When curling, you
must flex your bicep to rotate the weight
around your elbow to your shoulder. This
motion is different from the other lifts
because it's movement is circular. To
appropriately measure how much work a bicep
does during this exercise we will be looking
at Torque. Torque equals the force of
the weight times the radius (length of the
arm). Both Torque and Work have the same
units (N*m) but are not the same. "Torque
is an angular acceleration of an object
around an axis, while work is a scalar that
indicates an energy of an object along a
path." Since the dumbbell is taking a
circular path, instead of a vertical path like
the squats, we use the torque equation.
So if your arm is 0.5 meters long and you are
curling 50kg (Wow thats a lot!) then the net
torque of the weight is
(0.5m*(50kg*9.81m/s^2)=) 245.25 N*m.
