The respiratory muscles: responses to training and heavy endurance exercise

Johnson, M.A. ORCID: 0000-0002-8226-9438, 2005. The respiratory muscles: responses to training and heavy endurance exercise. PhD, Nottingham Trent University.

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Mechanisms that underlie the ergogenic effects of pressure-threshold inspiratory muscle training (IMT) remain unclear, and whether the respiratory muscles contribute to the blood lactate concentration ([lac ]B) of heavy endurance exercise has yet to be evaluated using a rigorous experimental design. Accordingly, this thesis evaluated: (I) the effects of IMT upon endurance exercise performance; (II) the mechanisms by which IMT improves performance; and (III) the contribution of respiratory muscle work to the ([lac-]B) of heavy endurance exercise. Additionally, as an essential methodological precursor to these primary empirical studies, this thesis also evaluated the theoretical validity and protocol dependency of the lactate minimum test.

The lactate minimum test underestimated maximal lactate steady state (MLSS) power by, on average, 12 W. Temporal changes in [lac-]B during the lactate minimum test did not reflect changes observed during constant power exercise, thus suggesting a flaw in the theoretical basis of the test. Furthermore, the lactate minimum power and temporal changes in [lac-]B were dependent upon several facets of the test protocol, including the muscle groups used to elevate [lac-]B, the starting power of the incremental phase, and whether intra-stage rest intervals were included during the incremental phase.

25 km cycling time-trial performance improved 3.0% following 6 weeks IMT in cyclists, and performance enhancements exceeded changes observed in a sham hypoxic training placebo group. However, although enhanced time-trial performance was accompanied by a reduced [lac']B and perceptual response to exercise, it was not explained by a (measurable) increase in maximal sustainable power output, as defined by the critical power function of the hyperbolic relationship between power and time to exercise intolerance.

A 1.0 mmol-l-1 (+25%) increase in [lac-]B was observed when isocapnic volitional hyperpnoea at a level commensurate with maximal exercise minute ventilation (VEmax) was superimposed on exercise at MLSS. These findings are the first to suggest that the respiratory muscles of humans make a significant contribution to the [lac-]B of heavy endurance exercise.

A 0.77 mmo1.1-1 increase in [lac-]B was observed when VE max and the associated breathing pattern were mimicked under isocapnic resting conditions, thus suggesting that at least part of the increase in [lac-]B when volitional hyperpnoea is superimposed on exercise results from lactate efflux from respiratory muscles.

Item Type: Thesis
Creators: Johnson, M.A.
Date: 2005
ISBN: 9781369316506
Divisions: Schools > School of Science and Technology
Record created by: Linda Sullivan
Date Added: 30 Sep 2020 09:44
Last Modified: 08 Sep 2023 13:15

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