5-10 minutes of static stretching, a couple simple exercises, or a combination of both, before and after your trip will go a long way to ease any discomfort from long periods of sitting.
A couple stretches;
1. Try lying down on your back on the floor. Next pull your knees toward your chest and hug them with both arms. Rotate gently back and forth, or side to side. This will utilize the floor to "massage" your lower back and relax those muscles.
2. Next, straighten your legs out, bend one leg to 90 degrees, grab that knee with your opposite hand and gently twist till your knee is over the straight leg. If you can touch the floor with your bent knee, that's great, but no need to push it. It's important on this stretch to keep your shoulders flat against the floor, this will maximize the stretch.
A couple exercises to try also;
1. Remain on the floor and bend both legs, hip distance apart. With your arms straight beside you, palms facing up, lift your hips until you form a straight line from your shoulders to your knees. This is called a "floor bridge." Lower your hips back down and repeat this movement 8-10 times. This will warmup muscles in your lower abdominals as well as your lower back.
2. Another simple movement that is effective for the lower back is to sit comfortably in a chair. Now lift your left knee up as high as is comfortable with out any straining. Now lift your right knee is the same manner. Alternate this movement slowly, almost like your marching while seated. This is a good exercise to also do during your long trip, while seated in a car or on a plane, to warm the muscles and increase blood flow to the area. This may prevent tightening in the muscles and lessen any discomfort.
More Answers from Michelle Theis , NASM Elite Trainer