the muscle force distribution, BoB assumes that the body will configure the muscle forces to maximize the fatigue resistance, which seems like a very good evolutionary strategy. This equates to minimization of a cost function that models muscle activity. BoB uses FMINCON and QUADPROG from the Optimization toolbox to perform this minimization.

This slide shows the activities of the muscles calculated in this manner. The redder the muscle, the harder it's working. The bluer the muscle, the less hard it's working. We've also attached a virtual camera to the pelvis, just to make it easier to see the muscles in the lumbar region of the spine.

As we now know the forces in the muscles surrounding each of the joints, we can calculate the total force that's occurring at that joint. The double-headed red arrow shows the magnitude and direction of the compressive load acting between adjacent vertebra in the lumbar region of the spine and the compressive loads at the shoulder. We've also plotted over towards the right-hand side the joint contact force at some joints around the body. And they're plotted against time.

But within BoB, we can also plot any biometric variable against any other variable. In this graph, the right elbow torque is plotted against the right elbow flexion. The current time is indicated by the circuit cursor moving along the plot's trajectory. We've also added some labels to the muscles.

The name of any of the muscles within the body can be displayed and they move as the muscles move. BoB can simultaneously display an unlimited number of subjects. This enables a comparison of the movement and forces across a sample of the population.

BoB comes in four variants. BoB Research, BoB Ergo, BoB EMG, and BoB Teaching. BoB Research is the core of the BoB package and contains all of the functionality already seen in this presentation. BoB Research is by far the most widely used variant of BoB and has been applied to many industrial development projects and is widely used in academic research projects.

BoB Ergo contains all of the functionality of BoB Research plus additional analysis tools used by the ergonomic analysts. This includes the ability to evaluate a large number of ergonomic assessments, including ISO, NIOSH, RULA, REBA, and other assessment metrics. Moreover, BoB can calculate the sensitivity of the ergonomic performance indicators to design variables to identify an efficient route to configuring the optimal workplace.

BoB EMG can integrate movement with EMG signals. In these graphs, raw and rectified EMG signals are shown synchronized to the motion. However, unlike in all previous illustrations in this presentation, where the most muscle activation is shown based on BoB's own internal calculations of muscle forces, here, the muscle activation color coding is based on the recorded EMG signals. So the muscle activity can be observed on the moving subject.

BoB Teaching is designed for teaching biomechanics at undergraduate and master's levels. BoB Teaching contains pre-loaded examples which illustrate a broad range of biomechanical principles. These examples range from simply supporting a static weight in the hand, through to motion capture sporting activities.

It is a tool to enable the student to experiment and investigate and acquire a deeper understanding of biomechanics by using interactively a musculoskeletal model. BoB Teaching also contains a student worksheet template for the instructor to use out of the box or to modify to suit their own particular requirements and style. BoB teaching is a very short learning curve for the student and requires minimal supervision.

And I mentioned some of the applications which BoB has been used for by the BoB development team and by other BoB users. BoB is widely used in sport for performance optimization, injury reduction, and monitoring return to play. BoB has been used to provide quantitative information on athletic movement and objective data on the forces occurring within the body. One example is tennis, where the joint angles are critical for good performance. BoB has been used to compare joint angles along the kinematic chain between players of differing abilities.

BoB been used extensively to analyze dance. A professional Irish Dance Company was experiencing an unacceptably high incidence of ankle injuries. A BoB analysis indicated that very high forces were occurring in these joints. Small changes were made to the choreography, so small that the audience wouldn't actually notice them, but it significantly reduced the ankle loads and the injury rates.

BoB has been used to study the technique of Paralympic athletes, particularly those using the sit skier. BoB's musculoskeletal model can be modified to represent the capabilities and disabilities of these athletes.

BoB has been applied to optimize the design of exoskeletons. In this study, BoB was used to model a person with and without an exoskeleton for exactly the same motion. From this, the sensitivity of the loads in the body to change in the spring rates in the exoskeleton was calculated and fed back into the design process to identify the optimal stiffness for the springs within the exoskeleton.

BoB's also been used by the manufacturer of automotive seating. This study examined the ingress and egress of older people into and out of passenger vehicles. Correlation was found between biometric measurements and comfort levels, which led directly to designs-- changes in the seat's design.

The UK Fire Service has used BoB to modify their vehicle evacuation protocols to reduce the risk of post-crash spinal trauma. BoB has also been used by the Spanish Police Service to inform their officers on prisoner restraint techniques.

A reduction in a fraction of a second during a pit stop is worth many millions of pounds to a Formula One team. BoB was used by Formula One team to objectively study the differing techniques of the 12 members of the pit crew during the wheel change and identify the best practice which could then be applied to the whole team. On completion of the study, the team was the fastest in the pit lane.

In summary, BoB introduces a human model into the MATLAB environment. BoB is a biomechanical toolbox for MATLAB. BoB makes extensive use of MATLAB's built-in mathematical analysis functions and graphics.

There's more information about BoB on our website where you can also download a trial version. Our website is bob-biomechanics.com. Thank you very much for your attention.