Ebook Athletic Footwear and Orthoses in Sports Medicine: Part 2

Part II Sport-Specific Recommendations Chapter 15 Walking and Running John F. Connors As more people strive to be fit, the popularity of walking and running continues to increase. It is imperative that the sports medicine practitioner has a basic under-standing and knowledge of running shoes and custom foot orthoses. Walking and running shoes must have the ability to absorb shock (cushioning), guide the foot through each step (stability), and withstand repetitive pounding (durability). This chapter further reviews lower extremity walking and running biomechanics, run-ning foot types and injuries, running footwear recommendations, and custom foot orthoses. Gait Biomechanics: Walking vs. Running The human gait cycle is complicated; it consists of a coordinated series of move-ments that involve both the upper and the lower extremities [1]. The gait cycle consists of a stance phase and a swing phase. During walking, the foot is in contact with the ground (stance phase) 60% of the time and off the ground (swing phase) 40% of the time. Both feet are in contact with the ground 20% of the time. The running gait cycle does not have a period of double stance, but does have a period of double float phase in which both feet are off the ground at the same time. Running consists of only a swing phase and a stance phase. Impact shock with running is greater than walking, reaching 2–3 times body weight. Walking has a wider base and angle of gait than with running, and as running speed increases, the impact forces increase, and the center of pressure moves toward the midline. While running, the heel contacts the ground in a more inverted position than walking, and as speed increases, the amount of energy absorbed by the muscles increases as well. J.F. Connors ( ) Private Practice, 200 White Road, Little Silver, NJ 07739, USA M.B. Werd, E.L. Knight (eds.), Athletic Footwear and Orthoses in Sports Medicine, 143 DOI 10.1007/978-0-387-76416-0_15, C Springer Science+Business Media, LLC 2010 144 J.F. Connors During running, the swing phase is longer compared to walking where the stance phase is longer. Stride length is longer with running and shorter with walking, and muscle activity is greater with running compared to walking. Subotnick [1] has reported on the fundamental differences between walking and running. Subotnick and Cavanagh [2] report that during running, the base of gait approaches zero and that there is an increased functional running limb varus because the feet contact the ground directly under the center of mass of the body. Video gait analysis allows the sports medicine specialist to assess the normal or abnormal mechanics of a walker or runner, assisting the practitioner to recommend appropriate running shoes and custom sport orthoses. Classification of Running Foot Types The Neutral Foot This is the ideal foot type for long distance running. The forefoot is perpendicular to the rearfoot with no obvious forefoot varus or valgus. The foot is perpendicular to thelegattheanklejoint.Thesubtalarjointisneutral;neitherpronatednorsupinated; the midtarsal joint is maximally pronated; and the metatarsal–phalangeal joints are neutral [1]. The Pronated Foot This is the flexible loose bag-of-bones low-arch foot that is excessively pronated. It is the most common of all biomechanical problems seen in a sports medicine practice. There is an increase in the range of motion at the subtalar joint and mid-tarsal joints which increases the parallel alignment on the midtarsal axis, permitting greater range of motion (abnormal motion). With the pronated foot during running, the key factor is for the foot to be neutral in the middle of midstance. When there is no sequential phasic resupination, torque and counter torque result, causing injury. Fatigue results when muscles work overtime against unstable fulcrums and when joints that should be stable and locked are unlocked and hypermobile [3]. The Cavus Foot This is the rigid high-arch foot type which has decreased or limited pronation. A neutral foot has the normal amount of pronation and dissipates stress and helps protect bone and soft tissue supporting structures, while a cavus foot which lacks normal pronation is associated with excessive shock to bone and supporting struc-tures. The cavus foot has a decreased range of motion, increased stiffness, and decreased pronatory compensation [3]. 15 Walking and Running 145 Classification and Selection of a Running Athletic Shoe A runner’s foot type (high arch, flatfoot, or normal arch) will help determine the appropriate type of running shoe. Shopping at a reputable running specialty store will also enable the patient to find the most appropriate running athletic shoe. Many running stores have a treadmill allowing the patient to try on different types of running athletic shoes. Normal Arch This is considered a neutral foot (normal pronator). This foot type is able to with-stand the stress placed on the body while running. A stability running shoe is recommended for this foot type because it offers stability in the rear foot and flex-ibility/cushioning in the forefoot, thus allowing the normal motion to occur in the body. Flatfoot Arch Pes planus foot type, an overpronator which has too much motion within the foot. Over the course of training, the body will eventually breakdown leading to overuse injuries. This is the most common foot type seen in a sports podiatrist’s office because this foot type leads to the majority of injuries seen by a specialist, plan-tar fasciitis, Achilles tendonitis, posterior shin splints, and runners’ knee. This foot type benefits from stability plus or a motion control running shoe. High Arch Cavus foot type, an underpronator which is rigid and considered a poor shock absorber and is susceptible to overuse injuries with distance running. Patients with this foot type do well with neutral/cushioned running shoes. These types of running shoes encourage motion to occur, thus decreasing the stress being placed on the lower extremity. A women’s foot is shaped differently than a man’s foot. Proper running athletic shoe selection for the female runner has been a problem. Carol Frey, a professor at The University of Southern California, studied 225 women aged 20–60 and found that more than half had narrow heels that caused problems when buying running shoes [4]. Running shoe companies are now making running and walking athletic shoes to accommodate this foot type. They are now making some running athletic shoesthatarebuiltnarrowerintheheel(rearfoot)andwiderinthetoebox(forefoot). It is very important to note that the shape of the foot should match the shape of the running shoe. For example, a high-arched foot has a curved appearance, so 146 J.F. Connors a b Fig. 15.1 (A and B) Brooks Ariel straight last running shoe for women. (Courtesy of Brooks Sports, Inc., Bothell, WA.) a curved last type of running shoe would be most appropriate. A flat/overpronated foot type will have a straighter foot type and will need to get into a straight last running shoe (Fig. 15.1). It is important to examine both the foot type and the shape of the foot before considering which running shoe is recommended. Stephen M. Pribut, a past president of AAPSM, practicing in Washington, DC, has recommended several factors to weigh when looking for a new running shoe, including [5] the following: • Past experience with shoes • Current Problems • Biomechanical Needs • Environmental Factors • Running and Racing Requirements Features to consider in the running shoe: • Cushioning – The ability of a shoe to absorb shock. • EVA (ethylene vinyl acetate) – Synthetic foam used in midsole. • Heel Counter – Aids in heel support and rearfoot stability. • Last – The form around which the shoe is built. ◦ Board Last – increased stability, overall support. ◦ Combination Last – improves stability, forefoot flexibility. ◦ Slip Last – lightness, cushioning. • Midsole Provides shoe cushioning. Considered the most important part of the running shoe as it is the cushioning and stability layer between the upper outsole. The most common materials for the midsole of a running shoe are ethylene vinyl acetate (EVA), polyurethane (PU), or a combination of the two. • Outsole bottom surface of shoe. On running shoes the tread is designed for straight ahead motion. • PU (Polyurethane) – Used in midsole. Firmer and more durable than EVA. • Toe Box – Surrounds toes. • Upper – The uppermost part of the shoe that encompasses the foot. ... - tailieumienphi.vn