The purpose of this dissertation was to prospectively track preschoolers' physical activity (PA) during childcare while investigating for seasonal differences in accelerometer measured PA between the fall and winter months in Fargo, North Dakota. This dissertation also evaluated the feasibility of a novel dance-based intervention for increasing PA and reducing sedentary (SED) time in childcare using short activity breaks (< 10 min) interspersed throughout the childcare day. Two studies were conducted as part of this dissertation. The first study (Paper 1) examined for seasonal differences in preschoolers' PA. The second study (Paper 2) evaluated the feasibility of a novel dance-based intervention for increasing PA and reducing SED time during childcare. Preschool aged children (3-5 years) were recruited from four childcare centers in Fargo, North Dakota, to participate in both studies. Children (N = 59) in study one wore an accelerometer during childcare for 5 days in October/November 2011 (fall) and for 5 days in January/February 2012 (winter). Significant decreases in all intensities of PA were observed from fall to winter. Levels of moderate-to-vigorous PA (MVPA) decreased by 17% (p < .01), while SED time increased by 3.2% (p < .01). Children averaged 6.1 min/hr of MVPA across the two assessment periods. Levels of MVPA among preschool children from this study fell within the range of estimates reported in the current literature. Findings from study one suggest that preschoolers' PA levels can substantially change across seasons. For study two, four childcare centers were randomly assigned (cluster randomized design) to take part in a novel dance-based PA intervention or to serve as a control site. Preschoolers (N = 61; intervention group [n = 30], control group [n = 31]) wore an accelerometer while at childcare for 5 days at baseline in January 2012 and for 5 days during the intervention in February 2012. No significant differences between groups in baseline to intervention period changes for MVPA or SED time were observed. Results from study two indicate that adding an additional 15-20 min of dance to preschoolers' childcare day did not significantly increase MVPA or reduce SED time.