Heart rate reserve (HRR)

Heart rate reserve (HRR) is the difference between maximum heart rate and resting heart rate, measured in beats per minute.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 443.} The Karvonen method uses it to set exercise intensity: multiply HRR by the target percentage, then add resting heart rate.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 443.} ACSM gives the same formula: target HR = [(HRmax − HRrest) × % intensity] + HRrest.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 345.}

A 40-year-old client with an estimated maximum of 180 and a resting rate of 70 has an HRR of 110; at 40% to 89% of HRR, the target is 114 to 168 beats per minute.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 443.} HRR accounts for the client’s own resting rate, and the reserve grows as fitness improves and resting heart rate falls.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 443.}

How do trainers use heart rate reserve?

• Always add resting heart rate back: leaving it out gives a zone too low to produce the intended gains.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 443.}
• ACSM classifies 40% to 59% of HRR as moderate and 60% to 89% as vigorous.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 345.} More trained clients can typically handle the upper range, 60% to 89%.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 445.}
• In the NSCA’s table, percentages of HRR closely match percentages of VO2 max: 70% of HRR matches 70% of VO2 max, or about 81% of maximum heart rate.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 579.}
• For individual prescription, ACSM prefers relative measures such as HRR over absolute ones such as METs, especially for deconditioned clients.^{5Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 347.}