# Movement: Lecture 9/10 part 2

 Muscles generally develop forces sufficient to maintain: a rotational equilibrium around a joint We assume that mm act to oppose: gravity Rotational equlibrium= the sum of all the moments that act around a joint's axis is equal to zero All the adductor moments are balanced by: equal and opposite abductor moments Mm+Mg= 0 moments: products of forces moment= force x distance When do we encounter disequilibrium? we don't always activate mm to counter the effects of gravity. Sometimes, we move in such a way that gravity assists our movements, as when we throw a ball from a height, or slam a book downward on the table Muscles generally develop forces sufficient to maintain: a rotational equilibrium around a joint What are the 3 assumptions of gravity and muscle wars? the opposing moments are exactly equalthe mm produce a moment that exceeds the moment which gravity producesthe mm produce moment that opposes the effect of gravity but is nevertheless smaller than moment that gravity produces Mm=Mg joint doesn't move so muscle's length remains constantisometric muscle action Mm>Mg joint moves as muscle shortens in concentric action Mm