Journal of Orthopaedic & Sports Physical Therapy - Bing Yu, PhD

Effects of Wearing Foot Orthosis With Medial Arch Support on the Fifth Metatarsal Loading and Ankle Inversion Angle in Selected Basketball Tasks

Michael T. Gross, Bing Yu, Jennifer J. Preston, Robin M. Queen, Ian R. Byram, W. Mack Hardaker, J. Marc Davis, Timothy N. Taft, William E. Garrett
STUDY DESIGN: Preintervention and postintervention, repeated-measures experimental design. OBJECTIVES: The objective was to investigate the effects of foot orthoses with medial arch support on ankle inversion angle and plantar forces and pressures on the fifth metatarsal during landing for a basketball lay-up and during the stance phase of a shuttle run. BACKGROUND: Proximal fractures of the fifth metatarsal, specifically the Jones fracture, are common in sports. Wearing foot orthoses with medial arch support could increase the ankle inversion angle and the plantar forces and pressure on the fifth metatarsal that may increase the risk for fifth metatarsal fracture. METHODS AND MEASURES: Three-dimensional (3-D) videographic, force plate, and in-shoe plantar force and pressure data were collected during landing after a basketball lay-up and during the stance phase of a shuttle run with and without foot orthoses with medial arch support for 14 male subjects. Two-way ANOVAs with repeated measures were performed to compare ankle inversion angle, maximum forces, and pressure on the fifth metatarsal head and base between conditions and between tasks. RESULTS: The maximum ankle inversion angle and maximum plantar force and pressure on the base of the fifth metatarsal during both tasks as well as the maximum plantar force and pressure on the head of the fifth metatarsal during the stance of the shuttle run were significantly increased (P<.026) when wearing foot orthoses. No significant differences were found in the maximum vertical ground reaction forces between foot orthotic conditions. CONCLUSION: Generic use of off-the-shelf foot orthoses with medial arch support causes increased plantar forces and pressures on the fifth metatarsal and may increase the risk for proximal fracture of the fifth metatarsal. Future studies are needed to investigate this risk, acknowledging that the differences noted in our study were small in magnitude and the foot type was not measured.

J Orthop Sports Phys Ther. 2007;37(4):186-191. doi:10.2519/jospt.2007.2327

KEY WORDS: fifth metatarsal fractures, foot orthoses, in-shoe pressure, Jones fracture

Comparison of Different Structural Foot Types for Measures of Standing Postural Control

Liang-Ching Tsai, Bing Yu, Vicki S. Mercer, Michael T. Gross
Study Design: Matched group comparison of 3 subject groups with 3 different foot structures for force plate and clinical measures of postural control. Objectives: To determine if subjects with different weight-bearing foot structure would demonstrate differences in static standing postural control, and to determine the reliability of study procedures. Background: Weight-bearing foot structure may influence postural control either because of a decreased base of support (supinated foot structure) or because of passive instability of the joints of the foot (pronated foot structure). Methods and Measures: Young adults were categorized based on weight-bearing foot structure into neutral, pronated, or supinated groups (15 subjects per group). Postural control in single-limb stance with eyes closed was assessed using force plate measures and by measuring duration of single-limb stance on a firm floor and on a balance pad. Force plate measures were normalized center-of-pressure average speed, and standard deviation and maximum displacement in the anterior-posterior and medial-lateral directions. Results: Individuals in the supinated group had significantly greater center-of-pressure average speed, greater maximum displacement in the anterior-posterior direction, and greater SD and maximum displacement in the medial-lateral direction than individuals in the neutral group. The individuals in the pronated group had significantly greater SD and maximum displacement in the anterior-posterior direction, used more trials to complete force plate testing, and had shorter single-limb stance duration than those in the neutral group. Conclusion: Individuals with pronated feet or supinated feet have poorer postural control than individuals with neutral feet, but perhaps through different mechanisms.

J Orthop Sports Phys Ther. 2006; 36(12):942-953. doi:10.2519/jospt.2006.2336

Key Words: balance, feet, pronation, supination

Comparison of Ball-and-Racquet Impact Force Between Two Tennis Backhand Stroke Techniques

Shyi-Kuen Wu, Michael T. Gross, William E. Prentice, Bing Yu

Study Design: A mixed design for kinetic comparison of 2 types of one-handed backhand strokes and 2 skill levels in tennis. Objectives: To develop and evaluate a model to estimate the impact force on the racquet during tennis stroke, and to compare the peak impact force between one-handed backhand stroke with a long backswing and one-handed backhand stroke with a short backswing and between the beginning and advanced players. Background: A one-handed backhand stroke is commonly used in tennis and may be associated with many upper extremity over-use injuries. An understanding of kinetics of the backhand stroke is essential for understanding injury mechanisms and prevention. Methods and Measures: Five male advanced tennis players and 4 male and 1 female beginning tennis players participated. Mean age was 32.2 ± 7.0 years. Each subject was instructed to use the 2 types of one-handed backhand strokes to hit balls from a tennis ball machine. Three-dimensional coordinates of critical body and racquet landmarks were obtained. A mathematical model was developed to estimate the contact duration and the peak impact force during a stroke. Results: The estimated peak impact forces were reproducible and comparable to those reported in the literature from direct measurements. A one-handed backhand stroke with a short backswing had a significantly shorter contact duration (0.008 ± 0.003 seconds) and a greater peak resultant impact force (330.0 ± 140.7) than that with a long backswing (0.016 ± 0.004 seconds and 180.8 ± 49.1 N). Skill level did not significantly affect the peak resultant impact force. Conclusion: A long backswing in a one-handed backhand stroke may reduce the load on the upper extremity and may assist in reducing the risks of tennis-related upper extremity over-use injuries.

J Orthop Sports Phys Ther. 2001;31(5):247-254.

Key Words: over-use injury, tennis, upper extremity load