Iso-elastic
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Iso-Elastic is a term for a type of arm used on a Steadicam. The arm of a Steadicam is used to isolate a film or video camera from the operator's movements. Steadicam arms all work in a fashion similar to a spring lamp; each arm has 2 sections (similar to and labelled like a human arm), both the upper and fore-arm sections consist of a parallelogram with diagonal springs (or wire under tension from 3 springs). The springs are tensioned carefully to counteract the weight of the camera and steadicam sled. This allows the camera and operator to move vertically, independently of each other. For example as the operator runs, the bouncing of his body are absorbed by the springs, keeping the camera steady. The arm also has unsprung hinges at both ends of each arm allowing it to bend in the horizontal plane (just like your elbow, not like a spring lamp).
A basic spring arm has a point at which it is in balance, just as a sping lamp with no friction. With the camera higher than this point it will outweigh the tension of the springs and lower. And if the camera too low the tension of the springs will raise it to the balance point. However the springs in an Iso-Elastic arm are tuned so that the system is balanced with the springs drawn very tight, close to their limit. Because of this high tension, the spring's tension don't change as much as the sled moves up and down. This means that the arm is closer to its balance point and easy to move in all the positions through its range of travel. When the arm is adjusted for cameras of different weights, the adjustment only affects the force of the lift, not the tension of the spring, so the arm always remains Iso-Elastic.
As a result the camera doesn't bounce up to the 'balanced' position after a move as easily, for example when the operator steps up onto a curb from the road. This allows the camera to be more isolated and independent of the operator's moves. The operator can of course also move the camera up or down, if wished.