Abstract
Physical activity (PA) and exercise are essential for promoting healthy lives in children and young people including those with chronic conditions such as congenital heart disease (CHD). Extensive evidence demonstrated the significant benefits of PA and exercise in improving overall health among CHD patients. While PA and exercise are integral core components of cardiac rehabilitation for adults with CHD, the provision is sporadic in adult services, and dedicated guidelines for paediatrics with CHD are notably lacking. Children and adolescents with CHD are encouraged to adhere to the general PA guidelines for healthy populations which emphasise moderate-to-vigorous PA instead of a range across intensities, due to the absence of specific recommendations. Furthermore, prescribing written exercise programmes is much less established in paediatric CHD populations. While continuous moderate-intensity exercise such as jogging, cycling and brisk walking is commonly prescribed, high-intensity interval exercise aligns with children’s natural PA patterns and has yielded equivalent or better increases in exercise capacity compared to continuous exercise. Previous research on high-intensity interval exercise among youth with post-Fontan physiology indicates that it is safe, feasible and enjoyable. However, this finding is limited to a single study thus further research on high-intensity interval exercise within this and any other CHD population is warranted. Therefore, this thesis aims to assess total PA levels by including light, moderate, vigorous PA, and sedentary time following an exercise programme and their relationship with exercise capacity and health-related quality of life of adolescents with CHD. Additionally, this thesis seeks to explore the potential effects of high-intensity interval exercise on cardiorespiratory, perceptual and enjoyment responses among healthyyoung people, to inform future high-intensity interval exercise studies and protocols designed for youth with CHD.
The aim of Study 1 (see Chapter 4) was to assess the total PA levels by including light, moderate, vigorous, moderate-to-vigorous PA (MVPA) and sedentary time; compare device-measured and self-reported PA measurements, and identify potential variables associated with meeting the World Health Organization (WHO) PA guidelines among young people with CHD based on the adapted New York Heart Association (NYHA) classification system I, II or III by Dua et al., (2010). Class I was for asymptomatic patients and patients in NYHA Class I, Class II was for patients classified in NYHA Class II who experienced slight limitations in PA, and Class III was for palliated or uncorrected CHD and patients in NYHA Class III and IV. Utilising a 24-hour GENEActiv accelerometer, the results demonstrate that total PA did not differ across NYHA classes. However, MVPA of participants in NYHA Class I was significantly better and achieved the WHO PA guidelines and the UK PA guidelines (73.6 ± 26.9 min·d-1) than Classes II and III (47.8 ± 25.0 min·d-1). Participants in NYHA Class II and III were more sedentary than those in Class I. Participants in this cohort tended to overestimate vigorous PA and underestimate light PA in a self-reported PA diary, resulting in a positive-moderate correlation with a lack of agreement between self-reported and device-measured PA measurements (rs = 0.519, P = 0.007). Those in NYHA Class II and III were significantly less likely to meet the WHO PA recommendation than those in Class I (OR 0.13; 95% C1, 0.02 – 0.78, P < 0.05).
Study 2 (see Chapter 5) investigated the association between accelerometry device-measured PA and ST with exercise capacity (using a cycle ergometer to quantify peak oxygen consumption) and health-related quality of life (using the Paediatric Quality of Life
Questionnaire) within the same participant cohort. Moderate, vigorous, total PA and MVPA were positively associated with exercise capacity at baseline and post-intervention, except for light PA and sedentary time. While MVPA and vigorous PA were initially positively correlated with health-related quality of life at baseline, only vigorous PA showed a positive association at post-intervention with overall health-related quality of life (ß = 1.68, P = 0.01), and other health-related quality of life subdomains such as physical (ß = 1.65, P = 0.02), psychosocial (ß = 1.70, P = 0.02), and school-functioning (ß = 1.89, P = 0.01). Overall, vigorous PA demonstrated a significant association with exercise capacity at both baseline and post-intervention, while the association with health-related quality of life varied. These findings showed that high-intensity exercise may be a feasible alternative to traditional continuous moderate-intensity exercise.
Study 3 (see Chapter 6) represented a pilot test for future high-intensity interval exercise (HIIE) studies in youth with CHD by comparing acute physiological, perceptual and enjoyment responses to moderate-intensity interval exercise (MIIE). There were no significant differences, with HIIE and MIIE found to be equally enjoyable based on the enjoyment questionnaire responses. Using a novel approach by applying a 40% delta (Δ) to determine HIIE intensity, more than half of the participants (63%, 12/19 participants) successfully achieved the HIIE cut-points during the protocol on the semi-recumbent cycle ergometer of at least ≥ 90% of maximum heart rate (HRmax). The highest percentage of HRmax (%HRmax) and the percentage of maximal oxygen consumption (%VO2max) for males and females were recorded at 92%HRmax and 95%HRmax and 82% VO2max and 83% VO2max, respectively.
In conclusion, the three studies presented in this thesis underscore the importance of assessing all PA intensity spectrum to capture individuals’ overall PA levels effectively. The risk of information loss was substantially reduced by considering time spent in light PA and ST, rather than solely focusing on MVPA. Furthermore, vigorous PA emerged as a significant predictor driving the positive association with health-related outcomes, representing a novel contribution from this thesis. While the personalised PA intervention programme implemented in this thesis has resulted in a progressive reduction in ST, albeit not statistically significant, it laid the groundwork for future research and intervention refinement. Finally, the findings of the high-intensity interval exercise study offer promising avenues for tailoring intervention to address the unique physiological and psychological needs of children and adolescents with CHD. These findings collectively contribute to the ongoing discourse surrounding PA interventions and health outcomes in the paediatric population with chronic medical conditions.
| Date of Award | 1 Oct 2024 |
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| Original language | English |
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| Supervisor | Guido Pieles (Supervisor) & Massimo Caputo (Supervisor) |