There are several ways to determine your Heart Rate Training Zones, some of which are more accurate than others. Testing in a lab where blood samples are drawn and measured for Lactic Acid is very accurate, but expensive. Subtracting your age from 220 (224 for women) is easy, but can be off by 15%, since everyone doesn’t fit the parameters of being “average”. Here’s a method for cycling, running and swimming that is a self test and which is quite accurate.

Cycling LTHR TT Test Long warm-up. Then ride a 30 minute time trial all out. Race effort. Use a flat, out and back course. 10 minutes into the time trial punch the lap button on your heart rate monitor. Afterwards, record your average heart rate for the last 20 minutes. Also record distance covered or average speed.
Running LTHR Test Warm up well. Then run a 30 minute time trial on flat course/track. Punch HR monitor ‘lap’ button 10 minutes into Time Trial. Average heart rate for last 20 minutes predicts Lactate threshold heart rate (LTHR).
Swimming LTHR Test In swimming, we refer to “T-Pace” quite often to prescribe intensities. Your T-Pace is the pacer per 100 yards that you can swim for a continuous 1,000 yards. This also predicts your LTHR. For example, we might say to swim 500 in T-pace +5. If your T-Pace were 1:40/100, than your T-Pace + 5 would be to swim that 500 yards at the pace of 1:45 per 100 yards. You will be able to get a feel for this with experience, so estimate how the intensity feels each time you swim so that you can be familiar with your zones by how an intensity feels (in other words, you are using your rating of perceive exertion- rpe). To determine T-Pace, swim a brief warm up set. After your warm up, swim a continuous 1,000 yards at a constant pace. Try not to go out so hard that you fade early in the swim, but go out as hard as you can and maintain that pace for the entire duration. Take your pulse/HR at the end of the swim and record both your HR and your time divided by 10. That will be your T-Pace.