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A Question of Foot Dominance

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Maria Cieslewski

on 10 December 2013

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Transcript of A Question of Foot Dominance

A Question of Foot Dominance
Biomechanics Lab
December 10, 2013

Graham Rech
Laurén Schaefer
Natalee Cifuentes
Liana Janick
Maria Cieslewski

Biomechanics Lab October 2013
Core Strength and Lower Extremity Alignment During Single Leg Squats¹
Compared the orientation of the lower extremity between males and females during the SL squat test

Where did it all begin?

Image: themetapicture.com

Problem
:
Leg preference is labeled by the function it is performing, so there are a lot of different opinions concerning what which leg is actually dominant

Characteristics of leg preference are different for each sport:²

Surfing
You ride a surfboard with your weight centered & you turn by swinging your front foot
Snowboarding
You ride a snowboard with your weight on your front foot & steering by swinging your back foot



Question:
Why is the kicking leg considered the dominant leg?

Image: whitelines.com

Image: geekfill.com

Purpose:
If you need stability in the back with surfing but stability in the front with snowboarding, which foot is the true “dominant” foot?
What specific characteristics about a foot determine its “dominant” orientation compared to the other “non-dominant” foot?

Questions:
Would a “right-footed” surfer then switch to “goofy” when transitioning to a snowboard then? And vice-versa?

Would they even maintain the same stance of having the R foot forward?

Is the front foot or the back foot, in either sport, considered the dominant foot?

Led us to ponder…

Image: SurfScience.com

So what is considered stable?
Balance: an even distribution of weight enabling someone or something to remain upright and steady; equilibrium of the body; steadiness³
Stability = Balance
If center of mass is over the base of support, then the object is stable or balanced

If the COM is not over the BOS, and the
line of force acting on the COM
(Fgravity) is landing outside the
base of support
, then the object will fall over⁴




Purpose:
What makes a foot “dominant?”

Right Image: Corolla Surf Shop, NC
Left Image: thesurfchannel.com
Middle Image: youtube.com

When going in a straight line, (like taking down off the face of a wave; “riding the line”) and the line of force from the COM (
red line
) is not above the BOS (the area between the feet;
yellow circle
)⁴
→you eat it; biff it; faceplant

Examples

Images: deviant.com

The bigger the
base of support
, the easier it is to balance⁴
Standing on two legs vs. one leg
Two-handed handplant vs. one-handed handplant

Examples

Images: Corolla Surf Shop, Corolla, NC

The closer the center of mass is to the base of support, the easier it is to balance⁴

Laying down on the board vs. standing
Bending your knees vs. keeping your legs straight


Examples

Right Image: nplusonemag.com

Left Images: Corolla Surf Shop, NC

The more perpendicular the surface of the
base of support

is to the

line of force
from the center of mass, the easier it is to balance⁴

Dropping in vs. “Riding the line”

Examples

Image: blog.spartascience.com

WE HAVE A HYPOTHESIS!

We hypothesized that leg dominance is the result of superior stability of the stance leg
Theory: Your “dominant foot” is the foot initiating action, so your non-dominant foot needs to more stable for balance purposes

How do we measure that? What can we measure as DPT 1s and P&O 1s?

A shift of
center of pressure (CoP)
is an indirect measure of postural sway and thus a measure of a person’s ability to maintain balance⁵
And we found this cool article…



By: Iain M Fletcher and Christopher S. Long
Department of Sport and Exercise Science
Location: University of Bedfordshire
Polhill Avenue, Bedford, MK41 9EA, United Kingdom; Tel: +44 (0)1234 793291;
E-mail: iain.fletcher@beds.ac.uk








Participants: “from an English League One soccer team”
Published on July 15, 2013 by the Journal of Athletic Enhancement


The Effects of Kicking Leg Preference on Balance Ability in Elite Soccer Players⁶


Journal of Athletic Enhancement⁷

Problem
: Soccer players are getting injured; higher incidence rate than other field sports
“If gross muscle performance for elite players is similar in dominant and non-dominant limbs, could a lack of balance be more relevant in terms of explaining injury discrepancies between preferred and non-preferred kicking legs?”⁶
Purpose
: “determine whether static and dynamic balance differs in elite soccer players preferred kicking and non-preferred kicking legs”⁶
Static balance
– Balance at rest (standing on one leg)
Dynamic balance
– Ability to anticipate and react to changes in balance as the body moves through space
Balance results from proprioceptive, visual, and vestibular input⁶
Hypothesis
: “there will be a significant decrease in static and dynamic balance for the preferred versus the non-preferred kicking leg”⁶

The Effects of Kicking Leg Preference on Balance Ability in Elite Soccer Players⁶

Participants:
5 students ranging in age from 22-26
3 females and 2 males

Everyone says they'd kick the ball with their
right leg
!

Heights
ranged from 65.5 +/- 5.5 inches
Weights
ranged from 150 +/- 33 pounds
Foot lengths
ranged from 9.75 +/- 1.25 inches for the Left Foot and 9.73 +/-1.38 inches for the Right foot
1 subjects feet were the same size
2 subjects left feet were bigger than their right
2 subjects right feet were bigger than their left

Subjects were asked to remain barefoot to eliminate any stability provided by footwear.
Pictures used with permission from parties involved.
PROCEDURE!!!!
Procedure
4 Dynamic Tests
1 10 second practice session with eyes open
3 repetitions of the following 4 tests:
1. Eyes open while standing on their preferred kicking leg (PKL) and tapping with their non preferred kicking leg (NPKL)
2. Eyes open while standing on their NPKL and tapping with their PKL
3. Eyes closed while standing on their PKL and tapping with their NPKL
4. Eyes closed while standing on their NPKL and tapping with their PKL
Pictures used with permission by subjects

And yes, this was staged and we forgot to tell her to take her other shoe off. For the data collection both shoes were off!
but how fast did they tap!?
Each measurement set contained: 10 seconds to the beat of a metronome set to 75 bpm (beats per minute)

Center of pressure measurements were used as the measure of balance in these activities (just wait until we get to the results!)

Center of pressure movement was tracked through the AMTI Force Plate set up in the biomechanics lab.

The software used to capture the data was Acqknowledge, and COP plots were recorded for further analysis and comparison.
METHODS
http://commons.wikimedia.org/wiki/File:Wooden_Metronome
Dynamic
and
Static
tests were conducted:

Static testing
was conducted to establish a baseline of balance within each the subject’s legs by balancing on one leg while holding arms at the side and the contralateral leg at 90 degrees of hip flexion
we did nothing...not in the scope of this research project anyway!

Dynamic testing
consisted of soccer centric moves that pertained directly to the game
using these moves reiterated familiar motions where the subjects would be more apt to use their PKL and NPKL’s as they normally would
in our experiment, we considered the tapping a more diverse move that subjects could perform without a sports centric skill set

Subject Selection

our experiment consisted of a total of 5 and mix of females and males, all right PKL
the experiment in the article consisted of only males with 11 out of 15 being right PKL.
how'd that compare to the methodology in the article we read?
RESULTS

images were then analyzed by Smallest Enclosing Circle
(per recommendation of Mike Wininger)

This technique uses the smallest circle possible to encompass all the points of a given plot
The circle has to come into contact with at least 3 points in a plane, or just 2 if those points reside directly opposite each other on the circle.
The smaller the area of this circle, the less variance present in the plot, or in this case, the less variance in CoP
A statistical ANOVA test would have been conducted to determine if the variance between the five subjects in the variables of leg dominance and eyes open/closed, were indeed significant or not. Since that was not the case, the areas of these circles from the three trials were averaged and then placed in a bar graph for visualization


Center of Pressure
per subject, per leg
eyes open and closed
RESULTS
data was collected in the form of CoP variance plots
since area software does not exist...
all collected under the same scale and saved via screen shot
From the graph, it can be observed that...

visual cues have a huge impact on balance since both trials with eyes closed yield large relative variance in CoP
it would appear that the preferred kicking leg has the least amount of CoP variance with each subject, hinting to the notion that our hypothesis has been rejected

*Without statistical analysis however, it is impossible to say whether or not these findings are significant.

The article had similar results in the dynamic activity of the hop and hold, using much more significant equipment and mathematical techniques
Discussion
Foot Contact
3 subjects used their hallux as the only tapping contact point
2 subjects used the entire forefoot as well as their hallux and 4 phalanges
Foot Position
3 subjects tapped more anterior to their bodies
1 subject tapped lateral to their body
1 subject tapped anteriolaterally
We could have made this better by...
specifying the part of the foot that should have been used to tap the floor
specify the location to tap as though not to add more deviation to the center of pressure mapping
Tapping Technique
Discussion continued...
NOISE
the subjects not being tested and group giving the experiment were not quiet
the metronome was sounding very close to the subject being studied but...the subject may have had a less or more difficult time altering their vestibulocochlear system to adjust to silence or noise within the room.
We could have made this better by...
Stating if the background noise should be present or not

perfect practice
makes perfect
practice session we allowed was with the subject's eyes open only
may have been beneficial for a practice session with eyes closed instead of open, or in addition to

Why?
allowing the subjects to practice with their eyes closed so that the balancing was due to their vestibulocochlear system (rather than visuals combined)
hand check!
we did not specify where to keep the subject's arms and hands
but...they all kept them by their sides!
None of the individuals tapped with their shoulders abducted, rather simply their elbows slightly flexed and their wrists moving in slight flexion and extension, and their phalanges flexed at both interphalangeal joints.
Why does it matter?
By keeping their arms closer to their body, the subjects were able to have a smaller COP displacement because their focus was on the foot tapping and not on the placement of their arms.
BIOMECHANICS
Let’s first set the scene

Static test: Single leg stance in 90 degrees of hip and knee flexion

Dynamic test
: Passing balance
The kicking leg did not do well in balancing the player,
Non kicking leg did well in balancing the player, these results were statistically significant.
Hop and hold
NO SIGNIFICANT DIFFERENCE

This deems the hop and hold test was not specific enough with regard to soccer.

Article Findings
Why is this important?
Soccer is a non contact sport with a high rate of injury, it would be really beneficial to the soccer community
(ahem soccer is the most popular sport in the world
, WORLD CUP!) to find a test with objective measures that can screen players for injury
HOLD UP
non-contact sport, where are all these injuries coming from?
Quick cutting movements, 50 turns per game
Stance leg=lots of shear forces and torque, constantly.

So, stance leg needs to especially good at landing and stabilizing.
This is why we test position sense and balance.


Stork test?!

not specific enough, we need something that can mimic game play, stance balance test requires a stretch and shortening cycle of .3s, anything more than that wouldn’t mimic movement in game play

BUT THERE ARE OTHER TESTS OUT THERE! Why don't we use those?

Balance discrepancies between kicking and non kicking leg exist.
Only apparent when specific balance tasks are used.
Thus, balance tasks that are used to screen players have to mimic actions SPECIFIC to soccer in order to explore foot dominance and non dominance.

So, what does this all mean?
THE END

QUESTIONS???
1. Balance. The Free Dictionary Web site. http://www.thefreedictionary.com/Balance. Published 1991.
Updated 2013. Accessed December 5, 2013.

2. Benda BJ, Riley PO, Krebs DE. Biomechanical relationship to center of gravity and center of pressure during
standing. IEEE Transactions on Rehabilitation Engineering. 1994; 2(1): 3-10. doi: 10.1109/86.296348.

3. Coleman, S. Balance: The Most Important Aspect of Surfing. SurfScience Web site. http://.surfscience.com/
topics/surfing-tips/intermediate-tips/balance-the-most-important-aspect-of-surfing. Published 2011. Accessed December 5, 2013.

4. Fletcher IM, Long CS. The Effects of Kicking Leg Preference on Balance Ability in Elite Soccer Players.
Journal of Athletic Enhancement. 2013; 2(3): 1-4. http://dx.doi.org/10.4172/2324-9080.1000114.

5. Journal of Athletic Enhancement. SciTechnol Web Site. http://.scitechnol.com/athletic-enhancement.php.
Published: 2013. Accessed: December 4, 2013.

6. Kroleski, G. Greg’s Surfing Adventures: Snowboarding For Surfers. SurfScience Web site. http://
surfscience.wordpress.com/2011/01/13/snowboarding-for-surfers. Published: January 13, 2011. Accessed: December 4, 2013.

7. Wilson JD, Ireland ML, Davis I. Core Strength and Lower Extremity Alignment During Single Leg Squats.
Med. Sci. Sports Exerc. 2006; 38(5): 945–952. doi: 10.1249/01.mss.0000218140.05074.fa. Accessed October, 2013.
REFERENCES
What is JAE all about?
Kinesiology
Sports Psychology
Athletic Injury Management
Athletic Training & Rehabilitation
Sports & Physical Education
Performance enhancement drugs and effects

What is their angle?
Promote research that makes a contribution in advancing knowledge in physical enhancement issues

SciTechnol
Subscription based online publisher (running 54 international Journals)
“publishes articles with assured quality, prompt, efficient peer review process and contributes in the field of science and technology by accelerating discovery and keeping pace with the running and advancing world.”⁷

Procedure continued...

Although continuing our data analysis with our results could have brought new supportive conclusions to the table, time and other constraints were evident.

Why does it matter?
If the data was analyzed between the eyes open vs. closed trials of leg dominance, an ANOVA test could have been performed.
If a greater amount of time was available for ANOVA to be used, the importance of our results could show if the experiment we performed was helpful in supporting our hypothesis.


During the experiment, due to the subject's COM passing over his/her BOS, he/she lost support while tapping.
This resulted in a handle full of times the subject lost his/her concentration and the data point had to be thrown out.

Why does it matter?
If we were to keep these plots, the data would be skewed in a negative way towards our hypothesis.
As a result, we threw out these images as data point outliers to give our results a more conclusive data collection.
ANOVA
Statistical Analysis
OUTLIERS
Leg dominance
due to:
COP displacement
vestibulocochlear systems,
visual and proprioceptive mechanisms

Dynamic or kinetic analysis of movement
:
Within our experiment only a dynamic study was done.
Our article provided results from a static analysis; however, their hypothesis was not supported by it.
Because our experiment was developed through our curiosity in the dynamic movement of soccer players and their preferred kicking legs, a static test was not performed.

Further Research
:
Obtaining peak pressure measurements
Peak pressure of the plantar surface of the foot could help identify which anatomical location on each foot the subject felt most stable on, as well as, muscle usage to correlate with EMG findings
Muscles being used to maintain a stable position when tapping through EMG testing

Force Plates to obtain COP plots
:
Illustrated the anterior/posterior or lateral movement of the stabilizing foot
Correlates to the usual movement of the forces measured when standing on a force plate
Full transcript