Intra-Workout Nutrition: What to Eat & Drink During Exercise

Why Intra-Workout Nutrition Matters

Most nutrition discussions focus on pre- and post-workout windows, but for sessions lasting more than 60–75 minutes, what you take in during exercise has a measurable impact on performance, muscle protein synthesis, and recovery. For endurance athletes, intra-workout fueling can be the difference between finishing strong and "hitting the wall." For strength athletes, it's less critical but still meaningful for high-volume sessions.

The key substrate depleted during exercise is muscle glycogen. Glycogen stores are finite — roughly 350–500g total (about 1,400–2,000 kcal), with most in skeletal muscle. At high intensities (≥70% VO2max), carbohydrates become the dominant fuel. Once glycogen runs low, the body cannot sustain high-intensity output regardless of fat stores.

Carbohydrates: The Foundation

How Much Can You Oxidize?

The gut has a rate-limiting step in carbohydrate absorption. Glucose (and maltodextrin, a glucose polymer) uses the SGLT1 transporter, which saturates at approximately 60g of carbohydrate per hour. Taking in more than this does not increase oxidation — it just causes GI distress.

However, fructose uses a different transporter (GLUT5). By combining glucose and fructose in a 2:1 ratio, you can oxidize up to 90g of carbohydrate per hour without exceeding either transporter's capacity. This is the science behind "multiple transportable carbohydrate" (MTC) products.

Carb Type	Transporter	Max Oxidation Rate
Glucose only	SGLT1	~60g/hr
Fructose only	GLUT5	~30g/hr
Glucose + fructose (2:1)	SGLT1 + GLUT5	~90g/hr
Maltodextrin + fructose (2:1)	SGLT1 + GLUT5	~90g/hr

When to Start Fueling

• <60 minutes: Water and electrolytes are sufficient. Glycogen from pre-workout nutrition is adequate.
• 60–90 minutes: 30–60g carbohydrate per hour. A single transporter source (maltodextrin/glucose) is fine.
• 90 minutes to 3 hours: 60–90g carbohydrate per hour using a 2:1 glucose:fructose blend. Start fueling at 45 minutes.
• 3+ hours (ultra-endurance): Up to 120g/hr has been tested in trained cyclists with gut adaptation. Requires several weeks of gut training to avoid GI distress.

Electrolytes

Sweat contains sodium, potassium, chloride, magnesium, and calcium. Sodium is the most important electrolyte to replace — it's lost in the highest quantities and drives thirst/fluid retention. Individual sweat rates and salt concentration vary dramatically (500–2,000 mg sodium/liter of sweat is the typical range).

Electrolyte	Loss Rate	Intra-Workout Target
Sodium	500–1,500 mg/hr	500–1,000 mg/hr in heat
Potassium	100–300 mg/hr	150–300 mg/hr
Magnesium	30–60 mg/hr	Supplementation is optional intra-workout; prioritize daily intake

Hyponatremia risk: Drinking excessive plain water during prolonged exercise dilutes blood sodium — a dangerous condition called exercise-associated hyponatremia. Always include sodium in your intra-workout drink during sessions over 90 minutes.

Protein: Does It Matter During Exercise?

For strength/hypertrophy training, some research suggests co-ingesting 20–40g protein with intra-workout carbohydrates during high-volume sessions (10+ sets, 2+ hours) may reduce muscle protein breakdown. The practical benefit is small for most people — if you've had a pre-workout meal with protein 1–2 hours before, intra-workout protein is not necessary.

For endurance athletes in multi-day competition or stage races, adding 10–15g protein per hour of exercise has been shown to spare muscle glycogen and reduce markers of muscle damage.

Hydration

Dehydration as little as 2% of body weight impairs aerobic performance. Drink to thirst for sessions under 90 minutes. For longer sessions, aim for 400–800 ml/hr depending on heat and sweat rate. Weigh yourself before and after training to calibrate your fluid needs.

Practical Intra-Workout Protocols

Strength Training (45–75 min)

• Water only, or water + electrolytes (300–500 mg sodium)
• Optional: 30–40g fast carbs (banana, sports drink) in the last 20 minutes if your next activity is within 2 hours

Endurance / HIIT (60–90 min)

• 30–60g carbohydrates per hour (1 gel or 500ml sports drink)
• 300–600 mg sodium per hour
• Water: 400–600 ml/hr

Long Endurance (90 min–4 hrs)

• 60–90g carbohydrates per hour (2:1 glucose:fructose)
• 600–1,000 mg sodium per hour
• Water: 500–800 ml/hr
• Optional: 10–15g protein per hour for ultra events or stage racing

Best Intra-Workout Products 2026

Common Mistakes

• Starting too late: Begin fueling at 30–45 minutes, not when you feel depleted. By the time you feel bonked, it's too late to recover performance.
• Using single-transporter carbs at high rates: Taking 90g/hr of pure maltodextrin saturates SGLT1, causing GI distress. Switch to a 2:1 glucose:fructose blend.
• Ignoring sodium: Low-sodium sports drinks and plain water in hot conditions set up hyponatremia risk and poor fluid retention.
• Trying new products on race day: Practice your intra-workout nutrition strategy in training first. GI tolerance is individual and improves with gut training.
• Fueling strength sessions like marathons: Short gym sessions don't require gels and drinks. Save them for when you actually need exogenous carbs.

The Bottom Line

For exercise under 60 minutes, water is your only intra-workout need. For sessions of 60–90 minutes, 30–60g carbohydrates and 300–600mg sodium make a meaningful difference. For events over 90 minutes, systematic fueling with 60–90g/hr of multi-transporter carbohydrates is the difference between optimal performance and hitting the wall. The products exist to make this easy — choose based on your GI tolerance, event duration, and intensity.