We sought to determine if compensatory vasodilator and/or pressor responses protect exercising muscle O2 delivery (O2D) under conditions of reduced arterial perfusion pressure, if this is exercise intensity-dependent, and if distinct cardiovascular response phenotypes exist. Ten healthy male subjects (19.5±0.4 years) completed two trials of a ramp protocol forearm isometric handgrip exercise test to exhaustion (2.5 kg increments every 3.5 minutes) in each of forearm above and below heart level (forearm arterial perfusion pressure (FAPP) difference of 29.5±0.97 mmHg). Forearm blood flow ((FBF (ml/min; brachial artery Doppler and echo ultrasound), mean arterial blood pressure (MAP; finger photoplethysmography), and exercising forearm venous effluent (ante-cubital vein catheter) measurements at the end of each work rate (WR) revealed the following. Group level (n=10) Δ FBF was compromised beyond 5 kg WR in above vs. below (P<0.05). There was no evidence of compensatory vasodilator (P=0.21) or pressor (P=0.63) responses. Peak O2D, WR and VO2 were significantly compromised by reduced FAPP (115.6±16.8 vs. 152.0±13.4 mlO2/min, 25.5±1.22 vs. 28.94±1.50 kg and 75.9±5.3 vs. 100.2±8.6 ml/min; P<0.05). In contrast, examination of individual responses revealed distinct cardiovascular response groups with (n=6) vs. without (n=4) compensatory vasodilation with the former having less compromise to submaximal O2D and peak WR (-94.12±23.42 vs. -223.40±36.01 mlO2/min), P<0.05 and -2.5±0.32 vs. -5.32±0.79 kg, P<0.05). In conclusion, exercising forearm muscle hypoperfusion due to reduced FAPP is not compensated for by pressor responses. However, there appear to be distinct phenotypes in which vasodilatory compensation does vs. does not occur, which in the former partially protects O2D and exercise performance. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2012-09-13 16:42:41.751
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/7465 |
| Date | 13 September 2012 |
| Creators | Bentley, ROBERT |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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