Transcript Effects of different shoe-lacing patterns on the biomechanics of running shoes

Effects of different shoe-lacing
patterns on the biomechanics of
running shoes
Journal of Sports Sciences Feb2009, Vol. 27 Issue 3, p267 9p.
Authors: Marco Hagen & Ewald M. Hennig
Sport and Movement Sciences, Biomechanics Laboratory,
University of Duisburg Essen, Essen Germany
Presented by: Kelly Gartland
Introduction
• Sport shoe research has been a major interest for 30+ years
• Lots of studies have been conducted that influence the design of
running shoes (varus wedges, varying amounts of padding)
• Some purposes of running shoes include
reduce impact shocks
reduce excessive pronation
pronation: rotation of the subtalar joint that involves
more weight being supported on the inside sole of the
foot
Other Research Studies
• Few studies have looked at mechanical coupling
between foot and shoe
• One study found that from the mathematical point of view,
the most frequently used X-lacing is the best and strongest
way (Polster 2002)
• Another study found that a soccer shoe with a special antipronation lacing technique was more effective in
controlling rearfoot motion (Sandrey et. al 2001)
• GOAL: To Study the effect of shoe-lacing on
the biomechanics of heel-toe running
Methods
• 20 Male Rearfoot Runners
-experienced
-symptom free
- chosen based on fit to a
US 10.5 experimental shoe
• Shoe: NIKE Air Pegasus
- manufacturer emphasizes that it is
built with a lateral crash pad that acts as cushion
and anti-pronation element
• Used X-lacing, or “zig-zag-lacing”
Lacing Conditions
Varied in
1. Number of pairs of eyelets used (1,2,3,6,7)
2. Tightness of the lace (weak, regular, or tight)
Figure 1. Lacing conditions: (a) 6-eyelet cross-lacing of conditions REG6, WEAK6, TIGHT6; (b) EYE12; (c) EYE135; (d) ALL7
Kinetic and Kinematic Measurements
• Ran each laced condition at a speed of 3.3m/s
across a piezoelectric force platform
(3.3m/s = 7.38mph)
• Running speed had to be within ±3% of target
• 5 successful trials per laced condition
• Factors evaluated
-ground reaction forces
-in-shoe pressure distribution
-tibial acceleration
-rearfoot motion measurements
Ground Reaction Force
• Newton’s Law of Reaction- Every action has an equal and
opposite reaction
• Piezoelectric force platform
• Measures the vertical component of the force in the
geometric centre of the platform
• Calculated the force rate by
taking highest differential quotient
of vertical ground reaction force
by time resolution of 1 ms
Peak Pressures
• Piezoceramic transducers placed on 7 anatomical
locations of the foot
• Fastened under the foot with adhesive tape
P=F/A
• ↑Area over which force is applied=↓Pressure
Tibial Acceleration
• Acceleration= ∆V/∆t
• Accelerometer fastened by an elastic strap to the
tibia between medial malleolus and tibial plateau
• This study did not find any significant differences in
peak tibial accelerations for the different shoe
lacing conditions
Maximum Pronation & Maximum Velocity of Pronation
• Used a goniometer
• Determined a neutral angle by placing participants in an upright
sitting position
• Neutral angle used as a reference point for all pronation and
supination measurements to be based off of
• Used the angular values to calculate maximum pronation and
maximum velocity
of pronation
Perception Tests
• Comfort/Stability Compared against the left foot which
wore the reference (REG6) shoe
• Evaluate on “anchored” 7 point scale with 1 being low, 7
being high, and 4 being the reference shoe
• Rank from 1 through 6
Perception Results
• Comfort
-Each condition= more comfortable than the Tight6
- Most favored for comfort= Weak6 and EYE135
• Stability
-ALL7 and Tight6= the most stable conditions
Shock Attenuation
The lower graph displays
maximum vertical force rates. It
demonstrates that the lowest
vertical force rates were observed
with the tightest and highest lacing
conditions. Does this contradict
the top graph?
The top graph displays peak
vertical forces. It demonstrates
that the lowest peak vertical forces
were observed with the lowest
lacing condition. Does it not make
sense to recommend the lowest
lacing?
Why the difference in peak vertical force and
maximum vertical force rate?
• Lacing Condition EYE12
- Weak foot-shoe coupling could result in the foot and
the shoe contacting the ground at different times
- Participants may have changed running style to
accommodate loose fit by increasing plantar flexion and
curling toes; this would result in decreased angle of impact
of the foot
- Weak foot-shoe coupling could result in foot slippage;
if foot slides forward within the shoe, less volume of
cushion can be used
Why the difference in peak vertical force and
maximum vertical force rate?
• ALL7
- better foot-shoe coupling could result in
the foot being able to directly use the air
cushion at impact
Peak Pressure Distribution
P=F/A
ALL7- ↑ foot-shoe coupling, heel can go deeper
into the cushioning material of shoe and can
distribute the force more evenly over a greater area
EYE12- ↑ loading rates even though ↓ peak vertical
forces; therefore, will have ↑ peak pressures under
the heel
Pronation and Pronation Velocities
• Pronation Data should be treated with caution… the goniometer was attached
to the heel counter of the shoe, in the lower and softer laced conditions with
weak foot-shoe coupling, the goniometer would not be able to account for
sliding of the foot within the shoe.
• Maximum pronation (⁰)= NO DIFFERENCE
• Pronation velocity (rad/s)= decreased for the REG6, TIGHT6, and ALL7
in comparison to the WEAK6, EYE135, and EYE12
• WHY?
-Mechanical Coupling and the Lateral Crash Pad
The foot goes deeper into the crash pad, becoming closer to the
ground, this reduces the pronation lever arm
What about the REG6 compared to the ALL7?
CONCLUSIONS
• Shoe lacing must be considered when making
biomechanical comparisons of running shoes
because it does make a difference
• Under these circumstances, the ALL7 lacing
condition resulted in reduced pronation velocity
and shock
• Further research should be conducted. Research
recommendations include should there be special
lacing techniques for different foot types, or
different running types