Fighter pilots face the same body stresses that hunters do when they have to remain still for long periods of time. Exercising your large muscles will help reduce stiffness and help keep you warm. Here are a few exercises you can do without any sudden motion.
Spinal twist – Inhale and sit up tall. Twist as far as you can comfortably to the left, exhale, and remain in that position for 5 gentle breaths, then switch sides.
Shoulder shrugs – Inhale and lift your shoulders up toward your ears, then squeeze them straight back. Exhale and squeeze your shoulder blades together and let your shoulders come back down. Inhale and squeeze your elbows toward each other in back. Exhale, and relax.
Back release – cross one ankle over the other thigh, exhale and lean forward over your legs. Hold for five breaths, exhale and put your foot back down. Repeat with the other leg.