una mujer morena realizando un estiramiento en la espalda en una pelota de pilates amarillo en un gimnasio

young core side outside weight loss gym active bodyweight female class muscles lifestyle strength abdominals girl crunches training pilates mat planking cross woman workout sport stomach floor healthy abs exercises fit exercise adult person health exercising plank fitness sports athlete people body blue indoor beautiful brunette gray ball yellow streching performing back stretch gym front large window parquet