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Mechanics and control of the
pes planus versus normal foot
during jumping and landing
Reporter: Reportor : Zong-Shein Chen
Supervisor : Sai-Wei Yang
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Introduction
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Pes planus (flat foot)
- the medial longitudinal arch of foot is lower
than established normal parameters
~ Forrester D et al. Imaging of the foot and ankle;1988
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The terms of pes planus :
- Flexible : An observable medial arch during
nonweightbearing and a flattening of the arch
during weightbearing
- Rigid : A stiff, flattened arch on and off
weightbearing
~ Lee MS et al. J Foot Ankle Surg; 2005
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Abnormal biomechanical behaviors
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The MLA collapses right down
Most of the plantar surface of foot contact with the
ground
More strain on the plantar aponeurosis
Facilitating dorsiflexion
Unlocking of the midtarsal joint
~ Prost WJ. Fam Physician; 1979
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In clinically and functionally, the rearfoot of flat
foot subjects is valgus and the forefoot is varus
~ Bertani A et al. Clin Biomech. 1999
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Greater inversion ankle moment
Greater peak plantarflexion ankle moment
Less forefoot adduction
Less forefoot total transverse plane ROM
~ Hunt AE et al. Clin Biomech; 2004
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Greater foot pressure under the second and third
metatarsal heads
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Greater foot pressure under the subhallucal area
~ Hunt GC. Examination of lower-extremity dysfunction; 1990
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Injuries relate to pes planus
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Pes planus are associated with a higher risk of
injury among physically active people
~ Kulthanan T et al. J Med Assoc Thai; 2004
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Subjects with pes planus feet exhibited greater
incidences of soft tissue and medial foot injuries
and knee injuries
~ Williams DS et al. Clin Biomech; 2001
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Sesamoiditis
Plantar fasciitis
Achilles tendinitis
Medial shin pain
Patello-femoral joint pain
Metatarsal stress fractures
Navicular and fibular stress fractures
~ Hunt AE et al. Clin Biomech; 2004
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Posterior tibialis tendon dysfunction
~ Kulig K et al. Med Sci Sports Exerc; 2005
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Risk sports for foot and ankle injury
~ DeLee et al. Br J Sports Med; 2003
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Jumping and landing
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Jump-landing protocols have been used to
measure postural sway
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In an attempt to reduce the landing force the
body must anticipate the landing and prepare for
it by increasing muscle stiffness
~ McKinely P, Pedotti A. Exp Brain Res ;1992
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Purpose
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Few investigations focus on the jumping and
landing biomechanical behaviors of pes planus
subjects
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The purpose in this study is to explore the
jumping and landing biomechanical behaviors
and the difference between pes planus and
normal subjects
Hypothesis
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Pes planus subjects have different jumping and
landing biomechanical behaviors from normal
foot subjects, including COP excursion way,
magnitude and direction of GRF, relative motion
of foot-leg-knee and the EMG activity of the
muscle
Methods - Participants
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Thirty adult, aged from 18 to 25 years old
Inclusion criteria :
- arch index (AI > 0.25)
- flexible pes planus
~Williams DS et al. 2000
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Exclusion criteria :
- Acute foot injuries
- Previous osseous foot surgery
- Diagnosed with inflammatory arthritis, diabetes
mellitus, congenital defects or neuromuscular
disease
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Control group
- Thirty adult, aged from 18 to 25 years old
- normal arch index (0.18<AI<0.25)
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Instrumentation
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Vision motion analysis system ~ VICON : to
collect kinematic data
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AMTI force plate : to collect kinetic data
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Surface EMG : to collect muscle activation data,
tibialis posterior, peroneus longus, medial and
lateral gastrocnemius, vastus medialis and
lateralis
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Procedures
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Four conditions, and 3 trials for each condition :
1. Vertical jump with both legs at maximum effort
and to land with both legs
2. Vertical jump with both legs at maximum effort
and to land on the dominant leg
3. Forward jump with both legs and to land with
both legs
4. Forward jump with both legs and to land on the
dominant leg
Data analysis
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Descriptive statistics and two-way ANOVA tests
will be used to compare the difference of testing
order effects and four experimental conditions
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Tukey’s post-hoc test will be used when an
overall significant differences are found
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An alpha level of 0.05 will be used to test for
significance
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Thanks for your attention
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Reference
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Lee MS, Vanore JV et al. Diagnosis and Treatment of Pediatric Flatfoot. J
Foot Ankle Surg. 2005;43:341-373
Hunt AE, Smith RM. Mechanics and control of the flat versus normal foot
during the stance phase of walking. Clin Biomech. 2004;19:391-397
Ledoux WR, Hillstrom HJ. The distributed plantar vertical force of neutrally
aligned and pes planus feet. Gait posture. 2002;15:1-9
Prost WJ. Biomechanics of the foot. Fam Physician. 1979;25:821-31
Hunt GC. Orthopaedic and sports physical therapy. Examination of lowerextremity dysfunction. Second Edition. 1990:395-421
Williams DS, McClay IS et al. Arch structure and injury patterns in runners.
Clin Biomech. 2001;16:341-347
Kulig K, Burnfield JM et al. Effect of foot orthoses on tibialis posterior
activation on persons with pes planus. Med Sci Sports Exerc;2005:24-29
Hertel J, Sloss BR et al. Effect of Foot Orthotics on Quadriceps and Gluteus
Medius Electromyographic Activity During Selected Exercises. Arch Phys
Med Rehabil. 2005;86:26-30