Making a HIIT: High-intensity interval training interventions in educational settings

High-intensity interval training (HIIT) is gaining interest in the school setting due to various factors, such as research associating higher intensity physical activity with lower cardiometabolic risk, its similarity children’s intermittent patterns of physical activity, and its time-efficient protocols. The aim of this thesis was to explore the effectiveness and feasibility of HIIT in schools. The first study was a published systematic review and meta-analysis on school-based HIIT (Chapter Two). It determined that compared to a control group, the group completing HIIT had significant improvements to cardiorespiratory fitness, body composition, and blood biomarkers. However, it identified that current studies had limited involvement of end-users, minimal integration within school practice, and poorly documented evaluations of their intervention implementation. The second study of this thesis, Making a HIIT, aimed to address these limitations. It was guided by self-determination theory and the theory of expanded, extended, and enhanced opportunities. Chapter Three provides its published protocol. In phase one, HIIT workouts were co-designed with students and teachers within the Health and Physical Education (HPE) curriculum. In phase two, these workouts were incorporated into HPE lessons for an 8-week intervention that was completed by students involved in the co-design process and additional students. A control group continued normal HPE lessons. Chapter Four presents the co-design process used in five classes at three schools (121 students, aged 12 – 14 years) to design 33 HIIT workouts. This included: 1) identifying barriers and facilitators to exercise to create evaluation criteria for the HIIT workouts; 2) using heart rate monitors and engaging in pre-made HIIT workouts; 3) defining HIIT parameters (intensity and interval length); 4) creating HIIT workouts using the parameters and evaluation criteria; 5) trialling and modifying the HIIT workouts based on class feedback and intensity data. Analysis of teacher interviews and student discussions determined the methodology was feasible within the HPE curriculum and supported educative outcomes. A comprehensive process evaluation of the Making a HIIT intervention is presented in Chapter Five. This was guided by the Framework for Effective Implementation. Three schools and 15 classes participated in phase two of Making a HIIT. Overall, 79% of eligible students (n = 308, mean age: 13.0 ± 0.6 years, 148 girls) provided consent. The average number of HIIT workouts provided by teachers and attended by students was 10 ± 3 and 6 ± 2, respectively. During HIIT workouts, the percentage of time students spent at ≥ 80% of heart rate maximum was 55% (interquartile range: 29% - 76%). On average, students rated their enjoyment of HIIT workouts as neutral to positive. Teachers found the workouts simple to implement but provided insights into the time implications of integrating the workouts into their lessons; elements that helped facilitate the HIIT workouts; and the use of HIIT within the classroom. This chapter identified areas for future focus, including methods for maximising dosage delivered, while providing promising insight into the satisfaction of HIIT expressed by students and teachers. Chapter Six expanded on the fidelity of Making a HIIT as discussion on the quantification of heart rate data in the current literature was warranted. It presented evidence of variation in the heart rate data within-students, between-students, and over time. Further, it discussed considerations for fidelity measurement in the school setting and presented rating of perceived exertion (RPE) as an additional option for achieving this. The within-person correlation between heart rate and RPE data (r = 0.39; p < 0.001) suggests RPE is a suitable option when HR is unavailable. Chapter Seven and Chapter Eight evaluated the effects of the HIIT intervention and the possible moderator role of the co-design process. The results of Chapter Seven indicate that the co-design process did not affect students’ initial levels of enjoyment, autonomous motivation, self-efficacy, perceived competence, relatedness, or autonomy during HIIT. Similarly, there were no differences in the groups over time, which could be due to the use of workouts that were designed to: be engaging; modifiable for different abilities; and encourage social interactions. Chapter Eight demonstrated that students completing HIIT had significant improvements over time in cardiorespiratory fitness, muscular power, and inhibition, but that these were not significantly different from the control group. This could be as: 1) the control group was still completing high-intensity physical activity during their HPE lessons; 2) the intervention, which occurred in ‘real-world’ context, was not as effective as previous controlled studies; and 3) the dosage of HIIT was too low for additional improvements in the intervention group to occur. This thesis makes significant and novel contributions to the literature on school-based HIIT through co-designing HIIT workouts, integrating Making a HIIT within the curriculum, and conducting an in-depth process evaluation. Combined, these enhance our understanding of school-based HIIT in an ecologically valid manner. Finally, this thesis identifies challenges that stem from ‘real-world’ implementation of HIIT interventions that warrant future investigation