PEMF therapy devices which use only one specific pulsed frequency like 15 Hz for the whole therapy time necessarily cause these manufacturers to advise therapy sessions once or twice a day for only 8 or 15 minutes. The reason for this 'advice' is that the body adapts to a specific pulsed frequency, making longer therapy times ineffective.
E.g. when you sit in a plane you experience the noise made by the motors of the plane. After a short while we hardly notice this noise anymore. This is because our body will 'adapt' to the surrounding noise disturbances and thus 'cancel the effect'.
The same is true for pulsed electromagnetic fields, pulsing the whole entire treatment session with the same frequency and intensity, which are a 'disturbance' for the body.
The human body does adapt to the used pulsed frequency and after just a few minutes the therapy effect starts to decrease. By changing the pulsed frequency every few minutes, this adaptation effect is avoided and effective PEMF therapy is obtained during the whole therapy session, not depending on the total therapy time, if the applied frequency steps are sufficiently spaced for each time step.
Each Parmeds model has 10 different treatment protocols. Each protocol consists of a series of pulsed frequencies and intensities and they run fully automatic in sequence during the total therapy time. Each protocol is associated with its own therapy time sequence and as such has beneficial therapy effects for the used protocol. This results in effective PEMF therapy for the full time of the chosen protocol.