KHP415Lab2
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KHP 415 - Biomechanics of Human Movement Laboratory
Lab 2 –Linear Kinematics (running kinematics)
Reading Assignment
: Enoka, R.M. (1994). Neuromechanical Basis of Kinesiology
, 2
nd
ed. Champaign, IL: Human
Kinetics, pp. 14-16 (available on Canvas).
Introduction
: In running events, a competitive athlete's goal is to cover a given distance in the shortest possible time.
From a biomechanics perspective, the goal is to cover the distance with the highest possible average velocity or speed.
By describing various kinematic aspects of running we can gain information about strengths and weaknesses in an athlete's performance that may lead to better running times or a reduced potential for injury. This laboratory focuses on some of the most basic descriptors of running performance—velocity, step length, step time, and step rate. The lab consists of two parts, the first focusing on distance running kinematics and the second on sprinting kinematics. Several students will be asked to run. Please come to class wearing appropriate clothing and footwear for running.
Purposes
: 1) To examine the association between step length, step rate, and velocity during running, and 2) to
examine the velocity profile for a 25 m sprint.
Equipment and supplies needed
: Please bring a calculator, graph paper, and a ruler so that you can plot results
from your analyses. All other equipment needs will be provided.
Definitions and Equations
:
Stride
–the basic unit of motion for walking and running reflecting one complete cycle of motion; commonly defined
as
the motion occurring between successive contacts of the same foot (i.e., right foot contact to next right foot contact)
Step
–one half of a complete stride (e.g., right foot contact to left foot contact)
Step length (SL)
– the distance traveled per step
Step time (ST
) – the time required to complete one step
Step rate (SR)
– the frequency at which steps are taken (i.e., number of steps per unit of time); inverse of step time
= d / t (1)
running velocity = step length / step time
= SL / ST
(2)
running velocity = step length × step rate
= SL × SR (3)
Part 1
– Association between step length, step rate, and running velocity
Data Collection
:
· Establish groups of approximately 8-10 students: one volunteer runner, one starter, 3-4 step counters, 2-3 timers,
1 data recorder.
· A 25-meter running course will be established for the tests. The starter will be positioned at the starting line. Step
counters will be positioned in the middle of the 25 meter measurement zone. Timers and data recorder will be
positioned at the finish line.
· The volunteer runner from each group will run through the 25 meter course two times at each of five self-
selected
speeds--very slow (slow jogging speed) ,slow, medium (comfortable distance running speed), fast (fast distance
running speed), and very fast (at or just below maximum sprinting capability). Be careful! No injuries, please! For each trial, the speed should be constant through the 25 m measurement zone. This will require the runner to start his or her
run approximately 10 m before the starting line.
· As the runner passes the starting line, the starter signals the timers to begin timing the run and the step counters
to begin to count the number of foot strikes over the 25 m course. As the runner crosses the finish line, the
timers stop their stop watches, compute an average of their times to the nearest 0.01 s, and supply the average
time for the run to the recorder. Similarly, the step counters report to the recorder an average of the number of
foot strikes (to the nearest 0.1 footstrikes) taken over the 25 m distance. These results, which will be shared with
all group members, are recorded initially on the data recorder's data sheet in Table 1 that follows.
TABLE 1. Raw data for 25 m run times and footstrike counts Subject:
Velocity/Trial
Distance (m)
Time (s)
Footstrikes (#)
Steps (footstrikes –
1)
Very slow (trial 1)
25
7.8
22.4
21.4
Very slow (trial 2)
25
7.9
22.6
21.6
Very slow (Avg.)
25
7.85
22.5
21.5
Slow (trial 1)
25
7.0
18.2
17.2
Slow (trial 2)
25
7.1
20
19
Slow (Avg.)
25
7.05
19.1
18.1
Medium (trial 1)
25
5.8
15.6
14.6
Medium (trial 2)
25
5.7
17
16
Medium (Avg.)
25
5.75
16.3
15.3
Fast (trial 1)
25
4.6
14.2
13.2
Fast (trial 2)
25
4.7
14.4
13.4
Fast (Avg.)
25
4.65
14.3
13.3
Very fast (trial 1)
25
3.3
12.4
11.4
Very fast (trial 2)
25
2.8
13.4
12.4
Very fast (Avg.)
25
3.05
12.9
11.9
Data Analysis:
Using the distance traveled (25 m), time, and step information for each speed condition from the table above, compute:
a)
average running velocity over the 25 m course, b) average step length (SL), c) average step time (ST), and d) average step rate (SR). Record the results below in Table 2.
TABLE 2. Average results for velocity, step length, step time, and step rate
Velocity condition
Ave. velocity (m/s)
Ave. SL (m)
Ave. ST (s)
Ave. SR (steps/s)
Very slow 3.18
1.16
.37
2.74
Slow 3.55
1.38
.39
2.57
Medium 4.35
1.63
.38
2.66
Fast 5.37
1.88
.35
2.86
Very fast
8.2
2.1
.26
3.9
Part 2--Velocity Profile of Sprinting Performance
Data Collection
:
Establish a group of approximately 12 students: one volunteer sprinter, a starter, 10 timers
Establish a 25 m sprint course with cones positioned at the start line and at 5, 10, 15, 20, and 25 m points.
The starter will be positioned at the starting line. Two timers will be positioned 5, 10, 15, 20, and 25 m from the start
line (i.e., 2 timers at each 5 m location).
The volunteer sprinter will complete three 25 m sprinting trials, beginning each trial from a standing start
.
For each trial, the starter, facing toward the timers, will give a loud "ready-set-go" sequence of verbal commands at
which time the runner will initiate his or her sprint to the finish line and all timers will start their stopwatches.
As the runner passes any given 5 m position, the timers at that location stop their stopwatches. A data recorder for
the group will then record in Table 3 below the average times (nearest 0.01 s) recorded at each 5 m position.
TABLE 3. Raw temporal data for sprinting Subject:
Time (seconds, to the nearest .01 s) at each 5 m position
Trial
5m
10m
15m
20m
25m
1
.925
1.805
2.225
2.96
3.705
2
.88
1.645
2.55
3.235
3.545
3
1.025
2.085
2.54
3.165
3.7
Average
.943
1.845
2.438
3.12
3.65
Data Processing
:
Based on the temporal data in Table 3, compute:
· the temporal midpoint for each 5 m interval [i.e., the average between successive 5 m times; e.g., if the time
recorded at the 5 m location was 0.86 seconds and the time recorded at the 10 m location was 1.74 seconds,
then the temporal midpoint of the 5-10 m interval = ((0.86+1.74) / 2) = 1.30 s; thus, this midpoint value is halfway
between 0.86 and 1.74 s; the temporal midpoint provides a reasonable estimate of the instant in time at which the
instantaneous speed during the interval matches the average speed computed for the 5-meter interval
· the time required to complete each 5 m zone
· the average velocity for each interval (i.e., interval distance / time required to complete the interval). Record your
results in Table 4 below.
TABLE 4. Average temporal and speed results for sprinting trials
Distance interval
Temporal midpoint (s)
Time per interval (s)
Average velocity (m/s)
0-5 m
.472
.943
5.3
5-10 m
1.394
.902
5.54
10-15 m
2.142
.593
7.33
15-20 m
2.779
.682
8.43
20-25 m
3.39
.53
9.43
Linear Kinematics Lab Report
:
Directions
: For this lab, you are required to complete a lab report by responding to the following questions. Your lab
report must be typed
. It should have a cover page that carries a report title, your name, and laboratory section.
Requested graphs or plots of results may be done by hand on graph paper or using spreadsheet and graphing
software like Microsoft Excel.
Part 1--Association between step length, step rate, and running velocity
1. In separate graphs, plot: a) step length as a function of running speed (step length on the vertical axis vs speed on
the horizontal axis), and b) step rate as a function of speed (rate on vertical axis). Each graph should not be
smaller than 8 cm x 8 cm (~3” x 3”). Note
: scaling of both horizontal and vertical axes should be limited to the
actual data ranges for speed and step length or rate, respectively, i.e., don’t start the vertical and horizontal axes
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