How to Fit Strength Training Into a Marathon Build

It's tempting to drop strength work entirely once marathon mileage ramps up — there's less time, more fatigue, and the long run understandably takes priority. But this is exactly the period where strength training earns its keep. As weekly mileage climbs, the cumulative load on tendons, joints and connective tissue rises sharply. Runners who stop lifting during their build are often the ones who pick up a niggle in weeks 8–14 of a 16-week plan, right when it matters most.

The goal during a marathon block isn't to build new strength — that should already be in place from your off-season or base phase. It's to maintain what you have with the minimum effective dose, so you arrive at race day durable rather than depleted.

This is a maintenance phase, not a development phase. Most runners do well with:

• 1–2 sessions per week, 25–35 minutes each
• Slightly reduced volume compared to base training (fewer total sets)
• Similar or slightly reduced load — this is not the time to be chasing new personal bests in the gym
• A hard focus on the exercises with the best return: squats, Romanian deadlifts, single-leg work and calf raises (see our four lifts every runner should do)

Timing matters more than the exercises themselves during a marathon build. A few principles we use with our own endurance clients:

• Never place a heavy strength session the day before a long run or a hard interval session
• The day after a long run is often a good slot — legs are already tired, so strength work adds minimal extra fatigue relative to skipping it
• If you can only manage one session a week, prioritise it in the first half of the week, away from your two hardest running days
• Keep sessions short and focused rather than trying to cram in accessory work — this isn't the time for extras

A marathon block typically moves through three phases, and strength training should shift with it:

• Base/early build (weeks 1–6): near-normal strength volume, 2 sessions a week
• Peak mileage (weeks 7–12): reduce to 1–2 sessions, lighter total volume, protect recovery
• Taper (final 2–3 weeks): drop to one short session, light load, purely to maintain movement quality and keep tendons "switched on" — not to build fitness. Some runners prefer to stop entirely in the final week; either is reasonable

• Stopping strength training completely at the first sign of high mileage — this is usually when it's needed most
• Trying to "make up" for a missed session by doubling up later in a fatigued state
• Ignoring calf and ankle work, despite it being one of the most common injury sites in marathon training
• Not adjusting gym load downward during peak mileage weeks, leading to compounding fatigue

If you're not sure how to balance this yourself, this is precisely the kind of programming decision a coach who understands both strength and endurance work should be making for you — see our approach to endurance coaching, or book a free call to talk through your race and current training.