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During-Workout Nutrition

Fueling during exercise for sessions over 60 minutes.

📖 The Story​

The Wall​

Mile 18 of the marathon. Sarah has been running for over two hours. She feels great until suddenly she doesn't. Her legs turn to lead. Her pace drops dramatically. Her brain goes foggy. She's "hit the wall"—the dreaded bonk that ends races.

She didn't fuel during the run. She thought she'd trained her body to burn fat. But at race pace, her body needed carbs, and she ran out.

The CrossFit Open workout: 20-minute AMRAP. Jake starts strong but by minute 12, he's moving at half speed. He didn't think a 20-minute workout needed fuel. But high-intensity glycolytic work burns through carbs fast.

The long bike ride. Elena rides for 4 hours on a beautiful Saturday. She packed water but no food—didn't want to stop. By hour 3, she's wobbly, irritable, and barely turning the pedals. She limps home and sleeps for 3 hours.

All three bonked for the same reason: They depleted their glycogen without replacing it during the activity.

The solution: During-workout nutrition—consuming carbohydrates while exercising to maintain energy supply.

When you need it:

  • Sessions over 60-90 minutes
  • High-intensity work over 45 minutes
  • Multiple sessions in a day
  • Competition with multiple events

When you don't:

  • Sessions under 60 minutes (usually)
  • Low-intensity, short-duration activity
  • Strength training with rest periods (glycogen recovery between sets)

🚶 The Journey​

What Happens During Extended Exercise

Glycogen Depletion Timeline:

DurationGlycogen StatusFuel Recommendation
0-60 minAdequate for most peopleWater only (usually)
60-90 minBeginning to deplete30g carbs/hour beneficial
90-120 minSignificantly depleted30-60g carbs/hour needed
2-3+ hoursCritically low60-90g carbs/hour (trained gut)

Key Variables:

  • Intensity: Higher = faster glycogen use
  • Pre-workout fuel: Better fueled = longer before needing more
  • Training status: Trained endurance athletes store more glycogen
  • Individual variation: Some deplete faster than others

🧠 The Science​

Why During-Workout Carbs Work​

1. Maintaining Blood Glucose

During extended exercise:

  • Muscle glycogen supplies contracting muscles
  • Liver glycogen maintains blood sugar
  • As liver glycogen depletes, blood sugar drops
  • Low blood sugar = bonking, cognitive impairment, fatigue

Ingested carbs during exercise:

  • Rapidly absorbed and enter bloodstream
  • Spare liver glycogen
  • Maintain blood glucose levels
  • Preserve CNS function (brain runs on glucose)

2. Sparing Muscle Glycogen

When you consume carbs during exercise:

  • Muscles can use blood glucose directly
  • Less reliance on stored muscle glycogen
  • Glycogen lasts longer
  • Exercise can continue longer at higher intensity

3. Research-Supported Recommendations

Activity DurationCarb RecommendationEvidence Level
<45 minutesNot neededStrong
45-75 minutesRinse mouth with carbs (can help)Moderate
1-2 hours30-60g/hourStrong
2-3+ hours60-90g/hour (requires training)Strong

Carbohydrate Absorption Limits​

Single carb source (glucose or sucrose): ~60g/hour max absorption

Multiple transportable carbs (glucose + fructose): Up to 90-100g/hour

  • Different transporters in the gut
  • 2:1 ratio glucose:fructose optimal
  • Requires gut training

Practical implication: If you need more than 60g/hour, use products with mixed carb sources.

The Gut Training Effect​

Your gut can be trained to:

  • Handle more carbs during exercise
  • Reduce GI distress
  • Absorb carbs more efficiently

How to train:

  • Practice race nutrition during training
  • Gradually increase intake over weeks
  • Don't try new fueling strategies on race day

👀 Signs & Signals​

When You Need During-Workout Fuel

SignalWhat It MeansAction
Sudden energy drop after 60+ minGlycogen depletingConsume carbs immediately
Mental fog during long sessionBlood sugar droppingCarbs + continue
Pace/power dropping steadilyRunning out of fuelCarbs to maintain output
Legs feel heavy, coordination offCNS fatigue from low glucoseCarbs urgently
Irritability, negative thoughtsBrain needs glucoseCarbs + recognize the sign
ShakinessHypoglycemia riskCarbs immediately
Nausea from fuelToo much, too concentrated, or wrong productReduce amount, dilute, change product
GI distressGut not adapted OR too much fat/fiber/proteinTrain gut, simplify fuel

Pre-Bonk Warning Signs:

  1. Early: Feeling "off," slightly foggy
  2. Moderate: Noticeable fatigue, pace dropping despite effort
  3. Severe: Confusion, disorientation, unable to continue

Prevention is easier than recovery. Once you bonk, it's hard to recover during the same session.

🎯 Practical Application​

During-Workout Fueling Guidelines​

Simple rule: If exercising over 60 minutes at moderate-to-high intensity, consider during-workout carbs.

ScenarioFuel During?
45-minute gym workoutNo
60-minute moderate runOptional (30g can help)
90-minute hard cyclingYes (30-60g/hour)
2+ hour long runYes (30-60g/hour)
CrossFit WOD under 20 minNo
CrossFit competition (multiple WODs)Yes (between events)
MarathonYes (60g/hour or more)
Strength training (any duration)Usually no (rest periods allow recovery)

Fueling Strategies by Activity​

Challenge: Stomach jostling makes eating harder

Solutions:

  • Gels are often better tolerated than solids
  • Take with water
  • Practice in training
  • Consider liquid calories (sports drink)

Typical marathon fueling:

  • Gel every 30-45 minutes
  • Water at aid stations
  • Start fueling at mile 5-6, not when you feel tired
  • Aim for 45-60g carbs/hour

Long training runs:

  • Practice race nutrition
  • Build up tolerance gradually
  • Find products your stomach tolerates

Hydration + Electrolytes​

Don't forget fluids. During-workout nutrition includes hydration.

Fluid guidelines:

  • 400-800ml per hour (varies by sweat rate, heat)
  • More in heat
  • Combine carbs + fluids (sports drink) for convenience

Electrolytes (mainly sodium):

  • Important for sessions over 60 minutes
  • Critical in heat
  • Sports drinks contain electrolytes
  • Heavy sweaters may need extra sodium

Signs of poor hydration during exercise:

  • Thirst (you're already behind)
  • Concentrated, dark urine
  • Headache
  • Dizziness
  • Reduced performance

📸 What It Looks Like​

Example: 3-Hour Long Run​

6:00 AM - Pre-run:

  • Oatmeal with banana and honey
  • Toast with jam
  • Coffee
  • 16 oz water

7:00 AM - Start running

7:30 AM (30 min in):

  • Few sips of water

8:00 AM (60 min in):

  • First gel (25g carbs)
  • Water

8:30 AM (90 min in):

  • Sports drink (15g carbs)

9:00 AM (2 hours in):

  • Second gel (25g carbs)
  • Water

9:30 AM (2.5 hours in):

  • Sports drink or chews (20g carbs)

10:00 AM - Finish

Total during-run fuel: ~85g carbs over 3 hours (~28g/hour)

Example: Century Bike Ride (100 miles, ~5 hours)​

Pre-ride breakfast: Large carb-focused meal

During ride:

TimeFuelNotes
Hour 1Sports drink, sip regularlyGetting started
Hour 2Half a bar + sports drink40g carbs
Hour 3Banana + sports drink~40g carbs
Hour 4Gel + bar + sports drink50g carbs
Hour 5Gel + sports drink35g carbs

Total: ~250-300g carbs over 5 hours (~50-60g/hour)

Example: Ironman Triathlon​

Swim (1.2 miles): Nothing during

Bike (112 miles, ~5-6 hours):

  • Sports drink in aero bottle (sip constantly)
  • Gels/bars every 20-30 minutes
  • Target: 60-80g carbs/hour
  • Total: 350-450g carbs on bike

Run (26.2 miles, ~4-5 hours):

  • Gels every 30-45 minutes
  • Cola/sports drink at aid stations
  • Target: 45-60g carbs/hour
  • Total: 200-300g carbs on run

Total race carbs: 550-750g over 10-12 hours

This requires extensive gut training and practice.

🚀 Getting Started​

4-Week During-Workout Fueling Plan​

Week 1: Assess Your Need

  • List your weekly training sessions
  • Identify sessions over 60 minutes
  • Note any current energy issues during long sessions
  • Determine which sessions might benefit from fueling

Questions:

  • Do you do any sessions over 60 minutes?
  • Have you ever "bonked" or hit the wall?
  • Do you currently fuel during exercise?

Week 2: Start Simple

For your longest/hardest session:

  • Try 30g carbs at the 45-minute mark
  • Use something simple (gel, sports drink, banana)
  • Note how you feel compared to unfueled sessions
  • Check for any GI issues

Start conservative: Better to under-fuel than overwhelm your gut.

Week 3: Refine and Increase

  • Add a second fueling point if session is 90+ minutes
  • Experiment with different products
  • Find what your stomach tolerates
  • Practice your competition fueling strategy

Goal: Find products and timing that work for you.

Week 4: Establish Routine

  • Create fueling protocol for long sessions
  • Practice the exact strategy you'll use in competition
  • Fine-tune amounts based on feedback
  • Build toward goal intake (45-60g/hour for endurance)

Remember: Nothing new on race day. Practice everything.

🔧 Troubleshooting​

Problem 1: "I Get Nauseous When I Eat During Exercise"​

Causes:

  • Too much at once
  • Too concentrated (not enough water)
  • Wrong product for you
  • Gut not trained

Solutions:

  1. Start smaller (15-20g instead of 30g)
  2. Dilute sports drinks
  3. Try different products (some stomachs prefer gels, others liquids)
  4. Train your gut over weeks, gradually increasing
  5. Eat earlier in the session before high intensity

Problem 2: "I Bonked Despite Eating"​

Causes:

  • Not eating enough
  • Starting too late
  • Under-fueled before starting
  • Intensity higher than fuel can support

Solutions:

  1. Start fueling earlier (mile 5, not mile 15)
  2. Increase intake (30g → 45-60g/hour)
  3. Ensure adequate pre-workout nutrition
  4. Match pace to fuel availability

Problem 3: "I Don't Like the Taste of Gels/Sports Drinks"​

Solutions:

  1. Try different brands (taste varies significantly)
  2. Use real food: banana, dates, fig bars
  3. Make your own sports drink (water + honey + salt)
  4. Alternate products to avoid flavor fatigue

Problem 4: "I'm Doing Keto/Low-Carb—Can I Still Fuel?"​

Reality check:

  • Fat-adapted athletes still use glycogen at high intensities
  • Very low-carb can work for low-moderate intensity
  • Performance at high intensity typically suffers without carbs

Options:

  1. Accept lower high-intensity performance
  2. Use "targeted keto" (carbs only around training)
  3. Reconsider strict keto if performance matters

Problem 5: "I Forget to Eat During Exercise"​

Solutions:

  1. Set watch/phone alerts every 20-30 minutes
  2. Make it automatic: "Every 4 miles, I eat"
  3. Use products that are easy to access (gels in pocket)
  4. Practice until it becomes habit

🤖 For Mo​

AI Coach Guidance​

Assessment Questions:

  1. How long are your typical training sessions?
  2. Have you experienced bonking or hitting the wall?
  3. Do you currently fuel during exercise?
  4. Any GI issues with during-workout nutrition?
  5. What are your goals (general fitness, race performance)?

Quick Decision Guide:

Session LengthRecommendation
Under 60 minNo during-workout fuel needed
60-90 minOptional (30g can help)
90+ minYes (30-60g/hour)
2+ hoursYes (45-60g/hour, gut training)

Common Coaching Scenarios:

"I'm running a half marathon—do I need gels?" → For most people (90-120 min), yes—gels help maintain energy. Take one at miles 5-6 and again at mile 10. Practice with the same gel in training.

"I bonked at mile 20 of my marathon" → Classic glycogen depletion. You probably under-fueled. For a marathon, aim for 45-60g carbs/hour, starting from mile 5. Don't wait until you feel tired—stay ahead of depletion.

"Gels make me sick" → Try different brands, take with water, start smaller amounts, or switch to sports drink/chews. Train your gut gradually. Some people tolerate real food (banana, dates) better than gels.

"I do strength training for 90 minutes—do I need to fuel during?" → Usually not. Strength training with rest periods allows glycogen recovery between sets. A pre-workout snack and post-workout meal are sufficient. Save during-workout fueling for cardio/endurance.

❓ Common Questions​

When exactly should I start fueling during exercise?​

For sessions over 60 minutes, start consuming carbs around the 30-45 minute mark—before you feel depleted. Don't wait until you're tired.

Can I just use real food instead of gels?​

Yes, many athletes use bananas, dates, rice cakes, or sandwiches (for ultra-endurance). Real food works; gels are just convenient. Find what your stomach tolerates.

Do I need electrolytes during exercise?​

For sessions over 60-90 minutes, especially in heat, yes. Sports drinks provide both carbs and electrolytes. Heavy sweaters may need extra sodium.

What if I can't stomach anything during exercise?​

Try liquid calories (sports drink) which are easier than solids. Start with very small amounts and train your gut over time. If nothing works, ensure excellent pre-workout fueling.

Does this apply to strength training?​

Usually not. Rest periods in strength training allow partial glycogen recovery. Unless you're doing very high-volume bodybuilding (2+ hour sessions), pre and post-workout nutrition is sufficient.

✅ Quick Reference​

During-Workout Fueling Quick Guide​

DurationCarbs/HourProducts
<60 min0 (water)—
60-90 min30gGel OR sports drink
90-120 min30-60gGel + sports drink
2+ hours60-90gMultiple sources

Product Carb Content​

ProductCarbs
Energy gel20-25g
Sports drink (20 oz)35-50g
Banana (medium)27g
Energy chews (packet)25-30g
Energy bar20-45g
Dates (3)50g

Timing Reminders​

  • Start at 30-45 minutes (not when tired)
  • Fuel every 20-30 minutes during long sessions
  • Set watch/phone alerts
  • Practice in training, not racing

💡 Key Takeaways​

Essential Insights
  • Sessions over 60 minutes benefit from during-workout carbs — Don't wait until bonking
  • Start early, fuel regularly — Begin at 30-45 minutes, not when you feel tired
  • 30-60g carbs per hour — Target range for most endurance activity
  • Train your gut — Increase tolerance gradually over weeks
  • Nothing new on race day — Practice your fueling strategy in training
  • Liquids are often easier — Gels + water or sports drinks
  • Strength training usually doesn't need this — Rest periods allow recovery
  • Prevention beats recovery — Once bonked, hard to recover mid-session

📚 Sources​

During-Exercise Nutrition:

  • Carbohydrate intake during exercise — Sports Med (2018) — Tier A
  • ACSM Position Stand: Nutrition and Athletic Performance — ACSM (2016) — Tier A
  • Multiple transportable carbohydrates — JISSN (2010) — Tier A

Practical Application:

  • IOC Consensus on Sports Nutrition (2011) — Tier A
  • Gut training for athletes — IJSNEM (2017) — Tier B

See the Central Sources Library for full source details.

🔗 Connections to Other Topics​