The Evolution of the Longitudinal Arch: Conflicting Results Found in the Relationship of the Structure of the Arch and Lower Extremity Injuries By Kaline Mulvihill

Study: Discuss the evolution of the longitudinal arch in human feet and the anatomical changes that have occurred Review the anatomy of the foot Examine several studies that have been performed on runners to determine if there is a correlation between arch height and common running injuries Analyze the methods and results of studies to determine if there is a correlation Discuss further research needed

Medial Longitudinal Arch Anatomy: Longitudinal arch can be split into 3 arches- transverse, lateral, and medial The medial arch is the one most commonly associated with running injuries

Anatomy Continued… The lateral arch includes the calcaneus, cuboid, and the fifth metatarsal. The medial arch, which is the highest point of the arch, includes the calcaneus, navicular, cuneiform and first metatarsal.

The human foot is made up of 26 bones, 30 joints and many tendons, muscles and ligaments. The foot is a complex structure that is a shock absorber and has extreme weight bearing capacity for upright posture and habitual bipedal locomotion unique to humans The human foot has evolved from a generalized grasping organ to a specialized organ for weight bearing and balance.

Evolution of the Longitudinal Arch: Ardipithecus ramidus kaddaba (Ethiopia): First foot remains found of bipedal ancestor Dates back more than 4 million year ago. The pedal phalanx was preserved, which had a large plantar curvature and features similar to apes and A. afarensis showing more primitive traits. Foot remains of Ardipithecus ramidus kaddaba

Australopithecus anamensis (Kenya) 4 million years ago almost complete tibia was found that shows more similarities with homo than afarensis. (more modern)

Australopithecus afarensis (Hadar, Ethiopia) 3.5 million years ago Foot bones showed dorsiflexion toes, which is a modern trait and the calcaneus had a wide tuberosity, depicting both primitive and modern traits. The phalanges were still long and were curved, which point to arboreal locomotion A. afarensis was fully bipedal based on the femur. A. afarensis may have had the first well-developed longitudinal arch

Australopithecus africanus (South Africa) “Littlefoot” was discovered and dated back about 3 million years ago primitive talus, but a modern non-opposable hallux. Paranthopus robustus (Ethiopia Kenya) 2.5 million year ago. The inferior side of the foot was expanded, indicating that there were developed plantar ligaments and most likely a well-developed longitudinal arch. Hallux = big toe

Homo Habilis (Tanzania, Kenya and South Africa) 1.75 million years ago non-opposable hallux and medial longitudinal arch, but some primitive, arboreal features were seen. Homo neanderthalenis very similar to modern humans. longitudinal arch was well developed, but was slightly medial compared to modern humans Homo florensiensis 94,000-13,000 years ago commonly referred to as the “hobbit” because of the small stature and long feet Florensiensis flat-footed structure with stubby big toes Through the evolutionary process, the modern human foot was developed, but is not perfect Injuries and specific foot pain exist

As the foot evolved, so did the type of locomotion: The development of the medial longitudinal arch made it possible and more efficient to run Humans have become skilled endurance runners During bipedal locomotion, the foot is the only structure that makes direct contact with the ground and is under extreme pressure from the body weight as well as maintaining balance While running, the pressure increases and can cause pain or injury

In 2009, over 500,000 people finished a marathon in the United States Running has evolved from a necessary locomotion to a recreational activity With this increase of runners, came an increase of running related injuries This sparked the interest in the structure of the foot and questions evolved on why injuries were occurring and how to prevent them.

Attempt to Classify Arch Types to Understand Injuries: Several measurements have been used to identify and classify arch heights as neutral, high or low. Some of these measurements include footprint parameters, anthropometic and radiographic technique The biological variability in bony and soft tissue shapes makes it very difficult or almost impossible to categorize arch height with footprint parameters and anthropometric, which are direct measurements of the external foot. Radiographic techniques are more reliable because it is looking at X-rays There is no general consensus on categorizing arches

Plantar Fasciitis is the 3rd most common running injury: In a study by Joao et al., it is stated that the arches are more elevated with those who suffer from plantar fasciitis. A possible explanation: the elevation of the plantar arch is higher than a normal arch, which would cause more strain on the plantar fascia to maintain arch structure during static position. Study also showed that the plantar arch configuration appeared to be more related to the origin of plantar fasciitis then the actual pain associated with it

According to a study performed by Gallo et al.: higher arches are correlated with bony related injuries lower arches are correlated with soft tissue damage They also said that these risks could be the cause of injuries: age, gender, weight, knee alignment, flexibility, training, frequency, race, distance, running experience, shoe age, lifestyle, previous injuries, and medical problems Another risk that many runners ignore is increasing mileage, which increases the risk of injury by over use

A study done on 295 Israeli soldiers found a higher incident of stress fractures among soldiers who had categorized high arches. The high arched individuals showed more femoral and tibial stress injuries, where low arch individuals have more metatarsal injuries. The United States Army performed a study on 248 soldiers who were in training The study showed a ratio of 2:4 for high versus low arches of injuries with lower extremities and the lower back.

Cresswell et al. performed a study to see the importance of the plantar intrinsic foot muscles found that these muscles were important to the medial side of the foot Weakness in these muscles could result in plantar fasciitis, hallux valgus, and medial tibial stress syndrome caused by reduced ability to control the foot These studies show a connection between arch height and injuries in the lower extremities, but with different methods and categorizations of arch height, there has been very little agreement on how or why arch height could be the cause of running injuries.

According to a study by Lohman et al, six out of ten runners were estimated to get injured each year Lohman et al. study focused on different running styles to prevent injuries Traditional shod running, POSE running, CHI running and minimalist running styles are compared Barefoot running Instead of focusing on the longitudinal arch, other studies have chosen to review running style and shoe technology to determine if these areas could help decrease the number of running injuries. Describe running styles, benefits and downfalls

Evolution of Running Shoes: Initial heel strike contact in running is a fairly new concept in the last few decades associated with the modern running shoes with thick cushioned heels The new style of shoes becoming popular are minimalist shoes Christopher McDougall’s 2009 publication of Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen. This book was the beginning of the minimalist movement. McDougall studied the Tarahumara Indians who are members of a tribe from Mexico’s Copper Canyon who routinely run hundreds of miles per week wearing nothing but sandals. These runners use a barefoot style running characterized by a short stride, light steps and footwear with minimal protection, but maximal flexibility

Conclusion: There are between 3-6 million runners in the United States Common injuries being seen are both bony and soft tissue injuries as well as stress on the ligaments. There is not a positive correlation between these injuries and the height of the arches, just possibilities of what might be causing the problems More research needs to be focused on footwear development for runners and research on new styles of running. This study gives a brief analysis on Chi, POSE and barefoot and minimalist running styles as well as the evolution of footwear for runners and the new research coming out on minimalist shoes. This study can be used to further investigate how new running styles and footwear can decrease the number of running injuries.