Cross-Training for Marathon Prep
Who says all your aerobic work has to come from pounding pavement? Cross-training—cycling, swimming, rowing, hiking, even elliptical—can seriously boost your marathon prep without trashing your legs.
Here’s the idea: you still get those long cardio sessions in, but without the impact. Can’t handle a 3-hour run? Do 90 minutes of running followed by a long bike ride. Nursing an injury? Swap the long run for a big swim day or a weekend hike.
Why It Works
Marathons aren’t just about muscles—they’re an aerobic war of attrition. And your heart, lungs, and energy systems don’t care if you’re getting your training from a bike or your sneakers—they just want time under tension.
Long cardio sessions on a bike, for instance, can train your energy systems to go the distance. Plus, activities like swimming or cycling work different muscle groups, which helps balance things out. That can mean better form, fewer overuse injuries, and honestly—less mental burnout.
You don’t need to run every day to build endurance. You just need to stay active and keep challenging your aerobic engine.
Real-Runner Bonus: Mental Refresh
Ever get sick of running? I do. Sometimes swapping a tempo day for a tough spin class can be the difference between burnout and bouncing back. Plus, if you’re busy, it’s nice to know you can still build fitness with a gym bike or pool when your schedule or body won’t let you run.
Some marathoners actually increase their total training load this way—fitting in more hours of cardio than their legs alone could handle.
The Upsides
- Less pounding = lower injury risk.
- Active recovery: A chill bike ride the day after a long run keeps blood flowing and soreness in check.
- Injury fallback: If you tweak something, you don’t have to hit the panic button. Swap in pool running or cycling and keep your fitness alive.
I’ve coached runners who’ve done 80% of their training on a bike and still crushed their race—especially triathletes who come in with monster aerobic bases from all the swimming and cycling.
But… Specificity Still Matters
Here’s the catch: no matter how fit you get on a bike or in the water, running a marathon is its own beast.
Running is high-impact. Your legs, joints, tendons—they need to feel that load. I’ve seen athletes with insane cardio from cross-training totally gas out on race day—not because they weren’t fit, but because their legs weren’t hardened to the task.
So cross-training is great, but it’s not a full substitute. It should support your running—not replace all of it.
Also, keep in mind the logistics: bikes, pools, gear… it can be a hassle. And if you’re new to something like swimming, it might wear you out faster than it helps.
Coach Story Time
Years ago, my Achilles flared up midway through marathon prep. My physio shut down long runs. I panicked. I was only 8 weeks out.
So I got on the bike—hard. Every Sunday, instead of my planned 20-miler, I did a 3-hour ride in the Bali hills. Sweaty, leg-burning misery—but it didn’t aggravate the Achilles.
I also did deep water running in the pool—45–60 minutes, mimicking the running motion with a float belt. I stayed consistent. And when race day came?
Guess what? I finished strong.
I hadn’t run longer than 15 miles going in, but aerobically, I felt solid. The legs got tired in the final 10K (as expected), but I made it to the start line healthy and crossed the finish line without bonking.
That’s the power of smart backup plans.
Substituting Long Runs with Cross-Training: What Actually Works
I’ve seen this done, and not just on paper.
One of my coaching friends trained for a marathon almost entirely on the elliptical after she got sidelined by a stress injury. On her long-run days, she hit the elliptical for 90 minutes straight—high resistance, dripping sweat—to mimic the time-on-feet.
She still managed two short runs a week to stay sharp. Race day came, and she finished. Slower than she’d hoped, sure, but strong and pain-free.
She told me afterward, “The hardest part was my feet — they were dying by mile 20.” And that tracks. No machine can fully toughen up your feet like pavement does. But her heart and lungs? Rock solid.
Coach’s Tip
If you’re swapping long runs with cross-training, try a combo move: run half the long-run distance, then jump on the bike or hit the pool to finish.
Example: 10 miles on foot, followed by 60–90 minutes of steady cycling. Boom — you get that marathon-style fatigue without as much impact trauma.
I’ve also had injured runners thrive with aqua jogging. It’s mind-numbing, yes, but it mimics running better than most alternatives.
And whatever you do, don’t drop running entirely. Even if mileage is low, you’ve gotta keep your muscles and tendons used to the movement.
Use your rest days or backup days for cross-training, and still apply that same “build-it-up” mentality—gradually increase the intensity and time, just like you would mileage.