Development and evaluation of new inspiratory muscle loading technologies for use in inspiratory muscle training

Inspiratory muscle training (IMT) is becoming more popular in sporting populations as contentious issues associated with the magnitude of its effect as an ergogenic training aid are gradually dispelled. The main reason for this is the increasing good practice in controlled intervention studies particularly through the use of appropriate outcome measures, for example time trial performance, but also the work done to identify potential mechanisms such as the blood flow redistribution model. The purpose of this thesis is to further improve the benefits afforded by IMT through the development and evaluation of new technologies. The key aim was to produce technologies that provide functional relevance to a sporting population by permitting normal, albeit loaded ventilation to take place in an ambulatory situation. A number of intermediate objectives have been achieved including the identification of the key limitations of existing technologies and their application, the development of new methods for the prescription of a dynamic inspiratory load via a series of human studies i.e. mouth pressure generation due to inspiratory drive during exercise, 3-Dimensional thoracic displacement and peripheral thoracic force generation, and the design, manufacture and evaluation of two new inspiratory muscle training technologies. These are a thoracic restricting technology that provides true ambulatory loading and a variable mouth occlusion technology that can be set to load in accordance with the specific pressurevolume characteristics of an individual. The former (thoracic restricting technology) has been developed into a first stage prototype and tested on a single subject to assess any changes to breathing pattern. The results suggest that suitable load location may minimise any adverse effects and has enabled further theoretical development to take place. The latter (variable mouth occlusion technology) has been implemented in a controlled study on a group of healthy male adults to assess its functionality and the suitability of a specific decaying load. The results suggest that the chosen load may have been unsuccessful in increasing the work of breathing and that specific aspects of the functionality require development thus enabling the selection of specific refinements for future interventions to be identified. The focus of future research is therefore the practical comparison of these new technologies with existing devices in order to fully understand the optimisation of inspiratory muscle training.