Chasing 1:45: A 12‑Week Half‑Marathon Journey

The Goal

Target: Half‑marathon (21.1 km) in 1 hour 45 minutes

• Average pace needed: 5:00 min/km (or 8:03 min/mile).
• What it demands:
  • Speed: Ability to hold sub‑5 min/km for sustained periods.
  • Endurance: Comfortable long runs at 5:30–5:45 min/km.
  • Mindset: Consistent weekly mileage, disciplined recovery, and the willingness to train at intensities that feel uncomfortable at first.

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Pre‑Requisites

Before diving in, make sure you meet at least one of the following benchmarks:

• Current half‑marathon PB: 2:00 – 2:10 (or a 5 km time ≤ 20 min).
• Weekly mileage: 20–30 km (12–18 mi) spread over 4–5 days.
• Base: Able to complete a 10 km run at a steady 5:45 min/km pace.

If you’re a few minutes slower, consider adding a 4‑week base‑building block (gradual mileage increase, easy runs) before starting the 12‑week plan.

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How the Plan Works

Workout Type	Purpose	Typical Pace / Effort
Easy Run	Build aerobic foundation, promote recovery.	5:45–6:15 min/km (conversational).
Tempo Run	Raise lactate threshold – the pace you can sustain “comfortably hard.”	4:45–5:00 min/km (≈85‑90 % max HR).
Interval Session	Develop speed and VO₂ max. Short, fast repeats with recovery.	4:00–4:20 min/km for work intervals; easy jog for recovery.
Long Run	Enhance endurance, teach the body to burn fat efficiently.	5:30–5:45 min/km (steady, relaxed).
Recovery / Cross‑Training	Allow adaptation, prevent overuse injuries.	Light activity (cycling, swimming, yoga) ≤ 60 min.
Rest Day	Complete physiological reset.	No structured activity.

Pace ranges are guidelines; adjust based on how you feel, weather, and terrain. Use perceived effort or heart‑rate zones if you prefer.

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Weekly Plan Table (12 Weeks)

Week	Mon	Tue	Wed	Thu	Fri	Sat	Sun
1	Rest	Easy 5 km	Tempo 6 km (4:55/km)	Easy 5 km	Intervals 5×400 m @4:10/km + jog 200 m	Long 12 km @5:45/km	Rest or cross‑train
2	Rest	Easy 6 km	Tempo 7 km (4:55/km)	Easy 5 km	Intervals 6×400 m @4:10/km + jog 200 m	Long 13 km @5:45/km	Rest or cross‑train
3	Rest	Easy 6 km	Tempo 8 km (4:50/km)	Easy 5 km	Intervals 4×800 m @4:20/km + jog 400 m	Long 14 km @5:40/km	Rest or cross‑train
4	Rest	Easy 7 km	Tempo 9 km (4:50/km)	Easy 5 km	Intervals 5×800 m @4:20/km + jog 400 m	Long 15 km @5:40/km	Rest or cross‑train
5	Rest	Easy 7 km	Tempo 10 km (4:45/km)	Easy 5 km	Intervals 6×400 m @4:05/km + jog 200 m	Long 16 km @5:35/km	Rest or cross‑train
6	Rest	Easy 8 km	Tempo 10 km (4:45/km)	Easy 5 km	Intervals 4×1200 m @4:25/km + jog 400 m	Long 17 km @5:35/km	Rest or cross‑train
7	Rest	Easy 8 km	Tempo 11 km (4:45/km)	Easy 5 km	Intervals 5×1200 m @4:25/km + jog 400 m	Long 18 km @5:30/km	Rest or cross‑train
8	Rest	Easy 9 km	Tempo 12 km (4:40/km)	Easy 5 km	Intervals 6×400 m @4:00/km + jog 200 m	Long 19 km @5:30/km	Rest or cross‑train
9	Rest	Easy 9 km	Tempo 12 km (4:40/km)	Easy 5 km	Intervals 4×1600 m @4:30/km + jog 400 m	Long 20 km @5:25/km	Rest or cross‑train
10	Rest	Easy 10 km	Tempo 13 km (4:35/km)	Easy 5 km	Intervals 5×1600 m @4:30/km + jog 400 m	Long 21 km @5:25/km	Rest or cross‑train
11	Rest	Easy 8 km	Tempo 10 km (4:35/km)	Easy 5 km	Intervals 3×800 m @4:00/km + jog 400 m	Long 16 km @5:20/km	Rest or cross‑train
12 (Race Week)	Rest	Easy 5 km	Tempo 6 km (4:30/km) – cut in half	Rest	Intervals 4×200 m @3:55/km (sharp)	3 km shake‑out run	RACE DAY – Half‑marathon 1:45 goal

Feel free to shift days to suit your schedule, but keep the order of intensity (easy → hard → easy) within each week.

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Detailed Workout Descriptions

Easy Run

• Duration: 5–10 km at a relaxed pace.
• How to execute: Keep breathing conversational, hands loosely at your sides, and focus on good form. Use these runs to recover from harder sessions.

Tempo Run

• Goal: Raise the pace you can hold for about an hour.
• Structure: Warm‑up 1 km easy → steady “comfortably hard” segment at target tempo pace → cool‑down 1 km easy.
• Feeling: You should be able to speak in short phrases, not full sentences.

Interval Session

• Goal: Improve speed and VO₂ max.
• Typical format: Warm‑up 1–2 km easy, then repeat the fast interval at the prescribed pace, followed by an equal‑time jog or walk for recovery, end with 1 km cool‑down.
• Tips: Use a stopwatch or a GPS watch to hit the exact interval time. Focus on consistent effort across repeats.

Long Run

• Goal: Build endurance and teach the body to burn fat.
• Pace: 30–45 seconds slower than race pace; stay relaxed, practice fueling (if > 90 min, take a gel or carbohydrate drink every 45 min).
• Mental trick: Break the run into segments (e.g., “first 5 km, next 5 km”).

Recovery / Cross‑Training

• Choose low‑impact activities that keep blood flowing without stressing the legs: cycling, swimming, elliptical, yoga, or a brisk walk.

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Notes & Tips

• Progression: Increase weekly mileage by no more than 10 % to avoid overuse injuries.
• Listen to your body: If you feel persistent soreness, swap a hard session for an easy run or an extra rest day.
• Nutrition: Prioritize carbohydrates the night before key workouts, stay hydrated, and consider a small carb snack 30 min before tempo/interval days.
• Mindset: Treat each workout as a piece of a puzzle. Consistency beats occasional “hero” runs.
• Personalised pace zones: Use a recent race or a time‑trial (5 km or 10 km) to calculate your easy, tempo, and interval paces rather than relying solely on generic formulas.
• Adaptive planning: If a week feels too tough, drop the mileage of the long run by 10–15 % and keep the intensity of the key session.
• Common mistakes to avoid:
  1. Running the long run too fast.
  2. Skipping easy days, leading to burnout.
  3. Ignoring proper warm‑up/cool‑down.
  4. Not tracking effort – a simple effort‑scale (1‑10) can be as useful as a watch.

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Frequently Asked Questions

Q1: I missed a workout. Should I do it later in the week? A: If you miss an easy run, replace it with a short easy jog. If you miss a key quality session (tempo or interval), treat the week as a “recovery” week and keep the long run, then schedule the missed quality session for the following week’s easy day.

Q2: My paces feel too hard. Can I adjust them? A: Absolutely. Use perceived effort: easy runs should feel easy, tempo runs “comfortably hard,” intervals “hard but sustainable.” If the numbers are too aggressive, add 10–15 seconds per km and re‑evaluate after a week.

Q3: I’m prone to shin splints. How can I stay injury‑free? A: Incorporate strength work (glutes, core, calves) 2 times per week, run on softer surfaces when possible, and keep weekly mileage growth gradual. Ice and foam‑roll after hard sessions.

Q4: Can I substitute a cross‑training day for a run? A: Yes, especially if you’re fatigued or dealing with minor niggles. Choose a low‑impact activity that maintains aerobic stimulus.

Q5: What if I’m already running 30 km per week? A: You can start at the higher end of the mileage ranges in the plan, but keep the relative intensity distribution (≈70 % easy, 20 % quality, 10 % long). Adjust the easy‑run distances upward gradually.

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Closing & Workout Suggestion

The beauty of chasing a 1:45 half‑marathon is that every step teaches you something about speed, stamina, and self‑belief. You’ve now got a roadmap; the rest is about showing up, listening to your body, and celebrating the small victories along the way.

Workout of the Week to Kick‑Start the Plan

• Easy 5 km (conversational pace) → 5 × 400 m intervals at 4:10 min/km with 200 m jog recovery → Cool‑down 2 km. This combo touches both endurance and speed, giving you a taste of the plan’s rhythm.

Give it a try, log how you feel, and let the journey unfold. Your 1:45 finish line is waiting – one training day at a time.

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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)