Resistance exercise (RE) can be explained as muscle contractions with loads greater than that performed during normal activities of life 1. Hence it increases muscle protein synthesis leading to muscle hypertrophy and elevated contractile force with increase in myofibril size and architecture known as adaptations. There is stimulated tendons, vascular, extracellular matrix and innervations performance 2±4. The most important key of this adaptive coordination response is the regulation by microRNAs (miRNAs) 5 although there is low understanding data about its role in muscle response to RE.
There are about 1900 miRNA species are detected in the human cells until now 17, 18. Approximately 30 miRNA species are involved in the regulation of skeletal muscle function, hyper trophy and atrophy. They may be involved in satellite cell generation and differentiation (miRNA-1, -133a/b, -206, -486) 19±21, myocyte cell cycle regulation (miRNA1, -15a, -16, -26a, -133a/b, -206, -221, -222, -451a and -486,) 7±9, 22±28 and fiber type formation and determination (miRNA-208a/b and -499a) 9, 29. Further miRNAs have reported to have overlapping influence on skeletal muscle stress soreness, protein catabolism and atrophy which may lead to muscle fatigue, including miRNA-378a, -378b 30±32, miRNA-23a/b 33±38-208a/b and -499a 7±9 33±38. Moreover, some miRNAs are involved in the regulation carbohydrate metabolism including insulin and glucose in response to RE; miRNA-21 39, 40, -148b 41 and -486 42, Furthermore, only miRNA-494 has found to be involved in mitochondrial synthesis and adaptation 43 and miRNAs-126 44, 45, -15a, 16 46, 47 have been found to increase angiogenesis in skeletal muscle.
miRNAs are known to act locally within the cells in which they are synthesized, but may escape to circulation meaning released from one tissue type to act in another. Also they can play a paracrine role in the otherbtissue 50. More or less, role of miRNA species expressed in skeletal muscle in response to exercise and increased in circulation following exercise is still unclear.