It is recommended that children engage in at least 60 minutes of moderate-to-vigorous physical activity (MVPA) per day; three occasions should specifically include vigorous physical activity (VPA) to promote cardiorespiratory and muscular fitness and maintain weight status. One evidence-based strategy to promote VPA in children is high-intensity interval exercise (HIIE). The current dissertation presents data from two laboratory-based studies investigating the cardiometabolic and perceptual responses to a body-weight resistance HIIE protocol (CIRC) compared to treadmill-based HIIE (TM) in boys and girls. The first acute study found similar mean heart rate (HR) responses (86 ± 6 %HRpeak for CIRC and 85 ± 4 %HRpeak for TM, P>0.05) yet a greater mean oxygen consumption (VO2) response to TM (70 ± 9 %VO2peak for CIRC versus 77 ± 5 %VO2peak for TM, P= 0.008) in boys. In contrast, mean HR and VO2 were similar in girls, but during group CIRC mean HR was higher than in both individual conditions [92 ± 7 %HRpeak (Group CIRC); 86 ± 7 %HRpeak (CIRC); 85 ± 4 %HRpeak (TM)]. Also in girls, VO2 responses were similar between CIRC and TM (76 ± 11 %VO2peak for CIRC versus 76 ± 10 %VO2peak for TM, P= 0.60). In both boys and girls, rating of perceived exertion (RPE), affective valence, and enjoyment responses were similar between CIRC and TM (P>0.05), and only RPE increased during exercise (P<0.001). This dissertation also presents results from a fitness- and skill-based HIIE intervention delivered to 4th and 5th grade students during physical education (PE). The intervention, which focused on promoting physical health outcomes, addressed critical gaps in the HIIE literature by adopting a theoretical approach that focused on the psychosocial experiences of the delivered intervention. Students participating in the HIIE intervention significantly improved their cardiorespiratory fitness and muscular strength relative to the control group (F(1,49) = 17.40, P<0.001, ηp2= 0.26; (F(1,54) = 5.67, P= 0.02, ηp2= 0.09), respectively). A greater amount of time was spent engaging in MVPA in the intervention group compared to the control group, based on both HR and accelerometer data (38.1 ± 7.9 vs. 32.8 ± 8.7 min/hr; P=0.025, ηp2= 0.08; 23.4 ± 5.0 vs. 15.7 ± 4.7 min/hr; P<0.001, ηp2= 0.45, respectively). However, only the accelerometer data supported that students in the intervention accumulated greater amounts of VPA during PE (4.5 ± 2.6 vs. 2.3 ± 1.3 min/hr; P<0.001, ηp2= 0.27). Participants and the physical educator reported favorable program satisfaction and feasibility ratings. Lastly, the program did not change students’ perceptions of autonomy, relatedness, and competence during PE, which did not differ from the control group and remained positive after the intervention (F(3,52) = 1.37, P=0.26, ηp2= 0.07). These results can be used to advocate for the implementation of fitness- and skill-based HIIE interventions that incorporate both physical fitness and motor competence components delivered in PE settings. The Self Determination Theory may be a suitable theoretical framework to guide future HIIE interventions given that this intervention increased students’ physical activity levels without negatively influencing their psychosocial perceptions towards PE, including their enjoyment and their perceptions of autonomy, relatedness, and competence.
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