Author ORCID Identifier

Defense Date


Document Type


Degree Name

Doctor of Philosophy


Physical Therapy

First Advisor

Virginia W. Chu, OTR/L, PhD

Second Advisor

Stacey C. Dusing, PT, PhD, FAPTA

Third Advisor

Peter E. Pidcoe, PT, DPT, PhD

Fourth Advisor

Sheryl Finucane, PT, PhD

Fifth Advisor

Leroy R. Thacker, PhD


Tummy time or awake, supervised, prone play is an important developmental play position in infancy. Engaging in more than 15 minutes of tummy time per day is associated with a lower risk of plagiocephaly, lower body mass index, and achievement of higher motor scores in full-term and at-risk preterm infants. However, there are significant gaps in the measurement of tummy time in current literature. Conventionally used subjective parent reports have not been validated against gold standard direct observation, and the feasibility and real-world validity of objective solutions such as wearable sensors has not been examined in full-term and at-risk preterm infants. The existing evidence for tummy time in infants also lacks a comprehensive evaluation of prone motor abilities and its impact on development, with only one study focusing on this topic in healthy full-term infants. Validation of sensitive measures and examination of additional tummy time parameters on health outcomes, especially in at-risk infants can assist in designing translational studies for tummy time. This dissertation aimed at bridging the gap between assessment and practice for tummy time in the form of three research papers. The first two papers (Chapter 2 and 3) included a sample of 32 infants aged 3-6 months (19 full-term and 13 preterm), observed across 3 days in the home environment. The first paper (Chapter 2) focused on testing the feasibility and validity of two wearable sensors (GENEActiv and MonBaby) for tracking tummy time at home. Findings suggest that the GENEActiv sensor is feasible and highly accurate for tracking tummy time at home in term and preterm infants. The purpose of the second paper (Chapter 3) was to, a) validate conventionally used parent recall for measuring tummy time against gold standard direct observation, b) compare the results with the GENEActiv sensor, and c) to explore the impact of prematurity on parent reporting. Results showed that parent recall has a moderate correlation with direct observation and may be used in population-based studies for full-term infants. Parents of preterm infants overestimated tummy time by 22 minutes per day. Compared to parent recall, the GENEActiv sensor was highly accurate for tracking tummy time in both term and preterm infants. The third longitudinal study (Chapter 4) focused on assessing the impact of early prone motor abilities on concurrent and long-term motor and cognitive outcomes in 39 very preterm infants. Findings suggest that prone motor abilities at 3-months of age predict gross motor outcomes at both 6- and 12-months of age. Prone motor abilities at 6-months of age are associated with gross motor, fine motor, and cognitive outcomes at 6-months of age in very preterm infants. Taken together, these three studies provide crucial information for the selection of appropriate tummy time assessment measures in healthy and at-risk populations and highlight the importance of tummy time in at-risk preterm infants. We discuss the clinical implications of our findings for intervention design and implementation.


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Available for download on Tuesday, December 12, 2023