The Last Eight Miles Are a Strength Problem

I've had this conversation inside and outside the gym more times than I can count. It usually starts with a question: Why do so many runners get injured every year?

The numbers are genuinely staggering. Depending on the study, somewhere between half and 8 in 10 runners will sustain a running-related injury in any given year. Think about that for a moment. Look around at the starting line of your next race. A meaningful portion of those people have been, or will be, hurt before the year is out. For a sport with no contact, no collision, and no opponent, that's a remarkable failure rate.

My answer to the injury question is always the same: strength. When your muscles fatigue, your bones and tendons begin to absorb the pounding of running. The structural load has to go somewhere. When the muscles can no longer manage it, something else pays the price.

The pushback I usually get goes something like this: "Well, look at so-and-so. They don't do any strength training, and they're doing fine." My answer is always the same: sure. But what if they did? They'd be even better. That's not speculation, it's what the research shows.

The Problem Isn't Fitness. It's Efficiency.

When we talk about what separates a 3:30 marathon from a 4:30 marathon, the conversation usually goes to mileage, VO2 max, and long runs. Those things matter. But one of the most underappreciated predictors of marathon performance is running economy, the oxygen cost of maintaining a given pace. Two runners with identical VO2 max scores can produce dramatically different race results if one of them is more economical at the speeds that matter.

Running economy deteriorates over the course of a marathon. Your form breaks down, your ground contact time increases, your stride shortens, your posture collapses, and the longer this goes on, the more oxygen you burn to maintain the same pace. By mile eighteen, a runner who has spent months only running has often lost much of the mechanical efficiency they had at mile one.

Strength training changes this equation. The specific mechanism isn't about building bigger muscles or burning more calories. It's about neuromuscular efficiency: how forcefully and how cleanly the muscles fire, how stiff the tendons are, how effectively the body stores and releases elastic energy with each footstrike. These are trainable qualities that respond to resistance, not mileage.

What the Research Actually Shows

A 2022 meta-analysis comparing heavy resistance training and plyometric training in distance runners found that heavy resistance training, particularly at near-maximal loads of 90% of 1RM, produced superior improvements in both running economy and time-trial performance. The mechanism is largely neurological: heavy lifting increases motor unit recruitment and firing rate, which directly translates into how muscles behave at race pace.

More recently, a 2025 randomized controlled trial showed that strength training improves not just running economy in fresh conditions but running economy durability, meaning athletes who lifted maintained their efficiency under fatigue rather than losing it. For a marathon, this is the finding that matters most. The question isn't how efficiently you run at mile five. It's how efficiently you run at mile twenty-two when your legs have forgotten what fresh feels like.

But here is the detail that most runners miss: the type of strength training matters enormously. A randomized trial involving 720 first-time New York City Marathon runners found virtually no difference in injury rates or finishing times between runners who followed a 12-week strength program and those who didn't. The program, however, consisted of light, self-directed bodyweight work, core circuits, hip abductions, and bodyweight squats. Three days a week, ten minutes a session.

This isn't a finding that strength training doesn't work. It's a finding that that kind of strength training doesn't work.

The Gym You Go To Matters

This is where I'm going to be direct, because the fitness industry has made this more confusing than it needs to be.

If your version of "keeping up with strength training" during marathon prep means Orange Theory, Burn Boot Camp, F45, or Madabolic, I understand why you believe you're checking the box. These are energetic, well-marketed programs, and the people who run them are often passionate coaches. But the training stimulus they deliver is fundamentally mismatched with what the marathon performance research prescribes. Their model is built on bodyweight circuits, light dumbbells, and high-repetition metabolic work. That will raise your heart rate. It will not produce the neuromuscular adaptations that improve running economy.

The doses that produce measurable changes in how your body performs at mile twenty-two are heavy compound lifts with progressive overload: barbell squats, Romanian deadlifts, single-leg variations, and loaded carries. Movements that require you to put meaningful weight on the bar and move it through a full range of motion. The research is consistent: near-maximal loading, not near-maximal sweating.

There is a version of "going to the gym" that does nothing for your marathon. It's very popular, it's very comfortable, and it feels productive. Don't confuse activity with the right training stimulus.

What You Should Be Doing

The prescription the evidence supports is straightforward: two to three sessions per week, at least ten weeks of consistent progressive loading, built around compound movements. The concern about adding excessive muscle mass or compromising aerobic development at heavier loads is largely unfounded for recreational athletes. Heavy lifting, programmed alongside a running schedule, does not meaningfully interfere with aerobic adaptation. What it does is improve the mechanical efficiency and force production qualities that determine how you hold together in the final third of a race.

Marathon training puts real demands on recovery, and there's no pretending otherwise. The solution isn't to lift as much as you always have alongside a full mileage ramp. It's to protect the strength work as a non-negotiable, scale volume and intensity intelligently, and understand that the long run and the squat rack are serving the same goal from different directions. Your Progression Fitness coach can help you figure this out.

The Last Eight Miles

The athletes most likely to abandon the gym, or to swap it for a group fitness class that keeps them moving without ever loading them properly, are also the athletes who suffer most in the final third of the race. Not because they're unfit, but because they've trained fitness without training durability. Those last eight miles aren't just an endurance problem. They're structural problems, and structures are built under load.

The runner who shows up on race day having maintained heavy compound lifting throughout training will carry something the mileage-only runner doesn't: legs that know how to hold their form when everything hurts. That's not a small thing at mile twenty-four. That's often the difference between the race you trained for and the one you survived.

Keep lifting. Lift heavy. The road will take care of the rest.

See you in the gym.

—JG