Can you finish an Ironman without losing muscle?
My finger hovered over the button that would confirm my spot at Ironman Copenhagen. “Am I going to lose a bunch of muscle?” I wondered. I’d worked hard to build my strength and size, and I didn’t want to lose it. If anything, I wanted to get even bigger.
But I’d just finished my first Spartan Ultra, and I was already craving another extreme challenge. Ironman, with its grueling 2.4-mile swim, relentless 112-mile bike, and unforgiving 26.2-mile run beckoned.
I’m not alone. The 140.6 is a long, hard day that requires massive cardio and loads of mental toughness. So naturally enough, it attracts all kinds of fitness enthusiasts who want to push their limits and see what they’re made of.
But can it be done without losing a bunch of muscle?
After two Ironman 70.3’s and two Ironman 140.6’s, I can say, it definitely can. But there are limits. First off, the bigger you are, the harder this is going to be.
Take a look at the picture to the right. That’s me at Ironman Elsinore 70.3 in 2023. I’ve added about 20 pounds of muscle over my lifting career. My FFMI is around 21.5, which means in a room full of 100 guys, I’m more muscular than 90 of them.
If that sounds like you or your goals, great! If you’re bigger and more advanced, this article can still help. But be sure to notice when I point out differences for bigger guys.
Second, when you run a full Ironman, those muscles will come at a cost. As you’ll see below, strength and endurance training are antagonistic. You won’t be able to train as hard or as often as dedicated triathletes. Moreover, upper body muscles are just dead weight you have to lug around the Ironman course. Bigger guys will always be slower!
If, however, you’re out there to push your personal limits in both strength and endurance, then this article is for you.
Here are links to the three main sections so you can skip around.
How to Minimize Acute Fatigue & the Interference Effect
Have you ever been at the finish line of an Ironman? The words bodybuilder, muscle bound, and strong man don’t spring to mind. Why is that? Why is it so hard to get bigger, fitter and faster? And what can we do about it?
To answer these questions, we need to dive into a bit of exercise science.
The Interference Effect
At its simplest, exercise is a matter of creating physical stress which leads to physical adaptation. When you lift something heavy, it stresses your body. All that stress, in turn, causes muscle growth. Likewise, when you go for a run, it causes a bunch of stress that improves your endurance. It's how our bodies adapt to changing environments.
But here’s the problem.
Strength training and cardio compete for the same resources along the same pathways. They are antagonistic. It’s like your body is playing tug-of-war between strength gains and cardiorespiratory fitness. When your body is adapting to one, it is far harder to adapt to the other.
So if you do a hard bike workout and then go straight into squats, you just made both workouts less effective. Your legs won’t adapt as much in response to the bike workout, and they certainly won’t respond well to the squats.
It’s as if your body gets so confused by the conflicting demands, it just gives up altogether.
Acute Fatigue
The Interference effect isn’t the only thing to consider. Strength and intense cardio training both create huge amounts of acute fatigue. They make you tired which makes it much harder to do any following activity.
Imagine you do a full upper body strength workout, and then immediately hop on your bike. Sure, your legs are fresh and should adapt well to cardio, but you’re probably too tired to give it your best effort. Instead, you suffer through a marginal performance and as a result you only get a marginal fitness stimulus.
If instead you had given yourself ample rest between sessions, you would have crushed your bike session pushing yourself hard enough to stimulate meaning adaptations.
Ok, if those are the problems, what’s the solution?
4 ways to minimize the interference effect and acute fatigue.
First, whenever possible, separate your cardio and strength sessions by 24 hours. If you can get your strength training down to two sessions per week, it helps immensely. (See below for scheduling strategies)
Second, if you must train strength and cardio on the same day, try to separate the sessions by at least six hours. An AM-PM split is best.
Third, the interference effect is mostly local, so upper body training is not going to have a strong negative effect on your run. Similarly, leg day isn’t going to have a big effect on your swim. Generally, an hour or two of rest can be enough to wipe away most of your acute fatigue.
Fourth, you should also prioritize your training. You don’t need to be fresh for every workout. For example, doing a zone 2 run on tired legs is way better than doing a tempo run on tired legs. So if you do a leg workout Sunday morning, and then go for a long run in the evening, that’s probably ok. Your legs are going to be roasted after the bike anyway, so you can think of it as good practice.
How to Program Your Lifting to Maintain Muscle During Ironman Training
Not only does cardio interfere with muscle growth and strength training, but if you do too much cardio, it actively signals muscle loss. Three factors determine how much muscle loss cardio will induce.
Intensity: Higher intensity cardio signals more muscle loss than lower intensity cardio. So if you’re on your feet walking all day, that doesn’t signal muscle loss, but a tempo run does.
Duration: The longer your training session, the more likely it is to signal muscle loss. Generally, anything over an hour is going to be catabolic.
Volume: The final factor is your total weekly training volume. If you train a lot, you’ll signal more muscle loss.
Naturally enough, this means Ironman training is especially catabolic. Of course, this makes total sense. Your body isn’t stupid. If you start training for an Ironman, your body can do the math. It doesn’t want to take 20 extra pounds of muscle on a 112-mile bike ride and a 26.2-mile run. That would be stupid. Absurd even. So your body wants to shed the extra weight.
To combat this, you need to send a strong anabolic signal. You need to lift weights.
Now, we need to thread the needle here. If you lift too much, your Ironman training will fall apart. You’ll keep your muscle, but you won’t finish your Ironman. What you need is a minimum-effective dose.
Fortunately, we don’t have to guess. Studies have found that 4-6 sets of lifting per muscle group is sufficient for most intermediate and advanced lifters to maintain their size and strength.
This assumes a couple of things.
First, it assumes you’re getting enough calories. (More on diet later)
Second, it assumes you are not doing tons of cardio.
This means that an absolute minimum effective dose is going to be around 4-6 sets per muscle group per week. A truly advanced lifter would almost certainly need more lifting volume to maintain his size during Ironman training. While for intermediate lifters, it offers a great starting place and is, in fact, the volume I ended up using.
Here’s what my training schedule looked like during my Ironman training.
A few quick notes on this program:
If you’re more advanced or need more volume you can try adding 1-2 sets per exercise. You’ll need to monitor your strength and weight to see if it’s sufficient.
Notice that it’s a two-day split. This gives you a chance to send two anabolic signals per week. Don’t do all your lifting in one day.
You can of course substitute any exercises that work similar muscle groups. For instance, you could substitute bench press for loaded push-ups.
I recommend that you find the exercises and rep ranges that feel best on your joints and cause the least fatigue. This will vary a bit from individual to individual.
Your legs take a beating from all the running and cycling. So about 10 weeks out from Ironman Cork, I cut out all leg strength training. My legs are the least developed part of my body. If you have advanced legs, you’re going to have a hard time maintaining your strength and size. Sorry, I can’t think of a way around that.
About 4 weeks out from the race, I dropped all strength training. This means I probably lost a little muscle at the end, but it was worth the added Ironman training to me.
If you’d like to learn more about how I train for strength and size, check out these articles:
Ok, so that’s the strength side of your schedule. Now, let’s take a look at the Ironman side.
How to add Ironman Training to your Schedule
Ironman training is time-consuming. Many programs have you training 7-10 hours a week for the better part of five or six months. As you approach your race, the training can extend to 12-15 hours a week.
A typical program will recommend that you:
Swim 3x per week
Bike 3x per week
Run 3x per week
When you add in family commitments, recovery time, lifting sessions, and work responsibilities, your week becomes quite packed. If you have a life outside of training, you'll need to allocate less Ironman training time.
This is further complicated by the necessity for recovery. Even lifting twice a week can make Ironman training more challenging. So, even if you have all the time in the world, you can't train intensely every day; your body will break down.
Fortunately, I can say that many Ironman finishers do FAR less than the majority of internet training plans, and yet they still finish strong.
What’s their secret?
They aren’t noobs. Similar to lifting, the longer you engage in endurance training, the more your body adapts. Your heart becomes larger and stronger, your capillaries become denser, and your mitochondria become denser and more efficient.
This is crucial because the adaptations themselves are not antagonistic. Your body is perfectly capable of having a significant muscle mass alongside a large and strong heart. It's only the training stimulus and active adaptation that can be antagonistic. So, if you take your time and progress gradually, you can build up your endurance while preserving muscle mass.
Additionally, swimming has a substantial skill component, as does cycling and even running. And mental toughness is another significant factor. Once you've completed an Ironman 140.6 or 70.3, you know what it takes and can push yourself harder next time.
Therefore, the amount of training required to complete an Ironman depends on your training experience. I highly recommend working your way up to a full Ironman and starting with a flatter, faster course. Flatter courses penalize extra muscle mass less than hilly courses.
That's how I approached it. I began with a 70.3 event in Elsinore (elevation 450 meters), followed by the 140.6 event in Copenhagen (elevation 1,100 meters). Both were relatively flat and fast. Then I moved up to Ironman Cork (elevation 1,700 meters), which allowed me to gain experience and increase my training age.
So, how much training do you need? For my first two Ironman events, I followed a low-volume plan that looked something like this:
Swim 2-3x per week
Bike 2x per week
Run 2x per week
I was a bit nervous about the swim, so I focused on that more than anything.
If you’d like to learn more about training for your first Ironman 70.3, check out my article, What to expect: A first-timer's guide to the Ironman 70.3.
In 2023, I decided to scale things back a bit further. My program ended up averaging something like this for my next two events:
Swim 1x per week
Bike 1-2x per week
Run 1-2x per week
Despite the reduced training volume, my times for all three disciplines improved. This year, I shaved 10 minutes off my half Ironman time (6hrs, 8 min) and completed Ironman Cork, which was a significantly tougher course than Copenhagen.
Swimming, in particular, is a skill-based discipline where I was able to make significant improvements with reduced training. I finished the swim at Elsinore in 38:34. Of course, more training would likely have resulted in greater improvements, but with this reduced schedule, I managed to maintain my strength, strike a reasonable work-life balance, and still make progress.
Combining strength and Ironman training, my schedule looked something like this most weeks. Notice how I aimed to minimize the interference effect and acute fatigue.
Finally, here are the major benchmarks I make sure to hit before a full Ironman. The more advanced your training age, the easier it is to achieve these goals.
Swim: Complete at least one 4-kilometer pool swim before the race, and supplement this with several open water swims. The aim is to enter the water on race day with as little swim anxiety as possible. It should feel like an extended warm-up.
Bike: Include 2 five-hour rides and 1 6-hour ride with elevation that’s similar to your race. You can build mountains of endurance on the bike. Embrace it.
Run: Gradually build your long run up to 18 miles. It's perfectly fine to walk portions, but be sure to maintain a brisk power walk.
Notice how much I prioritize cycling. It’s often said that an Ironman is a bike race with some swimming and running. It’s true. Plus, cycling is really easy on your joints, so there’s no excuse for not doing a ton of it.
How to fuel your training to preserve muscle during extreme cardio
Like I said above, strength and cardio compete for the same resources. You can think of them as two very unreasonable three-year-olds fighting over the last marshmallow. On top of that, cardio is catabolic while lifting is anabolic. When you train extreme endurance, your body assumes you must be running from a wooly mammoth or the zombie apocalypse. So, it’s perfectly happy to start tearing things down to burn them for fuel. Generally, this will be fat, but unfortunately, muscle works as fuel too.
Conversely, strength training is anabolic. It stimulates muscle growth. Your body assumes you’re staying and fighting the wooly mammoth. It wants to get bigger to survive.
With that in mind, here’s how I approached my diet.
1) You need calories.
This is not the time to worry about abs. Each time you do an epic Ironman workout, you’ll put your body into a massive caloric deficit and a catabolic state. For instance, on my last big ride before Cork, I rode 6 hours and burned over 4,000 calories. That’s at the extreme end, but you get the idea. To avoid losing muscle you need to eat plenty of calories. Over the course of my Ironman training I gained a couple pounds.
If you want to really optimize this process, here’s what I did. Over the preceding winter, I leaned out. The pic on the right is me, from February 2023. This not only made it mentally easier for me to gain some fat during training (I was nice and hungry!), but it kept my overall weight a bit lower on race day.
If you’re looking for some diet tips, check out my article, 10 ways to manage your hunger for year-round visible abs.
2) You need protein.
If you’ve built some muscle, then you know the importance of protein, so I won’t belabor this point. You’ll want to eat around 1g/lb/day. Be sure you eat a protein rich meal before and after your training. If you want to learn more about optimizing your protein intake, check out my article, Optimizing Protein Intake: Build Muscle, Lose Fat, Boost Recovery.
3) You want to get enough fat.
This isn’t the time for a low-fat diet. Eating enough fat will keep your injury risks down and keep your hormone levels up. This is particularly relevant with regards to your anabolic hormones. If you want to keep your muscle, you want plenty of natural anabolic hormones!
I aimed for at least 20% of my calories to come from quality fats and probably landed a bit higher than that.
4) You need carbs.
Carbs are the single best fuel for endurance training. They can also help you preserve your muscles.
First, I highly recommend you eat plenty of food and especially carbs during your long run and bike. Remember that I burned 4k calories on my long 6 hour ride. Not only is this important for minimizing muscle loss, but it’s important practice for race day. At my first full Ironman I had significant stomach cramps, and at my second half ironman I had muscle cramps. It has taken a fair bit of trial and error to get my race day nutrition dialed in. It’s best to get started during your training.
Second, you want to eat a carb rich meal before and after your training. This will help you recover and minimize muscle loss. On day’s you train 2x this is especially important. After the first workout, you really want to replenish your glycogen stores to ensure adequate recovery before the second session.
Bigger, fitter, faster!
Crossing the finish line at Cork felt amazing. It was a truly brutal race. At the time, I couldn’t care less that I’d preserved my muscle. The euphoria of finishing was all encompassing. But as the days turned into weeks, my eyes turned to hypertrophy training. As I write this, I’m in the middle of a massing phase. I’ve put my cardio on maintenance and turned my full attention to adding more muscle.
I’m not done with Ironman. I plan to race at least a 70.3 in 2024, and I have at least a few more 140.6’s left in me. I fully expect to finish my next Ironman faster and bigger. I don’t think I’ve hit my peak.
I bet you haven’t either. I hope you are able to use some of my insights to push yourself further than you thought possible to get bigger, fitter and faster!
Thanks for reading!
If you enjoyed this article and would like to learn more what it’s like tackling an Ironman, check out my article, Ironman Cork Review: battling the wind and waves in Ireland.
