UMass Amherst KIN 430 - Biomechanics Lab B (5 pages)

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Biomechanics Lab B



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Biomechanics Lab B

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Pages:
5
School:
University of Massachusetts Amherst
Course:
Kin 430 - Biomechanics
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Emily Weimer Biomechanics Laboratory B Linear Kinematics Introduction The purpose of this laboratory was to analyze the relationships between various kinematic variables including linear position displacement and velocity These variables were all studied during steady state human locomotion By looking at the linear position using a marker placed near the participant s body center of mass we were able to calculate and analyze the displacement velocity and acceleration We looked at the two different human locomotion patterns walking and running After obtaining the data we were able to calculate the velocity values during difference formulas including First Central Difference Method Forward Difference Method and Backward Difference Method Methods Participants placed a position marker near their center of mass presumably around the sacrum and then were asked to walk and run at their comfortable speed across the force platform Using the force platform ensured that the movements were captured by the motion analysis system Qualysis Participants were instructed to maintain a steady speed while walking or running through the camera s field of view The video cameras used in our laboratory recorded the participant s motion at 240 Hz Throughout motion the Qualysis system was able to determine the 3D position of the position marker placed on the sacrum throughout the duration of movement Following the in lab portion the data for complete stride of both walking and running was extracted We were able to differentiate this data to analyze an estimate of the instantaneous velocity over the full stride cycle for both walking and running Using the velocity data that we calculated we could then create an estimate of the instantaneous acceleration again for the full stride of both walking and running The formulas that were used were 1 First Central Difference Method v x x 2 t 2 Forward Difference Method v x x t 3 Backward Difference Method vn xn xn 1 t v velocity at time i x position at time i 1 x position at time i 1 t change in time time interval n number of data points Sample Calculations Here we were able to use the different equations to solve for horizontal velocity values Forward Difference Method 0 884 0 887 1 240 1 550 First Central Difference Method 0 871 0 884 2 1 240 1 549 Backward Difference Method 492 486 1 240 1 499 Results Time 0 0 004166 0 008333 0 0125 0 016666 1 0125 1 016666 1 020833 1 025 1 029166 Time 0 000 0 004 0 008 0 013 0 017 0 692 0 696 0 700 0 704 0 708 CM Horizontal 0 884 0 877 0 871 0 865 0 858 0 467 0 473 0 480 0 486 0 492 CM Horizontal 1 160 1 149 1 138 1 127 1 116 0 816 0 827 0 838 0 849 0 860 CM Vertical 0 911 0 911 0 911 0 911 0 911 0 910 0 909 0 909 0 908 0 908 Walking Horizontal Vertical Velocity Velocity 1 550 0 048 1 549 0 038 1 546 0 020 1 542 0 001 1 537 0 016 1 488 0 130 1 493 0 113 1 496 0 097 1 498 0 079 1 499 0 071 CM Vertical 0 938 0 934 0 929 0 924 0 920 0 956 0 952 0 948 0 943 0 939 Running Horizontal Velocity 2 63754 2 62814 2 60974 2 59228 2 57597 2 69830 2 67914 2 66000 2 64104 2 63163 Horizontal Vertical Acceleration Acceleration 0 266 2 259 0 468 3 370 0 809 4 430 1 082 4 305 1 344 4 133 1 089 3 898 0 894 4 019 0 676 4 093 0 392 3 092 0 222 2 065 Vertical Horizontal Vertical Velocity Acceleration Acceleration 1 0943 2 25719 0 4225 1 0926 3 33601 1 1202 1 0850 4 30259 2 7812 1 0694 4 05234 4 6819 1 0460 3 75003 6 5189 1 0018 4 58446 7 3604 1 0289 4 59642 5 6361 1 0488 4 57194 3 8508 1 0610 3 40380 1 9801 1 0653 2 25803 1 0148 Discussion When looking at the vertical displacement of the center of mass for both walking and running a similar trend can be noticed Both graphs have similar curves which suggests that there are similarities between the vertical displacements of the center of mass when walking and when running These results can be broken down further to notice that in the walking portion the vertical heights are lower than the running vertical heights This is due to walking having less of a bounce and a shorter flight phase than running The downward curve on the running graph also happens sooner than the downward curve of the walking graph which can be explained by the faster step land pattern of the foot hitting the ground that happens when running Lastly it is noticeable that both graphs appear to go through similar curve patterns When looking more closely it is noted that the walking curve goes through two up and down patterns in the 1 03second period while the running curve goes through almost 2 5 up and down patterns in only 708 seconds This is because the participant is able to complete more full cycles of motion in running than walking The average horizontal velocity for walking was 1 338 m s and the average horizontal velocity for running was 2 851 m s When comparing these averages to the data displayed in the graphs you can see that the average value happens during the downward curve from the high peak to the low peak The instantaneous velocities for the running period may differ from the average if the participant slowed down when reaching the end of the platform at the end of the running period Likewise with the vertical displacement the vertical velocity graphs for both running and walking display similar curve patterns but vary in their numeric values Because the flight phase is longer in running compared to walking the graph will display a higher vertical velocity in running during each complete cycle Flight phase in running will be greater because during a full cycle both feet will be off the ground at the same time whereas walking one foot is always in contact with the ground which translates into a smaller vertical velocity in the walking trial The vertical position will always be positive while the horizontal position may be negative or positive This is due to the fact that the body is in an upright position while walking or running so it is extremely difficult for the center of mass to move vertically up or down The motion capture grid was set for the ground to be the origin of this lab therefore in order for the vertical position to be negative the participant would have had to be below the ground Depending on where the participant is in comparison to the origin is how the horizontal values are determined looking at how far left or right the individual s center of mass is


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