When referring to the rate of perceived exertion rating scale, what does the number 6 represent?

The number 6 on the rate of perceived exertion (RPE) scale signifies a level of effort that is considered "too light to have a significant training effect." The RPE scale typically ranges from 0 to 10, where lower numbers correspond to easier levels of exertion and higher numbers indicate maximal effort. A rating of 6 suggests that the exercise is very easy and might not provide enough challenge to induce substantial physical adaptations or improvements in fitness. This level of exertion may feel comfortable, where an individual could easily perform many additional repetitions without fatigue, leading to the conclusion that it lacks the intensity needed for effective training stimulus.