Neurologically, sports performance can be envisaged as a search for a target in a space. If you are a beginner, then any training that takes you closer to the t

Neurologically, sports performance can be envisaged as a search for a target in a space. If you are a beginner, then any training that takes you closer to the target is beneficial. So eg a beginner learning tennis will benefit from playing badminton, squash, etc. However, as you become more expert then the risks are greater (your opponents are better) and the margins are increasingly minimal. So your training has to become incredibly specific. No more badminton if you want to be an excellent tennis player. Also, for even the world's finest sports players, performance degrades just minutes after practice or competition. This is the purpose of warming up : to fine-tune the nervous system, to bring your performance in the search space as close as possible to the target. Human systems are chaotic, so performance is subject to fluctuation from even the tiniest perturbations. This is why even the finest sports player cannot expect 100% reliable performance every single time.