Cerebral Palsy (CP) affects approximately seventeen million people worldwide (Graham et al., 2016). One of the most consistent abnormalities observed in children with CP is toe walking, characterised by excessive plantar flexion (Wren et al., 2005), which may be due to an increased sarcomere resting length. Evidence has suggested that CP muscle fibres contain elongated sarcomeres (Mathewson et al., 2015; Leonard et al., 2019), which leads to the postulation that the shortened plantar flexor muscles may facilitate optimum ankle torque production (Frisk et al., 2019). If optimal torque production occurred at shorter plantar flexor fascicle lengths in CP patients, this would imply that toe walking serves as a functional benefit by partially maintaining ankle moment during gait, in comparison to typically developed (TD) individuals. To test this hypothesis, we needed to establish if TD subjects, walking in their natural heel-toe pattern, operate with their fascicle lengths at optimal. Nine TD volunteers (Height 167.03 ± 5.16cm; Mass 75.40 ± 14.88kg; Age 29.00 ± 10.86years) participated in the experiment. Evoked isometric contractions of the plantar flexors at twelve different ankle angles were conducted (foot in relation to the tibia: 100°- 65°), with corresponding fascicle length of the medial gastrocnemius (MG) recorded using B-mode ultrasound. The fascicle length – ankle torque relationship was established for each individual, with the fascicle length producing the highest torque set as the optimal. The zone of optimal functioning was then determined using the fascicle lengths at approximately 80% of peak torque, on the ascending and descending curve. Additionally, participants were asked to walk in the laboratory while 3D motion capture and simultaneous ultrasound imaging of the MG were recorded. Trials were recorded for the subjects’ natural heel-toe walking pattern and during voluntary toe walking. During the stance phase of gait while heel-toe walking, the fascicles appeared to function in an isometric manner, with fascicle lengths residing within, or close to, the zone of optimal functioning. During toe walking, the fascicle lengths of the MG resided below the zone of optimal functioning. Consequently, the fascicles of the MG in TD individuals during normal gait appeared to operate in a mechanically efficient manner, within or close to the zone of optimal functioning. When investigating CP patients, we expect shorter MG fascicles at peak ankle plantar flexor torque in comparison to TD. Further, we expect the shortened fascicles during toe walking to correspond with their zone of optimal functioning. If this hypothesis proves true, effective treatment of toe walking in CP may be achieved by interventions aimed at normalising the resting sarcomere length of their plantar flexors.