Adverbs are modifiers of verbs. Adverbs do have correlation with the number and gender of the verb it modifies.

הוּא רָצְ מַהֵר	he runs fast
היִא רָצְ מַהֵר	she runs fast
הֵם רָציִם מַהֵר	they (masculine) run rast
הֵן רָציִם מַהֵר	they (feminine) run rast