Effects of Acute Endurance Exercise Performed in the Morning and Evening on Inflammatory Cytokine and Metabolic Hormone Responses

Abstract

Purpose: To compare the effects of endurance exercise performed in the morning and evening on inflammatory cytokine responses in young men.

Methods: Fourteen healthy male participants aged 24.3 ± 0.8 years (mean ± standard error) performed endurance exercise in the morning (0900-1000 h) on one day and then in the evening (1700-1800 h) on another day with an interval of at least 1 week between each trial. In both the morning and evening trials, the participants walked for 60 minutes at approximately 60% of the maximal oxygen uptake (VO2max) on a treadmill. Blood samples were collected to determine hormones and inflammatory cytokines at pre-exercise, immediately post exercise, and 2 h post exercise.

Results: Plasma interleukin (IL)-6 and adrenaline concentrations were significantly higher immediately after exercise in the evening trial than in the morning trial (P < 0.01, both). Serum free fatty acids concentrations were significantly higher in the evening trial than in the morning trial at 2 h after exercise (P < 0.05). Furthermore, a significant correlation was observed between the levels of IL-6 immediately post-exercise and free fatty acids 2 h post-exercise in the evening (r = 0.68, P < 0.01).

Conclusions: These findings suggest that the effect of acute endurance exercise in the evening enhances the plasma IL-6 and adrenaline concentrations compared to that in the morning. In addition, IL-6 was involved in increasing free fatty acids, suggesting that the evening is more effective for exercise-induced lipolysis compared with the morning.

Fig 1. Changes in plasma hormone and IL-6 during morning and evening of acute endurance exercise.

Plasma concentrations of adrenaline (a), noradrenaline (b), cortisol (c) and interleukin-6 (d) before (Pre), immediately after (Post), and 2 h after (Post 2 h) exercise. Data represent the mean ± standard error. * P < 0.05, ** P < 0.01, and *** P < 0.001, compared with values at pre-exercise. ^† P < 0.05, ^†† P < 0.01, and ^††† P < 0.001, compared with values immediately after exercise. ^# P < 0.05 and ^## P < 0.01, significant difference between the morning and evening values.

Fig 2. The relationship between the free fatty acids and IL-6 during morning and evening of acute endurance exercise.

Serum concentrations of free fatty acids (a) before (Pre), immediately after (Post), and 2 h after (Post 2 h) exercise. Data represent the mean ± standard error. *** P < 0.001, compared with values at pre-exercise. ^† P < 0.05, compared with values immediately after exercise. ^# P < 0.05, significant difference between the morning and evening values. The relationship between levels of interleukin-6 immediately post exercise and free fatty acids 2 h post exercise in the evening (r = 0.68, P < 0.01) (b).