Can carbohydrates exert ergogenic effects during resistance training? Original paper

Carbohydrate ingestion before and during exercise has well-known ergogenic (performance-enhancing) effects on endurance training performance. However, less is known about the ergogenic effects of acute (short-term) carbohydrate ingestion on resistance training performance.

This systematic review and meta-analysis of 21 randomized controlled crossover trials, with a total of 226 young adults (average ages of 20–30; 95% men, 5% women), examined whether acute carbohydrate ingestion (before or during exercise) can have ergogenic effects on resistance training performance, compared to a placebo or water-only control.

For this purpose, the researchers analyzed total training session volume (defined as number of sets times number of repetitions times training weight within one training session) and postexercise blood lactate and glucose levels. Additionally, they performed subgroup analyses to investigate how fasting status, training load, training duration, total number of maximal-effort sets, and carbohydrate dose modulated the effects.

Acute carbohydrate ingestion before or during exercise had a positive effect on the total training session volume compared to placebo. Also, carbohydrate ingestion before or during exercise increased postexercise blood lactate and blood glucose levels compared to placebo.

The subgroup analyses revealed that carbohydrate ingestion was more beneficial for training sessions with durations of ≥45 min and consisting of at least 8–10 working sets. In contrast, training sessions with durations of <45 min did not benefit from carbohydrate ingestion. Furthermore, fasting status influenced the outcomes — carbohydrate ingestion was only beneficial when training under fasted conditions (i.e., when compared to a control group that trained under fasting conditions while the treatment group ingested carbohydrates and were thus not in a fasted state, strictly speaking). However, when taken before training in a nonfasted state, carbohydrates had no beneficial effects.

Additionally, the number of maximal effort sets moderated the effect of carbohydrate ingestion on resistance training performance. In other words, the more maximal-effort sets performed in a training session, the more benefits one can expect from carbohydrate ingestion before or during the workout. Notably, training load (ranging from 55% to 85%) and carbohydrate dose (ranging from 0.3 to 2.5 grams per kilogram of body weight) did not modulate the performance-enhancing effects.

The findings of this meta-analysis suggest that carbohydrate ingestion before or during exercise has clear ergogenic effects on resistance training performance. However, one limitation of this study is that the study participants consisted primarily of men (95%). Thus, it’s unclear whether these findings are transferable to female athletes. Another limitation is that the study participants had a wide range of resistance training experience (2 months to over 5 years). The researchers did not analyze whether training experience influenced the outcomes.

There are two practical implications that can be inferred from this study:

• First, carbohydrate ingestion is most beneficial for longer training sessions (≥45 min with at least 8–10 sets) and when compared to training in a fasted state.
• Second, because the carbohydrate dose did not seem to influence the ergogenic effect of carbohydrates, the amount of carbohydrates ingested seems to be a matter of personal preference. The minimum ergogenic dose identified in this study was 0.3 grams per kilogram of body weight.