Unfortunately, sitting still for such long periods of time can lead to several issues including deep vein thrombosis which are blood clots. This condition is not restricted to traveling by air. It can happen when you sit for periods of longer than 4 hours in a car, a train, or bus. These bold clots form way below the surface where they can't be seen and the longer you sit, the higher your chances of developing one. Fortunately, there are some things you can do while in the airplane to reduce your chances of ending up with deep vein thrombosis.
There are some wonderful exercises you can do in your seat that will keep this condition from developing. They are simple and most do not require you get out of your seat. I love being able to exercise in my seat because I hate waking people up to get out into the aisle so I often focus on seat based exercises.
First, if it is at all possible, get up and walk the aisles as a way of stretching your legs and getting the blood moving. This is much easier on night flights when everyone is sleeping and the crew is sitting quietly in the back otherwise, you have to avoid drink carts. It is also easier in those larger planes such as the Airbus which has two aisles so you can walk in circles.
Second, stretch your upper body to help your posture because the longer you sit, the more likely you are to slouch. One good stretch is to grab one wrist with the other hand, pull it up as far as you can and then lean over to the opposite side for a few seconds and then repeat on the other side. I love these and do them quite frequently. I tend to do two or three on each side when I do it.
Third, simply squeeze your butt muscles by clenching them for at least five seconds and repeat ten times. If you want to vary this exercise clench both muscles for one set and then clench one at a time so you do the left butt and then the right butt so you do 10 on each side.
Fourth, roll your head so you stretch the neck. Lean your head to the left while facing forward so your ear is lowering to your shoulder and hold for a few seconds, then repeat on the other side. If one set doesn't feel like enough, repeat a couple more times.
The next one is good to do if you can get out of your seat into the aisles. There are often places where one can find a bit of space, such as by the doors of the back galley area. Stop here and do a full body roll down by starting with the head and rolling down slowly through the neck, back vertebrate by vertebrate until you are touching your toes or getting as close as you can. I don't think I've ever been able to touch my toes, even when I was a child, so I get as close as I can.
After touching your toes, bring one leg to your chest while rising on the other toe if you can. Other wise, just raise pull your leg to your chest and hold for a few seconds, then repeat on the other side. You can also left one leg off the ground and circle you foot at your ankle in a clockwise motion followed by a circle in the counter clockwise direction. Do the circles so you've done 10 on each side. Circling your feet can also be done in your seat if you don't have much under the seat in front of you. Yes, I've done it.
It is possible to perform all of these on your feet or most of them while sitting. It is recommended one combine multiple exercises to create a nice workout that you perform several times throughout the flight. Think about doing this in flights as short as four hours and plan to do them multiple times during a longer flight. In addition, these exercise will keep your legs from tingling or falling asleep.
I strongly recommend doing this every time you travel. It should be part of your regular routine when you are sitting. I do. Let me know what you think, I'd love to hear. Have a good day.