PURPOSE: To investigate the effects of oral ingestion of essential amino acids (EAA exercise on the global gene expression in skeletal muscle after sprint exercise. METHODS: Twelve healthy physically active subjects (age 20-30 years) performed three 30-s cycle sprints with maximal voluntary pedaling rate on a mechanically braked cycle ergometer with 20 min rest between the sprints. The braking force was set at 0.75 N/kg body weight. The subjects consumed either EAA + maltodextrin solution or flavored water (placebo) in a randomized order. A post exercise biopsy (m. vastus lateralis) was taken 200 minutes after the last cycle sprint. RNA was isolated from the frozen muscle biopsies using TRIzol protocol. Purification was executed using RNeasy Mini Kit (Qiagen). The RNA concentration was determined using the NanoDrop (Thermo Fischer Scientific) and quality assessed by Agilent (Agilent Technologies). The Affymetrix Gene Chip Whole Transcript (WT) Sense Target Labeling Assay Manual was used for complementary DNA (cDNA) generation, hybridization and array processing (GeneChip® Human Transcriptome Array 2.0). Differentially expressed genes in response to EEA in combination with the sprint exercise were analyzed using the Ingenuity Pathways Analysis (IPA) software application. To validate microarray data total RNA was reverse transcribed using random hexamer primers. Real-time PCR was applied to measure mRNA expression using RPS18 as reference to correct for potential variation in RNA loading. RESULTS: The IPA Network analysis showed an enrichment of activated genes related to collagen metabolism. Some of the genes in the pathway analysis were validated by the PCR analysis. The expression of COL15A1, COL1A1, COL2A1 and BGN was higher in the EEA condition compared to the placebo condition (P<0.05). CONCLUSION: Oral ingestion of EAA after sprint exercise increases expression of genes related to collagen metabolism. The functional role of an activation of collagen metabolism is not known, although it could be speculated that an altered collagen metabolism reflects an extracellular remodeling after exercise and that this process is enhanced by oral ingestion of EEA. SUPPORT: The study was supported by grants from the Swedish National Center for Research in Sports.