Journal of Applied Physiology, Vol 78, Issue 1 198-204, Copyright © 1995 by American Physiological Society
Time-dependent glycemic response to exercise in winter and spring in the subarctic
A. Weydahl, P. A. Balto, E. H. Einvik, B. R. Mikkelsen and R. B. Sothern
Division of Arctic Chronobiology, Finnmark College, Alta, Norway.
Twenty healthy athletes exercised for 30 min at four different times
(beginning at 1130 and 1630) in December (darkness period) and in April (18
h of daylight). Four hours after intake of a standardized meal, a 30-min
bike exercise with an intensity of 60% maximal O2 uptake was performed.
Blood samples (fingertip) were drawn at 1, 5, 10, and 30 min into exercise
and 5, 10, and 30 min after termination of exercise for determination of
blood glucose. Glucose values were normalized by reexpressing each as a
percentage of the starting value. The total area under the glucose-time
curves as well as the area below the starting value was calculated. Areas
were tested for the effect of sex, time of day, and season by analysis of
variance. For the group as a whole during exercise, a significant effect
was found by analysis of variance for sex, time of exercise, and season.
During recovery, significant differences were found for sex and time of
exercise but not for season. The minimal integrated glucose response to
exercise occurred in females, who also showed the most rapid return to
baseline values during the recovery period. Exercise in the morning
produced the smallest glucose response for both sexes and faster recovery
compared with exercise in the afternoon. This was also the case overall for
exercise in December compared with April. This finding implies that the
glycemic response may be influenced by season and timing of exercise, which
may be of importance for athletes involved in vigorous training and
patients with diabetes mellitus.
