At the first PT visit, the treating therapist will conduct a PT evaluation, educate the caregiver in proper positioning and benefits of tummy time, and provide intervention specific to the infant's group assignment. For the Passive Stretching Group, intervention will include caregiver instruction in passive stretching for lateral flexion and rotation of the neck, with the parent practicing the techniques. For the P-A Approach Group, intervention will include the interpretation of the infant's behavior for the caregiver while manual guidance is provided to the infant. At 3 subsequent PT sessions, group-specific intervention and continued caregiver instruction will be provided. Passive Stretching Group intervention components will include passive stretching and associated strengthening activities. P-A Approach Group intervention components will include environmental set-up and manual guidance. At the final PT visit in the study, a PT re-evaluation will be conducted, followed by group-specific intervention as needed.