There are hundreds of half marathon training plans online. Hal Higdon, Pfitzinger, Hanson, Nike Run Club — each with a slightly different philosophy but the same fundamental approach: a fixed schedule of workouts over 10-16 weeks.
The problem isn't the plans themselves. Most are well-designed by experienced coaches. The problem is that a static plan can't respond to your body.
Week 8 says "10 miles with 4 at tempo pace." But what if you slept 4 hours last night? What if your HRV has been declining for a week? What if you're coming back from a cold? The plan doesn't know, and it doesn't care.
Here's how to build a half marathon training plan that adapts to you.
Start with a proven framework
Don't reinvent the wheel. Pick an established plan as your starting framework:
- Beginner (first half): Hal Higdon Novice (12 weeks, 4 runs/week, peaks at ~25 miles/week)
- Intermediate (sub-2:00): Pfitzinger 12/47 (12 weeks, 5-6 runs/week, peaks at ~47 miles/week)
- Advanced (sub-1:40): Pfitzinger 12/63 or Hanson's Advanced (12 weeks, 6 runs/week, peaks at 55-63 miles/week)
These give you the structure: the long run progression, the workout types, the recovery week placement. What you're going to add is the adaptive layer that makes the plan respond to your body.
The adaptive layer: 4 rules
Rule 1: Adjust intensity based on recovery
Before every hard session (tempo, intervals, long run), check your recovery status:
- Recovery high (WHOOP 60%+, Oura Readiness 75+, or you feel genuinely fresh): Execute the workout as planned
- Recovery moderate (40-60% or Readiness 60-75): Reduce intensity — drop the tempo pace by 10-15 sec/mile, or shorten the interval reps
- Recovery low (below 40% or Readiness below 60): Convert to easy run or rest. There is no workout worth doing when your body can't recover from it.
This single rule — adjusting intensity based on recovery — is the most impactful change you can make to any training plan.
Rule 2: Monitor weekly training load
Track your weekly TSS (training stress score) and keep the increase to 5-10% per week during build phases. Most plans already follow this principle, but real life creates deviations:
- You miss a run due to travel, then try to "make up" miles on the weekend → load spike
- A workout goes harder than planned because you felt great → higher TSS than intended
- You add an extra easy run because the weather was nice → volume creep
Weekly TSS tracking catches these patterns. If you're already at target load by Thursday, Friday's planned workout might need to become easy or rest.
Rule 3: Respect the recovery weeks
Every 3-4 weeks, reduce volume by 25-30%. This is non-negotiable, but it's also the first thing runners cut when they're "feeling good."
Your recovery week should accomplish:
- TSB (training stress balance) trending toward zero or positive
- HRV baseline stabilizing or rising
- Legs feeling genuinely fresh by the end of the week
If these things aren't happening, your recovery week wasn't easy enough. Reduce more next time.
Rule 4: Taper by the numbers
The taper is where data-driven training pays its biggest dividends. Instead of following a generic "reduce by 40%" taper template, monitor your TSB and target:
- Race week TSB of +10 to +20: This is the sweet spot where fitness exceeds fatigue
- Reduce volume, keep some intensity: 2-3 short workouts with race-pace strides maintains neuromuscular sharpness without adding fatigue
- Watch HRV trend upward: Confirms the taper is working and your body is supercompensating
The 12-week structure
Here's a simplified framework for an intermediate half marathon plan:
| Week | Phase | Focus | Mileage |
|---|---|---|---|
| 1-2 | Base | Easy volume, 1 moderate workout | 25-30 mpw |
| 3 | Build 1 | Add tempo work | 30-35 mpw |
| 4 | Recovery | Reduce 25% | 23-26 mpw |
| 5-6 | Build 2 | Tempo + intervals | 35-40 mpw |
| 7 | Recovery | Reduce 25% | 27-30 mpw |
| 8-9 | Build 3 | Peak mileage, race-specific work | 40-47 mpw |
| 10 | Recovery | Reduce 30% | 28-33 mpw |
| 11 | Taper 1 | Reduce volume, maintain intensity | 30-35 mpw |
| 12 | Race week | Easy + strides, race on Sunday | 15-20 mpw |
The specifics (exact workouts, paces) depend on your fitness level and goal time. The structure — build/recover/build/recover/peak/taper — is universal.
Key workouts for half marathon fitness
The tempo run
What: 20-40 minutes at half marathon effort (roughly Zone 3-4, or 85-90% of LTHR)
Why: Teaches your body to sustain a moderately hard effort — the exact demand of racing a half marathon
Progression: Start with 20 minutes of tempo in week 3, build to 40 minutes by week 9
The long run
What: 90-120 minutes at easy effort (Zone 2), with the last 20-30 minutes at marathon or half marathon pace during build weeks
Why: Builds aerobic endurance, glycogen storage, and mental toughness for race day
Progression: Start at 8-9 miles, build to 13-15 miles for intermediate runners
The interval workout
What: 4-6 x 1000m at 5K effort (Zone 4-5), or 3-4 x 1600m at 10K effort
Why: Develops VO2max and running economy. Makes half marathon pace feel easier by training at harder intensities.
Frequency: Once per week during build phases, dropped during taper
Using AI to adapt your plan
The adaptive rules above work manually, but they work better with AI coaching. Here's why:
A training plan generates dozens of micro-decisions per week: Should I run today or rest? Should I do the scheduled tempo or back off? Am I tapering enough? Is my long run pace right?
An AI coach with access to your training data can answer these in seconds:
"Your TSB is -14 and WHOOP recovery is 62%. The plan says 6x1000m today. I'd suggest shortening to 4x1000m and running the recovery jogs at an honest easy pace. You'll get the neurological stimulus without digging deeper into fatigue."
That level of daily adjustment is what makes a human coach valuable. Now you can get it from an AI that sees all your data — your training load, recovery, sleep, and workout history — and adjusts in real time.
Pairform gives you exactly this: connect your Strava and WHOOP (or Oura, Garmin), and the AI coach sees your full training picture. Ask it any question about your plan and get a data-backed answer.
Race day execution
All the training data in the world doesn't help if you blow up on race day. A few evidence-based execution tips:
- Start 5-10 sec/mile slower than goal pace for the first 2 miles. Your adrenaline will make goal pace feel easy — resist the temptation.
- Run even or slight negative splits. The fastest half marathons are run with the second half 30-60 seconds faster than the first.
- Don't chase heart rate early. Your HR will be elevated from adrenaline and pre-race caffeine. Focus on pace and perceived effort for the first 5K.
- Save your kick. If you have something left at mile 11, that's perfect. Empty the tank in the final 2 miles.
The bottom line
The best half marathon training plan is one that responds to your body, not just a calendar. Start with a proven framework, add the adaptive layer (recovery-based intensity, load monitoring, data-driven taper), and use AI coaching to make daily micro-adjustments.
The difference between a good race and a great race is usually not the plan — it's the hundreds of small decisions made during training. Get those right, and race day takes care of itself.
Training for a half marathon? Connect your devices to Pairform and get AI coaching based on your actual data — free.