3 blocks of 12 minutes alternating 2 minutes at 105% of threshold pace and 2 minutes at 95% of threshold pace, with 3 minutes recovery between blocks. Trains the lactate production-clearance cycle without ever dropping below threshold.
Total 1h12 · No zone 5min
The lactate threshold (VT2, second ventilatory threshold, ~4 mmol/L) represents the metabolic tipping point beyond which blood lactate accumulation becomes exponential. Training this threshold shifts upward the intensity at which a runner can maintain a lactate steady state, which is the primary determinant of performance from 10K to half-marathon.
Z4 corresponds to lactate threshold intensity. Tempo efforts of 20-40 minutes at this intensity trigger threshold-specific metabolic adaptations: MCT4 upregulation and improved buffering capacity.