Obstructive Sleep Apnoea (OSA) is a breathing disorder characterised by repeated episodes of narrowing or complete collapse of the upper respiratory airways during sleep. The condition is associated with chronic intermittent hypoxia and overloading of the inspiratory muscles during sleep. Consequently, there is a need to better understand the impact OSA has upon the chemosensitivity and perceptual response to muscle loading. The central and peripheral chemoreceptors (i.e. ventilatory response to hypoxia and hypercapnia) was examined during wakefulness in OSA patients and endurance-trained (VO2max >55 ml·kg·min-1) and untrained individuals (VO2max <40 ml·kg·min-1). Central and peripheral chemosensitivity was re-assessed in OSA patients after receiving Continuous Positive Airway Pressure (CPAP) treatment. The perception of effort and activation of the locomotor muscles was examined before and after loading in Trained, Untrained and OSA groups. The perception of effort and activation of the inspiratory muscles was also examined before and after loading Trained, Untrained and OSA groups. Follow-up assessments were conducted to examine the impact of CPAP treatment on perception of effort before and after inspiratory loading in OSA patients. In chapter 4 patients with newly diagnosed OSA were shown to have an attenuated ventilatory response to hypoxia and hypercapnia (reduced central and peripheral chemosensitivity) compared with Trained and Untrained individuals. Body characteristics and cardiovascular fitness were found to explain the differential alterations in central and peripheral chemosensitivity. The ventilatory response to hypoxia and hypercapnia was unchanged following 3-months of CPAP treatment in OSA patients.In chapter 5 patients with newly diagnosed OSA were shown to generate higher relative forces before loading compared with healthy individuals. The relative Vastus Medialis and Lateralis Electromyography (EMG) amplitudes were increased during loading in healthy and OSA groups. Repeated loading of the knee extensor muscles at 50% of Maximal Voluntary Contraction (MVC) resulted in lower relative forces being produced at a rating of perceived exertion (RPE) of 14 in OSA patients. The relative Vastus Medialis and Lateralis EMG amplitudes were increased at RPE14 following loading in OSA patients.In chapter 6 patients with newly diagnosed OSA were shown to generate similar relative inspiratory pressures to healthy individuals before loading. The relative Intercostal EMG amplitude was increased during loading in healthy and OSA participants. Repeated bouts of inspiratory loading at 50% of Maximal Inspiratory Pressure (PImax) resulted in higher relative pressures being generated at RPE14 in OSA patients. The relative Trapezius EMG amplitude was increased at RPE14 following loading in OSA patients compared with Trained individuals. The relative pressures generated at the reference point were increased after 3-months of CPAP therapy in OSA patients. Central and peripheral chemosensitivity was attenuated in OSA patients and unchanged following 3 months of CPAP treatment. The perception of effort and muscle recruitment were impaired following loading of the inspiratory and skeletal muscles in OSA patients. CPAP treatment modified the perception of inspiratory effort at rest. These outcomes indicate OSA patients demonstrate a generalised neuromuscular impairment that is observed across a number of respiratory muscles and modified to some extent following CPAP treatment.