2.1. Search Strategy
This systematic review and meta-analysis was reported according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) (21). A computerized search was coducted from inception to August 2020 using various databases including PubMed, ISI Web of Science, Scopus, and supplementary Google Scholar search. The following terms and their combinations of MeSH and non-MeSH terms were applied, including: “beta hydroxy beta methylbutyrate”, “hydroxy methyl butyrate”, “HMB”, “exercise,” “sport supplements”, “endocrine response” “cortisol”, and “testosterone”. Reference lists of all studies were checked for further eligible articles identification.