RACERADAR
Lactate is a byproduct of anaerobic energy production. At easy paces, your body produces and clears lactate in balance. As you run faster, production exceeds clearance. The inflection point where lactate begins to accumulate rapidly is your lactate threshold (LT).
While VO2max sets your ceiling, lactate threshold determines what percentage of that ceiling you can sustain. Elite marathoners race at 80-88% of their VO2max — that percentage is largely determined by their lactate threshold. Two runners with identical VO2max values can have very different marathon times based on threshold fitness.
Tempo runs at your T-pace (roughly your 1-hour race pace) are the primary tool. Jack Daniels recommends two approaches:
Both achieve the same physiological goal: time spent at the metabolic threshold.
At threshold pace, you should feel "comfortably hard." You can speak in short phrases but not hold a conversation. Heart rate is typically 82-88% of max. It feels sustainable for about 60 minutes in a race setting but challenging in training.
Unlike VO2max, which has a genetic ceiling, your lactate threshold can be trained for years. Consistent threshold work over months and years steadily raises the pace you can sustain, which directly translates to faster race times at every distance.
Lactate threshold is the pace above which lactate accumulates faster than your body can clear it. Tempo runs at T-pace improve your threshold, letting you sustain faster paces for longer.