Now and then through the years, Unfamily Picnic attendees have been known to take a fall. Or a volleyball to the face. Or fall down stairs. Trip over a tree root.
In those instances, the ability to absorb and lessen the impact is vital. Practice at home by pouring marbles across the kitchen floor and attempting to answer the phone in under 30 seconds. You won't likely remain standing, but you will learn how to tuck and roll effectively.
This isn't as easy as it looks. The untrained sitter will suffer back soreness and stiffness in the knees and elbows. Rent something like the Harry Potter series of movies or 10 of your favorite James Bond flicks and watch them all in one session. This will prepare you for a full day's enjoyment in your favorite folding chair.
Carrying a Chinet plate heaped with a burger, bratwurst, potato salad, slices of watermelon, salad and ranch dressing plus some Rice Krispies Treats requires significant balance skills. Practice using an upside down Frisbee filled with expensive crystal goblets. Crystal can be replaced. But that perfectly grilled burger doesn't come along every day. Priorities people.