The Ring of Fitness itself is a reference to Ring Fit Adventure, an "exertainment" RPG where players use a ring-shaped controller to perform exercise maneuvers.
The "Hope nobody walks in" part of the description is in reference to how a number of Vtubers (both in and out of Hololive) make incredibly suggestive moans and other sounds from the physical exertion the game demands of them.[1]
The flat bonus applied to this collab is likely an error. The Bone Bros collab lacks this bonus despite having cutting board as an ingredient while this collab does not have cutting board as an ingredient, which suggests the code for this bonus was misplaced.