Biomechanics Laboratory A Biomechanics Lab Instrumentation Introduction The ability to accurately describe human motion is an integral step in the understanding and analysis of human movement Kinematics provides us with a means of describing the displacement velocity and acceleration of an object Kinetics provides us the means of determining forces applied from the environment on the body as well as those that arise from within the body There are many methods that can be used to gather kinematic information Some of these include the use of potentiometers goniometers electromagnetic tracking and cameras systems Cameras are the most widely used because of their accuracy simplicity and versatility The cameras require the application of reflective markers onto specific landmarks on a subject The reflective markers reflect the light emitted by the cameras The reflected light is then recorded onto analog tape VHS or saved onto some digital media format PC hard drive Kinetic data are typically collected using a force transducer These can range from small specially designed devices to large general purpose force platforms that are installed in the ground Most force transducers give off an electrical signal that is proportional to the load being applied to them This signal is recorded to some form of digital media for later analysis In this lab activity you will become familiar with the equipment that is available in the UMass Amherst Biomechanics Lab for collecting kinematic and kinetic data Methods Marker Application This experiment will require subjects to have reflective markers placed on five anatomical landmarks greater trochanter lateral condyle of the knee lateral malleolus calcaneous head of the fifth metatarsal Using some adhesive the markers are stuck to the surface of the skin However this is not an ideal situation This is because the skin and any underlying tissue is able to move over the underlying bones Therefore the movement of the marker may not necessarily be the movement of the bone Ideally the markers would be attached directly to the skeleton This has actually been done using instruments termed bone pins Since this procedure is rather uncomfortable placing markers on the skin at sites such as bony landmarks where there is minimal underlying tissue is acceptable Analog and Digital Cameras The biomechanics laboratory uses digital cameras manufactured by Qualysis These will be used for the present experiment The subject will be required to walk through the data collection volume calibrated area that the cameras can see of the cameras while wearing the reflective markers To gain an appreciation for these high tech digital cameras let s compare them with the older analog cameras Analog and digital cameras operate on same basic principals The main difference is in the editing process Analog editing consists of numerous steps which involve digitization of the data path editing of the data checks whether or not the data collected is truly representative of the specified limb and interpolation filling in of missing data points using a mathematical linear interpolation method These steps require an extraordinary amount of time The time can exponentially increase as we add in numerous trials and conditions You can spend many hours collecting and editing data for only one subject Digital cameras are able to digitize convert coordinated in three dimensional space to coordinated that are meaningful to the computer in real time The data that you see the computer monitor is data that is digitized The elimination of this time consuming step reduces a significant portion of the editing process Moreover the newer digital systems incorporate better path editing algorithms which require less human correction All this means that digital cameras will only require a fraction of the time analog cameras require to collect and edit data Force Platforms The AMTI force platform used in this lab detects the forces acting on the surface recording the interaction between the participant and the ground It returns forces in three dimensions X Y and Z The single force applied by the individual to the ground is broken down into three components acting along the platform s coordinate system axes during the signal transformation Force platforms come in many sizes force capacities and sensitivities The force platform in the biomechanics laboratory is a strain gauge platform When the platform is struck deformation of the plate results in a change in the resistance of the strain gauge The corresponding change in the voltage of the bridge circuitry of which the strain gauge is a part is detected and amplified An analog to digital converter changes the analog voltage change to a digital signal that can be interpreted by the computer Applying the appropriate conversion factor yields the change in force usually measured in newtons Assignment Your assignment must be submitted as a Word document Submit your assignment through Turnitin in Moodle Answer the following questions 1 Do an Internet search for motion analysis systems Identify three other companies aside from Qualysis that produce commercial kinematic measurement systems Aside from studying human motion for research purposes what are the other major applications of kinematic measurement technology 2 View the following YouTube video http www youtube com watch v VsVkaIaoU38 Note that the letter between the two a s in the web address is a capital I sounds like eye What is the major difference between an AMTI force platform which we have at UMass and a Kistler force platform How does this affect the kinds of activities that each type of platform is best suited for studying 3 Based on an Internet search identify a biomechanics laboratory at another university Briefly describe the equipment they have and the types of research they do