Fuel and fluid homeostasis during long-term exercise in healthy subjects and type I diabetic patients.
OBJECTIVE
This study was designed to examine metabolic and hormonal effects of long-term exercise in healthy subjects and insulin-dependent (type I) diabetic patients.


METHODS
Two studies were performed. First, 16 healthy males (32 +/- 3 yr) were studied during a semitriathlon competition (2 km swimming, 90 km biking, and 21 km running). Second, 9 type I diabetic males (41 +/- 2 yr) and 17 healthy matched control subjects were studied during a 75 km cross-country skiing race. Blood samples were taken before and immediately after exercise, and also during the ski race.


RESULTS
During the semitriathlon race, serum insulin, C-peptide, glucagon cortisol, growth hormone ACTH, prolactin, and plasma renin activity increased two- to ninefold, whereas serum testosterone fell. Apart from a fall in magnesium, serum electrolyte concentrations remained unchanged. Before long-term skiing, patients reduced their insulin dose by 30-40%. They were hyperglycemic during the initial part of the race, but near normoglycemic thereafter. There were large interindividual variations in the increments of counterregulatory hormones, whereas serum testosterone and luteinizing hormone fell quite uniformly. Plasma renin activity and aldosterone concentrations rose similarly in diabetic and healthy subjects, whereas the rise in antidiuretic hormone was slightly greater in diabetic patients. During the initial part of the race, serum atrial natriuretic peptide fell in both groups.


CONCLUSIONS
Severalfold increments in hormone concentrations contribute to the maintenance of fuel and fluid homeostasis during long-term exercise. With an appropriate adjustment of insulin dose and diet, also type I diabetic patients can participate in competitive long-term exercise.
Koivisto
V A
VA
Second Department of Medicine, Helsinki University Hospital, Finland.
Sane
T
T
Fyhrquist
F
F
Pelkonen
R
R
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000503:physiopathology*; D004573:Electrolytes / Q000097:blood; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005934:Glucagon / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006706:Homeostasis; D006728:Hormones / Q000097:blood*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000097:blood; D008297:Male; D012016:Reference Values; D012083:Renin / Q000097:blood; D012865:Skiing; D013177:Sports / Q000502:physiology; D014882:Water-Electrolyte Balance
D001786:Blood Glucose; D002096:C-Peptide; D004573:Electrolytes; D006728:Hormones; D007328:Insulin; D013006:Growth Hormone; D005934:Glucagon; D012083:Renin; D006854:Hydrocortisone