Carbs Around Your Workout: How Much Do You Really Need?

Why does one coach swear you must slam carbs the moment you finish training, while the next calls it pointless? It rarely comes down to conflicting research. It comes down to a question almost nobody asks: for whom?

Most advice about carbs around training comes from elite sport, where athletes train twice a day and every hour of recovery counts. If you hit the gym three or four times a week and then drive home, different rules apply. Three things decide whether a dose of carbohydrate before, during or after your session does anything at all: how long you train, how hard, and how full your stores already were.

So let us sort through when carbs around training matter and when they are overrated.

Why carbs around training matter in the first place

Carbohydrate is the preferred fuel the moment things get intense. Your body stores it as glycogen in muscle and liver, and how full those stores are directly limits how hard and how long you can work. At high training volumes, only an intake of 8 to 12 g per kilogram per day tops the stores up completely.¹

Muscle glycogen is the local energy reserve sitting right inside the fibre, tapped with every hard rep. The more intense the effort, the bigger the share carbohydrate takes in the energy mix. Fat carries the load at low intensity, but the moment you reach for the barbell or run intervals, glycogen takes over. That is why it makes sense not to run the stores permanently empty.

The state of those stores decides not only your performance on the day but also how well your body adapts to training. A review of glycogen resynthesis makes the point that glycogen is far more than a simple fuel tank. Its level helps steer signalling inside the cell.

For everyday training this means one thing to start with: anyone who trains intensely on a regular basis and avoids carbohydrate across the board risks empty stores and, with them, less performance. The more interesting question is whether precise timing around training makes the difference, or whether the daily total is what ends up mattering. That is where it gets interesting.

Carbs before training: when a pre-workout meal earns its place

A carbohydrate meal before training pays off mainly when you arrive fasted. The key meta-analysis on the topic found that carbohydrate before and during resistance training raises training volume, but the effect only becomes clearly measurable after a fast of 8 hours or more (effect size 0.39).³

King and colleagues pooled 21 crossover trials in 2022. The picture is reassuringly clear once you look closely at where the effect actually sits.

Read the chart from the zero line: bars that cross the dashed zero are not statistically reliable. For short sessions under 45 minutes and in the fed state, that is exactly what happens. So if you train for 50 minutes in the afternoon after a normal lunch, an extra dose of carbs beforehand adds little you can measure. Train fasted before breakfast or after a long working day with no food, and the benefit is more noticeable.

Do you even need carbs during your workout?

For most strength sessions the answer is no. Carbohydrate during the effort only becomes relevant once you work at high intensity for over 60 minutes. The ISSN framework then suggests roughly 30 to 60 g per hour, intended for long, intense endurance efforts, not a typical strength session under an hour.¹

It gets interesting at the threshold. One review notes that even shorter, very intense efforts of 45 to 60 minutes above 75 per cent of maximal oxygen uptake can benefit slightly, probably through an effect in the central nervous system rather than refilled stores.⁴ That applies to continuous endurance work, not resistance training with rest between sets.

After training: how urgent is refuelling, really?

Less urgent than the myth of the open window suggests. Glycogen resynthesis runs in two phases: in the first hours after the effort, the emptied store drives its own refill, and roughly 1 g of carbohydrate per kilogram optimises this rapid phase. In hours four to 24, what counts most is the total carbohydrate amount, not the form or the timing.²

That is welcome news for anyone who would rather not stand in the changing room with a shaker. The rush only makes sense when the next hard session is close.

For you as a recreational lifter, usually with 24 hours or more until the next session, this means your stores refill on their own before you train again, as long as the daily total is right. Fast topping up only earns its keep when you train twice on the same day or put a hard session in both morning and evening. It works much the same for protein. Just how small the famous window actually is, our article on the anabolic window after training lays out.

How many carbs do you need per day?

The daily total is the real lever, not the timing of any single dose. As a rough range for strength athletes, roughly 3 to 5 g of carbohydrate per kilogram of body weight has become common, and more at high training volumes. The ISSN framework cites up to 8 to 12 g per kilogram for high volumes to keep the stores full.¹

An honest caveat belongs here. The often-quoted figure of 5 to 8 g per kilogram comes from a position stand on ultra-endurance sport and does not transfer directly to resistance training.⁸ For a recreational lifter, the real need usually sits in the lower to middle part of the scale, depending on training frequency and total calories.

The scale is a guide, not a rigid prescription. It shows where most strength athletes land when they set their carbs by weekly training volume rather than a single meal. If you want to build your full macro split and see how carbohydrate sits alongside protein and fat, our guide to calculating your macros walks you through it.

Does low-carb stall your muscle growth?

Here the evidence turns honestly murky. Very low carbohydrate over weeks appears to blunt the signalling pathways of muscle growth, yet barely touches maximal strength. A recent review describes how low carbohydrate availability over 8 to 12 weeks raises amino-acid oxidation and dampens the building signals, while strength is preserved.⁵

So much for one side. There is an equally serious counter-position, and fairness is part of an honest read.

Both sides reconcile once you separate the endpoints cleanly. Maximal strength survives a carbohydrate restriction surprisingly well. The signalling pathways of hypertrophy and anaerobic peak output, in sprints or long sets to exhaustion, do suffer when the stores are chronically empty.⁵ For the average lifter trying to build muscle, that argues against a permanently very low-carbohydrate diet, without a single gram at the wrong moment ever becoming the problem.

One point many people overlook: stronger cell signals do not automatically mean better results. A theoretical framework on deliberately training with low glycogen shows that the "train low" strategy does fire up signalling pathways and gene expression, yet this translates into better performance in only about 37 per cent of studies.⁷ That is a warning in both directions: neither "more carbs is always better" nor "more signalling equals more muscle" holds up.

A deliberate carbohydrate periodisation, studied in endurance sport under the name "sleep low", can improve performance there.⁹ But that is a different goal from building muscle and does not carry over to strength sport. If you run both anyway, the interaction itself is worth a look: cardio and muscle growth shows how much endurance work really blunts strength adaptation. For you, the message stays simpler than the internet often makes it.

Carbohydrate supplies the energy, protein supplies the building blocks. Once your carbs are set across the day, a post-workout meal with enough protein rounds off recovery, for example a serving of plant-based protein powder with 24 g of protein.¹⁰

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