"260 at 70 bpm . Step 3. Calculate heart rate reserve (HRR) HRR = HR max – HR rest = 190 – 70 = 120 bpm Step 4. Calculate exercise int ensity ACSM guidelines = 40 – 85% HRR Lower target (40%) = (HHR × 40%) + HR rest = (120 × 0.40) + 70 = 48 + 70 = 118 bpm Upper target (85%) = (HHR × 85%) + HR rest = (120 × 0.85) + 70 = 102 + 70 = 172 bpm Using this method, according to ACSM guidelines, Mariella should exercise somewhere between 118 and 172 bpm . Borg Scale An alternative to using heart rate methods is the RPE method of measuring exercise intensity. However, you should note that it is diffi cult to give a general recommendation for RPE, as it is by its very nature open to personal interpretation; that is, what I consider to be a 12 may be different to what you consider to be a 12. RPE can be a useful way of measuring exercise intensity when heart rate monitoring is difficult or inappropriate. For example, some types of medication (e.g. beta blockers) given to people with hypertension lower the heart rate, and therefore heart rate measurement is not appropriate for people on this type of medic ation. The Borg Rating of Perceived Exertion (RPE) Scale is one way to measure perceived exertion. In medicine, this is used to document the patient’s exertion during a test, and sports coaches use the scale to assess the intensity of training and competit ion. The original scale introduced by Gunnar Borg rated exertion on a scale of 6 -"