Mechanics and control of the pes planus versus normal foot during jumping and landing

1. Mechanics and control of the pes planus versus normal foot during jumping and landing Reporter: Reportor : Zong-Shein Chen Supervisor : Sai-Wei Yang

2. Introduction • 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 • 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

3. Abnormal biomechanical behaviors • 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 • In clinically and functionally, the rearfoot of flat foot subjects is valgus and the forefoot is varus ~ Bertani A et al. Clin Biomech. 1999

4. 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 • Greater foot pressure under the second and third metatarsal heads • Greater foot pressure under the subhallucal area ~ Hunt GC. Examination of lower-extremity dysfunction; 1990

5. Injuries relate to pes planus • Pes planus are associated with a higher risk of injury among physically active people ~ Kulthanan T et al. J Med Assoc Thai; 2004 • 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

6. 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 • Posterior tibialis tendon dysfunction ~ Kulig K et al. Med Sci Sports Exerc; 2005

7. Risk sports for foot and ankle injury ~ DeLee et al. Br J Sports Med; 2003

8. Jumping and landing • Jump-landing protocols have been used to measure postural sway • 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

9. Purpose • Few investigations focus on the jumping and landing biomechanical behaviors of pes planus subjects • The purpose in this study is to explore the jumping and landing biomechanical behaviors and the difference between pes planus and normal subjects

10. Hypothesis • 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

11. Methods - Participants • Thirty adult, aged from 18 to 25 years old • Inclusion criteria : - arch index (AI > 0.25) - flexible pes planus ~Williams DS et al. 2000

12. Exclusion criteria : - Acute foot injuries - Previous osseous foot surgery - Diagnosed with inflammatory arthritis, diabetes mellitus, congenital defects or neuromuscular disease • Control group - Thirty adult, aged from 18 to 25 years old- normal arch index (0.18<AI<0.25)

13. Instrumentation • Vision motion analysis system ~ VICON : to collect kinematic data • AMTI force plate : to collect kinetic data • Surface EMG : to collect muscle activation data, tibialis posterior, peroneus longus, medial and lateral gastrocnemius, vastus medialis and lateralis

14. Procedures • 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

15. Data analysis • Descriptive statistics and two-way ANOVA tests will be used to compare the difference of testing order effects and four experimental conditions • Tukey’s post-hoctest will be used when an overall significant differencesare found • An alpha level of 0.05 will be used to test for significance

16. Thanks for your attention

17. Reference • 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 lower-extremity 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