Shockwaves are acoustic waves: the noise produced by thunder or an explosion are just some examples of the role played by such waves. Thanks to the shockwaves, energy can travel for long distances.
From a physical point of view, they are defined as “high energy acoustic waves”. Shockwave is an acoustic wave which carries high energy to painful spots myoskeletal tissues with subacute, subchronic and chronic conditions. The energy promotes regeneration and reparative processes of the bones, tendons and other soft tissues.
Shockwaves are characterized by jump change in pressure, high amplitude and non-periodicity.
The kinetic energy of the projectile, created by the compressed air, is transferred to the transmitter at the end of the applicator and further into the tissue.
When a shockwave goes through a fluid, it generates many pressure differences responsible for the formation of gas bubbles and of the phenomena defined as “cavitation”, in fact the reduced pressure produced within the halfwave, will enable water to change into its gaseous structure forming a bubble, of different dimension, according the amount of energy created.
A second wave will hit the bubble giving way to a violent implosion which will form a jet of water, the so called “jet stream”, which is greatly accelerated by the low pressure existing inside the bubble field (speed of 2700-3000 km/h). This water jet, when hitting the neighboring tissues, will create micro-lesions the entity of which will depend upon the numbers and energy of the impulses (Delius et al. 1998).
Regarding the analgesic effect, many theories have been put forward:
- Shockwaves modify the excitability of the cell membrane; the pain receptors will no longer be able to generate their potential inset of pain
- Shockwaves stimulate the pain receptors to create a high number of nervous impulses which in turn stop the transmission of the signal to the cerebral centre, therefore the pain threshold rises (“Gate Control” theory)
Dr. Luciano Cesare Bassani
Specialist in Physical Medicine, Rehabilitation & Physiatrist