Morning-to-evening difference of biomarkers of muscle injury and antioxidant status in young trained soccer players

Abstract

The aim of this study was (i) to evaluate whether homocysteine (Hcy), total antioxidant status (TAS), and biological markers of muscle injury would be affected by time-of-day (TOD) in well-trained soccer players. In a counterbalanced order, 20 soccer players participated on two different occasions between 07:00 and 08:30 h and between 17:00 and 18:30 h. Fasting blood samples were collected from a forearm vein during each session. The results showed that the values of white blood cells (WBC), neutrophils (NE), lymphocytes (LY), and monocytes (MO) are higher in the evening than the morning. Although there was no TOD effect on blood lactate (Lac) levels, significant difference was observed for urea (URE), creatinine (CRE), and blood glucose (GLC) indicating higher evening levels. Moreover, the results also showed diurnal variations of core temperature, resting Hcy levels, and all biological markers of muscle injury [i.e., aspartate aminotransferase (ASAT), creatine kinase (CK), lactate dehydrogenase (LDH)].These parameters were lowest in the morning and tended to rise throughout the day. Furthermore, biomarkers of antioxidant status [i.e., TAS, uric acid (UA), and total bilirubin (TBIL)] displayed a significant effect of TOD with higher morning levels. In conclusion, the present study confirms the diurnal variations of Hcy, selected biological markers of cellular damage, and antioxidant status in young trained soccer players. Our finding suggests the fact that muscle damage and inflammation could be more important in the evening and that antioxidant status is more efficient in the morning.