Half Marathon Training Plan: Build a Personalized Plan with AI

The half marathon is the most popular race distance for a reason. It's long enough to require real training but short enough that you can fit preparation into a busy life. Whether you're targeting a sub-2:00, sub-1:45, or sub-1:30, the same training principles apply — but the paces, volume, and specifics change dramatically based on your fitness level.

This guide covers how to build a personalized half marathon plan using AI, with exact training paces based on your current fitness — and how to get it imported to TrainingPeaks so every workout is on your calendar.

Finding Your Starting Point: VDOT for Half Marathon Training

Your training paces should be based on your current fitness, not your goal time. If you've raced recently, use the VDOT calculator to find your training zones:

Recent Race Time → VDOT → Half Marathon Prediction

5K: 20:00     → VDOT 52 → Half: 1:32:00
5K: 22:00     → VDOT 46 → Half: 1:42:00
5K: 25:00     → VDOT 40 → Half: 1:57:00
5K: 28:00     → VDOT 36 → Half: 2:10:00
10K: 41:30    → VDOT 52 → Half: 1:32:00
10K: 46:00    → VDOT 46 → Half: 1:42:00
10K: 52:30    → VDOT 40 → Half: 1:57:00

No recent race? Run a hard 5K effort (a local parkrun works) and use that time. It's the fastest way to establish your current fitness baseline.

Half Marathon Plan Structure: 12-16 Weeks

A half marathon plan should be 12-16 weeks depending on your starting fitness:

• 12 weeks: For runners already running 20+ miles/week consistently
• 14 weeks: For runners at 15-20 miles/week
• 16 weeks: For runners under 15 miles/week or returning from a break

Phase 1: Base Building (Weeks 1-4)

Goal: Establish consistent mileage and aerobic foundation.

• 4-5 runs per week, mostly at Easy (E) pace
• One tempo-style workout per week (15-20 minutes at Threshold pace)
• Long run: 8-10 miles at easy pace
• Weekly mileage: starting point + 0-10% increase per week

Phase 2: Strength (Weeks 5-8)

Goal: Develop lactate threshold and aerobic power.

• Two quality sessions per week (one threshold, one interval or tempo)
• Threshold workouts: 2-3 x 10-15min at T pace with 2-3min recovery
• Interval workouts: 5-6 x 1000m at I pace with equal recovery
• Long run building to 12-14 miles, some with goal-pace segments
• Recovery week in week 7 (reduce volume 20-25%)

Phase 3: Race Specific (Weeks 9-12)

Goal: Practice half marathon pace and build race-day confidence.

• Two quality sessions: one race-pace, one threshold/VO2max
• Race-pace sessions: 4-6 miles at goal half marathon pace within a longer run
• Long run peaks at 13-15 miles (some plans include 14-mile runs with goal-pace miles)
• Recovery week in week 11

Phase 4: Taper (Final 1-2 Weeks)

Goal: Arrive at race day fresh and sharp.

• Volume drops 30-40% from peak week
• One short quality session (abbreviated threshold or goal-pace work)
• Easy runs get shorter, not slower
• 2-3 days before the race: shakeout run with a few strides

Training Paces by Goal Time

Sub-2:00 Half Marathon (VDOT ~40)

Easy:      10:56-11:40/mi
Threshold: 9:09/mi
Interval:  8:22/mi
Long Run:  10:30-11:30/mi
Race Pace: 9:09/mi

Weekly volume: 25-35 miles
Long run max: 12-13 miles

Sub-1:45 Half Marathon (VDOT ~46)

Easy:      9:54-10:30/mi
Threshold: 8:14/mi
Interval:  7:31/mi
Long Run:  9:30-10:30/mi
Race Pace: 8:00/mi

Weekly volume: 30-40 miles
Long run max: 13-14 miles

Sub-1:30 Half Marathon (VDOT ~52)

Easy:      8:38-9:11/mi
Threshold: 7:09/mi
Interval:  6:33/mi
Long Run:  8:30-9:00/mi
Race Pace: 6:52/mi

Weekly volume: 40-55 miles
Long run max: 14-15 miles

Sample Week: Sub-1:45 Plan (Build Phase)

Monday:    Easy Run - 5mi @ 9:54-10:30/mi
Tuesday:   Threshold Run - 8mi total: 2mi warmup, 3x10min @ 8:14/mi
           with 2min jog recovery, 2mi cooldown
Wednesday: Rest or easy cross-training (30min)
Thursday:  Easy Run + Strides - 6mi easy + 6x100m strides
Friday:    Rest
Saturday:  Long Run - 13mi @ 9:45-10:15/mi, final 3mi @ 8:00/mi (race pace)
Sunday:    Recovery Run - 4mi @ 10:30+/mi

Weekly total: ~36 miles

Common Half Marathon Training Mistakes

Running Every Day Hard

The biggest mistake. Your hard days should be genuinely hard, and your easy days should be genuinely easy. If every run is "moderate," you're too tired for quality sessions and too fast for recovery. Follow the 80/20 rule: 80% easy, 20% hard.

Long Run Too Fast

Your weekly long run should be at Easy pace — 1:00-1:30/mile slower than half marathon pace. The exception: race-specific long runs where you run the final 3-5 miles at goal pace. Don't turn every long run into a time trial.

Ignoring the Taper

Many runners feel guilty reducing volume before the race and sneak in extra miles during taper week. This costs them on race day. Proper tapering is when your body absorbs 12+ weeks of training. Don't skip it.

No Race-Pace Practice

If you've never run at goal half marathon pace for more than 2 miles, race day will be a rude awakening. Include race-pace segments in your long runs and at least one dedicated race-pace workout per week during the race-specific phase.

Starting Too Aggressively

Week 1 should feel easy. If you're struggling in the base phase, your plan is too ambitious. Scale back and build gradually. A plan that's slightly too easy is infinitely better than one that breaks you by week 6.

Cross-Training for Half Marathon Runners

Smart cross-training prevents injury and builds fitness without the impact stress of running:

• Cycling: 30-60 minutes at easy effort. Builds aerobic fitness with zero impact. Great for recovery days.
• Swimming: Full-body recovery. Excellent for active rest days.
• Strength training: 2x per week for 20-30 minutes. Focus on single-leg exercises (lunges, step-ups, single-leg deadlifts) and core stability. See our injury prevention guide for specific exercises.
• Yoga/mobility: 15-20 minutes post-run or on rest days. Hip openers and hamstring work.

Race Day Strategy

Pacing

Start 10-15 seconds per mile slower than goal pace. The first 3 miles should feel almost too easy. Settle into goal pace by mile 4-5. If you feel strong at mile 10, accelerate slightly for a negative split. If you're struggling at mile 10, maintain current effort and focus on form.

Fueling

Most runners can complete a half marathon on pre-race nutrition alone if they eat properly the morning of. For runners targeting over 1:45, one gel at mile 7-8 provides a useful boost. Practice fueling during training long runs — never try anything new on race day.

Mental Strategy

Break the race into thirds. Miles 1-4: restraint. Miles 5-9: rhythm. Miles 10-13.1: grit. The middle miles are where most half marathons are won or lost — don't let a crowd of 10K runners pull you out too fast.

Generate Your Plan and Import to TrainingPeaks

A personalized half marathon plan with exact paces, progressive long runs, and proper periodization takes about 10 minutes to generate with AI. TrainingDojo is the only tool that generates the plan AND imports it directly to TrainingPeaks — no manual entry of 50+ workouts.

Tell the AI your recent race time, goal, weekly availability, and race date. It builds a complete plan using the periodization principles described above, with every workout at your exact VDOT-based training paces.

Ready to start training? Generate your personalized half marathon plan and import it to TrainingPeaks in minutes at trainingdojo.app/generate.