Exercise genomics, epigenomics, and transcriptomics: a reality check!

The exercise genetic studies assumed that the relation between genotype and phenotype was rather direct and simple, and that an allele of interest would have a large effect size on a relevant exercise trait. Complex traits are influenced by genes and alleles with small effect sizes; and the regulation of transcription, translation, and other cellular processes is widely distributed and highly complex. An illustration of this enormous degree of genomic complexity can be obtained from the findings of the Encyclopedia of DNA Elements Consortium project, resulting from the contributions of hundreds of scientists from around the world. The impetus provided by the impressive wave of genome-wide association studies publications on complex traits so has nurtured a major shift in understanding of the genomic architecture of these traits. In spite of all the progress made in genomics and bioinformatics, it remains an extraordinary challenge to define causal relationships between DNA variants, epigenetic events or gene expression profile, and a relevant phenotype.