The Gymnastic HERO archetype is an archetype made by LHK and used by Irina in the Yu-Gi-Oh! The Shadow Approachers. It consists of LIGHT Warrior-type monsters who represent some basic or advanced Gymnastic/contorting poses. The deck specializes on Special Summoning from Spell Cards making that archetype a real collaboration with a Spellcaster deck with Spell Counters or such stuff. The Xyzs have effects that can activate only when a detached Xyz Material is a specific Gymnastic HERO monster written on that card. Last but not least the Spells have effects that can Special Summon Gymnastic HEROes.
The Flexible Gymnasts are the Compositions of the Deck, since they need the only Base monster of the Deck, "Gymnastic HERO - Extended Leg" and they are named after each of Irina's sisters, included herself. Also, Irina is the only of the sister which is incarnated into two cards, including "Ultimate Gymnastic Princess, Irina" which is the Love proof of her with Jaden Yuki.
All Pendulum Monsters (save for "Bridge Split") that this deck have are based of yoga poses which are linked to contortion.
The Xyz Monsters of the Gymnastic HERO archetype appeared as Fusion Monsters with no effect and the Fusion Materials being the Gymnastic HEROes appeared in the Xyz version's text.