Variable Resistance Machines
Some resistance training machines (like the Nautilus equipment pictured here) use “cams” which vary the resistance throughout the range of motion to match a person’s strength.
Variable resistance machines typically employ a “cam design” to match the resistance to the strength of the muscles throughout the range of motion. An example of the application of this technology with a bicep curl machine is described below.
During a bicep curl, the resistance is greatest at 90 degrees when the weight is farthest from the body (and farthest from the axis of rotation). The resistance is easiest at top and bottom of the movement. Using variable resistance machines, the resistance can be altered so that a person gets a maximal challenge throughout the range of motion.