The effect of ischemic preconditioning on neuromuscular fatigue

Abstract

Ischemic preconditioning (IPC) was initially developed as a protective technique against ischemia/reperfusion injuries, however it has since been employed as an ergogenic aid. Existing literature has demonstrated that IPC can elicit small ergogenic effects, which have been attributed to improved skeletal muscle oxygen delivery and extraction. However, recent studies have also suggested that IPC may augment neural drive, evidenced by improved surface electromyography (sEMG) signal parameters recorded concomitant to improved exercise performance. However, inferences made from sEMG measures warrant further investigation with more accurate assessments (i.e. interpolated twitch technique) in order to substantiate notions of augmented neural drive. Therefore, this thesis investigated the capacity of IPC to augment neural drive via central and peripheral mechanisms associated with sustaining neuromuscular function during exercise. Study 1 attempted to define any changes in neural drive that IPC may elicit following a sustained maximal isometric contraction. Whilst IPC improved skeletal muscle oxygen delivery and extraction, central and peripheral fatigue development remained unaffected. The use of an isometric exercise protocol in Study 1 may have inhibited any neural effects by preventing adequate muscle perfusion. Therefore, Study 2 utilised a maximal dynamic exercise protocol to assess the effect of IPC on neural drive. The addition of a dynamic exercise protocol made no impact on the capacity of IPC to augment neural drive. Furthermore, no benefits to oxygen delivery or extraction were observed throughout the exercise, suggesting the humoral benefits conferred by IPC may be more related to the impairment of tissue oxygenation imposed by the exercise. The final study (Study 3) of this thesis combined both dynamic exercise and tissue oxygenation deprivation (via hypoxia) in an attempt to create optimal conditions for observing an effect of IPC on neural drive. The use of hypoxia successfully demonstrated a relationship between impaired tissue oxygenation and the humoral benefits of IPC, however as previously observed, the capacity for IPC to elicit any significant effect on neuromuscular function remained non-existent. This thesis suggests that IPC is unable to influence parameters of neural drive during and following maximal single limb isometric and dynamic exercise. However, the findings suggest a task-dependant relationship between the humoral benefits of IPC and the level of tissue deoxygenation imposed by the exercise. Overall, the cumulative body of work in this thesis provides novel insights into the relationship between IPC and neuromuscular mechanisms associated with attenuating exercise-induced skeletal muscle fatigue.

Date of Award	2019
Original language	English