Van Alsenoy, Ken K.2024-10-242024-10-242024-10https://eresearch.qmu.ac.uk/handle/20.500.12289/13880Custom foot orthoses (CFOs) possess a unique surface geometry tailored to an individual’s foot, serving as an interface to redirect ground reaction forces. Their effect is defined by altering the orthotic shape in contact with the foot and choosing material characteristics to redirect or dampen these forces. In sports, CFOs have proven effective at mitigating injury risks and are part of a treatment plan for several lower limb and foot injuries. To date, empirical evidence for the impact of CFO materials on running and sprinting-related outcome measures is limited. The overarching aim of this PhD thesis wasto investigate the effect of CFO materials on running mechanics (kinetics and kinematics), running economy (RE), sprint performance, footwear comfort, and fatigue perception in uninjured recreational runners. It comprises one systematic review and meta-analysis, and two double-blinded randomised controlled crossover studies, resulting in five peer-reviewed publications. In the systematic review (article 1), with a meta-analysis of four studies (three weak and one moderate quality) revealed that oxygen consumption during submaximal running is reduced in the most comfortable footwear condition compared with the least comfortable footwear (MD: -2.06 mL.kg−1 .min−1 ; 95%CI: - 3.71, -0.42; P = 0.01). This finding underscored the importance of measuring footwear comfort along other variables such as running mechanics and RE. Article two compared EVA and TPU CFOs on RE, running mechanics and comfort at two different running speeds. CFOs had no statistically significant effect on RE, irrespective of materials or running speed. Peak braking force reduced with EVA by ∼4% compared to CON (P = 0.027). Propulsive loading rate increased with TPU ∼18% compared to CON (P = 0.009). Footwear comfort remained consistent across all conditions. Although these results were associated with moderately low submaximal running speeds in a rested state, examining the effects of CFOs on similar outcome measures when runners are fatigued or engaged in higher intensity exercises like sprinting appeared justified. Article three and four explored fatigue perception after repeated sprint exercises and constant velocity running, respectively. In Article three, both EVA and TPU increased sprint distance by respectively ∼0.6m (P = 0.004) and ∼0.4m (P = 0.018), without altering fatigue-induced mechanical changes. Article fourfound no significant differences in outcome measures between fatigued and fresh conditions, except for a reduction in loading rate (P = 0.046), increased minute ventilation (P = 0.020) and increased breathing frequency (P = 0.019). Further research focused on a hybrid (HYB) CFO, combining EVA in the heel and TPU in the forefoot. Article five showed reduced peak frontal plane angles (ankle eversion: P < 0.001,  2 = 0.72) and angular velocities (ankle eversion: P < 0.001,  2 = 0.64; ankle inversion: P < 0.001,  2 = 0.60) between conditions. Statistical non-parametric mapping revealed that HYB resulted in the largest proportions of significant changes during stance, when compared to control. In conclusion, the studies in this PhD thesis enhances the understanding of EVA, TPU and HYB CFOs in healthy recreational runners. For athletes, the findings could potentially expand the scope of foot orthoses use during sport activity, since it is not affecting RE. The small yet significant changes in running mechanics that were associated with material choice, could help guide clinicians in CFO prescription, whether using single materials or in combination.Thesis