Marathon training plan: a 16- to 20-week program

This guide offers a comprehensive structure, tailored to the Québec context, to help you build your training plan. Whether you’re aiming for your first marathon or a personal best, the principles remain the same: gradual progression, patience, and listening to your body. Let’s look at how to organize these four or five months of training to be in peak condition on race day.

Prerequisites before aiming for a marathon

Before you even open a training calendar, make sure you have a solid foundation. The marathon isn’t the right distance to start running. Ideally, you should already have at least six months to a year of regular running under your belt.

• Be able to run comfortably 3 to 4 times a week without injury.
• Have already completed a 10 km race, and preferably a half-marathon.
• Be able to handle a weekly mileage of about 30 to 40 km before starting the plan.
• Have a pair of shoes suited to your stride. Visiting a specialty store for a gait analysis is a wise investment.
• Get medical clearance if you’re over 40 or have a history of cardiovascular issues.

If you don’t meet these criteria, take a few months first to build your basic endurance. The marathon will be waiting for you next year, and you’ll enjoy it more if you’re well-prepared.

The structure of a 16- to 20-Week training plan

A good marathon training plan is divided into distinct phases, each with a specific goal. This periodization allows the body to adapt gradually while avoiding overtraining.

Phase 1: base training (weeks 1–6)

The goal is to build fundamental endurance. You build up mileage at moderate intensity, without worrying about speed. Most runs are done at a comfortable pace—that is, at a pace where you can hold a conversation. This is the time to develop your aerobic capacity and strengthen your tendons, ligaments, and muscles.

Phase 2: development (weeks 7–12)

We introduce high-intensity work: threshold sessions and interval training. Volume continues to increase, and long runs get longer. This is the most demanding phase, where you truly build the ability to sustain prolonged effort at marathon pace.

Phase 3: peak (weeks 13–16 or 18)

Training volume reaches its peak, and long runs top out at around 30 to 35 km. This is where you simulate race conditions, particularly in terms of nutrition. Sessions specifically at marathon pace become central to your training.

Phase 4: taper or Fine-Tuning (last 2 weeks)

You gradually reduce training volume to allow your body to fully recover and store energy. Counterintuitively, it’s by running less that you’ll become stronger on race day.

Types of runs to include

A balanced training plan combines different types of workouts, each targeting distinct physiological systems. Varying your workouts is the key to progress.

• The long run: the cornerstone of the marathon training plan. Run at a slow pace, it acclimates the body to endurance and improves fat utilization as fuel.
• The threshold session: a sustained but controlled effort, typically lasting 20 to 40 minutes at a pace that’s uncomfortable but manageable. It pushes back your lactate threshold, allowing you to maintain a faster pace for longer.
• Interval training: fast repetitions interspersed with recovery periods, for example, 6 sets of 800 metres. This type of training builds aerobic power and running efficiency.
• Recovery run: Run very slowly, this promotes blood circulation and the elimination of metabolic waste without adding fatigue.

To determine your precise paces for each of these sessions, our pace calculator provides reliable guidelines based on a recent time over a known distance.

Progressive weekly volume

The golden rule is to never increase your training volume by more than 10% from one week to the next. This gradual progression gives your body time to adapt and significantly reduces the risk of injury.

An effective training plan follows a cycle of three weeks of progression followed by a lighter week—known as a recovery week—during which volume is reduced by about 20 to 30%. These recovery weeks are essential: it is during rest that the body gets stronger, not during exercise.

An intermediate runner aiming to complete a marathon can increase their mileage from a starting point of 35 km per week to a peak of 55 to 65 km. More ambitious runners aiming for a specific time can increase their mileage to 70–90 km or more, but this requires experience and excellent recovery ability.

The long run: building up to 30–35 km

If you had to choose just one training session, this would be it. The long run prepares both the body and the mind. Gradually increase its distance, typically by 2 to 3 km per week, with a reduction during recovery weeks.

A typical progression might look like this: start at 18–20 km at the beginning of the plan, then work your way up to 25, 28, 30, up to a maximum of 32 to 35 km three weeks before the race. It’s generally not recommended to exceed 35 km in training: the risk-benefit ratio becomes unfavorable, as accumulated fatigue does more harm than good.

Run these sessions slowly—about 45 to 75 seconds per kilometre slower than your target marathon pace. The goal isn’t speed, but endurance and adaptation. Some long runs may include sections at marathon pace to help your body get used to the race rhythm.

Nutrition and the 30-Kilometre wall

The infamous “wall” occurs when glycogen stores are depleted, usually around the 30th kilometre. The body can only store about 90 to 120 minutes’ worth of glycogen at marathon intensity. Without external fuel, hitting the wall is inevitable.

The solution lies in a nutrition strategy honed during training:

• Consume 30 to 60 grams of carbohydrates per hour during the race, in the form of gels, energy drinks, or candy.
• Start fuelling early, as early as the 45-minute mark, without waiting until you feel fatigue.
• Hydrate regularly in small amounts, incorporating electrolytes during prolonged efforts.
• Test everything during training on your long runs. Don’t try anything new on race day—no new gels, drinks, or unusual meals.

In the days leading up to the race, many runners increase their carbohydrate intake to maximize glycogen stores. This carb-loading, combined with a well-executed taper, makes all the difference in the final kilometres.

Tapering in the last two weeks

Tapering is the most misunderstood phase, yet one of the most critical. After months of accumulating fatigue, these two weeks allow for supercompensation: the body recovers and comes out stronger than before.

• Reduce your total training volume by about 20 to 30% in the first week, then by 40 to 60% in the final week.
• Maintain some intensity to stay sharp, but shorten your workouts.
• The last long run, around 30–35 km, should be done three weeks before the race.
• Get plenty of sleep and watch your diet.

Many runners feel nervous, sluggish, or even under the weather during the taper. This is normal; it’s called “taper legs.” Trust the work you’ve done and resist the urge to run more. The harm you could do to yourself at this stage far outweighs any potential benefit.

Common mistakes to avoid

• Increasing your mileage too quickly: the number one cause of overuse injuries.
• Running slow workouts too fast: Endurance is built at low intensity. Too much intensity leads to exhaustion.
• Neglecting recovery: Sleep, rest days, and lighter training weeks are not optional.
• Skipping strength training: core exercises and weight training prevent injuries.
• Improvising your nutrition: Testing your nutrition strategy on race day is a recipe for failure.
• Starting too fast on race day: Discipline in the first few kilometres pays off after the 30th kilometre.

Adapting your training to the Québec climate

In Québec, most marathons take place in the fall, in September or October. This means that the bulk of training happens during the summer, often in the heat and humidity. This reality requires a few adjustments.

• Schedule your long runs early in the morning, before the heat of the day sets in.
• Be extra vigilant about hydration and electrolytes during the hot months.
• Don’t get discouraged if your pace slows down in high humidity—your body is working harder than it seems.
• If you’re training for a spring marathon, a good portion of your workouts will take place in cold weather and on snowy or icy surfaces. Adapt your gear with removable spikes and plan for treadmill sessions as needed.

Check the marathon calendar to choose a race that fits your training schedule and seasonal preferences.

An example of a typical week

Here’s what a typical week might look like during the build phase for an intermediate runner aiming to complete a marathon with a total mileage of about 55 km:

• Monday: Complete rest or light walking.
• Tuesday: Interval training, 3 km warm-up, 6 sets of 800 m at a steady pace with 2 minutes of recovery, 2 km cool-down. About 11 km.
• Wednesday: Easy endurance run, 8 km at a conversational pace.
• Thursday: Threshold session, 3 km warm-up, 6 km at threshold pace, 2 km cool-down. About 11 km.
• Friday: Rest day or cross-training—cycling or swimming.
• Saturday: Very slow recovery run, 6 km.
• Sunday: Long run, 28 km at a slow pace, with nutrition practice.

This structure alternates between effort and recovery while covering all essential types of workouts. Adjust the distances and paces according to your level and goals.

Conclusion

Training for a marathon is a demanding but deeply rewarding endeavour. By following a gradual progression over 16 to 20 weeks, varying your workouts, paying attention to your nutrition, and fine-tuning your training intelligently, you’ll give yourself the best chance of crossing the finish line in style. Patience and consistency always beat poorly balanced intensity. Ready to take on the challenge? Check out the race calendar in Québec to find the marathon that will become your next goal.