Stop Fading on Long Runs 4 Weeks Before Marathon Training: Best Fatigue Fighting Strength Exercises
- Marie Whitt
- May 11
- 6 min read
A few months back in the PT clinic, I was working with a runner with multiple races on his upcoming calendar, struggling with repeat knee.
But as we talked more, I realized that while, yes, the knee was holding him back from running longer and faster...
The moment that really stuck with him was what happened during a half marathon he ran in Atlanta.
He told me:
“I felt good through mile 8 or 9… but by mile 10, my legs were just dead. I felt like I completely fell apart.”
And he kept coming back to that phrase during the evaluation: “I just fell apart at the end.”
So I dug deeper and asked how did his running feel during the race?
What stood out to me was his response that he wasn’t out of breath.
He didn’t feel aerobically maxed out.
His legs just… couldn’t keep up.
So naturally, he assumed:
Maybe he didn’t run enough mileage in preparation for the race
Maybe his long runs weren’t long enough
Maybe he just needed to take time to build better endurance
And I told him, these are all viable options however...
Given his symptoms (especially paired with the knee pain), there was something else going on.
I told him, this is likely a muscular capacity problem.
Meaning, your muscles haven’t been trained to handle a certain amount of work such as long distance, intensity and speed, or both.
Because here’s the key:
You can have adequate aerobic fitness (running fitness and endurance)…and still have your race limited by your legs.
And that’s exactly what happened for this runner.
His lungs were ready, but his legs were his weak link.
So how did we diagnose this?
We used what I call my The Leg vs Lungs Framework to help determine whether his race fell apart because of a mileage/endurance problem or a leg-strength problem.
Because chances are, if you're feeling like your legs are dead before you finish your long run and you're falling apart the last few miles, this could be happening to you too:
The Leg vs Lungs Framework
Take a look at your current strength training and ask:
Are most of your exercises bilateral (both legs working at the same time)?
Are you finishing sets thinking: “I could’ve done 5+ more reps”(instead of 2 more max)?
Are you doing anything that trains eccentric quad control?
If you answered:
“yes” to mostly bilateral work
“yes” to not pushing close to fatigue
or “no” to eccentric work
…this is likely your gap. But if you're unfamiliar with eccentric strength, allow me to elaborate.
Eccentric What?
Eccentric quad strength is often overlooked because it’s a bit more nuanced.
You don’t often see it mentioned in Runner's World.
And you don't just accidently stumble into strength training it.
Quick breakdown:
Your quad muscles work in two ways:
Concentric → shortening (like going up stairs)
Eccentric → lengthening under load (like going down stairs)
So imagine this:
You’re slowly lowering yourself down a single step over 2–3 seconds.
That control? That’s eccentric strength.
And it matters a lot for running, especially as we start to run with greater amounts of fatigue.
Because as you accumulate fatigue during a race, this is often the first thing to go as both mileage and speed are wearing you down.
When you haven't deliberately trained this kind of strength, this is why your legs can feel like they just “die” late in a run, in addition to the potential lack of muscular work capacity we talked about above.
So instead of just running more…
I want to show you how to stop your legs from being your weak link and instead build fatigue-resistant, endurance-ready legs.
Why Your Legs Feel Dead at the End of Long Runs (And How to Fix It)
Circuit:
4 sets each // LIGHT & medium weights
*super set just means bite-sized circuit. Rest as needed between ea set.
SUPER SET 1:
Single-leg hip thrust
8 reps ea leg X heavy-moderate weight
Controlled Reach-Back Step Down
6 reps ea leg X body weight to light weight
SUPER SET 2:
Front foot Elevated Split Squat (weighted isometric)
10-20 sec hold ea leg X moderate weight
Lateral Lunge
6 reps ea leg X moderate-heavy weight
How to Build Fatigue-Resistant Legs for Long Runs
Single-leg Hip Thrust
Don't be scared off by thinking you need a big ol' barbell...
THE SECRET: you can do this at home. With a couch. And a dumbbell. But don't miss out the magic of stronger glute AND hamstrings. Yes, eccentric quad strength is crazy important; without strong quads, you can't go the distance in your long runs. But strong hamstrings are what carry you to the finish line.
This exercise places you in a position that looks like running, challenging the strength and power of your posterior chain, both glutes and hamstrings working together . Because remember: your quads are one muscle group. but they never work alone. They're opposites, or antagonists, are teammates. And we need all the team members to be equally strong.
Controlled Reach-Back Step Down
Nope, this is not your run-of-the-mill step down. Stick with me here.
PRO TIP: the best cue I can give you is reach those toes back! Pretend there's a target behind you that you have to boop with your toes. (This is NOT just stepping down off a box or a bench!) When you are actively reaching back behind you, you are training your swing phase.
So not only are you in a position that resembles your running stride, but you challenging your single leg balance, your eccentric quad control, and your glute strength all at once. The reason I love this exercise: you glutes and your quads are learning how to balance work together in a position that looks like your running stride while actively getting stronger at the same time.
Front Foot Elevated Split Squat (weighted isometric)
It's tiny, but mighty.
THE KEY: don't discount a good, weighted isometric. These can be extremely helpful with building stronger, fatigue resistance quads (think: time under tension) and happier patellar tendons in case you're constantly battling runner's knee as weekly mileage climbs. And yes, you can do this without your front elevated on a yoga block, plate, old textbook etc. But I want you to try it...
Elevating that front foot helps to turn this basic isometric into a harder-working, running specific, quad blasting exercises that ALSO works on restoring hip internal rotation. Think of this exercise as a double-whammy: yes, your quad is work hard here (don't forget to shift 80-90% of your body weight forward). But in order to even get into this position, you are asking your hip to enter into a greater range of mobility (specifically hip internal rotation). Nothing ever works in isolation so opportunities like this one that allow you to build muscular strength while also working on hip mobility are what build stronger, injury-resistance runners.
Lateral Lunge
Seems basic, I know but...
THE REASON: I've been missing out on lateral lunges because they can be awkward to perform correctly. But they're great for building glute and quad strength in what we call the frontal plane, or moving side to side. Yes, we run forward, however, our glutes still help control the minor, but important rotations that occur within our hips with every stride we take.
Not to mention, for my runners struggling with repeat glute med tendinopathy, weak glutes in general, or runners with repeat knee tendon issues, this specific movement is great loading tendons under heavy load but also with "time under tension", meaning this specific movement take a bit more time to complete each rep.
This increased time and demand for control can be final piece in both glute strength, knee tendon rehab, and building long-run-resistant legs.
NOTE: when doing a lateral lunge, I want the weight in the opposite hand of the working leg. Meaning, if you're lunging with your L leg, I want the weight in your R hand. As you lunge left, actively bring the weight in front of your L shin, or very close to it. I find this cue helps you to sit back into that left hip more, helping you complete the movement more successfully.
WRAPPING UP
So if you’ve been finishing your long runs feeling like your legs just give out…
I need you to remember:
It’s not always your endurance.
And it doesn’t always mean you need more miles.
Sometimes, it’s simply this:
Your legs haven’t been trained to handle the load yet
Because remember, you can be aerobically ready, and still be limited by your strength.
So instead of asking, “Do I need to run more?”
Start thinking,“Are my legs actually prepared and strong enough to hold up to the mileage I'm asking of them?”
Because when you build the kind of running-specific strength that holds up at mile 10, 19, and beyond...
That’s when your marathon training starts to feel different.
And when you stop falling apart…and start finishing strong.
Dare to Train Differently,
Marie Whitt, PT, DPT //@dr.whitt.fit
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