Steppin' Out-- 
Using Inquiry to Challenge
Alexander's Stride Analysis
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Standards Addressed::
Science as inquiry; access and choice among a variety of technologies;
cross-disciplinary; authentic assessment; appropriate manipulation of data;
quantification and articulation with math curriculum; original analysis.
This series of labs addresses Content Standards A, B, and C; Program Connection
C; and Teaching Standards A through F.
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Link
to National Science Education Standards
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Content Connections::
Body systems; biomechanics; variation; sampling; taxonomy and classification;
evolution;
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Duration: 2-3 days
Introduction and background:
In assessing prior knowledge, students can readily distinguish
between walking, jogging, and running trackways in humans.
Less apparent, but easily distinguishable, is the phylogenetic
progression of leg position as described by pace width and angulation,
comparing amphibians, reptiles, and mammals.
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R. McNeill Alexander's
classic research into biomechanics of stride presents evidence that suggest
that the relative stride length calculation can factor out
leg length in measuring the relationship between stride length and speed.
(photos presented from Dynamics of Dinosaurs and other extinct
giants, Columbia University Press, 1989. ISBN # 023106678)
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Relative Stride=
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length of stride
(meters)/leg length (meters)
leg length = femur + fib/tib + ankle length
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He then presents some insights about the speed/stride length
relationship as it relates to body size, using dogs, humans,
and camels as an example.
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In order to compensate for the body size, Alexander suggests
a calculation of dimensionless speed, which appears to allow
for comparative data among animals of varying sizes and shapes.
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Dimensionless speed=
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speed/(leg length x gravitational accel)^1/2
Alexander also suggests that this dimensionless speed
calculation applies to bipeds as well as quadrupeds, hoppers as well as
striders, and is applicable regardless of surface characteristics, thermoregulatory
differences, and other factors.
Applying Inquiry to the Problem:
A traditional approach to this subject
would take the calculation at face value and then apply it to additional
organisms; that is, applying the calculation with supplementary evidence.
Alexander himself has used the calculations to analyze unkowns, most notably
dinosaur trackways.
We chose to challenge the equations
rather than accept them per se. Immediately upon presentation of the original
equations, participants asked critical questions about sample size, age
of organisms, gait characteristics, as well as the assumptions Alexander
suggests in his dimensionless speed argument.
As a group, we chose a representative
sample of organisms. We then broke into teams and designed investigations
to test the peripheral aspects of the equations. In each case we began
with a null hypothesis: in this case, the null hypothesis was that Alexander's
equations did not adequately contend for these factors.
Each team had to choose the appropriate
tools, measuring devices, and yardsticks for their own experiments. Each
set of protocols and results is linked below.
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Assessment: Working in
teams, students first proposed their research topic and organisms. They
had to account for sample size, data collection, and presentation. Assessment
was by written lab report and presentation of findings to the whole group.
Part of the lab report had to suggest further research areas. See the links
for specific assessment results and applications.
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Discussion: This inquiry-based
design aspect turned out to be engaging, and generated some interesting
results.
students led in formulating questions
students chose experimental subjects (organisms)
students designed, organized, and presented original data
students had access to and used a variety of tools and technologies
to solve their problems.
Links
Rhodes College
Aptos High School
