Put simply, biofeedback is intended to bring physical reactions that lie below the threshold of perception into consciousness, so that they can then be consciously weakened or strengthened according to their respective characteristics. This term has recently been used more frequently for pelvic floor training devices, but originally comes from TENS therapy (transcutaneous electrical nerve stimulation), where stimulating current via electrodes triggers (primary) muscle contractions. In the area of ​​pelvic floor training with love balls, the biofeedback effect occurs primarily through the activation of the so-called fast-twitch muscle fibers (fast-responding muscle fibers that tend to perform contractions at a high frequency). When these are activated by vibrations, you can amplify a barely perceptible impulse by "joining in" other muscles in the pelvic floor area, e.g. the "slow-twitch" muscle fibers: These are not as sensitive, but are strong. With these, you can then carry out a muscle contraction, i.e. an active training movement - or several, if you like. It is important that you relax after the active phase during a longer period of use, so Viball should be able to be completely "released" without slipping out of the vagina. This requires a size that causes a brief stretching sensation when inserted. This is why Viball is available in six sizes. During the relaxation phases, you can allow the vibration impulses to have a passive and erotically stimulating effect. For men: Bio-feedback is also possible with anal use, there are also corresponding "receptors" in the anal region, and the vibration also has a stimulating effect on the prostate.