Serena Williams is instructing her daughters on exercising together. On Christmas, the 42-year-old tennis champion posted a video on Instagram showing her 6-year-old daughter, Olympia Ohanian, assisting her 4-month-old baby sister, Adira River, with a “workout.” Williams, who shares daughters Olympia and Adira with her husband Alexis Ohanian, 40, is seen speaking to her eldest daughter in French as she demonstrates how to lift and lower the infant during the exercise session.

“Slowly, slowly … like this,” Williams instructs Olympia in the video, using the French word for “gently.” Olympia, dressed in a ruffled red dress, delicately lifts her baby sister, who is wearing holiday pajamas, from the ground and then lowers her back down, holding her hands throughout the process — creating a heartwarming rendition of baby sit-ups.