As for the physiological results of this study, researchers predicted that cortisol levels in individuals playing the bottom role (one that follows orders, receives stimulation, is bound, etc...) would have an increase in cortisol levels followed by a drop in cortisol after the scene was over. In other words, people that are knowingly about to place themselves in a situation that includes physical pain and other stressful activities, such as sensory deprivation, were predicted to have an increase in stress hormones and once the activity ends, are likely to have a decrease in stress hormones. To sum up this highly climatic portion of the study, their hypothesis did indeed turn out to be true.
In regards to testosterone which is often an indicator of status in dominance hierarchies, it was hypothesized that perhaps individuals that assume top roles (gives orders, provides stimulation, etc...) would have a higher baseline testosterone level. This however was not the case, bottoms had higher levels of testosterone (both males and females) than tops. The authors suggest that one explanation for this occurrence is that testosterone levels could have been increased due to the anticipation of an endurance-like challenge. This explanation for heightened testosterone in bottoms makes sense considering in S&M, you've got to be prepared to take it like man.
