Abbott AL, Bartlett DJ. Infant motor development and equipment use in the home. Child: Care Health & Development. 2001; 27: 295–306.
This study concluded “parental education with respect to moderate use of equipment and provision with adequate floor time (tummy time) to practice and experiment with motor abilities might be required to enhance motor outcomes of vulnerable infants.”

American Physical Therapy Association. Lack of time on tummy shown to hinder achievement of developmental milestones, say physical therapists. News Release. 2008; August 6, 2008.
In the national survey of 400 pediatric physical and occupational therapists, two-thirds of those surveyed say they’ve seen an increase in early motor delays in infants over the past six years. Those physical therapists who saw an increase in motor delays said that the lack of “tummy time”, or the amount of time infants spend lying on their stomachs while awake, is the number one contributor to the escalation in cases.

Bartlett DJ, Kneale Fanning JE. Relationships of equipment use and play positions to motor development at eight months corrected age of infants born preterm. Pediatric Physical Therapy. 2003; 15: 8–15.
In this study, researchers examined the relationships between the use of infant equipment, play positions, and motor development in high risk, premature infants. Through parent reports the researchers determine that therapists should consider the use of infant equipment and specific play positions to enhance motor development and discuss ways to develop early motor skills with parents.

Berger SE, Nuzzo K. Older siblings influence younger siblings’ motor development. Infant & Child Development. 2008; 17(6): 607-615.
In one of the first attempts to study the effects of older siblings on the onset of motor milestones, this study begins to document the interaction between social and motor development and introduces a new set of questions. It is noted that parents set aside special ‘tummy time’ so that infants have the opportunity to get used to being on the floor and to strengthen the muscles they will need to crawl.

Davis BE, Moon RY, Sachs HC, Ottolini MC . Effects of sleep position on infant motor development. Pediatrics. 1998; 102(5): 1135-1140.
The purpose of this study was to determine the relationship between sleep position and the age of achieving specific motor milestones in the first year of life. Results of the study indicated that the average ages of attaining rolling from tummy to back, sitting supported, crawling, and pulling to stand were significantly earlier in the infants who slept on their tummy than infants who slept on their back.

Hotelling BA. Tools for teaching – newborn capabilities: parent teaching is a necessity. The Journal of Perinatal Education. 2004; 13(4): 43-49.
This column states that infants need tummy time for general upper body strengthening. Parents learn that the best time for tummy time is when the infant is awake and supervised.

Jantz JW, Blosser CD, Fruechuting LA. A motor milestone change noted with a change in sleep position. Archive of Pediatric and Adolescent Medicine. 1997; 151: 565-568.
This was the first study to investigate the relationship between change of sleep position and early motor development. At 4 and 6 months of age, 257 infants were studied to determine whether the recommended change in sleep position was having an impact on their motor development. Their results indicated that the 4 month old infants who slept on their back or side were less likely to roll over than tummy sleepers.

Majnemer A, Barr RG. Association between sleep position and early motor development. The Journal of Pediatrics. 2006; 149: 623-29.
To compare motor development among infants using different sleep positions, Canadian researchers studied 4 and 6 month olds who had been sleeping on their backs or on their tummy. Researchers found that at 4 months, motor scores were lower in the group that slept on their backs, and by 6 months, the differences increased, with motor delays documented in 22% of babies sleeping on their backs. At 15 months, the back sleep position continued to be linked to delayed motor performance. Researchers concluded that the rate at which an infant develops motor skills seems to be influenced by factors such as the positions they adopt during sleep and awake time. While sleeping on their backs may somewhat delay the rate at which infants reach certain milestones, daily tummy time while the infant is awake tends to overcome some of the delays linked to sleeping on their back.

Monson RM, Deitz J, Kartin D. The relationship between awake positioning and motor performance among infants who slept supinePediatric Physical Therapy. 2003; 15: 196–203.
The purpose of this study was to examine the relationship between gross motor development and whether an infant was placed on their tummy during awake time at 6 months of age in infants who slept on their backs. This study specifically examined the relationship between gross motor development and whether an infant was placed on their tummy during awake time instead of on their back. The study makes a final point that physical and occupational therapists should educate parents about the need for supervised tummy time in early infancy.

Msall ME. Measuring outcomes after extreme prematurity with the Bayley-III Scales of infant and toddler development: a cautionary tale from Australia. Archive of Pediatric and Adolescent Medicine.2010; 164(4): 391-393.

Pin T, Eldridge B and Galea MP. A review of the effects of sleep position, play position and equipment use on motor development of infants. Development Medicine and Child Neurology. 2007; 49: 858-867.
The review concluded that healthy infants, born at term, who spent time on their tummy when awake, achieved developmental milestones significantly earlier than those who did not or who spent limited time in prone when awake in the first 6 months of life.

Ratliff-Schaub K, Hunt CE, Crowell D, Golub H, Smok-Pearsall S, Palmer P, Schafer S, Bak S, Canteu-Kiser J, O’Bell R; CHIME Study Group. Relationship between infant sleep position and motor development in preterm infants. Journal of Developmental & Behavioral Pediatrics. 2001; 22: 293–299.
This study examined whether motor development varies among sleep position preferences in premature infants. The results of this study revealed that preterm infants whose sleep position was on their back had better performance on the item tested while the infant was on their back (rolling from supine to side), but fewer percentages of these infants received credit on the items tested while they were on their tummy (such as maintaining head at certain degree and lower head with control).

Salls, JS, Silverman LN, Gatty CM. The relationship of infant sleep and play positioning to motor milestone achievement. American Journal of Occupational Therapy. 2002; 56: 577-580.
This study included 22 full-term infants recruited from well-baby visits at 2, 4, and 6 months of age. A questionnaire was given to the caregivers to gather information about demographic, primary sleep position, and estimated amount of awake time on baby’s tummy every day. The results of this study found that infants spent very little time on their tummy during the wakeful hours before 4 months of age. Some delay in the development of antigravity neck extension was found at 2 months of age, but no differences were found at later ages.

Sarwark JF, Aubin CE. Growth considerations of the immature spine. The Journal of Bone and Joint Surgery. 2007; 89: 8-13.
Discussion on the development of the spine.

Stein MT. Infants need daily “tummy time” for early motor development. Journal Watch Pediatrics and Adolescent Medicine. 2007.
Researchers in Canada compared motor skills in healthy white infants at either 4 or 6 months of age. Two standardized tests were used to evaluate infant motor function, and parents recorded infant positioning while awake. At 4 months, infants in the back sleeping group had lower motor scores and were significantly less likely than tummy sleepers to achieve prone extension on their arms. At 6 months, differences in motor development between the back and tummy sleeping infants increased significantly; 22% of infants sleeping on their backs had gross motor delays and also were less likely than tummy sleepers to sit and roll. Among back sleepers, more time spent on the tummy while awake was positively correlated with better motor performance.