Chasing 1:40 – A 12‑Week Half‑Marathon Training Journey

The goal

Target: half marathon in 1 hour 40 minutes (average pace ≈ 7:38 per mile / 4:45 per km).

Getting to 1:40 takes three things: enough speed to hold sub-8 miles for most of the race, enough endurance for 10 to 12 mile runs at manageable intensity, and the head to push through the fatigue that usually shows up around mile 10.

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Pre-requisites

Before starting, check the baseline:

• Current half-marathon PB: 1:45 to 1:50 (or a 10K in 50 min or under).
• Weekly mileage: 15 to 25 miles (24 to 40 km) for the past 4 weeks.
• Injury-free: no lingering aches that worsen when you run.

If you’re slightly behind, plan on a 2-week build-up of steady running first.

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How the plan works

Workout	Purpose	Typical pace / effort
Easy run	Develop aerobic fitness, aid recovery	60–70% max HR, ~1:30–1:45/mi slower than race pace
Tempo run	Train lactate threshold (pace you can hold for an hour)	85–90% max HR, ~7:50–8:00/mi (slightly slower than race pace)
Interval (speed)	Increase VO₂ max and running economy	Hard effort, 90–95% max HR. 5K–10K race pace or faster for short reps
Long run	Build endurance, train fuel metabolism	Easy to moderate, 60–75% max HR. Finish last 2 to 3 mi at goal race pace
Recovery / cross-train	Maintain training while lowering joint stress	Light activity (cycling, swimming, yoga), 30 to 45 min
Rest	Full day for muscular repair and glycogen replenishment	—

Pace numbers are reference points. Heart-rate zones or perceived effort work fine without a watch.

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Weekly plan (12 weeks)

Week	Mon	Tue	Wed	Thu	Fri	Sat	Sun
1	Rest	Easy 4 mi (9:00)	Tempo 3 mi @ 7:55	Easy 4 mi	Rest or cross-train	Long 7 mi (9:15)	Easy 3 mi
2	Rest	Easy 4 mi	Interval 5×400 m @ 5K pace, jog 400 m	Easy 4 mi	Rest or cross-train	Long 8 mi (9:10)	Easy 3 mi
3	Rest	Easy 5 mi	Tempo 4 mi @ 7:50	Easy 5 mi	Rest or cross-train	Long 9 mi (9:05)	Easy 3 mi
4	Rest	Easy 5 mi	Interval 4×800 m @ 5K–10K pace, jog 400 m	Easy 5 mi	Rest or cross-train	Long 10 mi (9:00)	Easy 4 mi
5	Rest	Easy 5 mi	Tempo 5 mi @ 7:45	Easy 5 mi	Rest or cross-train	Long 11 mi (8:55)	Easy 4 mi
6	Rest	Easy 5 mi	Interval 6×400 m fast, jog 400 m	Easy 5 mi	Rest or cross-train	Long 12 mi (8:50)	Easy 4 mi
7	Rest	Easy 6 mi	Tempo 5 mi @ 7:40	Easy 6 mi	Rest or cross-train	Long 13 mi (8:45)	Easy 4 mi
8	Rest	Easy 6 mi	Interval 5×800 m fast, jog 400 m	Easy 6 mi	Rest or cross-train	Long 14 mi (8:40)	Easy 4 mi
9	Rest	Easy 6 mi	Tempo 6 mi @ 7:38	Easy 6 mi	Rest or cross-train	Long 12 mi (goal-pace finish)	Easy 3 mi
10	Rest	Easy 5 mi	Interval 4×1200 m @ 10K pace, jog 400 m	Easy 5 mi	Rest or cross-train	Long 10 mi (steady)	Easy 3 mi
11	Rest	Easy 5 mi	Tempo 5 mi @ 7:40	Easy 5 mi	Rest or cross-train	Long 8 mi (last 2 mi @ 7:38)	Easy 3 mi
12 (race week)	Rest	Easy 4 mi	Rest	Easy 3 mi (optional strides)	Rest	Race day, half marathon 1:40	Rest

Distances are in miles. Multiply by 1.609 for kilometers.

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Detailed workout descriptions

Easy run

1. Start with 5 to 10 min of easy jogging.
2. Settle into a pace where full sentences flow naturally.
3. Close with 5 min of easy jogging and static stretches.

Tempo run

1. 10 min at an easy pace.
2. Hold tempo pace for 20 to 30 min (a notch below goal race pace). If steady pacing is hard, aim for “comfortably hard”: speaking comes in short bursts.
3. Cool down 10 min easy.

Interval (speed) session

1. Warm up 10 to 15 min easy plus 4 to 5 strides.
2. Run the repeats at target interval pace (e.g. 5K pace for 400 m reps). Keep effort even rep to rep.
3. Recover with a jog or walk for the listed time (usually equal to work duration).
4. Cool down 10 min easy.

Long run

1. Start aerobic and conversational.
2. Shift to a steady effort in the second half.
3. In weeks 9 to 11, run the final 2 to 3 mi at goal race pace to practice holding speed when tired.
4. Cool down and stretch thoroughly.

Recovery / cross-train

Low-impact work, swimming, cycling, or elliptical, for 30 to 45 min. Keep it easy. This is restoration, not a second hard session.

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Notes and tips

• Building mileage: no more than 10% weekly increase to prevent injury.
• Body awareness: if soreness lingers, swap a hard workout for an easy run or take a day off.
• Nutrition: test race-day fuel on long runs (gels, sports drinks, or solid food). Aim for 30 to 60 g carbs per hour.
• Fluids: know your sweat rate. Aim for fluid loss under about 2% of body weight.
• Strength: two 20 to 30 minute sessions a week (core, glutes, posterior chain).
• Without a watch: heart-rate zones and perceived exertion work fine.
• Visualization: picture yourself running the hard miles (10 and 11). Self-talk can save real seconds.

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FAQ

Q: I missed a key workout. What should I do? A: Replace it with an easy run and continue the rest of the week normally. Avoid back-to-back hard sessions.

Q: My assigned paces feel wrong after a few weeks. A: Run a recent time trial (5K works well) to recalibrate. Shift training paces by the same percentage.

Q: Is it okay to replace a run with a bike session? A: Yes, on cross-train days. Keep effort light to moderate. Don’t substitute for quality speed or tempo work.

Q: I have a history of shin splints. What precautions help? A: More grass or trail running, lower-leg strengthening, and don’t ramp mileage too fast.

Q: What if race day is much warmer than training? A: Do at least one long effort in heat, or simulate it with extra layers. Adjust the fluid plan to match.

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Closing and suggested workout

A 1:40 half is within reach if you stay consistent and progress sensibly. Every mile builds the engine and the confidence.

To kick off the program, try the week 1 tempo:

• Warm up 10 min easy.
• Hold 7:55 min/mi for 3 mi (right below goal pace).
• Cool down 10 min easy.

Notice your breathing, track how your legs feel, and recognize you’re laying the groundwork for 1:40.

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References

• 1/2 Marathon 12 Week Beginner | running Training Plan | TrainingPeaks (Blog)
• 1/2 Marathon 16 Week Beginner | running Training Plan | TrainingPeaks (Blog)