On Borg's RPE scale, which level is recommended for improving cardiorespiratory fitness?

Borg's Rating of Perceived Exertion (RPE) scale is a subjective measure used to gauge an individual's exertion level during physical activity. The scale ranges from 6 to 20, where the numbers correspond to perceived intensity.

For improving cardiorespiratory fitness, a level of 11 to 16 is recommended. This range corresponds to a moderate to somewhat hard intensity. Training at this intensity level has been shown to effectively enhance cardiovascular and respiratory function, leading to improvements in overall aerobic capacity. Individuals at this exertion level can typically maintain their performance for a longer duration, facilitating endurance training without excessive fatigue.

Levels outside this recommended range might not provide the same benefits for cardiorespiratory enhancement. For example, perceived exertion levels of 1 to 5 indicate a very low level of activity, which is not sufficient for significant fitness improvements. Levels 6 to 10 still reflect a low to moderate intensity that may also fall short of the demands necessary for enhancing cardiorespiratory capacity. Meanwhile, perceived exertion levels of 16 to 20 would suggest a very high intensity that may not be sustainable for most individuals over extended periods, which could lead to fatigue or the risk of injury.

Thus, training within the