Aerobic capacity

Aerobic capacity is maximal aerobic power, also called VO2 max, maximal oxygen uptake or maximal oxygen consumption.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 106.} VO2 max is generally regarded as the single best measure of aerobic fitness.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 106.} It depends on how well the body delivers oxygen through cardiac output and uses it, measured by the arteriovenous oxygen difference.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 106.}

The NSCA expresses lactate threshold as a share of aerobic capacity: about 50% to 60% in untrained people, 70% to 80% after training, and 80% to 90% in aerobic endurance athletes.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 111.}

In practice

• Expect most improvements in maximal oxygen consumption to fall between 10% and 30% after 6 to 12 months of aerobic training.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 112.}
• Clients can maintain their gains on as few as two sessions a week if duration and especially intensity stay the same.^{4Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 451.}
• Match the test to aerobic fitness: a 50-yard sprint isn’t a valid measure of aerobic capacity, while field options include the 1.5-mile run and the Yo-Yo intermittent recovery test.^{5Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 192.},^{6Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 272.}

What VO2 max can miss

The NSCA’s personal training text treats aerobic capacity and VO2 max as the same thing.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 106.} Its strength and conditioning text also uses aerobic capacity to describe trained muscles: greater capacity lets an athlete perform at a given absolute intensity with more ease.^{7Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 138.} In its example, a marathoner who runs at 75% of maximal oxygen uptake may hold 80% after training, so before-and-after VO2 max measurements may not reflect competition performance.^{7Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 138.}