Within 7 days, Greenville has experienced an ice storm and a snow storm. Needless to say, we've been doing a lot of our training indoors over the past week.
Indoor training, whether it's running on the treadmill or riding on the trainer, is common for most endurance athletes. It’s efficient, controlled, and time‑effective. But when it comes to supporting those sessions with proper fuel and hydration, this is where many athletes struggle to get things right.
Some athletes intentionally underfuel, assuming that indoor sessions “don’t count” as much as outdoor workouts. Or athletes feel safe cutting calories because there's no risk in running out of fuel - you just stop and you are home. Others, however overfuel, grazing out of boredom or because nutrition is sitting on a table within arm’s reach.
The sweet spot lies in fueling intentionally.
Why Indoor Workouts Change Your Fueling Needs
Indoor training is different from outdoor training in a few key ways:
The Overfueling Trap: Easy Access + Boredom
On the flip side, indoor setups make it very easy to overconsume:
How to Fuel Indoor Workouts
1. Fuel Based on Session Type, Not Location
Use the same framework you would outdoors:
2. Plan your fueling
To avoid mindless eating/fueling and boredom-based decisions:
Liquid carbs are especially useful indoors:
You sweat more indoors due to:
Indoor training is different from outdoor training in a few key ways:
- Steadier power/pace → fewer natural breaks (no coasting/resting)
- Less cooling → higher sweat rates and cardio strain
- Higher mental fatigue → fueling mistakes from boredom or distraction
Even if your watch, power meter or app shows similar numbers to training outside, indoor sessions often feel harder—and physiologically, they often are.
The Underfueling Trap: “It’s Just Indoors”
Many athletes assume:
The Underfueling Trap: “It’s Just Indoors”
Many athletes assume:
- They're burning fewer calories inside
- Shorter or more controlled sessions don’t require fuel
- They can “make it up later”
- Treadmill running can be more metabolically demanding due to constant pacing, being "locked" into an effort, less stopping/walking and reduced air resistance.
- Trainer rides often produce more effort (and fatigue from constant pedaling) than outdoor rides of the same duration.
- Repeated underfueling indoors adds up, leading to poor recovery, stiff muscles and increased injury risk
Bottom line: If it’s a quality session (tempo, intervals, long run/ride), it deserves fuel....indoors or out.
The Overfueling Trap: Easy Access + Boredom
On the flip side, indoor setups make it very easy to overconsume:
- Bottles are easy to access
- A table of snacks (gels, chews, applesauce, candy, coke) within arm's reach
- Eating to stay entertained (snacking is a distraction) rather than to meet physiological needs
- Disrupt energy balance goals
- Make it difficult to truly understand fueling and hydration needs
- Create GI distress during harder efforts
How to Fuel Indoor Workouts
1. Fuel Based on Session Type, Not Location
Use the same framework you would outdoors:
- Easy, <60 minutes: 30-40g carbs + 16-20 ounce water
- Moderate to hard, 60–90 minutes: ~30–50 g carbohydrate per hour + 20-24 ounce water/hr
- Hard or long, 90+ minutes: 60–90 g carbohydrate per hour + 24-28 ounce water/hr
2. Plan your fueling
To avoid mindless eating/fueling and boredom-based decisions:
- Decide before the workout what you'll consume (and when)
- Have a pre-workout snack in the hour before the training session
- Prepare bottles (hydration) and fuel ahead of time
- Have next to you only what you plan to use (ok to have extra available nearby)
Liquid carbs are especially useful indoors:
- Easier to digest when intensity is steady or high
- Help meet carb needs without overdoing solid foods
- Similar to outside fueling/hydration needs
You sweat more indoors due to:
- Minimal airflow
- Higher ambient temperature
- No coasting or downhill breaks
- Stronger "locked in" efforts
Indoor Hydration Guidelines
- Start your workout in a hydrated state
- Keep on a schedule (don’t rely on catching up mid‑session)
- Aim for at least 16–24 oz per hour, adjusting for sweat rate.
- Make sure your sport drink contains sodium (at least 250-400mg sodium per hour)
Keep Yourself Cool
Fueling and hydration work best when paired with cooling.
Use at least one strong fan (two is better).
Fueling and hydration work best when paired with cooling.
Use at least one strong fan (two is better).
- Better cooling = lower cardio drift
- Better cooling = lowered RPE
- Better cooling = more accurate fueling needs
- Better cooling = easy digestion and absorption
- Better cooling = more productive training session
Key Takeaway
- Indoor workouts often require equal or greater fueling than outdoor sessions.
- Underfueling indoors is common due to the belief that indoor workouts don't require as much fuel as outdoors.
- Overfueling happens when nutrition isn’t planned.
- Fuel the work, not the setting.
- Hydration (fluids and sodium) and cooling are critical indoors.