Eating When It's Easy: Base Training Nutrition

What's the best way to fuel for long, easy "base mile" workouts?

For those not familiar with “base miles” or “base training,” it means doing long, easy-to-moderate workouts to build up aerobic endurance. This applies to any endurance sport, including running and cycling.

The good news is that it’s relatively hard to screw up base training nutrition. Yes, you are exercising for long periods of time, so you need to eat and drink something, but it doesn’t really need to be dialed in. As long as you don’t completely deprive yourself of food and water or eat a whole turkey mid-effort, your fuel choice shouldn’t have a massive impact on your workout.

A little more about base training before we talk fuel.

A lot of cyclists I know hate base training because, by definition, you can’t sprint, hammer climbs, or do anything else decidedly macho. Some runners I know find it tough because you actually need to focus on slowing down.

I don’t mind base miles on the bike because it’s a nice chance to chat with my pals—and I’m a blabbermouth. However, I struggle with running base miles. I tend to run solo and it messes with my flow state. Also, not suffering is boring.

But I continue to suffer through not suffering because it’s more-or-less universally accepted that base miles matter. A broad review of “training intensity distribution among well-trained and elite endurance athletes” in the journal Frontiers Physiology suggests that making 80 percent of your workouts “high volume, low intensity training” is just the ticket for the fast train to Badassville.

Base training improves your aerobic threshold.

As we’ve discussed before, your body shifts between burning fat and glucose/glycogen for fuel. The easier you go, the more you burn fat. The harder you go, the more glycogen you tap.

Base training improves your aerobic threshold. If you do it on the regular, you’ll be able to exercise harder before going anaerobic—which is when your body switches to using glucose and glycogen instead of fat.

The benefit of increasing your aerobic threshold is that your body will become better at fueling from its own resources (body fat) and be less dependent on eating and drinking sugar. Of course, if you’re going hard, you’ll still need to take in fuel, but you’ll be able to go longer before you bonk.

Thanks for the physiology lesson, but what should I eat?

You’re not going hard during base miles, so you burn glycogen slower. With that in mind, you don’t need to be as ultra-focused on consistently eating fast sugar. You also don’t need to worry about topping off glycogen before heading out.

That said, you still need fuel; you’re still burning calories—probably a ton of them! Also, the transition from fat to glycogen utilization isn’t a light switch; it’s a sliding scale. So, even if you’re going super slow for super long, eventually you’ll still run low on glycogen.

Long rides aren’t a great time for fasted state training. If you’re going longer than a couple hours, still stick to the 30g-60g (120-240 calories) of carbs an hour guideline, but it can be on low side—and it doesn’t need to be fast sugar. Balanced snacks that combine carbs, protein, fat, and even fiber are great.

Personally, I lean into “real foods” during base training. Standards include fruit, trail mix, and just about any kind of sandwich that’ll keep in a sweaty jersey pocket for several hours. (Tuna salad is a hard pass, mostly.)

Running brings a different set of challenges because tolerating anything but sugar as your gut bounces up and down can be rugged. Consider using base miles to do some “gut training” with harder-to-digest foods if ultramarathons are on your roadmap. Otherwise, you might want to stick to the sugar.

And what about drinking?

You still need to stay hydrated. However, if you’re not exerting yourself, you’re probably not sweating as much, so if you want to take a break from electrolytes and drink straight water, you’ll probably be okay.

That said, electrolytes never hurt. And if you’re training in hot climates, they tend to be a good thing.

The foremost expert on base training nutrition is you.

Spend some time researching nutrition for base training and you’ll find a lot of expert advice with a lack of scientific sources. In fact, one of the coolest sources I found on the topic actually turned it around and asked athletes what they do.

While I stand by my advice above, it’s largely based on common sense, personal experience, and feedback with other (successful) athletes. I recommend using these suggestions as a base. Pay attention to how you respond to different ways of feeding during base training—and lean into the things that work best for you. Because base miles are, by definition, lower impact, they’re also a safer space to experiment with nutrition and learn about your body.

No matter what you’re going to try, here’s one piece of advice that applies to everyone. If you’re going long, always keep a piece of food and a water bottle on hand, just in case. Maybe just not a tuna sandwich.