Continuity mistake: Near the end of the movie, right before the semi-finals, they say that only eight men are left. When they introduce the men, they only call out six names.
Continuity mistake: When Michael leaves the Cutlers' mansion he takes a white truck. When he is outside the gates right before he runs a red light you can see the headrests behind him. But when he is on the expressway they've disappeared. Then when he gets to the airport they reappear.
Continuity mistake: In the beginning of the movie Sylvester Stallone is driving his truck into the driveway of his son's school, you do not see the eagle hood ornament on his truck at this time. But as he parks the truck in front of the school you now see the eagle on the top of the hood.
Continuity mistake: The shot of the truck from atop a hill, right after the boy and Stallone fight over the radio being on or off, shows the truck moving on the wrong side of the highway (against traffic). The two cars behind the truck are in the correct lane.
Continuity mistake: During the final of the arm-wrestling championship, Lincoln Hawk's nose is bleeding. Then it's not. Then it is. It goes back and forth.
Answer: It's a regrip to get leverage. Yes it's legal. The best arm wrestler in the world Devon Larratt does it with perfection. Usually works only in a strap match.