The World Health Organization (WHO) has recommended air travellers on long-haul flights to exercise their legs in order to avoid the risk of deep vein thrombosis.
A deep vein thrombosis is a blood clot that develops in the deep veins, normally in leg veins.
Immobility can lead to the formation of these blood clots, particularly in tall people who are placed in a cramp space during air travel, or those who are very short and their feet don't touch the ground.
In a study released on Friday, the WHO estimated that one in 6,000 long-haul passsengers were at risk.
That is one passenger per 20 long-haul flights carrying 300.
Frequent travellers, the obese, and women taking birth control pills are other at risk groups.
Flights longer than four hours double the risk of deep vein thrombosis, as immobility is the leading cause of the risk.
In certain cases the blood clot can travel through the body to the lung and block the flow of blood.
The WHO special advisor Shanthi Mendis advised air travellers to exercise their calf muscles, get up and walk every so often to exercise their legs, and avoid wearing tight costraining clothes.
As well as taking precautions during the flight, make sure to get
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