1Alphonse Bertillon (1883)• French physician• Credited with starting field of anthopometry•Determined that certain physical characteristics did not change in adulthoodAnthropometry(Chapter 3 – Body Segment Parameters)Tuesday October 16thDr. Moran2What is Anthropometry?• Studies the physical measurements of the human body• Used to study differences between groups••Age••Body Type• Professional Fields: ergonomics, automotive, etc.• Mostly care about the inertial properties of the body and its segmentsDrillis & Contini 1966Body Segment Parameters• Length•• Location of segmental center of gravity – (also known as center of mass COM)•• Before a kinetic analysis can occur these properties must either be OR estimated3Some Important Assumptions1.) Segments behave as bodies» Not true as we know that segments are composed of bones & soft tissues. All of which bend, stretch, etc.2.) Some segments » Ex: Foot – represented as one segment by many researchersAssumptions (con’t)3.) Segmental mass distribution similar among a population Important researcher chooses a good match For instance, if you wanted to estimate the segment parameters for a pediatric subject, then you would want to be sure that the average segment parameters come for a similar group4Body Segment Parameters1.) Length2.) 3.) Volume4.) Center of Mass5.) 6.) Moment of InertiaQuestion: How can we determine these BSP values for a participant in our study?DIRECT MEASURESegment properties are determined directly from the participant. Only possible witha cadaver specimen because each segmentwould need to be disconnected and analyzed.MEASUREEstimation of parameters is necessary for living participants. There are numerous techniques to estimate these values(Table of Proportions)W.T. Dempster: Space Requirements of the Seated OperatorUS Air Force (1955)Outlined procedures for DIRECTLY measuring parameters from cadavers (8) AND included tables for proportionally determining parameters from cadaver values.Link to Full PDF: http://www.ulb.ac.be/medecine/anatemb/biblio/dempster1955.pdf5BSP Determination MethodsCADAVER STUDIESMATHEMATICALMODELINGKINEMATICA laser-aligned method for anthropometry of hands (Highton et al., 2003)Body Benchmark Study2007 -http://www.bodybenchmark.org/home• Program Objective: to develop a NEW anthropometric measurement, body volume index (BVI) that can be used in healthcare• 2-yr clinical research project• Starting August 2007• Countries involved: US, UK, mainland Europe• 1stdedicated obesity measurement tool that is quick, safe and cost-effective• What is BVI?• a 3D scanner determines weight distribution by body segment6BSP Parameters• Segment Length: most basic body dimension • Can be measured from • Dempster et al. (1955, 1959): summarized estimates of segment lengths and joint center locations relative to anatomical landmarks» This allows one to ESTIMATE the location of a joint by palpating and measuring the easily identifiable bony landmarks»Whole Body Density• Human body comprised of many types of tissues of different densities• Ex: cortical bone (specific gravity > 1.8)muscle tissue (just over 1.0)fat (< 1.0)• Average density is a function of body type -7Average Density (con’t)• Drillis & Contini (1966)• Ponderal Index • c = » w = body weight (lbs)» h = height (inches)• D = 0.69 + 0.0297c kg/l• Ex: Find the whole-body density of Dr. Moran (5’ 10”; 150lbs).In general (1) the density of distal segments is > than proximal segments(2) Determining Segment MassMethod #1 - Proportion• Key Concept: • Simply weigh subject and then multiply by the proportion that each segment contributes to the total.» Handout (Table 3.1 from supplemental text)» Ex: What is the mass of the left leg of a person that weighs 167 Kg?m = m =8Determining Segment MassMethod #2 – Mathematical Modeling• The total mass of the segment is:M = ∑ miwhere miis the mass of the ithsegmentmi= diVi» Ex: A tape measure is used to take thigh circumferences every 1 cm. For one measurement the circumference is 23.9 cm. Assuming a circular cross-section, what is the mass of that segment if the average density is 1.059 kg/l.circumference = 2 π r Segmental Center of Mass• How to determine the center of mass?• Cadaver Studies: find the center of balance point» Dempster (1955) calculated the COM as the distance from the endpoints of the segment» xcg= xproximal+ Rproximal(xdistal– xproximal)» ycg= yproximal+ Rproximal(ydistal– yproximal)• In Vivo Studies: the cross-sectional area and length of segment are necessary to approximate the segmental COMx = (1/M) ∑ mixi Ex: From the cross-sectional slice of the thigh compute its contribution to the center of mass of the thigh if the circumference was taken 12 cm from the hip joint. mixi =9Segmental Center of Mass (con’t)From Table 3.1 calculate the coordinates of the center of mass of the foot given the following coordinates: lateral malleolus(84.9, 11.0), head of the 2ndmetatarsal (101.1, 1.3).»xcg= xproximal+ Rproximal(xdistal–xproximal)»ycg= yproximal+ Rproximal(ydistal–yproximal)=Each segment has its own COMThe total body COM is the weighted average of the segmental COM10Limb and Total Body COM• How can you compute the COM of a limb or combination of segments?• First compute the COM of each individual segment• Use the mass proportional value for that segment• Use these formulas:xlimb=∑ Psxcg∑ Psylimb=∑ Psycg∑ PsReuleaux’s MethodUsed for Center of Rotation Calculation• Reuleaux’s Method (1876)• Determines the center of rotation for ONE segment• Can be a 2D, graphical technique• Must be 2 points attached to a segment• Step #1: • Step #2: draw a perpendicular line in the midpoint of this line• Step #3:11A1B1A2B2Joint Centers of Rotation• It is important that true centers of rotation can be identified relative to anatomical markers placed on skin• Functional Techniques: hip joint12Mass Moment of Inertia• Rotational Inertia: the resistance of a body to change in its rotational motion. The angular or rotational equivalent of mass.• Classically defined as the “second moment of mass”: it is the summed distance of mass particles from an axis• Any time a movement involves accelerations we need to know the inertial resistance to these movements. (F = ma; M = Iα)• Consider the moment of inertia about the