The TRAVELER'S JOURNAL: March eighth, with insights on in-flight exercises.

Last time, we offered tips to overcome the atmospheric shortcomings of an airplane cabin. Sitting inactive for hours on end is uncomfortable and possibly even dangerous. Recent research indicates that sitting too long can cause dangerous blood clots to form in the legs. Getting up and walking around the cabin will help, but here's a simple exercise routine you can do right in your seat.

The idea is to visualize taking a slow jog around a park. With simple, rhythmic movements keeping your toes on the floor, alternately raise each heel, rocking slowly from side to side, forward and back. Then imagine that same jog, with your elbows pressed on your knees.

Step three: roll each shoulder forward and back in large circles. Next, exercise your neck. Turn your head slowly to look over each shoulder, then forward and back, and finally side to side.

Lay both arms along your thighs, palms down. Turn your hands over, spread your fingers, and make a fist. Relax and return to the original position. Then tense your legs and stomach muscles, bend slightly forward and try to raise your toes. Next, roll each foot in large circles to the fullest extent of your ankle's flexibility. Finally, clasp your hands behind your neck and alternately and slowly raise each knee to touch the opposite elbow. Repeat this routine every few hours during a long flight, and you'll arrive with spring in your step, bounce in your back, and color in your cheeks, both upper and lower.

One final caution: before you get too far along in your exercise routine, it's wise to let your seatmate know what you're doing.