What changes in the parent-child relationship occur when infants become toddlers

Well as a mother of 2 toddlers.
When children move from infancy into toddlerhood, the parent-child relationship begins to change its focus. During infancy, the primary function of the parent-child relationship is nurturance and predictability, and much of the relationship revolves around the day-to-day demands of caregiving: feeding, sleeping, toileting, bathing. The attachment relationship develops out of these day-to-day interactions.
As youngsters begin to talk and become more mobile during the second and third years of life, however, parents usually attempt to shape their child's social behavior. In essence, parents become teachers as well as nurturers, providers of guidance as well as affection. The process of socialization—preparing the youngster to function as a member of a social group—implicit during most of the first two years of life, becomes explicit as the child moves toward his or her third birthday. During toddlerhood, children often begin to assert their desire for autonomy by challenging their parents. Sometimes, the child's newfound assertiveness during the "terrible twos" can put a strain on the parent-child relationship. It is important that parents recognize that this behavior is normal for the toddler, and that the healthy development of independence is facilitated by a parent-child relationship that provides support and structure for the child's developing sense of autonomy. In many regards, the security of the initial attachment between infant and parent provides the child with the emotional wherewithal to begin exploring the world outside the parent-child relationship.

May strike workers if the load swings, twists, or turns.