The Effect of Mixed Exercise and Metabolic Stress in Relationship to Age in Healthy Men

Hyperglycemia (rest controlled) will be induced by i.v. injection of 25 mL of dextrose 50% over 3 minutes with the subject supine.

Saline (rest controlled) will be induced by i.v. injection of 25 mL of saline over 3 minutes with the subject supine.

"Monitored exercise of 7-minute biking, 2-minute arm weights and a blood draw at the 10-minute time point will be repeated 3 times,which takes 30 minutes.~Bilateral arm curls begin at 20 pounds and decrease by 5 pounds as needed to sustain 2 minutes of exercise at a rate of 1 complete curl every 2 seconds."

Blood will be sampled every 10 min from 0700 to 1300 h. Each intervention will begin at 0800 h after 1 h of baseline sampling, and be completed by 0900 h. Intervention is followed by 4 additional h of sampling to capture recovery (total sampling 6 h). Ten-min samples are for Te, LH, ACTH, cortisol, and GH. Glucose will be checked every 30 min. At 07000 h an archival serum sample will be obtained for safety-monitoring purposes.

Beginning at 1900 h on the evening prior to each study visit, subjects will remain fasting except for water, diet soda, and other non-caloric and non-caffeinated fluids, until 1300 h the next day.