I’ve been trying to think of a simple application of the forces we’ve discussed in gymnastics. Let’s apply our rules to a simplified muscle up. Our athlete to the right starts from a hang and pulls / pushes himself up to a support (with the elbows straight and rings turned out of course). We’re not going worry about a false grip, pull with bent elbows, flip over, or the dip push up.
Let’s start with a simple force diagram for a hang. There is the force due to gravity and the athlete is exerting a force on the rings with his grip which is equal to the force due to gravity:
F(athlete) = F(gravity)
Let’s assume our athlete, let’s call him Bob, weighs 70 pounds. So, in a still hang gravity is exerting 70 pounds of force. Bob is creating a force upward amounting to 70 pounds. In order for Bob to pull himself up he must exert more than 70 pounds of force upward.
As long as the athlete exerts more than 70 pounds of force upward, he will move upward. When Bob reaches a support, he will again be exert 70 pounds of force, again upward, thus stopping his movement.
F(athlete) > F(gravity)
Our Bob, being brilliantly coached, will hold his support for more than 2 seconds and hopefully lift up to a 2 second L support. He will then reduce the force on the rings to less than 70 pounds and lower himself to an inverted hang. Way to go Bob.