Year of Award


Document Type


Degree Type

Master of Science (MS)

Department or School/College

Department of Health and Human Performance

Committee Chair

Matt Bundle

Commitee Members

Chuck Dumke , Reed Humphrey


Blood Flow, Doppler, Cycling


University of Montana

Subject Categories

Other Analytical, Diagnostic and Therapeutic Techniques and Equipment | Sports Sciences



Chairperson: Matthew Bundle Ph.D.

The delivery of oxygen to working muscle in order to support aerobic respiration has long been recognized as one of the critical elements conferring endurance performance. Oxygen is transported from the environment to the active cells by the cardiovascular system, which is classically understood to deliver progressively greater amounts of gas to support increased levels of aerobic metabolism. However, the vast majority of existing studies have used modes of exercise that activate relatively small volumes of muscle and consequently have relatively small demands for oxygen delivery. We measured blood velocity using pulsed Doppler ultrasound and simultaneous measures of femoral artery diameter using sonography while highly fit subjects (n=5; mass: 65.25 ± 3.25 kg; VO2 max: 71.3 ± 3.4 mL O2 ·kg-1·min-1) exercised across a range of cycling power outputs (130W - 410W) supported by aerobic metabolism. Artery diameter was unchanged between rest (9.9 ± 1.7 mm) and exercise at all intensities (9.9 ± 1.1mm). Blood velocity increased up to 15.9 ± 5.4 cm s-1 at the greatest common power output completed by the subjects (370 W). Peak single artery flows were 11.4 l min-1 at 250W, at greater power outputs (up to 370W) the measured values of flow were largely unchanged or even decreased slightly (mean = 9.7 ± 0.6 l min-1). Our results are 12.3% greater than the previously highest measures known to science and indicate the importance of the structural and functional factors within the respiratory system necessary to supply sufficient oxygen in order to sustain strenuous exercise.



© Copyright 2015 Tucker W. Squires