ong distance flying can be quite demanding.  Your body must cope with rapid travel across many time zones (causing disruptions to the body's 'biological clock') and disruptions to normal sleep, eating and exercise patterns.  Your body may be more sensitive to the effects of alcohol and caffeine, due to  low humidity and reduced air pressures when flying at altitude ( aircraft are only pressurised up to an equivalent altitude of 2440 metres above sea level. )    Now great concern is being expressed about the effects on the body's circulation by sitting in one place - and being inactive - for extended periods of time.

Blood circulation, muscle relaxation and exercise in flight  

When you are sitting upright and inactive for a long period of time, several things can happen:

• muscles can become tense, resulting in backache and often,  a feeling if excessive fatigue during and after the flight
• the normal body mechanism for returning fluid to the heart can be restricted; gravity can cause the fluid to collect in your feet, resulting in swollen feet (moreso after a long flight)
• the central blood vessels in your legs can be compressed (particularly the undersides of the thighs, by the seat) - this can make it more difficult for blood to return to the heart
• prolonged immobility may be a risk factor in the formation of blood clots in the legs - deep vein thrombosis (DVT).  (Particular medical conditions may increase the risk of formation of blood clots if associated with prolonged immobility.)  DVT is not peculiar to air travel - it can arise from other circumstances of prolonged immobility.

Medical research indicates that factors that may increase the risks of blood clots in the legs include:

• personal or family history of DVT
• recent surgery or injury (especially to lower limbs or abdomen)
• blood disorders (leading to increased clotting tendency)
• immobilisation for a day or more
• increasing age (above 40 years)
• oestrogen hormone therapy (including oral contraceptives)
• pregnancy
• tobacco smoking
• former or current malignant disease
• obesity
• dehydration
• heart failure or congenital blood clotting abnormaliites
• varicose veins.

If any of these conditions apply to you, seek medical advice prior to flying.

During your flight  and while seated, regularly move your feet and legs (as a minimum, for five minutes every hour).  Get up and move about the cabin every hour or so.  Do the exercises that will be recommended in the airline's in flight magazine or the entertainment system.  

Compression stockings may assist in preventing swelling of the feet and ankles and may improve the return of blood to the body from the lower legs.  (Stockings can be purchased from medical and surgical supply companies.  They will need to be individually fitted to your leg measurements.)

Avoiding jet lag  

The main cause of jet lag is associated with travelling to a different time zone, without allowing the body (and brain) a chance to adjust to the new night-day cycles (particularly when travelling west to east).  In general, the more time zones you cross during your flight, the more your biological clock is disturbed.  The common symptoms of jet lag include sleeplessness, tiredness, loss of appetite or appetite at odd hours.  You can minimise the effects of jet lag by - if possible:

• getting a good night's sleep before your flight
• allowing a day or two to adjust to the new time zone after arrival (it may help to set your watch to your destination's time a day or so before you fly)
• fly direct, to minimise flight time; this allows more time to relax on arrival
• if you can't sleep at your destination, try some light exercise, go for a brisk walk or do some light reading.  (It generally takes the body's biological clock approximately one day to adjust per time zone crossed.)

To help your body adjust to flying and maintain your personal comfort and well-being, consider the following:

• drink plenty of fluids
  drink juice, non-caffeinated soft drinks and especially water, to help prevent dehydration, fatigue and headaches.  Minimise intake of alcohol and coffee.  Moisten the face regularly to help reduce the effects of dry cabin air.
• eat lightly
  on longer flights, to avoid indigestion.
• exercise
  occasionally walk down the aisle
  gently bend your neck down towards each shoulder
  move your shoulders upward, the lower slowly
  wiggle your toes; raise one foot at a time
  exercise your calf muscles in the lower leg while seated by regularly flexing and rotating ankles for a few minutes
• on descent
  with increasing air pressure on descent, your ears and sinuses can become uncomfortable, or even hurt.  To minimise this, yawn or swallow frequently while pinching your nostrils closed.  If this does not work, try pinching your nostrils together and blowing gently into your cheeks with your mouth closed.

Acknowledgement to information provided by Qantas Airways Ltd and Ansett Australia limited.