A complete, science-based full marathon training plan covering all four phases — base building, development, peak, and taper. Built for first-timers and returning runners alike.
A full marathon training plan is a structured 12–20 week programme that progressively builds your aerobic capacity, muscular endurance, and race-specific fitness to cover 42.2 km (26.2 miles). A well-designed plan balances stress and recovery across four distinct phases, peaking your fitness 2–3 weeks before race day and then tapering to arrive fresh on the start line.
The plan is not just a schedule of runs — it is a system for managing training load so your body adapts without breaking down. Most running injuries happen when runners do too much too soon, which is why progressive overload (increasing volume by no more than 10% per week) is the non-negotiable foundation of every marathon plan.
The base phase focuses on building aerobic capacity with easy, conversational-pace running. If you are new to distance running, this phase establishes your weekly mileage foundation. If you are returning from a break, it rebuilds your connective tissue's tolerance for load. Most runs in this phase should feel easy — you should be able to hold a conversation throughout.
The development phase introduces quality sessions — tempo runs, marathon-pace efforts, and progressive long runs. This is where your fitness improves most rapidly. Tempo runs (20–40 minutes at a comfortably hard pace) build lactate threshold, while marathon-pace miles teach your body to run efficiently at race speed.
Peak training is the hardest and most rewarding phase. Your long runs reach 30–35 km, weekly volume is at its highest, and marathon-pace sessions become longer and more specific. This is also the phase where injury risk is highest — monitor your body closely and do not be afraid to back off for a day if something feels wrong.
The taper is a planned reduction in training volume (not intensity) over 2–3 weeks before race day. Volume drops 20–40% each taper week while you maintain some quality sessions. Many runners feel sluggish and anxious during the taper — this is normal. Trust the process: your body is storing glycogen, repairing micro-damage, and preparing to perform.
A typical week in the development phase of marathon training looks like this:
The long run is the single most important session in marathon training. It builds your aerobic engine, trains fat metabolism, and prepares your legs for the demands of race day. Key principles:
Marathon training requires significant nutritional support. Key principles:
PacecraftAI builds your full marathon plan around your race date, fitness level, and weekly schedule — and adapts it automatically every week based on how training is going.
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