Carbohydrates are one of the most discussed topics in sports nutrition. Some consider them essential for performance, while others question whether they are needed at all. As is often the case, the reality lies somewhere between these extremes.
Research in recent years provides an increasingly detailed picture of when and how much carbohydrate is really needed during training – and when adding more no longer brings benefits.
What do carbohydrates do during training?
During training, the body draws energy from three main carbohydrate sources: glucose in the bloodstream, liver glycogen and muscle glycogen. In prolonged, demanding exercise in particular, muscle glycogen is a key factor limiting performance.
Several studies have shown that consuming carbohydrates during exercise supports performance primarily by maintaining blood glucose and regulating the use of the body’s own stores, rather than simply increasing total energy intake [1,2]. It is worth including carbohydrates in training when a session lasts more than 90 minutes or includes clearly high-intensity sections. Even in shorter sessions that are intense or undertaken with depleted energy stores, a small amount of carbohydrate can support performance and improve recovery.
In practice, this can mean taking small, regular portions of carbohydrates during long training sessions. For example, Jollos Energy Chews, with each piece containing 10 g of carbohydrates (in a 2:1 ratio) and electrolytes (salt, potassium and magnesium), allow precise dosing and work particularly well when drinking is difficult or you want to keep the strain on your stomach low.
How much carbohydrate is needed?
Research evidence shows fairly consistently that around 60–90 grams of carbohydrate per hour is the optimal amount for most endurance athletes during prolonged (>2–3 h) exercise [1–3].
When carbohydrate intake has been increased above this level (for example, 100–120 g/h), studies have found:
- greater use of absorbed (exogenous) carbohydrate
- but no additional performance benefit
- and in some cases even greater muscle glycogen use and poorer performance towards the end [1,2].
This means that optimal fuelling is individual and depends on the situation. Adjustable concentration is therefore an advantage for many: for example, High-Energy Sports Drink, whose standard recipe contains 10 g of carbohydrates per 100 ml (carbohydrates in a 2:1 ratio), allows you to increase or decrease the carbohydrate amount according to the duration and intensity of the session and the weather.
Why does the carbohydrate source matter?
Glucose and fructose are absorbed from the intestine through different transport mechanisms. Combining them therefore allows greater total absorption than glucose alone.
For this reason, glucose–fructose combinations (most commonly in a ratio of around 2:1) have become standard practice in endurance sport [2,3]. More recent studies have also tested greater total amounts and alternative ratios (for example, 0.8:1), which can increase the use of exogenous carbohydrate, but without any additional benefit in sparing muscle glycogen [4].
In practice, this means that carbohydrate composition affects tolerance and absorption, but performance is still determined by the whole picture.
What if an athlete otherwise eats few carbohydrates?
One of the most interesting findings in recent years is that even athletes adapted to a low-carbohydrate diet benefit from consuming carbohydrates during training.
Studies have shown that as little as around 10 g of carbohydrate per hour can prevent hypoglycaemia during exercise and improve performance, regardless of the underlying diet [5].
This makes small, easily portioned products useful even when the aim is not to ‘fuel to the max’, but to support blood glucose and the ability to keep going.
Carbohydrates and recovery – training does not end with the last interval
The importance of carbohydrates does not end when the workout finishes. Replenishing muscle and liver glycogen is central to recovery, particularly when training is frequent or intense.
Studies have shown that:
- severe depletion of muscle glycogen slows recovery
- consuming carbohydrates after training speeds up glycogen resynthesis
- carbohydrate intake during training can reduce the deficit from which recovery begins [1–3].
For recovery, carbohydrates work particularly well together with protein. For example, Nosht Palkkari, with a serving containing 20 g of protein and 31 g of carbohydrates, supports muscle protein synthesis and the replenishment of glycogen stores at the same time.
Summary
Carbohydrates are not essential for every training session, but when used correctly, they are one of the most effective ways to support both performance and recovery.
The key is not to maximise the grams, but to optimise the amount, timing and form according to the demands of the session. When this works, carbohydrates are more than energy – they are a tool for better training.
Sources
1. King AJ et al. (2019). Liver and muscle glycogen oxidation and performance with dose variation of glucose–fructose ingestion during prolonged exercise. European Journal of Applied Physiology.
2. King AJ et al. (2018). Carbohydrate dose influences liver and muscle glycogen oxidation and performance during prolonged exercise. Physiological Reports.
3. Jeukendrup AE. Multiple transportable carbohydrates and endurance performance. Referenced in several studies (background literature in King et al.).
4. Podlogar T et al. (2022). Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingestion at 120 g·h⁻¹ versus 90 g·h⁻¹. European Journal of Applied Physiology.
5. Prins PJ et al. (2025). Carbohydrate ingestion eliminates hypoglycemia and improves endurance exercise performance in triathletes adapted to very low- and high-carbohydrate diets. American Journal of Physiology – Cell Physiology.
The author, Jussi Hildén, is the product developer behind Nosht and Jollos products, holds a Master of Science in Food Sciences and is an experienced endurance athlete.
