Ratings of perceived exertion are commonly used to gauge the perceived level of effort that is experienced by an exercising individual. The most common such scales range from either 6 through 20 or 1 through 10. Each scale provides descriptors corresponding to the level of difficulty as perceived by the individual. These ratings are commonly used in sports nutrition research to assess the efficacy of a dietary technique or supplement in enhancing performance. Although this is not a direct indicator of performance, it can be useful for providing evidence of a potential ergogenic capacity and can suggest that more research is needed to confirm an ergogenic benefit.