Aerobic Capacity

In most endurance-training contexts, aerobic capacity is essentially VO2 Max: how much oxygen you can use at maximal effort, typically expressed relative to body weight (ml/kg/min). It describes the upper range of your aerobic system.

A higher aerobic capacity gives you more room to support higher intensities, but it is not the only thing that decides performance.

Key characteristics

• It’s an upper limit: once you’re near max, you can’t “will” the oxygen system much higher.
• Track trend, not single readings: watch/platform VO2 Max is usually an estimate and can swing with heat, hills, fatigue, and sensor noise.
• Not a performance switch: two athletes with similar VO2 Max can race very differently due to threshold ability, economy, and durability.

Estimation

Lab test (direct VO2 Max measurement)

A graded test to exhaustion with gas analysis.

Field estimate (more practical for training)

If you care about training decisions and progress, a repeatable field estimate is often more useful than a one-off lab value.

Aerobic capacity vs. aerobic threshold

• Aerobic capacity (VO2 Max) describes your upper aerobic range.
• Aerobic threshold (AeT) describes the upper edge of easy aerobic work.

Effective endurance training can improve VO2 Max, but it also raises AeT and AnT as a percentage of VO2 Max, so you can work closer to your limits for longer.

How Trainingload.ai uses aerobic capacity

• Aerobic ceiling context: VO2 Max helps explain high-aerobic potential, especially for interval work.
• Trend tracking: estimated VO2 Max is treated as a trend metric and cross-checked with recent load, fatigue, and performance.
• Not alone: Trainingload.ai interprets aerobic capacity with threshold ability, efficiency, durability, and recovery.

Related docs

• VO2 Max Levels
• Aerobic Threshold
• Anaerobic Threshold
• Chronic Training Load

References

• Joe Friel: Common But Confusing Training Terms