Urinary Metabolomic Changes and Potential Exercise-Induced Muscle Damage Biomarkers Identification in Trained Young Males Following Acute Intermittent Rowing Training

(1) Background: This study aims to explore the changes in urinary metabolomic profile among trained young males following acute intermittent rowing training (AIRT), and to identify potential urinary biomarkers associated with exercise-induced muscle damage (EIMD). (2) Methods: 22 trained young males were recruited to perform AIRT. The changes in blood biochemical indexes associated with EIMD were analyzed. EIMD occurrence was evaluated using blood biochemical indexes, muscle function, and pain assessment. The changes in urinary metabolites were determined using untargeted metabolomic analysis. (3) Results: Four blood biochemical indices, including creatine kinase, lactate dehydrogenase, creatine kinase-MB, and hydroxybutyrate dehydrogenase, were significantly elevated immediately after AIRT. Furthermore, an obvious immune response appeared, and countermovement jump performance significantly decreased. Among 384 urinary metabolites, 33 were significantly upregulated, and 12 were downregulated immediately after AIRT. Upregulated metabolites were mainly involved in phenylacetate metabolism, ammonia recycling, the urea cycle, and glutathione metabolism. Four potential urinary biomarkers were identified, including 2'-Deoxycytidine, cytosine, Phenylacetaldehyde, and Pyridoxamine. (4) Conclusions: AIRT induced EIMD in all participants and significantly altered urinary metabolite profiles. The changes in urinary metabolites and pathways were due to the metabolic adaptation to oxidative stress, inflammatory responses, and ammonia metabolism imbalance. The selected four potential urinary biomarkers provide important evidence for the further development of a non-invasive, urine-based method for the immediate assessment of EIMD.