Ice bath therapy is a factor of time and temperature. The higher the temperature the longer is the required immersion time.
Because modern ice baths do not use ice but have a digitally controlled chillers maintaining the temperature at a pre-set level throughout the therapy session. This enables both lower temperatures and shorter sessions to achieve an improved therapeutic effect.
Also, when the ice bath has jets, like the ECB Spa, there is chilling by both conduction and convection (wind chill) leading to a much more penetrating cold and ensuring the tissue is chilled to the therapeutic level.
Many elite football clubs, rugby clubs and Olympic training facilities are now using temperatures in the 6C to 10C range with some even as low as 4C. When combined with the windchill effect the therapy sessions are most often in the 3 to 6 minute range.