In Martorano's 2002 study, "Sweet and Low," a strong correlation was found between alpha (fast) brainwaves and concentration ability. The dominance of delta (slow) waves, or an imbalance between alpha and delta, led to distractibility and an inability to achieve optimal athletic performance. At the end of the study, athletes showed improved athletic performance (feeling in the zone) due to better brain circulation. This increased concentration ability remained unchanged even after treatment.