Final answer:
The ACSM recommends an initial exercise intensity of 60% to <90% of Heart Rate Reserve (HRR) for healthy adults with fair to excellent fitness levels. This range encompasses moderate to vigorous intensity and must be adjusted based on an individual's maximum and resting heart rates, as well as their overall fitness level and other health factors.
Step-by-step explanation:
According to the ACSM (American College of Sports Medicine) 2018 guidelines, the appropriate initial exercise intensity for healthy adults with a cardiorespiratory fitness classification of fair to excellent is 60% to <90% of Heart Rate Reserve (HRR). HRR is calculated by taking the difference between your maximum heart rate and your resting heart rate. Using the HRR method allows individuals to customize their training intensity based on their current fitness levels, which corresponds to a range from moderate to vigorous intensity according to HHS guidelines.
For example, if an individual's estimated maximum heart rate is 200 bpm, and their resting heart rate is 60 bpm, their HRR would be 140 bpm (200-60 bpm). For an initial exercise intensity at 60% of HRR, one would target 84 bpm above resting (0.6 x 140 bpm), which would be 144 bpm as the exercise heart rate.
It is important to note that individual fitness levels, ages, and existing health conditions can influence appropriate exercise intensity. Furthermore, additional health benefits can be gained by increasing the duration and intensity of the physical activity beyond the ACSM's basic recommendations. Engaging regularly in physical activity is correlated with many health benefits including improved cardiovascular health, increased muscle strength, and better psychological well-being.