Pulling your baby up into a sitting position is another good way to strengthen the muscles in her shoulders, core, arms, and back, says Steve Sanders, Ed.D., author of Encouraging Physical Activity in Infants. Even though you’re doing the pulling, your baby will naturally flex her abdominal muscles and work to keep her head in alignment with her body, which helps strengthen the muscles and build balance. While your baby is on her back, grasp her forearms and gently pull her toward you. You can start doing sit-up exercises around 6 weeks; if she’s too young to support her head, instead of pulling her by the forearms, place your arms behind her shoulders with your hands behind her head to keep it from flopping back. You may only be able to pull your baby up an inch or two at first, Dr. Sanders says, but as she gets older she’ll go farther, eventually advancing into a full sitting position. This exercise is fun for your baby since she’s getting closer to your face, but you can make it even more entertaining by being extra animated and giving her a kiss at the top of each sit-up.

Did your mom ever tell you to cycle your baby’s legs to help relieve gas? Well, it’s not only a natural method for pushing air out of his system—it’s also a good way to work the legs, hips, knees, and abs. This move helps increase flexibility as well as his range of motion. “Put your baby on his back and gently move his legs up and around, as if he were pedaling a bicycle,” says Dr. Chintapalli. Coo, smile, sing, or make choo-choo or vroom noises while you do the motion. Repeat the movement three to five times, take a break, and then repeat. Keep going as long as your baby shows interest by smiling, making eye contact, and kicking.

Picking up objects is a great way to build your baby’s grasping ability, improve hand-eye coordination, and help develop the muscles in her shoulders, arms, and hands, says Angela Thacker, regional director of The Little Gym, a national chain of children’s gyms. As soon as she starts grasping at items, usually around 3 or 4 months, use what you have around the house—rattles, small toys, and other objects of varying sizes and shapes—as her personal weights. Sit your baby in her high chair or bouncy seat and place a small assortment of these items in front of her. Encourage her to lift one, check it out, put it down, and then lift it again or move on to a different one. You may have to demonstrate how it’s done the first few times, but she’ll get the idea quickly, especially if her “weights” make a sound, light up, or offer some other reward for a job well done.