A total of 23 participants (data available in present submission and in GSE58608) completed three months of supervised aerobic exercise training of one leg. Skeletal muscle biopsies have been collected before and after the training period. We have investigated differences between trained and untrained leg and before and after training by studying the gene and isoform expression. Additional samples present in this study has been previously published (GEO accession number GSE58608). Overall design: Analysis of transcriptome in skeletal muscle biopsy samples in response to exercise training in 22 participants (of the total 23 participants). One biopsy is collected from each leg before and after training period.