Undergraduate Honors Theses

Thesis Defended

Spring 2016

Document Type


Type of Thesis

Departmental Honors


Integrative Physiology

First Advisor

William C. Byrnes, Ph.D.

Second Advisor

David E. Sherwood, Ph.D.

Third Advisor

Susan M. Hendrickson, Ph.D.


The determination of an individual’s physiological responses to a graded exercise test (GXT) is a fundamental tool in the field of exercise physiology utilized in clinical, applied and/or research settings. A GXT often requires the use of a two-way breathing valve, which directs inspiratory and expiratory airflow. Although the two-way breathing valve allows for the collection and measurement of expired air, it also imposes resistances to airflow. Airflow resistances are different between the commonly used Hans Rudolph 2700 and the Daniels’ two-way breathing valves. The differences in airflow resistance may increase the work of breathing, which may alter an individual’s physiological responses to a GXT. Thus, the purpose of this study was to examine differences in physiological responses during a GXT when using a Hans Rudolph 2700 versus a Daniels’ breathing valve. Fourteen healthy male subjects (7 recreationally active and 7 endurance trained) aged 18-35 years old volunteered to participate in this study. On two separate occasions, subjects performed identical GXTs. One GXT used the Hans Rudolph 2700 breathing valve and the other utilized the Daniels’ breathing valve. The GXTs were completed on a treadmill and consisted of a submaximal and a maximal phase. During the submaximal phase, speed was increased one mph every four minutes. Running economy (RE), expired ventilation (VE), heart rate (HR) and arterial oxygen saturation (SaO2) were measured during this phase. The maximal phase increased grade 1% every minute until volitional exhaustion. Peak oxygen consumption (VO2peak), VE, HR and SaO2 were measured during the maximal phase. Endurance trained subjects had significantly better RE (p<0.02), lower VE (p<0.01) and higher SaO2 (p<0.01) when using the Daniels’ valve. There was no difference between valves in endurance trained subjects for peak VO2, VE, HR, or SaO2. Recreationally active subjects had no significant differences in any of the measured parameters between valves. These findings indicate that the assessments of an endurance trained individual’s RE, VE, and SaO2 are altered between the Hans Rudolph and Daniels’ two-way breathing valves during submaximal exercise. Caution should be used when using the Hans Rudolph 2700 to determine physiological responses during submaximal exercise and when comparing research results that use two-way breathing valves with different airflow resistances at submaximal exercise.