I hope that I'm not hijacking this thread by asking the following question(s)...but they are related to how to condition forearm and wrist motions and power (in this case, for a specific purpose).
The real-world application is analogous in some (but not all) ways to riding a sled prone along a rough curving track progressing down the side of a hill. More specifically, one is lying prone, supported by their legs, stomach, and both elbows in contact with the deck of the sled. The rider's forearms extend forward and each hand grips a (near vertical) handle that rotates about an axis parallel to the forearm and positioned just below it. Unlike a conventional sled, where the pair of hands normally work in unison to steer the sled, in this vehicle, each handle controls a separate function (e.g. roll and yaw or pitch in flying an airplane) via a rotation of the handle as described above.
In general, the force required to rotate a handle is roughly proportional to the magnitude of the deviation of the handle from a vertical alignment of the handle (in either a clockwise or a counter-clockwise rotation).
As our hypothetical sled progresses down the hill, the rough nature of the track produces vertical and lateral accelerations of the sled which, in turn, are transmitted to the rider's body via his contact points with the sled, and his gripping the handles. These accelerations are a combination of predictable and unpredictable (random) forces in both direction and magnitude. In some cases, they may be substantially greater in magnitude than the forces required to rotate the control handles.
My first question is: What muscle groups participate in the rider controlling the sled (e.g. staying onboard while commanding the desired control inputs, and minimizing unintentional commands due to the accelerations) under these circumstances?
My second question is: The rider inputs desired control function via a rotation of the handle about it's axis more or less parallel to the forearm. What muscles are involved in these rotations, and what exercises are appropriate to strengthen these muscles and preserving their range of motion?
My third question is: What exercises would be most useful in conditioning the other muscles that participate?