Last updated: 3 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
VO2 reserve (VO2R) is the range between resting VO2 and VO2 max. The Karvonen formula applies the same principle to heart rate: HRR = max HR − resting HR; target HR = resting HR + (intensity% × HRR). Training at 60-70% of HRR (heart rate reserve) corresponds to Zone 2 aerobic base work. This method accounts for individual resting heart rate variation — a person with a low resting HR (45 bpm) has a larger HRR and thus higher training zones than someone with a resting HR of 70 bpm at the same max HR.
- HRR = max HR − resting HR
- Target HR = resting HR + (intensity% × HRR)
- More accurate than %max HR alone
- Karvonen formula (also called heart rate reserve method)
In practice
VO2 reserve (the difference between VO2 max and resting VO2) offers an alternative way to express exercise intensity that some researchers argue is more precise than percentage of VO2 max alone, since it accounts for individual variation in resting metabolic rate — though in practice, percentage of VO2 max and heart rate reserve remain more commonly used in everyday coaching due to their simpler, more accessible measurement.
FAQ
What is VO2 reserve and how does it differ from VO2 max?
VO2 reserve is the difference between VO2 max and resting oxygen consumption, used as an alternative intensity reference point that accounts for individual resting metabolic variation, unlike percentage of VO2 max which doesn't factor in resting VO2.
Is VO2 reserve commonly used in practical coaching?
Less commonly than percentage of VO2 max or heart rate-based measures, mainly because it requires more detailed metabolic testing data that isn't as readily accessible as simpler heart rate or pace-based training zone methods.