Forty years of sports performance research and little insight gained

A systematic review and meta-analysis of published studies revealed that hard training and deliberate practice in sports accounted for only 1% of the variance in performance among elite-level athletes.
Reference
https://www.ncbi.nlm.nih.gov/pubmed/27217246
https://pdfs.semanticscholar.org/8177/d5d8897d192225b1c58b6842cdfec54bd8...