The adaptability of the respiratory muscles to training and/or emphysema was investigated. The diaphragmatic (DIA) length-tension curve of the emphysematous animals shifted significantly towards the left; maximal tetanic tensions were generated at shorter absolute DIA lengths. This decrease in DIA length occurred in proportion to the hyperinflation and mainly occurred due to a loss in the number of sarcomeres. In states of acute DIA shortening, were no adaptations in length occurred, we noted marked alterations in the twitch characteristics and in the shape of the force-frequency curve; at acutely shorter DIA lengths, a disproportionately greater excitability was required in order to reach a given submaximal tension. In the chronically shortened DIA, however, the re-establishment of a new shorter length allowed for the twitch characteristics, the force frequency curve and the maximal tetanic tension to remain unchanged. Therefore, the dropping out of sarcomeres in the chronic condition appears to maintain normal DIA function. Training produced no effects on the contractile or structure properties of the DIA. / The acutely shortened DIA fatigued at a faster rate when initial tensions were comparable as to the optimal length. In emphysematous animals, however, the DIA showed a significantly greater resistance to fatigue. The mechanisms responsible for the enhanced DIA endurance were biochemical increases in the oxidative capacity with a concomitant decrease in the glycolytic capacity. Histochemically, the DIA from sedentary emphysematous animals revealed a selective fast fiber atrophy which was prevented by endurance training. The intercostal muscles revealed histochemical and biochemical evidence of adaptations consistent with a greater resistance to fatigue.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.71865 |
| Date | January 1983 |
| Creators | Farkas, Gaspar Andrew. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Division of Experimental Medicine.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000217451, proquestno: AAINK66586, Theses scanned by UMI/ProQuest. |
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