The ankle and foot are incredibly complex, with a variet of connecting bones, ligaments, tendons and muscles.

Bones and Joints
The ankle is made up of two joints: The ankle joint and the subtalar joint. The ankle joint includes two bones (the tibia and the fibula) that form a joint that allows the foot to bend up and down. Two bones of the foot (the talus and the calcaneus) connect to make the subtalar joint that allows the foot to move side to side. The tarsal bones connect to the 5 long bones of the foot - the metatarsals.

The large Achilles tendon is the most important tendon for walking, running and jumping. It attaches the calf muscles to the heel bone to allow us to puch off and up on the toes. There are another 12 tendons that cross the ankle. They are responsible for movements of the ankle, foot, and toes; some of these tendons also help support the arches of the foot.

Muscles
The muscles of the foot are classified as intrinsic and extrinsic. The intrinsic muscles are located within the foot and cause movement of the toes and are flexors (plantar flexors), extensors (dorsiflexors), abductors, and adductors of the toes. Several intrinsic muscles also help support the arches of the foot.

The extrinsic muscles are located outside the foot, in the lower leg. The gastrocnemius muscle (calf) is the largest. They have long tendons that cross the ankle, to attach on the bones of the foot and assist movement.

The problem of altitude illness starts when acclimatization does not keep pace with your ascent to high altitude. This often happens when you ascend too quickly or go from sea level to high altitude in a day. It's helpful to follow some basic guidelines if you plan to travel to high altitude.
Preventing Altitude Illness

The best way to prevent altitude illness is by making a slow, gradual ascent to altitude and give yourself time to acclimatize. Rates of acclimation are not the same for everyone. So it is difficult to determine the amount of time you will require. Some general guidelines include the following:

•    Avoid flying directly into high altitude. Start at or below 10,000 feet and walk up
      gradually.
•    Climb high and sleep low. This is the climber's golden rule. Once you reach 10,000
      feet, avoid increasing your sleeping elevation more than 1000 feet per night.
•    For every 3000 feet you ascend, spend two nights at the same elevation.
•    Eat a high carbohydrate diet (70% of calories) while at altitude.
•    Avoid alcohol.
•    Stay hydrated. Remember that acclimatization often results in fluid loss and
     dehydration occurs more quickly at high altitude, so it's important to replenish
      loss fluids.


Recognizing Altitude Illness
After ascending to 8000 feet or more, you may notice symptoms of altitude illness. These include:

•    A headache is often the first warning sign of altitude illness.
•    Dizziness
•    Loss of appetite
•    Shortness of breath
•    Trouble sleeping
•    Nausea
•    Vomiting
•    Fatigue or weakness

Most symptoms of altitude illness tend to be worse at night. For the majority of people, the symptoms won't interfere with daytime activity and disappear in a couple of days as you acclimate.

If your symptoms increase or persist the best treatment is to descend to lower altitude. Certain medications can help treat altitude illness; however, these are temporary solutions that only treat the symptoms.

If left untreated, altitude illness can progress into the very severe and life-threatening conditions called high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). These two conditions are recognized by changes in a person's level of consciousness, coordination, and severe breathlessness. They are medical emergencies that require immediate descent and medical attention.

Taking a trip to a high altitude can be a wonderful experience if you know how to do it safely. For more information about traveling to high altitude, see Preventing Altitude Illness During Active Vacations.