Carbohydrate as a Pre-Workout

Pre-workout carbohydrates improve performance during endurance exercise, and may potentially boost resistance training as well.

Carbohydrates are the most widely consumed dietary nutrient. Carbohydrates can be taken as a pre-workout thanks to two main benefits:

• Providing energy. Carbohydrates act as an immediate energy source that enhances endurance exercise performance, and may potentially help resistance training as well.
• Increasing glycogen. A high-carb diet can increase glycogen, enhancing performance during prolonged (>90 min) endurance exercise.

Overview

Carbohydrates are one of the three main dietary macronutrients alongside protein and fat. The human body turns the carbohydrates we eat into glucose to use as energy. The remainder is stored in muscle (~500 g) and liver (~100 g) tissue for later use in the form of glycogen. Glycogen is a major source of energy during exercise.

As such, consuming carbohydrates before a workout has two major benefits:

• Providing you with an immediate source of energy
• Maintaining or increasing your glycogen levels

There is strong research evidence to suggest that consuming (or supplementing) with carbohydrates improves performance during endurance exercise. In addition, there is early evidence that it can also enhance performance during resistance training, particularly if it is high-volume.

Because of this, endurance athletes are known to practice carbohydrate loading: eating large amounts of carbohydrates before an endurance event in order to elevate glycogen levels above normal. Carbohydrate loading is typically done by consuming high-carb meals such as pasta for 1-3 days prior to an endurance event. Research demonstrates that carbohydrate loading enhances performance during endurance activity that is over 90 minutes in duration.

Carbohydrates are frequently included in pre-workout formulas aimed at both endurance and high-intensity sports. In addition, several specific types of carbohydrates – such as dextrose and isomaltulose – are sometimes used.

How Carbohydrates Might Help Pre-Workout Formulas

Providing immediate energy

Your body turns the carbohydrates you eat into glucose – a simple carbohydrate it can use to meet its energy needs. This glucose is absorbed into the bloodstream, after which it can be distributed to cells all over the body to power them.¹ Your body – and particularly your muscles – need plenty of energy during a workout, which means eating something that contains carbs and some other nutrients 10-90 minutes before a workout can improve your performance.

Increasing glycogen stores

The human body stores extra glucose in the form of glycogen in the muscles and the liver. This glycogen is used as a major energy source during any sort of physical activity. Consuming larger amounts of carbohydrates for several (1-3) days – a practice called carbohydrate loading – raises the body’s glycogen levels above normal.² This is particularly relevant to prolonged (>90 min) endurance activity because it is sufficient to deplete your glycogen.

Read more: Carb loading

Stimulating the brain’s reward centers

Recent research reveals that a carbohydrate mouth rinse can increase performance during endurance exercise by stimulating the mouth’s taste receptors, which in turn activate brain areas linked to reward. ³

Carbohydrate Pre-Workout Uses and Benefits

Carbohydrates are a popular pre-workout nutrient. Although most people take carbohydrates in the form of food – like the ever-popular pre-workout banana – they are also widely used as a standalone supplement and an ingredient in pre-workout formulas.

These uses are backed by decades of scientific research. It is widely accepted that carbohydrates act as an immediate energy source for the body, which means they are used as the major energy source during any physical activity. In addition, there is a large volume of research demonstrating that carbohydrate loading and carbohydrate consumption before endurance activity enhances performance and reduces fatigue.

There is also some evidence that just swishing, and not even swallowing carbohydrates can enhance endurance exercise performance. In addition, early research suggests that pre-workout carbohydrate consumption can also boost resistance exercise (e.g. lifting weights) performance, particularly if it is high-volume. However, more studies are needed to confirm this.

Finally, research evidence on the effects of pre-workout carbohydrates on vertical jump, sprinting, and team sports performance is mixed, with some negative and some positive findings.⁴

Research

Human Research

The effects of carbohydrate consumption on exercise performance has been studied extensively. There is strong evidence that carbohydrate loading and consuming carbohydrates immediately before an endurance workout can enhance performance (faster run/cycling times, longer time until fatigue).

In addition, there is some early evidence that ingesting carbohydrates before resistance training can be beneficial.

Glucose supplementation before high-intensity exercise may improve performance

This randomized, double-blind study examined the effects of carbohydrate supplementation before and during high-intensity cycling. Five moderately-trained participants performed 1 hour of high-intensity cycling in the following four conditions: pre-exercise glucose (30 g dissolved in 300 ml drink) supplementation followed by placebo during the workout;  30 g glucose pre-exercise and during exercise; or placebo during both periods.

The study found that power output was greater at the 40-60 minute point in the pre-exercise glucose plus placebo group compared to placebo only. The addition of glucose during exercise did not have any additional benefits.

• The researchers concluded that “pre-exercise ingestion of G (30 g in 10 % solution) results in less drop-off in PO during 1 hour of high-intensity exercise performance, and that no further benefit is observed when the same amount of G is also ingested every 15 min during exercise.” ⁵

Taking a protein/glucose/creatine supplement while resistance training results in higher muscle mass and strength when taken around workout time

This randomized study examined the effects of supplement timing on muscle and strength gains from resistance exercise (weightlifting). Men with resistance training experience took a supplement containing protein, creatine, and glucose either immediately before and after training, or in the morning and in the evening.

The study demonstrated that taking the nutritional supplement before and after exercise resulted in a greater increase in muscle mass and strength, as well as higher muscle creatine and glycogen levels. This study confirms that ingesting a source of protein and/or glucose before and/or after training time is beneficial for gaining more muscle and strength.

• The researchers concluded that “Supplement timing represents a simple but effective strategy that enhances the adaptations desired from RE-training.” ⁶

Carbohydrate supplementation appears to improve endurance exercise performance

This review looked at the results of a total of 61 studies that examined the effects carbohydrate supplementation on endurance exercise performance. In total, 82% of the studies showed that carbohydrate supplementation resulted in improved exercise performance in exercise lasting anywhere from 1 hour to over 2 hours.

• The researchers concluded that “Use of multiple transportable carbohydrates (glucose:fructose) are beneficial in prolonged exercise…” ⁷

This review examined studies that looked at the effects of carbohydrate mouth rinses on exercise performance. A total of 11 studies were found and analyzed. The researchers found that in 9 out of 11 studies, the mouth rinse improved exercise performance (as shown by increase in power output) during moderate or high-intensity endurance exercise lasting for about 1 hour by 1.5 to 11.59%.

• The researchers concluded that “An activation of the oral receptors and consequently brain areas involved with reward (insula/operculum frontal, orbitofrontal cortex, and striatum) is suggested as a possible physiological mechanism responsible for the improved performance with CHO mouth rinse.” ⁸

Carbohydrate loading appears to improve endurance and performance during endurance exercise lasting over 90 min

This review examined the benefits of increasing muscle glycogen levels through carbohydrate (CHO) loading. The researchers looked at studies of CHO loading and exercise performance of various lengths. Although loading increased muscle glycogen content in all studies, the review found no benefit of CHO loading on high-intensity exercise lasting less than 5 minutes or moderate-intensity running or cycling lasting for 60 to 90 minutes.

On the other hand, for endurance exercise lasting more than 90 minutes, CHO loading increased endurance (time until fatigue) by 20%, and performance (such as time needed to cover a distance) by 2 to 3%. The researchers noted that the likely explanation is that this type of exercise is intense and long enough to deplete muscle glycogen stores.

• The researchers concluded that “Thus the only benefit of increasing pre-exercise muscle contents above normal values comes in exercise lasting >90 minutes.” ⁹

Carbohydrate supplementation may improve performance during high-volume resistance training

Whereas the benefits of CHO supplementation for endurance exercise are proven by many studies, its effects on resistance training are not as clear-cut. As such, this review paper examined research studies looking at the benefits of carbohydrate (CHO) supplementation in resistance-training exercise (e.g. weightlifting). The researchers propose that CHO supplementation before and  during resistance training can help maintain or increase performance by supporting optimal muscle glycogen levels, especially during high-volume training at moderate intensity.

• The researchers concluded that “On the basis of the current scientific literature, it may be advisable for athletes who are performing high-volume resistance training to ingest carbohydrate supplements before, during, and immediately after resistance training.” ¹⁰

Dosage for Pre-Workout

• There is no set dose of carbohydrates used as a pre-workout in research
• Supplements contain a wide range of carbohydrate dosages
• The amount of carbs you need before a workout varies greatly on type of exercise, your body weight, and other factors
• Generally speaking, we recommend consuming 20-40 g of carbs 10-90 minutes before your workout
• The closer your meal/supplement is to your workout, the smaller it should be to prevent digestive discomfort
• There is also a large amount of evidence that consuming carbs during endurance exercise can increase performance and spare glycogen [Kerksick C et al. International Society of Sports Nutrition position stand: nutrient timing. J Int Soc Sports Nutr. 2008 Oct 3;5:17.]

Available Forms

• Carbohydrates can be taken as food or a supplement, and come in many different forms, such as glucose, sucrose, fructose, dextrose, and isomaltulose. However, there is not much difference between them as a source of energy for your body.