お願いマッスル (Onegai Muscle) is the opening theme song for the 2019 anime television series *How Heavy Are the Dumbbells You Lift?* (ダンベル何キロ持てる?), a fitness comedy about high school girls discovering weight training. The track was added to maimai でらっくす Splash (DX Splash) on October 30, 2020, alongside SEGA's other rhythm titles CHUNITHM and オンゲキ. The song features the vocal performances of the anime's two leading characters: Hibiki Sakura (紗倉ひびき), voiced by Ai Fairouz (ファイルーズあい), and the impossibly muscular personal trainer Naruzo Machio (街雄鳴造), voiced by Kaito Ishikawa (石川界人). The music was co-composed by Karasuyasabou (credited as "Side Chest Karasuya") and Massive New Krew (credited as "6-Pack Honma"), with lyrics by Karasuyasabou, all three pseudonyms referencing specific muscle-building exercises and results. In maimai, the song originally played alongside the anime's actual opening animation sequence as its background video. This was removed starting with the FESTiVAL PLUS update due to licensing changes, leaving only the jacket art in subsequent versions. The Master chart (level 12+, constant 12.7) was designed by はっぴー and features 510 total notes with an unusually high 96 Slide notes, demanding smooth and accurate sliding across the touch panel. The Expert chart (8+, constant 8.6) was designed by シチミヘルツ (Shichimi Hertz) and incorporates 76 Touch notes into its 362-note layout.