Psychobiologic responses to exercise at different times of day.

The primary purpose of this investigation was to determine whether selected psychobiologic responses to running exercise vary as a function of the time of day at which exercise is performed. Twelve adult males completed four bouts of randomly assigned, submaximal exercise (20-min runs at 70% VO2max) at 0800, 1200, 1600 and 2000 h. Since selected personality traits have previously been shown to influence circadian rhythms, personality assessments (i.e., Eysenck Personality Questionnaire, EPQ; Morningness-Eveningness Questionnaire, MEQ; Spielberger's State-Trait Anger Expression Inventory, STAIX; and State-Trait Anxiety Inventory, STAI) were made during the initial testing session. The group studied scored within the normal range on the traits assessed by the EPQ, STAIX, and STAI. Also, subjects were not able to be classified as either "morning" or "evening" types based on MEQ scores. Ten minutes before as well as 10 and 20 min following the exercise bouts, state anxiety, state anger, blood pressure, and heart rate were assessed. Multivariate ANOVAs (four time of day conditions x three trials) revealed significant main effects for the trial factor for state anxiety, state anger, heart rate, and systolic blood pressure. State anxiety, state anger, and systolic blood pressure were found to be reduced at both the 10 and 20 min post-exercise assessment periods when compared with pre-exercise levels. ANOVAs performed on the difference scores showed that the mood improvements and cardiovascular changes were independent of the time of day that exercise was performed, and these findings were confirmed by ANCOVAs, which adjusted for differences in initial values across the four time of day conditions.(ABSTRACT TRUNCATED AT 250 WORDS)