The effects of duration and time-dependent, high-intensity exercise on hematological properties and inflammation-related parameters in rats were studied. 20, 60, and 120 min of high-intensive exercise were performed daily for 8 weeks. None of the complete blood count (CBC) factors were affected by the exercise, except for the leukocyte concentration which, in the 20 min group, showed an increase of 47% compared to the control, but this was decreased after 60 min by 30% compared to the control. As exercise was performed for 60 min or longer, serum concentrations of $Fe^{++}$, unsaturated iron biding capacity (UIBC), and total iron biding capacity (TIBC) were significantly elevated in comparison to the control, where 20 min of exercise did not show any change. Both levels of interleukin-6 (IL-6), a pro-inflammatory cytokine, and interleukin-10 (IL-10), an anti-inflammatory cytokine in the serum, were elevated in response to the high-intensity exercise, however the rate of IL-6 increase was higher than the rate of exercise intensity increase, thus the offset of inflammation might be suggested. The concentration of nitric oxide (NO) in the serum became high in response to the exercise. Overall, the current observation suggests that inflammation-like responses to high-intensity exercise might be due to high circulation of blood flow and high oxygen requirement, resulting in systemic damages. However, under the current high-intensity exercise conditions, more than 20 min of exercise might not be suggested for health care purposes.