UBC SCHOOL OF HUMAN KINETICS HKIN 363 Mechanics ..., Study notes of Biomechanics

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UBC SCHOOL OF HUMAN KINETICS

HKIN 363

Mechanics and Kinetics

RESOURCE NOTES

I. Course Information

The University of British Columbia

School of Human Kinetics

Human Kinetics 363

Course Outline

Summary:

This objective of this course is to build on the principles of physics acquired in Human Kinetics

163, high-school Physics or entry-level university Physics and apply them to a quantitative

analysis of human movement. Examples of movement will include those pertaining to exercise,

sport, and physical activity in addition to more general activities such as walking and in the

rehabilitation environment. The student should gain an understanding of the use of a quantitative

analysis to explain how mechanical principles govern human motion. At the completion of this

course it is desired that each student be able to: 1) to understand how 2D rigid body dynamics

can be used to quantify human motion, (2) understand the cause and effect relationship between

force and linear and angular motion, and (3) perform mathematical analysis of complex human

motion in two dimensions.

Dates: Lectures: Tuesday and Thursday, 9:30 am – 11:00 am MacMillan 166 (2357 Main

Mall)

Laboratories: L1A Monday 8:30 am,

L1B Tuesday 3:30 pm,

L1C Wednesday 4:00 pm,

L1E Friday 8:30 am.

Each lab session is two hours long. We will meet at either Osborne or WMG room 120.

Instructor: Dr. David Sanderson, room 29, War Memorial Gym

Office hours: Tuesday and Thursday 8:30 am or by appointment

Teaching Assistants: Tamika Heiden (tamika@interchange.ubc.ca)

Natalie Vanicek (nvanicek@interchange.ubc.ca)

Office hours: By appointment

Prerequisites:

Human Kinetics 163, either all of HKIN 290, 291 or (b) all of ANAT 390,391.

Textbook (Required):

Title: Biomechanical Basis of Human Movement

Authors: J. Hamill and K.M. Knutzen

Publisher: Lippincott Williams and Wilkins

WebCT Resources:

There are considerable resources on the WebCT site for this course. You must have an WebCT

account access this course. You can go through the elearning site (http://www.elearning.ubc.ca)

or from the “My UBC” portal (http://my.ubc.ca).

Course Learning Objectives:

1. Understand and use the concept of a free-body diagram as it applies to human movement.

• identify drag (surface, skin, form), lift, thrust and how they affect motion.
• identify how Magnus force is created
• explain how objects can be made to change their direction as they move through space
• explain buoyancy and solve problems using buoyancy, gravity, thrust and lift
• explain how swimmers can use drag forces to move through the water

4. Analysis of human movement

This section will build on both the current course and the preceding course and put the

student into a position to complete a sophisticated description/analysis of human movement.

The student will be able to explore movements in many domains, including sports,

rehabilitation, and ergonomics.

It is expected that students will analyse forces acting on an object and predict their effects on it. Specifically, it is expected that students will:

• identify workplace and community situations involving Newton's laws
• Apply mechanical principles and anatomical knowledge to describe motion and to describe control of that motion

Course Structure:

Lecture Format. The lecture component will be two 90-minute lectures. Rather than all the

lectures being didactic there will also be group discussion on topics presented by the

instructor. Class participation component will entail analysis of movements provided

primarily on video tape but also through photographs and Power Point presentations. There

will be time allocated within the lecture to address the issues of analysis and

coaching/teaching components. There will be an opportunity to compare each presentation

and form a class consensus. The instructor will facilitate discussion. The group work is

modelled after the discussion by McKay and Emmison, 1995)^1.

Laboratory Format. There will be a two-hour laboratory component. There is a laboratory slot

for four days and maximum enrolment in the course will be restricted by the number of

students who can fit into the laboratory room. The lab work will comprise a series of 6 labs.

Some of these will be done on computer in the War Memorial Gym microcomputer lab

(room 120). Others will involve participation in a gym or out-of-doors. Three computer

programs will be used during this course – Microsoft Excel, Microsoft Word, and HMA

Technology’s HU-M-AN. By now you will be familiar with Excel and Word. HU-M-AN is a

program that allows you to digitise video images. In the fashion you will be able to create

numeric data from video clips and use these data to compute joint, segment angles, in

addition to computing joint and segment angular velocity and acceleration. All labs will

include quantitative and qualitative analysis. During these sessions, students will acquire the

necessary skills that will enable them to perform quantitative analysis of human movement.

Each lab requires a written report. The format for the written report can be found on the

WEBCT page (http://www.elearning.ubc.ca/login) under resources. Essentially, the report

will be no longer than 4 pages and will be done in a format specific for a scientific

conference.

(^1) McKay, J. and Emmison, M. (1995). Using learner-centred learning (LCL) in undergraduate sociology courses. Australian and New Zealand Journal of Sociology 31(3)102.

Week Date Laboratory Exercise Location Problem

set

1 Jan-5 No labs none

2 Jan-12 Lab 1: Lab tour and HU-M-AN practice Computer Lab 1

3 Jan-19 Lab 2:100 m Sprint Data Collection Field Hockey pitch 2

4 Jan-26 Lab 2:100 m Sprint Data Analysis Computer Lab 3

5 Feb-2 Lab 3: Sprint Start Data Collection Osborne Gym A 4

6 Feb-9 Lab 3: Sprint Start Data Analysis Computer Lab

Feb-16 READING

BREAK

7 Feb-23 Lab 4: Vertical Jump Data Collection Osborne Gym A 5

8 Mar-1 Lab 4: Vertical Jump Data Analysis Computer Lab 6

9 Mar-8 Lab 5: Muscle Torque Data Collection Osborne Gym A 7

10 Mar-15 Lab 5: Muscle Torque Data Analysis Computer Lab 8

11 Mar-22 Lab 6: Rowing Data Collection Osborne Gym A 9

12 Mar-29 Lab 6: Rowing Data Analysis Computer Lab

13 Apr-5 No Labs

Evaluation Profile

Learning objective Method Value

1, 2, 3, 4 Written examinations 60 marks

Mid-term 20 marks Final 40 marks

5, 6, 7 Labs 40 marks

5 labs each worth 8 marks

Total 100 marks

To go to the Virtual Biomechanics Lab, use either Netscape (3.0 or newer) or Internet Explorer.

You must go to the respective site and then follow the instructions if you need to download

either browser.

Signing onto the Virtual Lab

Go to Remote Address: http://www.elearning.ubc.ca and logon (or select the logon option).

You will need an interchange account to access this site. Select “Course Listing”, select “Human

Kinetics”, Select “HK363” and sign in with your UserID and password.

363 HOMEPAGE: VIRTUAL BIOMECHANICS

Once you have logged onto the 363 Webpage, there are 6 options for you to choose from.

Virtual Labs Takes you to the labs and notes sections

This is where some of your labs are

Pops up in a new browser window

Resources Contains helpful resources including background notes, problem sets

with answers, course readings, and exam hints

Pops up in a new browser window

Password Allows you to change your password from you student number (default)

to something else

Quizzes Takes you to a variety of multiple choice questions for each of the 5

sections covered in this course

Useful for short answer exam questions and quick concepts

Answers are returned immediately

Bulletin Board An interactive bulletin board that can be used to ask the instructor/TA

questions

Also enables students to interact with one another in order to solve

problems

Links Useful links to biomechanics sites worldwide

Check it out…you may be surprised!

III. Biomechanics Methods

Marker Placement

The next stage of setup is marker placement. Highly

reflective markers are placed at various landmarks,

allowing accurate identification

of specific structures on the recorded film. In this case,

the marker landmarks approximate the centres of

rotation of the different segments being analyzed. These

include the greater trochanter (hip), lateral tibio-femoral

joint line (knee), lateral malleolus (ankle), talus (heel),

and fifth metatarsal (forefoot). When light is directed

from the vicinity of the camera, the markers are

illuminated as they reflect the light back towards the

camera lens.

Light Placement

The reflective markers demonstrate a narrow angle of

reflection, therefore light placement is important in

order to achieve maximal illumination of the

markers.

Film Calibration

The last portion of the setup phase is film

calibration. This involves filming an object of a

known length. The actual and filmed length of the

object, a metre stick in this case, will be inputted

to the computer in the next stage. This permits the

calculation of a screen pixel: actual size ratio.

Digitizing Phase

Once the setup is complete, the movement is filmed, and the digitizing phase can begin. In this

stage, the motion is analyzed by quantifying the changes in location of the joint markers. At the

UBC Biomechanics lab, we use the Peak Motus Motion Measurement System to measure

movement kinematics.

This process begins by manually indicating the locations of the markers in the initial frame. This

is achieved by positioning a "cross-hair" over the markers on the computer screen and clicking

the mouse to select the location. The computer then records the x and y coordinates of the cross-

hair as the marker location. This manual process is repeated for all of the markers in the first

frame. Then computer then automatically follows the markers as the movement progresses,

recording the x and y coordinates of each marker in each frame. Now you are ready to complete

the Virtual Digitizing Session.

Once coordinate data have been obtained for each marker in each frame, the data can be fed into

a spreadsheet program such as Excel, as shown below, and analyzed from both linear and

angular perspectives. The data can also be represented graphically once this is done.

Linear Kinematics

The coordinate data can be examined in the context of linear kinematics, or in the context of

changes in the locations of the markers over time. In other words, each frame will provide a

vertical position which can then be plotted against percent stride on a graph. For instance, the

This section summarized the methods used to collect and process kinematic data. For each of the

kinematic labs, both linear and angular, these techniques were used. Once the data had been

digitized they were processed to compute the respective data and stored in files that can be

loaded by Microsoft Excel. You should now be able to work with those files to complete your

assignments.

Kinetics Methods

Force Platform Kinetic Data Acquisition

A Kistler force platform and Kistler force pedals are used to acquire kinetic data in the

biomechanics lab. This equipment uses 4 piezoelectric transducers, located at the corners of the

platform to measure the applied forces. Forces are measured in three planes: vertical,

anteroposterior (AP ), and in the lateral direction. (For our purposes, we will assume that the

lateral forces for a walker are negligible). The force platform is then connected to an amplifier

using electrical wires. The amplifier boosts the signal from the force platform so that the

computer can "hear" the data. The amplifier is also connected to the computer using electrical

wires. The Force platform is activated by powering up the amplifiers and connecting it to the

Peak Motus Motion Measurement System. It is then ready to measure movement kinetics. As an

athlete applies a force to the force platform, the data from the force platform is passed through

the amplifiers and fed into the computer.

If an person lunges forward and sideways from a force

platform, a 3 dimensional force is applied to the force

platform. This force is called a resultant vector and

can be broken into its three component vectors. These

lie in the vertical (Fz), AP (Fy) , and lateral (Fx)

directions. The Kistler force platform measures these

components and passes them on to the computer.

The force applied to the force platform, however, is not the force that we are

interested in. It is the reaction force of the platform on the athlete that is of interest. Newton's

third law states that for every force there is a reaction force that is equal in magnitude and

opposite in direction. For example, as the athlete's foot applies a force to the force platform, the

force platform exerts a ground reaction force on the foot that is equal in magnitude and

opposite in direction to the resultant force. This can also be broken into three vectors, which are

oriented in the vertical, AP , and lateral directions. These are also equal in magnitude and

opposite in direction to the corresponding force components applied to the force platform. The

Now you are ready to go to the Virtual Kinetics Data Acquisition page to see how the data are

collected.

Once the data have been collected, it can be copied into a spreadsheet program (e.g.Excel). The

forces can be input with respect to time as shown in the Excel spreadsheet below.

The data can then be manipulated to

produce graphs which graphically

represent the data. A graph plotting

vertical force and AP (anterior-posterior)

force with respect to time is shown

below. The red line is Vertical GRF

(ground reaction force) plotted against

time, and the blue line is anterior-

posterior GRF plotted versus time. It is

important to note that the computer

records the data for as long as it is told,

and not just during the time that the

person is in contact with the force

platform. Because of this, the computer

records forces of zero for the points

before and after the contact made by the

athlete. This can be seen in the graph

below, where the computer sampled the data for two seconds, yet the athlete only made contact

with the force platform for 0.6 seconds.

The graph below shows the vertical ground reaction forces plotted with respect to time during

walking. As you can see, the vertical GRF increases sharply upon heel strike, then dips

somewhat during the stance phase. Finally, the forces rise again and fall off as the subject leaves

the platform.

The next graph shows the analysis of the AP (anterior-posterior) GRF forces during walking.

Upon heel-strike, the reaction force is in a negative direction. This is because the acceleration is

negative at this point (i.e. the athlete is slowing down). During the stance phase, the acceleration

becomes less and less negative as the athlete moves over the base of support, finally becoming

positive midway through the stance phase. The acceleration continues to increase in magnitude

because the subject pushes off the force platform which results in a GRF propelling the athlete

forward. The acceleration drops off as the subject leaves the force platform.