The Effect of a Maximal Aerobic Exercise Session in the Morning and Afternoon on Certain Hematological Factors in Young Athletes

Blood is the third component of the circulatory sys tem where changes occur following exercise-induced increase in metabolism. The purpose of the present research was to examine the effect of a maximal aerobic exercis e session in the morning and the afternoon on certain hematologi cal factors in young male athletes. Thus, 21 athlet es were randomly selected from the students of Physical Edu cation in the University of Tehran and were divided into a morning group (N=10; 20.9±0.99 years, 67.35±6.27 kg , and 180.4±4.28 cm) and an afternoon group (N=11; 21±0.63 years, 67.13±9.13 kg, and 176.9±9.01 cm).Th e morning and afternoon groups performed the seven- station Bruce protocol from 8 to 10 A.M. and 3 to 5 P.M. re spectively. The present research is quasi-experimen tal with a pretest-posttest design. Blood samples were collect ed from both groups before, immediately after, and 2 hours after the exercise. Mean and standard deviation were used for data description and repeated measures ANOVA a s well as Bonferroni test were applied for hypothesis testing at the 0.05 significance level. The result suggest ed significant differences in the levels of hemoglobin and erythro cytes of the two groups at different stages of blood samp ling. No significant difference was observed in the level of hemoglobin and erythrocytes before and two hours athe exercise. Measurement of the level of leukocytes in the two groups and at different stages of blood sa mpling indicated significant differences, and both groups showed significant differences in the level of plat elets at different stages of sampling (P ≤0.05).Comparison of the two groups revealed that th ere is no significant difference between the morning and the afternoon group in the levels o f hemoglobin, platelets, erythrocytes, and leukocyt es before, immediately after, and two hours after the exercise . Based on the results of the research, it can be a rgued that a maximal aerobic exercise session in the morning and the afternoon changes the level of hemoglobin, pla telets, erythrocytes, and leukocytes, and that the time of exercise has no effect on the amount of change.