The bisolator is a body attachment that assists in keeping your muscles under constant tension during certain exercises. It does not require batteries or electricity to function.
When using free weights, the muscle lifting the weight against gravity is what creates resistance. However, this exertion is not constant, as the exercise is carried out through its range of motion, which has the weight being moved through varying degrees of horizontal and vertical motion.
When performed correctly, the standing bicep curl exercise will require maximal muscular effort when the forearm is parallel to the floor (perpendicular to the direction of gravity), as the weight is moved against gravity.
As the weight is moved past this "sticking point", its motion becomes more horizontal than vertical, and the force required by the muscles decreases.
The bisolator helps keep the muscle under tension throughout a larger range of motion, allowing you to get more muscle stimulation for each rep.
The bisolator allows additional stimulation through the range of motion for biceps (arm), triceps, quadriceps, and hamstrings.