Yes — the Regulation applies to both home-use treadmills and studio/gym treadmills.
Treadmills are listed in Annex II, point 4 ("Toys, leisure and sports equipment"), as "sports equipment”. The general scope is set in Article 1 — "electrical and electronic household and office equipment" — and qualified by Recital 8, which limits application to products "intended for use in the domestic environment".
"Domestic environment" is defined in Annex I, point 2 as "an environment where the use of broadcast radio and television receivers may be expected within a distance of 10 m of the equipment concerned". This is a functional test, designed to exclude equipment intended for industrial environments (factories, workshops, plants where EMC Class A is expected and operating conditions differ fundamentally. Fitness studios and gyms are not such industrial environments; they are typically equipped with broadcast receivers (TVs, audio) within line-of-sight of the treadmills and therefore meet the definition of "domestic environment”.
Studio/gym treadmills are therefore subject to the same off-mode, standby and networked-standby requirements as home-use units.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.