Leg day for marathon training: the strength work runners actually need

Marathon training isn’t just about stacking up miles until your legs beg for mercy. If you want to run faster, avoid injuries, and not end up hobbling like a baby giraffe after long runs, you need strength training. What you don’t need is the kind that has you texting your physio from the floor.

Do runners need leg day?

Yes. The evidence is clear: adding strength training to a running plan improves running economy and endurance performance in both recreational and elite runners. Running economy is how efficiently your body converts oxygen into forward movement — the better your economy, the further and faster you go for the same aerobic effort.

A strong set of legs changes how you run, in a good way. Stronger glutes and hamstrings produce more force per stride, which means more distance per step and less total ground contact time per kilometer. Less ground contact time is directly correlated with better running economy. In practice: you go further for the same perceived effort, and you still have functioning legs at mile 20.

How often should runners train legs?

One leg session per week is the standard recommendation during marathon training, and it’s the right one. Two sessions is possible during base phase or lower mileage weeks, but it requires careful timing and honest self-assessment about recovery. Three or more is how you start looking up the difference between shin splints and a stress fracture.

One solid leg session per week, at the right intensity and at the right point in your training week, is enough stimulus to maintain and even build strength during a marathon block. You are not trying to increase your squat PR. You are trying to keep the muscular foundation strong enough that it can support 35+ miles of weekly running without falling apart.

When to schedule leg day around your long run

Not the day before a long run, and not the day after if you can help it.

Leg day famously creates delayed onset muscle soreness (DOMS). Running on legs in peak DOMS isn’t impossible, but you’ll compensate your gait to protect sore muscles, which shifts load onto structures that weren’t expecting it. That’s how niggles become injuries.

The practical rule is to put at least one full day between your leg session and your long run. Two days is better. If your long run is Sunday, lifting Thursday or Friday gives you the buffer you need.

During peak mileage weeks, when your legs are already carrying significant load, consider reducing weights further rather than skipping the session entirely. A lighter session at 50% of your usual working weight keeps neuromuscular patterns sharp without adding meaningful soreness.

Best strength workouts for marathon runners

Heavy (ish) leg day in the gym

This is the non-negotiable: compound lifts are the most efficient use of your limited training time. A consistent heavy-ish leg session reduces ground contact time, improves force production, and delays fatigue. The caveat is low volume and well-managed intensity. You want enough stimulus to adapt, not enough to leave you useless for the next four days.

Plyometrics

Plyometrics train your muscles and tendons to store and release energy quickly — also known as reactive strength. When your foot lands during a run, your Achilles tendon acts like a spring: it absorbs impact, stores that energy elastically, and returns it to propel your next stride. The more efficiently that system works, the less muscular effort required per stride.

For marathoners, a little goes a long way. You’re not training for explosive power — you’re making the spring mechanism more reliable.

Best plyometric exercises for runners:

• Box jumps
• Lateral jumps
• Bounding strides
• Skipping rope

Keep total reps low (20–40 per session to start). Plyometrics can be combined with your heavy lifting session if you’re short on time — do them first, when your legs are fresh and your nervous system is still paying attention.

Daily Mobility & Prehab

Five to ten minutes most days: foam rolling, calf raises, glute activation, basic stretching. It’s the least exciting part of training and the most consistently skipped. It also works.

Reformer Pilates & Yoga

It might scream ‘posh lady in the suburbs in Lululemon tights’, but both Reformer Pilates and yoga deliver strength, mobility, and flexibility in a single session — something most gym routines miss entirely. During marathon training, yoga sits at the intersection of recovery and active conditioning. Most teachers give options throughout, so you don’t need to be performing inversions between track sessions.

Yin yoga

Different enough to deserve a separate mention. Yin yoga holds stretches for minutes, not seconds — long enough to reach the deep connective tissue that conventional stretching and foam rolling barely touches. It’s the closest thing to genuine passive recovery you’ll find outside sleep.

Runner’s leg day vs “normal” leg day

If you’re a regular gym-goer, you’re probably familiar with a legs-push-pull split — the setup that notoriously destroys your legs for several days. For marathon training, that kind of strength work will seriously compromise your plan. Good luck running intervals when you can barely contain yourself sitting down.

During marathon training, keep the structure but drop the intensity significantly. A solid leg session should sit at 60–70% of your one-rep max, leaving 2–3 reps in the tank at the end of each set. This is not the time to chase failure. Leg day now means leaving the gym thinking “I’m not sure that was enough” — because we both know it will hurt more than expected by tomorrow morning.

To give you a sense of what that reduction looks like: if pre-marathon you are squatting 80kg and deadlifting 100kg for 8–12 reps. During training, that becomes 60kg squats and single-leg deadlifts with a 24kg kettlebell. Same movements, different purpose.

How to fit strength training into your marathon plan

The answer is compromise. If you work full time and you’re serious about marathon training, then I suggest you quit your job. Or go part time. 

In an ideal week, your training includes at minimum:

• 1x leg day
• 1x yoga or Reformer Pilates
• 1x yin yoga

Add four runs and you’re at seven sessions, which means at least one double day. That’s normal. What’s less sustainable is cramming strength into the same day as a long run or a hard intervals session — pick one hard thing per day. If you can only manage three runs to make this work, three runs a week can be enough for a marathon if the quality is there.

Common strength training mistakes marathoners make

Not strength training at all

Skipping strength work entirely is like trying to build a house on sand - eventually something’s going to sink or crack. Strength training improves your running economy and reduces your risk of overuse injuries. Even 1 short session per week can make a huge difference.

Going too hard on leg day

Yes, you can squat until you can’t feel your quads, but don’t expect to run well the next day. The goal is to build resilience, not destroy your legs.

Skipping mobility work

Joints move better when muscles fire correctly. Skipping mobility work means your lifts get sloppier, your gait degrades under fatigue, and minor tightness turns into persistent tightness turns into a problem.

Not adjusting weights during peak mileage weeks

Your body can only adapt to so much at once. In peak mileage weeks, scale the weights back even further, or drop a set to avoid digging a recovery hole you can’t climb out of before race day.

Best leg day exercises for marathon runners with lifting experience

This is my personal go-to for marathon training (I also use this during half marathon training). It covers the best leg exercises for runners and hits all your main muscle groups. The goal is to get through the session without shaky legs or a pulled hamstring. No ego-lifting!

Best leg day exercises for marathon runners without lifting experience

If you’re mid-block and adding strength for the first time: go easy, start lighter than you think you need to, and don’t go straight to back squats without checking your form first.

Swap back squats for goblet squats until your technique is solid. Replace single-leg deadlifts with kickback Romanian deadlifts until you’ve built the balance and posterior chain strength for the full single-leg version. The movement pattern matters more than the weight.

If budget allows, two or three PT sessions to learn compound lifts properly will pay off across every future training cycle.

Will strength training make my marathon easy?

No. Nothing will. But it will make you better prepared for the parts that aren’t easy — which is most of it. Stronger legs mean more efficient movement, higher fatigue tolerance, and a better chance of finishing on two legs.