Authentic Pilates? Classical Pilates ? Clinical Pilates??? With so many styles of Pilates it can be hard to know what the different descriptions mean. These are my personal distinctions of the definitions:
Archival /ɑːˈkʌɪv(ə)l/ adjective
Archival Pilates is where there is actual documentation of Joseph Pilates teaching his Method either as film, photographs or in his own written words.
Classical Pilates adheres most closely to the exercises, the order, the original intentions and apparatus of Joseph Pilates as verified by the Pilates Elders. Within this category there are some variations and additions such as Romana’s Criss Cross.
The Elders added their own voice, style and creativity but always were clear when they did so, never claiming it was from Joseph Pilates. For example, Thread the Needle was created by Eve Gentry as part of the Gentry Technique.
Contemporary Pilates is Pilates-inspired or Pilates-based exercises. The exercises are often modified to suit the ability of the client and there is no order followed. (In Classical Pilates different abilities are catered for by either omitting an exercise or by using a different piece of apparatus to develop the technique.)
The apparatus has been modified as well, such as the footbar on the Reformer can be set at varying heights or options of lighter spring tension. This can allow for more breadth of variation and modification. Contemporary Pilates exercises may clearly derive from an authentic Pilates exercise or only have the tiniest nod to Pilates, blink and you miss it!
I hope this helps to give some clarity to the various definitions! Remember a lot of the time they are marketing/ branding terms!