Analysis of Movement - US Figure Skating

Orlando 2009
Biomechanics II:
Analysis of Movement
An overview and advanced discussion of the effects of movement,
with a focus on the technology available to analyze skills
and support science-based instruction.
Charlene Boudreau
Director, Sports Sciences & Medicine
U.S. Figure Skating
Supporting the ART and BUSINESS of SCIENCE-based coaching.

Technique is largely determined by mechanical factors.
Some common technique tips…
1. Gut-Butt Connection
2. Alignment!
3. Two-head turn to the top.
4. …
5. …
6. …

In order to teach a new skill and/or coach an existing one,
we must establish some sense of flow in movement/skill analysis.
MECHANICALLY, what do I see in the skill?
Is it good?
Is it bad?
Why is it happening?
MASS - DISTANCE - TIME
Is it important?
Is it mental?
Is it physiological?
How can I fix it?
Is the body size
APPROPRIATE?
Top 3 Precautions to Avoid Missing the Mark:
1. Don’t Lose it in Translation.
2. Prioritize Feedback.
3. Focus on Critical Features (AP-MM).
Are the muscles
SMART enough?
Are the muscles
FUELED enough?
A prelude to… Deterministic Modeling.

PRINCIPLES OF
SKILL ANALYSIS
SCIENCE-BASED INSTRUCTION
Deterministic Modeling
shows relationships
between the result of a
performance and the
factors contributing to it.
Time in air
Jump Success
V R
in air
Rhythm/
Timing
The method is used to:
Take-off
angle
Horizontal
momentum
Angular
momentum
Moment of
inertia
Time to
position
Focus, objectify and prioritize training
emphasis and feedback.
V H
and V V
at take-off
Body
Mass
V H
on
approach
Body position
Physique
Improve understanding of factors
contributing to sport performance.
Identify factors that are most sensitive
to training/overtraining effects.
Entry
pattern
Leg force
Guide equipment design and rule
changes.
Guide quantitative research.
Critical Features
©CHARSolutions, LLC
Critical Features describe specific body movements which may be observed
in order to determine if the mechanical factors have been performed ideally.

PRINCIPLES OF
SKILL ANALYSIS
SCIENCE-BASED INSTRUCTION
Deterministic Modeling is a Three-Step Process:
Step 1 – Identify the errors associated with critical features.
• Determine mechanical factors affecting the execution of the skill.
• Identify true deterministic factors, ie those not directly connected to any lower factor.
• Eliminate factors athlete cannot affect in time frame being considered.
• Observe athlete performance on remaining factors.
Step 2 – Evaluate and prioritize the errors.
• Maximize impact subject to motivational needs.
• Important factors are those strongly related to the result.
• Sensitive factors are those that can change.
• Exclude errors that appear to be caused by other errors.
• Consider time frame.
Step 3 – Intervene via feedback, practice, training.
Implementation
Pre-requisites:
What makes a difference?
What can change?
How long might it take?
How do I go about it?
TECHNOLOGY CAN HELP!!!

PRINCIPLES OF
ANALYSIS OF
MOVEMENT
Research – Casey, King & Smith
About 10 years ago, there was a study done on the characteristics
most critical to successful completion of the triple axel.
Speed of rotation, jump height, jump distance were investigated.
Skaters with rotation speeds of 5 rev/sec or more were more
successful in completing triple axels.
THE RESULTS
Jump heights were not appreciably different among singles, doubles
and triples!
Take-offs and jump distances were shortest for triples, probably due
to larger skids. Skid widths ranged from 1.25 to 3.00 inches.
Time to bring arms and legs into tightest position was a major factor in
rotational speed.
Axel Rotational Velocity (m/s)
Single Double Triple
3.6 4.5 5.0
2.5 4.1 4.6
2.4 4.5 4.7
2.8 4.1 5.4
3.2 4.1 5.0
The application of biomechanics principles minimizes “trial and error” coaching and fosters the development of effective
teaching strategies and training programs that are specific to the unique needs of individual skaters and teams.

PRINCIPLES OF
ANALYSIS OF
MOVEMENT
Research – Casey, King & Smith
Frames (30 fps)
Time in Air (s)
Jump Ht (in)
Jump Ht (m)
Triple Zone Ladies
Triple Zone Men
10
0.333
5.4
0.14
11
0.367
6.5
0.16
This research team
defined the relationship
between jump height, time
in air and number of video
frames during the flight of
a jump.
12
13
14
15
16
17
0.400
0.433
0.467
0.500
0.533
0.567
7.7
9.1
10.5
12.1
13.7
15.5
0.20
0.23
0.27
0.31
0.35
0.39
18
0.600
17.4
0.44
These values assume that the skater’s
center of mass is at the same height at
take-off and landing.
19
20
21
0.633
0.667
0.700
19.4
21.5
23.7
0.49
0.55
0.60
22
0.733
26.0
0.66
23
0.767
28.4
0.72
24
0.800
30.9
0.78
25
0.833
33.5
0.85
26
0.867
36.3
0.92
The application of biomechanics principles minimizes “trial and error” coaching and fosters the development of effective
teaching strategies and training programs that are specific to the unique needs of individual skaters and teams.

PRINCIPLES OF
ANALYSIS OF
MOVEMENT
Projectile Motion
“An object that leaves a surface with
both horizontal and vertical velocity will
follow a parabolic or symmetrical arcshaped
pattern in the air.”
TRANSLATION: The up and down
parts of the flight path of a skater’s
jump will be symmetrical.
“The greater the height of the
trajectory, the longer the air time
associated with the parabola.”
TRANSLATION: The higher you go,
the more time you get to spend in the
air. (Imagine a water hose!)
The application of biomechanics principles minimizes “trial and error” coaching and fosters the development of effective
teaching strategies and training programs that are specific to the unique needs of individual skaters and teams.

PRINCIPLES OF
ANALYSIS OF
MOVEMENT
Projectile Motion
The specific flight path a skater
follows is determined by the
velocity and angle at take-off.
Important Factors:
Approach speed (V H
)
Upward press (V V
)
There may be a trade off between
jump height and rotational
velocity.
You need enough time to complete
the rotations, pull in arms and
legs, open to check out for landing,
and to distribute rotations equally.
The application of biomechanics principles minimizes “trial and error” coaching and fosters the development of effective
teaching strategies and training programs that are specific to the unique needs of individual skaters and teams.

PRINCIPLES OF
ANALYSIS OF
MOVEMENT
Conservation of Rotational Momentum
Rotational momentum quantifies the amount of
rotational motion that a skater possesses about her axis of
rotation (usually longitudinal axis).
Since rotational momentum remains constant…
If moment of inertia ↑, then rotational velocity ↓.
If moment of inertia ↓, then rotational velocity ↑.
Rotational momentum is created during the entrance
to a spin or during a jump preparation and take-off.
It combines both how fast a skater is rotating and the
current body position:
Rotational momentum = V R X moment of inertia
On the ice, rotational momentum is created when the
forces the skater applies to the ice with her blade
create a torque.
Once in the air, however, there is no surface for the
skater to push against, so rotational momentum
remains constant from jump take-off until landing.
The greater the rotational momentum going into a
jump or spin, the greater potential for rotational
velocity during the jump or spin.
The best jump take-offs and spin entries are ones
that convert horizontal velocity into vertical velocity
and initiate rotation.
The greater the rotational momentum going into a
jump or spin, the harder it will be to pull the arms and
legs into a tight position and hold it.
Enter strength, timing, skids, patterns, take-off
movements, air position, etc.
The application of biomechanics principles minimizes “trial and error” coaching and fosters the development of effective
teaching strategies and training programs that are specific to the unique needs of individual skaters and teams.

ANALYSIS
TECHNOLOGY
MOTION ANALYSIS
In 1999, a motion analysis
program was developed at the
University of Delaware.
Technical, logistical and
financial complications forced
it closed.
With support of the United
States Olympic Committee
and U.S. Figure Skating, the
University of Delaware is
reviving the program.
The new motion analysis program
continues to focus on the mechanical
determinants of multi-revolution jumps:
• Body measurements (anthropometrics)
• Rotational energy at take-off (angular
momentum)
• Body position in air (moment of inertia)
• Jump height (air time)
The new program boasts
modern software and new
personnel with the abilities to:
• Analyze critical features
• Assess revolution capacity
• Provide real-time analysis
• Suggest strategies
• Evaluate strategies
• Develop norms
Imagine all the “What if”
scenarios!!

ANALYSIS
TECHNOLOGY
Closer to home…
Affordable.
Friendly.
EFFECTIVE!