Training Intensity Levels:

Level 5: Sprint pace, really hurting and struggle to maintain intensity (95-100% of Max HR)

Level 4: Speed endurance pace, need to focus to maintain intensity (90-95% of Max HR)

Level 3: Endurance pace commonly known as Lactate Threshold - can't talk easily but can think clearly (80-90% of Max HR)

Level 2: Moderate endurance pace, can speak a few sentences at a time (70-80% of Max HR)

Level 1: Easy endurance pace, can speak in full sentences (60-70% of Max HR) (more)