The most common question I get is: "Do I have to pay for them?" The answer is yes. You pay for the products that work. But there is a lot of research that shows that more agility does not mean more protection. A 2013 article published in the journal Movement Disorders concluded that there was no "strong evidence" to show that "automotive jump training improves maximal power output, strength, or muscle mass." The authors also found no evidence to support any claim that jumping increases muscular endurance, nor did they find any evidence of increased muscle activation or blood flow. In a 2011 study in the Journal of Strength and Conditioning Research, Dr. Paul S. Gee of St. Bonaventure University reported that no improvement in maximal vertical jump or vertical jump power was observed after one year of jumping. For the same reason, there is no good evidence that "brawling" improves strength. The only research that exists that seems to show a positive effect from brawling, comes from a 2014 study by Michael P. Gormley et al.. For a brief summary of the results, click here. For an explanation of the study, click here. For a more detailed description, click here.