Final answer:
The lactate threshold is one of the best determinants of an athlete's optimal pace in distance running and cycling events.
Step-by-step explanation:
When expressed as a percentage of VO₂max, one of the best determinants of an athlete's optimal pace in events such as distance running and cycling is their lactate threshold.
The lactate threshold is the exercise intensity at which lactic acid starts to accumulate in the muscles faster than it can be cleared away. It is often expressed as a percentage of the athlete's VO₂max.
A higher lactate threshold means that the athlete can sustain a higher intensity of exercise for a longer period of time, making it a critical factor in determining an athlete's optimal pace in endurance events.