MicroRNAs (miRNAs) are a class of non-coding small RNAs representing one of the 
most exciting areas of modern medical science. miRNAs modulate a large and 
complex regulatory network of gene expression of the majority of the 
protein-coding genes. Currently, evidences suggest that miRNAs play a crucial 
role in the pathogenesis of heart failure. Some miRNAs as miR-1, miR-133 and 
miR-208a are highly expressed in the heart and strongly associated with the 
development of cardiac hypertrophy. Recent data indicate that these miRNAs as 
well as miR-206 change their expression quickly in response to physical 
activity. The differential regulation of miRNAs in response to exercise suggests 
a potential value of circulating miRNAs (c-miRNAs) as biomarkers of 
physiological mediators of the cardiovascular adaptation induced by exercise. 
Likewise, serum levels of c-miRNAs such as miR-423-5p have been evaluated as 
potential biomarkers in the diagnosis and prognosis of heart failure. On the 
other hand, the manipulation of miRNAs levels using techniques such as 'miR 
mimics' and 'antagomiRs' is becoming evident the enormous potential of miRNAs as 
promising therapeutic strategies in heart failure.