# The Workout That Builds Half Marathon Speed
Half marathon runners who want to boost their race pace need to understand the science behind speed endurance work. One session stands out in training plans designed specifically for the 13.1-mile distance: the tempo run paired with shorter speed intervals.
This workout combines two physiological adaptations that half marathon performance demands. The tempo segment trains the lactate threshold—the effort level where lactate accumulates faster than your body clears it. Running at threshold pace (roughly 25-30 seconds slower than 5K pace) teaches your aerobic system to sustain harder efforts. Runners typically hold this effort for 20-40 minutes depending on their fitness level.
The speed work component, often added after the tempo portion, sharpens leg turnover and neuromuscular power. Short intervals at faster paces build the leg speed needed to kick in the final miles of a half marathon when fatigue sets in.
The workout structure looks like this: warm up for 10-15 minutes, run 20-30 minutes at threshold pace, recover with 2-3 minutes of easy running, then add 4-8 repetitions of 2-3 minute intervals at half marathon goal pace or slightly faster. Finish with a cooldown.
This session trains race-specific energy systems. The threshold component develops aerobic capacity while teaching the body to sustain pace when lactate rises. The interval work prevents the glycogen depletion that undermines performance in the final miles.
Runners should incorporate this workout once weekly during their 8-12 week half marathon build, typically 4-6 weeks before race day. Recovery matters as much as the session itself. The day after demands easy running or rest to allow adaptation.
Skipping this workout leaves half marathoners relying solely on long runs and easy miles, which build