Anaerobic Threshold Calculator

The anaerobic threshold (AT), also called the ventilatory threshold 2 (VT2) or onset of blood lactate accumulation (OBLA), is the exercise intensity above which lactate accumulates faster than it can be cleared. It corresponds to roughly 85-95% of maximum heart rate in trained individuals.

The terms are often used interchangeably, but strictly LT1 (lactate threshold) is where lactate first rises above baseline, and LT2/AT (anaerobic threshold) is where it rises steeply. AT is at a higher intensity than LT1. Racing a 5K or 10K is typically performed at or slightly above AT.

AT-specific training includes sustained efforts at threshold pace (tempo runs), long intervals at AT intensity, and race-pace simulation. Research shows that combining high-volume low-intensity training with targeted threshold work produces the greatest improvements in AT over time.

A 30-minute maximal time trial is a common field test for AT. Warm up thoroughly, then run or cycle at maximum sustainable effort for 30 minutes. Your average heart rate over the last 20 minutes approximates your AT heart rate. This is sometimes called the functional threshold power (FTP) test in cycling.

At AT intensity, breathing becomes noticeably laboured. You can speak a few words but cannot hold a conversation. It is often described as 'comfortably hard' or the pace you can sustain in a one-hour time trial. Above AT, effort becomes increasingly difficult to sustain beyond a few minutes.