- Aug 14, 2018
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For a typical lifting session of an hour or so, drinking carbs during training makes little measurable difference to performance. Where the research starts to support intra-workout carbs is long sessions, high-volume work, and training in a fasted or under-fuelled state — context matters more than the supplement industry's blanket claims.
Most of the classic sports-nutrition research on carbohydrate during exercise comes from endurance sport, where the benefit is unambiguous for events lasting beyond about 90 minutes: muscle glycogen runs low, blood glucose drops, and ingesting carbs maintains output. Reviews by Asker Jeukendrup and others established that picture solidly. Resistance training is a different demand. A hard lifting session depletes glycogen locally and partially — studies measuring it directly find roughly a quarter to a third of glycogen used in a typical high-volume session for a muscle group — and performance within the session is limited more by metabolite build-up and neural fatigue than by fuel availability, provided you started the session fed.
That "provided" is doing real work. If you train first thing in the morning on an empty stomach, or your last meal was six hours ago, or you're deep in a diet, then carbs (and some protein) during the session move from pointless to genuinely useful, because your starting fuel state is compromised. The same logic applies to the increasingly common two-hour-plus high-volume sessions: at some point late in a long workout, declining blood glucose becomes a real limiter, and 20–40 grams of carbs an hour is cheap insurance. There's also a modest body of research suggesting carbohydrate during training slightly reduces cortisol response and muscle damage markers, though the practical size of that effect is debated.
The honest hierarchy for most lifters: total daily intake first, a decent meal with carbs and protein two or three hours before training second, and intra-workout drinks a distant third. If your sessions run long or you train fasted, a simple carb drink is fine and evidence-supported — it just isn't the missing piece for a fed lifter doing a standard hour.
One more angle from the research worth knowing: swishing a carb drink and spitting it out improved endurance performance in some studies, apparently via brain receptors rather than fuel — a neat reminder that some "energy" effects are the nervous system, not the tank.
Protein during the session is the other half of the marketing pitch, usually sold as essential amino acids or BCAAs. The research case there is weaker still: if your daily protein intake is adequate and you ate protein within a few hours of training, amino acids during the session add nothing measurable in the studies we have. The exception, again, is the genuinely fasted trainee, for whom a small amount of protein plus carbs around the session is a reasonable patch for a suboptimal schedule. Convenience products survive because the edge cases are real — they're just not most people's situation most of the time.
Do you train fed or fasted, and have you honestly noticed a difference with carbs during the session — or did it just become a habit that stuck?
Most of the classic sports-nutrition research on carbohydrate during exercise comes from endurance sport, where the benefit is unambiguous for events lasting beyond about 90 minutes: muscle glycogen runs low, blood glucose drops, and ingesting carbs maintains output. Reviews by Asker Jeukendrup and others established that picture solidly. Resistance training is a different demand. A hard lifting session depletes glycogen locally and partially — studies measuring it directly find roughly a quarter to a third of glycogen used in a typical high-volume session for a muscle group — and performance within the session is limited more by metabolite build-up and neural fatigue than by fuel availability, provided you started the session fed.
That "provided" is doing real work. If you train first thing in the morning on an empty stomach, or your last meal was six hours ago, or you're deep in a diet, then carbs (and some protein) during the session move from pointless to genuinely useful, because your starting fuel state is compromised. The same logic applies to the increasingly common two-hour-plus high-volume sessions: at some point late in a long workout, declining blood glucose becomes a real limiter, and 20–40 grams of carbs an hour is cheap insurance. There's also a modest body of research suggesting carbohydrate during training slightly reduces cortisol response and muscle damage markers, though the practical size of that effect is debated.
The honest hierarchy for most lifters: total daily intake first, a decent meal with carbs and protein two or three hours before training second, and intra-workout drinks a distant third. If your sessions run long or you train fasted, a simple carb drink is fine and evidence-supported — it just isn't the missing piece for a fed lifter doing a standard hour.
One more angle from the research worth knowing: swishing a carb drink and spitting it out improved endurance performance in some studies, apparently via brain receptors rather than fuel — a neat reminder that some "energy" effects are the nervous system, not the tank.
Protein during the session is the other half of the marketing pitch, usually sold as essential amino acids or BCAAs. The research case there is weaker still: if your daily protein intake is adequate and you ate protein within a few hours of training, amino acids during the session add nothing measurable in the studies we have. The exception, again, is the genuinely fasted trainee, for whom a small amount of protein plus carbs around the session is a reasonable patch for a suboptimal schedule. Convenience products survive because the edge cases are real — they're just not most people's situation most of the time.
Do you train fed or fasted, and have you honestly noticed a difference with carbs during the session — or did it just become a habit that stuck?