Doctoral Dissertations

Date of Award

12-1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Education

Major Professor

Edward T. Howley

Committee Members

Dixie L. Thompson, Naima Moustaid, David Bassett Jr.

Abstract

This study examined the physiological effects of an acute reduction in cortisol (C) during exercise in humans. The effects of normal C (NC) were compared to metyrapone-induced low C (LC) on plasma substrate availability and utilization during 2 h of exercise @~60% V02max in 5 men and 4 women. The C responses were compared to pre-exercise (PRE) levels and to a rest day (CON). At rest, C was attenuated by- 70% during LC compared to NC, whereas resting plasma glucose (GLU), lactate (LA), glycerol (GLY), hydroxybutyrate (HYD), alanine (AL), branched chain amino acids (BCAA), insulin (I), glucagon (GLG), growth hormone (GH), epinephrine (EPI) and norepinephrine (NOR) were similar under LC and NC (p>0.05). During exercise under NC, plasma C increased compared to PRE whereas it remained unchanged during LC. During NC, plasma C was elevated at 90 min (compared to CON) and at 120 min (compared to CON and PRE). The exercise response of GLU and LA were similar during NC and LC. Plasma GLY, HYD, BCAA and AL were higher (p <0.05) under NC. Plasma I declined (p<0.05) to a greater extent but GH, EPI and NOR tended to be higher (0.05

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