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NEWS Sep 09 2003
Toronto Waterfront Marathon
September 9, 2003
Hyperpronation of the Foot in Marathon Runners by Colleen Cody, Pedorthist
The Centre for Sport & Recreation Medicine.
Colleen Cody, B.A., R.T.O., C.Ped.(c)
Hyperpronation of the Foot in Marathon Runners
Forty-two kilometres of pounding is very difficult on the feet and the body. That's about 70 steps per minute per foot as you run, and almost 22,000 steps during a four-hour marathon!
Some Quick Facts on Shock Absorption –
- Initial ground contact forces for a runner.
- Vertical Thrust 2-3 times Body Weight
- Forward Shear 50% Body Weight
- Medial Shear 10 Times Body Weight
- These forces must be dissipated in less than 1/3 of the time (0.2 seconds) than available when walking.
- Peak impact forces generally occur in the first 20-30ms after foot contact.
- Runner's feet contact the ground 800-1200 times per km. This means dissipation of 56 metric tons of force per kilometre!
The Route of Shock Absorption — Initially the medial foot arch, along the lower lateral leg muscles and membrane between the Fibula and Tibia to the Fibular joint at the outside of the knee, travelling onto the Biceps femoris (Hamstring muscle), to the Ischial tuberosity, into the Gluteus maximus and Sacroiliac muscles, then into the Multifidi and medial portions of the Quadratus lumborum. Any tight, shortened muscles or joint misalignment may cause interference with the dissipation of these forces leading to chronic injuries, which will occur at the weakest point.
What happens if the runner in question experiences hyperpronation of the foot and normal shock absorption cannot be dissipated through the medial arch?
Pronation is a normal action affected during both walking and running; the arch of the foot lowers and raises much like a spring enabling the body to absorb impact. Hyperpronation, also called excessive pronation, over-pronation, low medial foot arches and flat feet, is the most common biomechanical foot problem in adults and is of particular concern for distance runners due to the repetitive action and duration of their races. The feet of runners with hyperpronation tend to be longer, looser and unstable in contrast to the supinated high arched foot, which is short, tight, painful and rigid.
Hyperpronation strains the structures of the foot, ankle and knee, hip and thigh. This condition chronically stresses the ligaments of the foot followed by the joint capsules and ultimately the joints themselves, which may in time become arthritic. When running these strained joints separate and undergo a functional deformity, which may if untreated, become converted into a fixed structural deformity.
The following clinical problems may be exhibited in runners with hyperpronation:
- Lower back pain.
- Trochanteric bursitis. (upper thigh pain)
- Iliotibial track syndrome. (lateral femoral condyle pain)
- Popliteus tendonitis with lateral knee pain.
- Valgus stress with medial knee pain. (medial collateral ligament)
- Lateral (peroneal) compartment syndrome.
- Distal fibular stress fracture in runners.
- Tibial stress syndrome (shin splints) especially in runners.
- Anterior tibial strain with anterior compartment syndrome. (shin splints)
- Patellar mal-tracking and malicious misalignment syndrome as seen in hyperpronating runners. (mid-anterior knee pain)
- Posterior tibialis tendon strain. (pain and swelling behind medial malleolus)
- Calcaneonavicular and deltoid ligament strain. (pain at the arch and inner ankle)
- Plantar fasciitis. (pain and tenderness radiating from the heel to the arch)
- Hallux valgus. (painful big toe and developing bunion)
- Metatarsalgia. (pain under the second and third toe joints)
- Splay forefoot with pressure calluses.
- Painful adaptive shortening of the peroneal muscles.
- Cuboid syndrome of subluxation secondary to stress. (pain lateral border of mid-foot)
- Non-specific chronic foot strain and acute foot strain in runners.
- Morton's foot with runner's stress fractures of the 2nd, 3rd and 4th metatarsals.
- Painful impingement of the antero-lateral talar process on the sulcus calcaneus. (tenderness anterior to the lateral malleolus)
- Lateral ankle pain due to calcaneo-fibular impingement.
The runner who hyperpronates during stance phase may hypersupinate (roll to the outside of their foot) in compensatory anticipation of heel strike, leading to excessive wear on the outer heel. Excessive supination in a runner's heel strike may be associated with the following:
- Limited tibial internal rotation.
- Increased risk of inversion ankle sprain.
- Iliial stress syndrome.
- Peroneal tendonitis.
- Iliotibial band friction syndrome.
- Trochanteric bursitis.
Hyperpronation of a runner's foot in the support phase of gait (between heel strike and toe off, when the foot is in contact with the ground) may be associated with the following:
- Excessive internal tibial rotation.
- Increase second metatarsal stress with fracture.
- Plantar fasciitis.
- Posterior tibial tendonitis.
- Achilles tendonitis.
- Achilles shortening.
- Mid-tibial stress syndrome.
- Medial knee pain.
A good support phase in the gait cycle enables a runner to propel forward in toe off with less energy expenditure and better stride length than a poor support phase. Restricting a foot from excessively pronating will improve the ability to absorb the ground reaction forces associated with running and may minimize the risk of related injuries. A customized foot orthotic in a professionally fit running shoe constitutes ideal management of symptomatic pronation in marathon runners.
Colleen Cody, Pedorthist
The Centre for Sport & Recreation Medicine
College Park, 777 Bay Street
416-597-9755
http://www.thecentre31.com