| Summary: | The relationship between level of movement skill and fitness in children and adolescents plays an important role in improving physical activity (PA) and health. Children with poor motor proficiency and coordination categorised as having movement impairment (MI) often choose a more sedentary lifestyle as a consequence of their movement difficulties and inefficient movement patterns. The literature has highlighted the association between movement difficulties and disengagement with sport and play; citing physiological and psychosocial aspects as limiting factors. Furthermore, children with MI who do engage in PA often participate at lower intensities and fail to attain recommended levels. Consequently, there is limited knowledge regarding how youth respond to various exercise intensities in relationship to MI. Additional research is warranted to fully understand the neurophysiological mechanisms (underpinnings) and limitations that may explain the association between PA and movement skills in MI. Therefore, the aim of this thesis is to better understand the physiological and perceptual responses during and following exercise of different intensities for exercise prescription in children and adolescents with movement impairment (MI). A comprehensive, systematic literature review was conducted of the recent available studies on interventions focused on PA and fitness in children and adolescents with MI (Chapter 2). This review provided the background for the other three studies included in this thesis and evaluated the efficacy of interventions on physical fitness and psychosocial outcomes. The findings highlighted the range of intervention designs that have the potential for improving physical fitness and performance, however, larger RCT studies with follow-up periods are needed. In Chapter 3, a review of the common methods used to describe and measure components of fitness was summarised. The primary focus of this chapter was to review the background literature validating and providing a rationale for the methods used throughout this thesis. In Chapter 4, the physiological and perceptual responses during and following an acute bout of high and low-intensity exercise was explored in a randomized crossover design (study 1). Participants were categorized as MI (n=17) and no movement impairment (NMI) (n=21) on the Bruininks-Oseretsky Test of Motor Proficiency 2 Short Form (BOT-2 SF) and performed an incremental bike test to establish aerobic capacity. Heart rate (HR), rating of perceived exertion (RPE), muscle strength (torque) and fatigue (EMG) was assessed pre-and post-exercise in the following two sessions. Significant differences in maximal oxygen uptake (V̇O2peak) (MI: 31.5±9.2 vs. NMI: 40.0±9.5 ml·kg·min1), PPO (MI: 157±61 vs. NMI: 216±57 watts, p < .05) and LI workload (MI: 85±38 and NMI: 121±29 watts, p < .05) was observed. Average HR during HI cycling was reduced in MI compared to NMI (140±18 and 157±14, p < .05), but not for LI (133±18 and 143±17 bpm, p > .05) or RPE at either intensity for legs (MI: 8±2 vs. NMI: 7±2, p > .05) and overall (MI: 7±3 vs. NMI: 6±2, p > .05). The results highlighted a reduced exercise capacity in MI compared to NMI and potentially suggest central (i.e., motivation and perceived adequacy) rather than peripheral factors may limit exercise performance in MI. In Chapter 5, the criterion validity of the Åstrand-Rhyming (A-R) cycle test and the Chester Step Test (CST) for assessment of V̇O2peak in field settings was conducted (study 2). The first part of this study established the criterion validation (n=18) and reliability (n=8) of the Åstrand cycle test to measure and estimate aerobic capacity in children and adolescents. The second part consisted of validating the CST for mass screening purposes (n=20) utilised in Chapter 6. The A-R cycle test overestimated V̇O2peak by 10-15% and demonstrated a moderate reliability (R=0.84) when repeated. Similarly, the CST overestimated V̇O2peak by 10% confirming that submaximal data should be interpreted with caution but are a feasible option for measuring aerobic fitness across varying levels of MI. To further build upon the findings in study 1 and 2 (Chapter 4 and 5), the final study aimed to provide a pathway for identifying adolescents (13-14 year olds) with MI and lower fitness levels based on an adapted screening process within Year 9 students (n=522). Individuals performing in the < 25th percentile of their class were invited to join the EPIC (Engagement, Participation, Inclusion and Confidence in sport and play) feasibility study, a 6-week gym intervention (EPIC Club) offered twice weekly consisting of cardiovascular and strength training elements. Out of the 155 adolescents identified and recruited to join EPIC, 31 participants enrolled in the study. Pre- and post-intervention assessments were performed to monitor changes in fitness outcomes. The intervention pilot period had a high attendance rate (~90%) with participants reaching target exercise intensities between 65-95% HRmax during the sessions. However, no significant changes were observed pre- and post-intervention. Collectively, these studies provide novel insight on the physiological underpinnings and perceptual factors contributing to exercise tolerance in MI. Furthermore, the screening process and targeted recruitment approach for the EPIC study intervention served as a feasible pathway for identifying adolescents with MI and lower fitness levels in school settings. Strategies that increase fitness parameters and development of movement skills in childhood may be a vital target for improving PA and play in youth with MI.
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