[The relationship between physical exercise and gut microbiota in the human being: a systematic review].

BACKGROUND the relationship between physical exercise and gut microbiota has opened new therapeutic frontiers for many inflammatory diseases. However, there is still a lot of uncertainty about how to administer exercise. OBJECTIVES to review the literature to bridge this gap and examine the relationship between cardiorespiratory fitness (CRF) and microbiota. DESIGN systematic review. SETTING AND PARTICIPANTS studies involving humans who undergoing exercise programmes of any lengths, intensities, and types were included. The research was carried out through PubMed, Scopus, and Web of Science. MAIN OUTCOME MEASURES the primary outcome was change in gut microbiota composition (α and β-diversity), while the secondary outcome was the CRF level. RESULTS the 15 studies included (all with PEDro scale <=5) used aerobic training alone or combined with resistance exercises. In general, exercise has shown positive effects on the microbiota, influencing the faecal count of some bacterial phyla (in particular Bacteroidetes, Firmicutes, and Proteobacteria), with a weak tendency towards proportionality in relation to training duration and intensity. However, the evidence supporting the exercise effects on the gut microbiota and the relationship with CRF are of low quality. CONCLUSIONS despite the weak evidence in favour of the effects of the practice of physical exercise on the intestinal microbiota, there are still many aspects that need to be explored. In particular, future studies shall have higher quality and methodological rigour, standardize the methods for outcome assessment, and determine type and thresholds of interventions intensity and duration.