According to Jose Canseco, 85 percent of big leaguers use steroids. Ken Caminiti reported that 50% of players used steroids, but later reversed that estimate and stated that the figure was lower. MLB survey testing revealed a utilization rate of 5–7%, but those figures are unlikely to be trustworthy. Baseball's drug culture has been criticized as a reason for its declining popularity. Players on steroids appear more muscular and stronger than normal humans. They also have larger hearts with greater blood flow, higher levels of testosterone, and smaller testes with less sperm. Many users report feeling more aggressive and having more energy after using performance-enhancing drugs.