ESC-100 Introduction to Engineering Fall 2013

Transcription

1 Lab 4 Biomechanics of Human Motion Physical activities such as walking, running, and jumping are essential for daily function, as well as for recreational or competitive athletics. However, these and other human movements subject the musculoskeletal system to tremendous forces that can, over time, result in acute or chronic injury. An increased understanding of the spatial and temporal force distributions resulting from these movements may thus enable professionals ranging from doctors to coaches to better prevent and treat injury. The purpose of this lab is to collect and interpret the force profiles produced by some everyday human movements. Specifically, you will obtain vertical and parallel force curves in walking, jogging, and jumping using a Pasco 2-axis force platform. In addition to presenting your experimental data, your lab report will contain a discussion with answers to the questions in bold listed throughout the Procedure below. This report differs considerably in format from the memos you have prepared thus far. Detailed format guidelines will be provided as a separate document. These guidelines may seem long and intimidating, but are actually straightforward and likely already familiar to you! Also, your individual Professor will review what content should be in each report section for this lab. Procedure Note: You will meet in your home section classroom to discuss some introductory concepts, after which your Professor will bring your section to Butterfield 106 to collect your data. Perform the following activities with the force platform sitting on level ground. For each activity, please save the resulting force versus time curve and data, and

2 record the peak force experienced during the activity in the table below. 1. Standing: First, stand upright and still on the force plate. Do you see vertical and/or horizontal forces being recorded? Based on your pre-lab assignments, does the vertical force reading match expectations? 2. Walking/Jogging: Starting several paces away, walk toward the platform and step on it as you continue to walk forward (make sure your step is at or near the center of the platform). Study the vertical and horizontal forces applied by your foot. Repeat this exercise while lightly jogging. In each case, in what direction does your foot apply force to the platform in order to move you forward? In what direction does the platform apply force to your foot? 3. Vertical Jumping: Stand on the platform and jump vertically. Look at the graph of force versus time to determine your hang time, or how much time you spent in the air. What factors are related to your hang time? Do you apply any horizontal force to the platform when jumping (and landing) vertically? 4. Angled Jumping: From off of the platform, jump onto the platform so that you land on both feet close to the center platform. How does the resulting force profile differ from the landing part of the force profile in the previous activity? Can you think of implications (if any) for athletes in terms of causes and prevention of injury? Activity Standing Walking Jogging Vertical Jumping Angled Jumping Peak Force (N) Other questions to answer in the Discussion section of your lab report: You might decide the peak force experienced during different activities is a good metric with which to compare their injury potentials. However, what does the use of this metric alone neglect (hint: you are collecting force versus time information!) What metric (calculated from the experimental data) would you use to compare activities and why? References: 1. 2-Axis Force Platform (PS-2142) Instruction Manual. Pasco Scientific Co.

3 Lab 4 Biomechanics of Human Motion Pre-lab Assignment After reading the lab handout (distributed along with this pre-lab), answer the following questions (typed) and bring them to lab. Make sure to cite any references used. Also, these questions are meant mainly to familiarize you with the concepts; short answers are encouraged, and don t worry about being right, particularly for Problems 1 and 2c. 1. For one of the activities to be performed in the lab, do some research (if using an online source, please make sure that it is an educational institution with the url ending in.edu) to find what maximum force levels are typically experienced by collegiate and/or professional athletes. How do you think your own maximum force would compare for the same activity? 2. Read about basic bone structure at the following website ( the link is also clickable on the copy of this prelab posted on Nexus). Using the information there and, if necessary, from academic (ending in.edu) sources, answer the following: a. Bone, just like most other tissues, is made up of cells and the extracellular matrix (ECM) that surrounds the cells. What is the ECM macromolecule that is responsible for bearing loads in the long bones of the leg? (hint: it is a protein; you can find it by looking at the figure showing the structure of compact bone near the top of the page). b. In what direction is this molecule oriented with respect to the long leg bones and why (in what direction does your leg mostly bear load)? c. Finally, given what you found above, what do you think the implications are for injury potential in the case of purely vertical versus angled impacts?

4 ESC-100: Bioengineering Laboratory Addendum Pasco Force Plate Procedure When you get to the studio classroom, the hardware will already be set up. Please follow the instructions below (some steps may already be done depending on if a group used the equipment just before you): 1. Plug in the power supply to the interface port 2. Open Data Studio (a link is on the desktop) 3. Close the window asking you what activity you would like to perform (if it pops up) 4. Click the Setup button 5. Click Choose Interface, Select PASPORT, and Click OK 6. A new window for Normal and Parallel Force should appear as shown below: 7. For each required activity, do the following: a. Press Start you should see force values appear and fluctuate b. Press the small tare button on the side of the force plate to set the baseline normal and parallel force to 0. c. Perform the activity four times (to give you four trials), making sure to step/land toward the center of the plate. It is not necessary to stop the run between each trial; just step off the plate for a moment so you can easily distinguish between trials later. d. Press Stop

5 e. Select File Export Data and export the data for the current run. Save the file as a.txt file, which should be the default file type for example, your file names for the standing activity could be stand_normal and stand_parallel When you open your file in Excel, you will need to change the file type to All files and choose the delimited option your Professor can show you how to do this. f. To view the graph of force versus time for your activity in Data Studio, double click the Graph option in the list of Displays on the bottom left part of the program window. DO NOT export the graph image; you will clean up and plot the data you exported in the previous step using MS Excel after you have completed all the activities and returned to your home classrooms. Processing and Graphing your Data In the results section, you should have the following: A table indicating the peak force (average and standard deviation, since you performed four trials) experienced in the normal AND parallel directions for each activity. A two-panel figure for each activity, with the panels showing plots for normal force versus time and parallel force versus time. Make sure your plots have titles and axis labels (including the appropriate units) and are accompanied by captions. To create the plots, you will need to open your data for each activity in MS Excel and remove extraneous data (the segments of time before and after the activity corresponding to zero force readings). If you are unfamiliar with MS Excel, your Professor can show you how to do this once you have returned to your home classroom. Once you have created your plots and finished the Results section, look at the questions in bold from the original lab handout. You are required to answer these questions in the Discussion section, and hopefully you will be able to do so by combining your knowledge from the pre-lab and your interpretation of the experimental data. Good luck!