Isotonic Drinks & Gels Dosage: How Much to Take (Evidence-Based)
Isotonic drinks and gels are the backbone of endurance fuelling — they deliver carbohydrates, electrolytes, and fluid to sustain performance during prolonged exercise. Getting the isotonic drinks & gels dosage right is one of the highest-leverage nutrition decisions an endurance athlete makes. Too little and performance fades; too much overwhelms gut absorption capacity and causes GI distress.
Studied Effective Dose Ranges
The carbohydrate dosage in endurance fuelling has been studied extensively. Key evidence points:
- For exercise lasting 45–75 minutes, small amounts of carbohydrate (even mouth rinsing without swallowing) can support performance (Carter et al., 2004).
- For efforts over 90 minutes, exogenous carbohydrate oxidation rates determine the upper practical ceiling. Single-transporter carbohydrates (glucose or maltodextrin alone) can be oxidised at roughly 60 g per hour. Dual-transporter blends (glucose + fructose) can raise this to approximately 90 g per hour (Jeukendrup, 2010).
- Most isotonic sports drink powders and gels are formulated at carbohydrate concentrations that sit close to blood plasma osmolality, allowing fast gastric emptying.
A typical 500 ml serving of an isotonic drink provides around 30–40 g of carbohydrate. A standard energy gel contains roughly 20–25 g. These can be combined to reach target hourly intake.
Dose by Goal and Bodyweight
The sport nutrition research community has moved away from strict per-kilogram carbohydrate targets for during-exercise fuelling in favour of train-the-gut approaches and hourly targets:
| Session length | Carbohydrate target per hour |
|---|---|
| Under 60 min | 0–30 g (small amounts or none needed) |
| 1–2 hours | 30–60 g |
| Over 2.5 hours | 60–90 g (dual-transporter blends required above 60 g) |
Bodyweight plays a less direct role during exercise than in daily intake calculations. The gastric emptying and intestinal transport limitations are capacity-based, not body-mass-scaled.
Upper Limits
Gut tolerance is the practical upper limit for most athletes. As noted, intestinal glucose transport saturates at roughly 60 g per hour; adding fructose opens a second transporter pathway, allowing higher total rates. Going beyond 90 g per hour from supplements during exercise is associated with increased GI discomfort and does not produce additional performance gains in most tested conditions (Jeukendrup, 2010).
Electrolyte upper limits are less acutely constraining during exercise because sweat losses create tolerance for higher intakes. Sodium in isotonic products is typically in the range of 300–700 mg per litre, which is safe and appropriate for most exercise durations.
Timing Relative to Dose
- Before exercise: a carbohydrate-rich meal 3–4 hours prior supports glycogen stores. A small carbohydrate snack 30–60 minutes before is optional and individual.
- During exercise: begin fuelling within the first 20–30 minutes of efforts over 60–90 minutes; waiting until hunger or fatigue sets in means glycogen has already dipped.
- Gels vs drinks during exercise: gels are calorie-dense and must be taken with water (not isotonic drink) to avoid hypertonic GI load. Isotonic drinks provide fluid alongside carbohydrate.
- After exercise: isotonic drinks taken post-exercise aid early glycogen resynthesis and rehydration simultaneously.
Practical Protocol
A worked example for a 2-hour cycling or running session:
- Hour 1: 500 ml isotonic drink (approx. 30–40 g carbohydrate) + 1 gel with 200 ml water at the 45-minute mark (approx. 20–25 g carbohydrate) = 50–65 g total.
- Hour 2: repeat the same pattern, targeting 60–75 g.
- Total: 110–140 g carbohydrate over 2 hours — within evidence-based ranges.
At maxfit.ee the isotoonilised-joogid-ja-geelid category includes OstroVit Isotonic Drink 1500g Pirn, PowerBar Iso Active 600g Sidrun, and OstroVit Isotonic 500g Apelsin. For gels, the energiageelid category carries PowerBar PowerGel options in several flavours.
FAQ
Should I take isotonic drinks or gels during training sessions under an hour?
For most people, plain water is sufficient for sessions under 60 minutes. Small carbohydrate intakes can benefit high-intensity sessions even under 60 minutes, but an isotonic drink is generally more useful from 60–90 minutes onward, when glycogen depletion becomes a limiting factor.
How do I avoid stomach problems with gels?
Always chase gels with plain water rather than isotonic drink to prevent a hypertonic bolus in the stomach. Practise fuelling in training before race day — the gut can be trained to tolerate higher carbohydrate rates with repeated exposure. Start with lower doses and build up.
Can I mix gels with isotonic drink?
Combining both is fine provided you account for total carbohydrate per hour. The risk is accidentally exceeding intestinal absorption capacity (roughly 90 g/hour) if you also consume high-carbohydrate foods. Track the total carbohydrate from all sources together.
References
Carter, J. M., Jeukendrup, A. E., & Jones, D. A. (2004). The effect of carbohydrate mouth rinse on 1-h cycle time trial performance. Medicine & Science in Sports & Exercise, 36(12), 2107–2111. https://pubmed.ncbi.nlm.nih.gov/15570147/
Jeukendrup, A. E. (2010). Carbohydrate and exercise performance: the role of multiple transportable carbohydrates. Current Opinion in Clinical Nutrition & Metabolic Care, 13(4), 452–457. https://pubmed.ncbi.nlm.nih.gov/20574242/
