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Title: Physiological consequences of the work of breathing and of inspiratory muscle training
Author: Brown, Peter Ian
ISNI:       0000 0004 2678 3138
Awarding Body: Nottingham Trent University
Current Institution: Nottingham Trent University
Date of Award: 2009
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A reduced blood lactate concentration ([lac-]B) is commonly observed during whole-body exercise following inspiratory muscle training (IMT). However, whether the inspiratory muscles are, in part, the source of these reductions remains unknown. Accordingly, this thesis investigated: (I) the contribution of the respiratory muscles to the systemic [lac-]B and (II) the effects of IMT upon inspiratory muscle lactate exchange and clearance. In addition, the thesis also evaluated the determinants of inspiratory muscle strength (maximal inspiratory mouth pressure; MIP). All subjects were healthy, active and free of pulmonary and respiratory muscle disease. Under resting conditions, 10 min intense volitional hyperpnoea at 85% of maximal exercise minute ventilation (VE max) increased [lac-]B by 0.96 mmol.L-1. This was attenuated by 25% following 6 wks IMT. 8 min volitional hyperpnoea at 90% VE max imposed upon exercise at the maximal lactate steady state (MLSS) increased [lac-]B by 0.99 mmol.L-1. Following 6 wk IMT, the steady state and hyperpnoea-mediated increase in [lac-]B were lower by 8 and 26%, respectively. Relative to pre-IMT, loading the trained inspiratory muscles using a low-intensity pressure threshold resistance (15 cmH2O) immediately following maximal exercise accelerated both lactate exchange and clearance capacities by ~70%. Collectively these findings support the notion that the respiratory muscles are capable of net lactate production and are the first to suggest that IMT increases their capacity for lactate clearance. This thesis also demonstrates that the respiratory muscles are responsible, in part, for the reductions observed in [lac-]B during whole-body exercise following IMT. Finally, baseline MIP was positively correlated with the strength of the chest wall inspiratory muscles. The IMT-mediated increase in MIP was negatively correlated with the relative increase in chest wall muscle strength. Therefore, these findings are the first to demonstrate that the lower the initial strength of the chest wall inspiratory muscles, the lower the MIP and the greater the improvement in global inspiratory muscle strength following IMT.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available