The purpose of this study was to investigate the performance enhancing capabilities of cycling specific orthotics during maximal cycling and how they relate to subject specific foot morphology and function. Twelve recreational cyclists took part in the study: eight male (age, 38 ± 8 yr; height, 180.41 ± 3.55 cm; body mass, 80.90 ± 6.50 kg) and four female (age, 35.92 ± 20.82 yr; height, 176.57 ± 1.94 cm; body mass, 77.20 ± 2.05 kg). Navicular height measurements were taken in weight bearing and non-weight bearing conditions to describe foot mobility. Subjects performed 2 maximal sprints (4s) on an isokinetic cycling ergometer at a cadence of 120rpm separated by 4mins of recovery in either conventional insoles or CSOs. Once completed the insole type was changed and the sprint protocol was repeated. Crank and joint-specific powers were obtained from instrumented force cranks and inverse dynamics methods respectively. Results from the paired samples t-test show no significant difference on a group level. Single subject analyses using magnitude based inferences show subjects could be grouped based on response (positive=2, non-responders=4, negative=6). Post-hoc analysis of joint-specific powers revealed negative responders tended to demonstrate reduced ankle reduced ankle power and range of motion (F= 4.97; d.f. 1, 9, p= 0.05), (F= 7.52; d.f. 1, 9, p= 0.02). The results highlight the need for caution when considering orthotic interventions and confirms the importance of the dual role of the ankle plantar flexors in cycling.