The best performance enhancer is probably just exercise. There is a story about Bobby Fisher playing some guy and the position was likely one that would just result in a draw. His opponent offered a draw based on the position but Bobby turned it down and played it out and one. Later, Bobby was asked why he decided to play out this draw-ish position when he had lost to this player the last time they played. Bobby's response was that he could tell that the guy had put some weight and likely had a sedentary lifestyle and would likely get tired and make a mistake, which is what happened. Bobby was a pretty big believer exercise helping chess early on.