Zone 4: Threshold — The Edge of Your Aerobic Limit

Zone 4: Threshold — The Edge of Your Aerobic Limit

Zone 4 training is where you sit at the border between aerobic and anaerobic energy systems. It’s controlled discomfort — hard, focused work that raises your ability to sustain speed.

Why Zone 4 Is Worth It

You raise your lactate threshold

This is the point where lactate builds faster than you can clear it. A higher threshold = faster race pace.

You increase maximal sustainable speed

The harder you can work before going anaerobic, the faster you race.

You improve your body’s ability to clear lactate

Your muscles get better at processing lactate back into usable energy.

You build mental toughness

Zone 4 teaches you how to stay calm and controlled under stress — exactly what you need late in a race.

What Zone 4 Feels Like

• Hard, but not quite “max”

• Talking is difficult

• Legs feel heavy but not failing

• Breathing is strong, rhythmic, and deep

You should feel “on the limit but in control.”

Simple Zone 4 Session

4 × 5 minutes threshold with 2 minutes recovery

Push hard, hold form, recover well.

Zone 4 is the gateway to faster racing.