Sub-3:45 Marathon: Training Plan, Pace and Strategy

3:45 is the least glamorous marathon mark — and the most interesting one. It sits exactly where the field of ambitious amateur runners splits: under 5:20 per kilometre, without the training load of a sub-3 project. What lies in between is less a question of talent than of dosage: enough volume for the aerobic base, enough race pace for economy, and a race strategy that does not turn the second half into an arithmetic problem.

What 3:45 means: 5:20 per kilometre

42.195 kilometres in 225 minutes works out to exactly 5:20 per kilometre, or 11.25 km/h — roughly 8:35 per mile. The gap from sub-4 is bigger than the 15 minutes suggest: between 5:41 and 5:20 per kilometre sits a six per cent increase in speed, and over three hours and 45 minutes that does not scale linearly but progressively.

In practice: do not calculate with 5:20, race at 5:15 per kilometre. The buffer of about three and a half minutes covers what is systematically lost in a race — aid stations, one toilet stop in cool weather, running the racing line through corners, and the fact that virtually every marathon course measures 200 to 400 metres "too long" in the end. Whoever plans to the edge runs against the clock instead of the field.

Converting your own fitness helps: 3:45 in the marathon corresponds to roughly 1:47 in the half marathon, 46 minutes for 10 km and 22 minutes for 5 km. Before starting a 16-week block, at least two of those times should sit within ±4 per cent.

The fitness check: between 3:30 and 4:00

The typical sub-3:45 candidate does not come from nowhere: they have been running for two to four years, have one or two marathons between 3:50 and 4:10 behind them, and have plateaued since. That is precisely where the opportunity lies, because between sub-4 and sub-3:45 what is usually missing is not base fitness but structure. Four criteria show whether the jump is realistic:

• Half marathon under 1:50: The single most important marker. Run 1:47 to 1:50 and the endurance for 3:45 is already in the body — only race-pace familiarity is missing.
• 10 km in 44 to 46 minutes: Shows that basic speed is sufficient to stop 5:15 per kilometre feeling permanently "hard".
• 30 km in training under 2:55: A relaxed 30 km at 5:50 average without a collapse over the final five kilometres is the best practical test.
• Two years of continuous training: Tendons, bones and the ability to tolerate 60 kilometres per week grow more slowly than the cardiovascular system. A jump from 40 to 70 weekly kilometres inside one block usually ends in injury.

Meet two of the four criteria and sub-3:45 is realistic within 16 to 18 weeks. Meet none and the route via a sub-4 marathon is the smarter intermediate step — the jump from 4:00 to 3:45 is considerably harder than the one from 3:45 to 3:30.

The training plan: 55 to 75 kilometres per week

In the peak phase (weeks 11 to 15 of an 18-week block) weekly volume sits at 55 to 75 kilometres across five sessions, following the 80/20 principle: roughly 80 per cent of volume easy, 20 per cent quality. A typical build week:

• Monday: Rest day or 30 to 40 minutes of easy cross-training.
• Tuesday: Threshold session, e.g. 4 × 2,000 m at half marathon pace (around 4:55 to 5:00/km) with 2 minutes jog recovery. 13 to 15 km total.
• Wednesday: 10 to 12 km easy at 6:00 to 6:20 — deliberately slower than race pace.
• Thursday: 12 km with 8 km at marathon pace (5:15/km). The key session of the week.
• Friday: Rest day or 6 km recovery.
• Saturday: 10 km easy plus 5 × 20-second strides.
• Sunday: Long run 28 to 34 km, with the final 8 to 10 km at marathon pace.

That adds up to 70 to 78 kilometres. The order of stimuli matters: the threshold session on Tuesday and the long run on Sunday are the two sessions that count; everything else serves fatigue processing. Run Wednesday too fast and you pay for it on Sunday.

The long run: the last part counts

The classic mistake in sub-3:45 training is treating the long run as pure distance work: 32 km at a steady, slow 6:30. That trains endurance but not the ability to hold pace in the final third of a race. A progressive long run is more effective: easy for the first two thirds, then the final 8 to 10 km at target pace. That simulates exactly the situation from kilometre 30 onwards where the race is decided.

Three rules for the long run:

• At most three runs over 30 km in an 18-week block. More adds no benefit but costs recovery.
• Never faster than race pace in the fast block. The long run is not a disguised race; fatigue should come from duration, not intensity.
• Practise fuelling: from kilometre 12, take 30 to 60 grams of carbohydrate every 30 to 40 minutes. The gut needs training just like the legs — see fuelling for the marathon.

Two sessions per block should serve as a rehearsal: 32 km with 12 km at race pace, including race-day shoes, race belt and the planned gel brands. If that session runs under control, the goal is realistic.

Race strategy: halfway decides

For 3:45 the halfway mark is 1:52:30. Pass it in 1:48 and you feel magnificent — and pay from kilometre 30 at 20 to 40 seconds per kilometre. The arithmetic is brutal: two minutes too fast in the first half typically costs four to six minutes in the second. That is exactly the difference between 3:45 and 3:52.

The strategy that works is unspectacular:

• Kilometres 1 to 5: 5 to 10 seconds per kilometre slower than target pace. Start-line congestion costs time anyway — use it instead of fighting it.
• Kilometres 6 to 25: Metronome. 5:15 per kilometre, controlled breathing, a watch check every 5 km rather than per kilometre.
• Kilometres 26 to 35: This is where it gets honest. If you have run evenly to this point you can hold the pace; if you went out too fast you feel it now. Check the legs, not the ego.
• Kilometres 36 to 42: If the legs are carrying you, this is the place for a negative split — the final 7 km 5 to 10 seconds faster. If not: hold the pace, do not fight.

A word on hills: at 3:45 the profile matters more than at 4:30 because less reserve remains. Reckon 15 to 20 seconds of loss per 10 metres of climbing and run hills at equal effort rather than equal pace — slightly slower uphill, controlled faster downhill without braking hard. Details in hill training for runners.

The mistakes that live between 3:30 and 4:00

• Too much volume, too little race pace. Run 80 km per week but never 5:15 and you race 5:30 — the economy is missing. At sub-3:45 the share of marathon-pace work matters more than the last volume increase. The marathon training plan shows how the individual building blocks fit together.
• The threshold session too hard. 4 × 2,000 m is not a race. Run them in 4:40 instead of 4:55 and you train a different energy system while sabotaging the long run.
• Long runs without structure. 34 km at the same pace every time is busywork. The benefit comes in the final third.
• Skipping strength work. Two 20-minute sessions per week — squat, a deadlift variation, calf raises, single-leg work — are the cheapest insurance for the last ten kilometres. Templates in strength training for runners.
• Underestimating the taper. Two weeks of volume down 40 to 60 per cent with intensity retained delivers two to three per cent at this level — nearly five minutes. Cut only in race week and you leave it on the table.
• Race day without a buffer. Start corral too far back, fuelling unplanned, no gels of your own. At 5:15 per kilometre every improvised minute is one you do not get back.

The 18-week build at a glance

• Weeks 1–5, base: 45 to 60 km, one threshold session, long runs from 20 to 26 km. The goal is tolerance, not speed.
• Weeks 6–11, build: 60 to 72 km, long runs of 26 to 30 km with 6 to 8 km at race pace, threshold work as 3 × 3,000 m.
• Weeks 12–15, specific: 65 to 75 km, two runs over 30 km, one of them with 12 km at target pace. The rehearsal sits in week 14.
• Weeks 16–17, taper: volume down 30, then 55 per cent, short race-pace stimuli retained.
• Week 18, race: opener sessions, carbohydrates up, no experiments.

A down week belongs between blocks: volume down 30 per cent, no quality. That week is not a step backwards but the precondition for the next block to work — the principle is covered in the deload week.

How Peakora plans a sub-3:45 goal

In the Peakora engine you start with a race goal and a current personal best; the planner derives target pace, training zones and the distribution of sessions from that. For a 3:45 goal this means: threshold sessions automatically land in the right range (not too hard), long runs get a race-pace block over their final kilometres, and volume rises in steps of no more than 10 per cent per week. The recovery monitor tracks TSB and ACWR in parallel — if load climbs too high, the engine shortens the following week instead of letting you drift into overtraining. And because the taper is anchored in the periodisation, the final two weeks remain what they should be: a reduction in fatigue with sharpness retained.

Anyone training towards a time mark for the first time should review the plan honestly after four weeks: are the race-pace sessions getting easier, do the long runs hold up? If not, the plan is not wrong — the goal is too ambitious. A block at 3:55 followed by one at 3:45 beats a block that ends in injury.

Frequently asked questions about the sub-3:45 marathon