In certain circles, the question of whether or not to have carbohydrates before resistance exercise has been a little contentious. The contention essentially centers around two issues, namely, 1) whether additional carbs prior to exercise will result in weight, and 2) whether additional carbs will provide added energy and therefore better strength during a given workout.
Carbs Before Aerobic vs Resistance Exercise
Having some carbs before an intense jog, cycle or swim makes pretty good sense. This is because when you are performing any type of intense aerobic/ part anaerobic exercise, your body’s muscle and liver carbohydrate stores (i.e. glycogen) are the primary energy source. So depending on the intensity and duration, your body’s carbohydrates stores are often a limiting factor to exercise performance1. The question however, of whether carbohydrate intake prior to intense weight training benefits performance is not as clear cut2. This is because there is a bit of debate as to which of the body’s main energy cycles primarily fuel a standard weight training workout. Because the average set of 8-10 reps normally lasts between 10-20 seconds, it was originally believed that almost all of the energy used during resistance exercise comes from the ATP-PC (phosphocreatine) system3. However, as the length of weight training increases, with repeated sets and exercises, the body relies more on its carbohydrate stores and this has been proven in a number of studies4-6.
Explaining Conflicting Effects of Pre-Carb Intake
But up until now, the studies that have explored whether carbohydrate supplementation prior to weight training can improve performance have yielded conflicting results5, 7-9. In the latest study exploring the issue, the authors reasoned that part of the reason for the conflicting results in prior studies was that they did not control for ‘central fatigue’. After a period during maximal isometric contractions a certain amount what is called ‘central fatigue’ sets in; leading to a reduction in muscle force10. Central fatigue refers to a fatiguing in the neural recruitment of motor units in muscle10. However, the extent to which central fatigue affects the strength of contraction differs significantly between individuals. A way of controlling for this factor is by providing external electrical stimulation to the muscle via electrodes placed on the surface of the skin/muscle. Such stimulation serves to maximally stimulate motor unit recruitment in muscles10.
Effect of Pre-Carb When Controlling for Central Fatigue
With this in mind, researchers from the Department of Kinesiology at Mississippi State University set out to reassess the effects of consumption of carbohydrates prior to and during exercise on force output and time to exhaustion using single leg static contractions. However, while performing the single leg static contractions, the subjects were subjected to simultaneously electromyostimulation to control for the effect of central fatigue on contractions.
As an aside, the study involved six healthy, resistance trained male subjects, who participated and won or placed in the top 3 positions in their perspective weight classes at state and national level bodybuilding and power lifting competitions2. So they were well and truly ‘real life’ subjects.
Compared to placebo, carbohydrate consumed at a rate of 1 g per kilogram of body mass prior to and 0.17 g per kilogram of body mass every 6 minutes during the exercise protocol improved time to exhaustion2.
Carb Intake Prior To and During Resistance Exercise Fights Fatigue
Results of the study suggest that carbohydrate ingestion before and during static muscle contractions can increase force output and increase time to exhaustion2. This can be extrapolated to say that carbohydrate supplementation before and during resistance exercise might help increase the training volume of athletes.
So if you’re an avid bodybuilder or just an average Joe Blow that loves to workout in the gym don’t be afraid to throw down some carbs before and/or during your workout, especially if you find you fatigue towards the end of your workout.
1. Wildman R, Kerksick C, & Campbell, B. Carbohydrates, physical training, and sport performance. Strength Cond J. 2010;32:21–29.
2. Wax B, et al. Effects of carbohydrate supplementation on force output and time to exhaustion during static leg contractions superimposed with electromyostimulation. Journal of Strength and Conditioning Research. 2012;26(6):1717-1723.
3. MacDougall JD, et al. Biochemical adaptation of human skeletal muscle to heavy resistance training and immobilization. J Appl Physiol. 1977;43:700–703.
4. Essen-Gustavsson B & Tesch PA. Glycogen and triglyceride utilization in relation to muscle metabolic characteristics in men performing heavy-resistance exercise. Eur J Appl Physiol Occup Physiol. 1990;61:5–10.
5. Haff GG, et al. Carbohydrate supplementation attenuates muscle glycogen loss during acute bouts of resistance exercise. Int J Sport Nutr Exerc Metab. 2000;10:326–339.
6. Vollestad NK, et al. Glycogen breakdown in different human muscle fibre types during exhaustive exercise of short duration. Acta Physiol Scand. 1992;144:135–141.
7. Kulik JR, et al. Supplemental carbohydrate ingestion does not improve performance of high-intensity resistance exercise. J Strength Cond Res. 2008;22:1101–1117.
8. Lambert CP, et al. Effects of carbohydrate feeding on multiple-bout resistance exercise. J Strength Cond Res. 1991;5:192–197.
9. Conley MS, et al. Effects of carbohydrate ingestion on resistance exercise. J Strength Cond Res. 1995;9:201.
10. Bigland-Ritchie B, et al. Central and peripheral fatigue in sustained maximum voluntary contractions of human quadriceps muscle. Clin Sci Mol Med. 1978;54(6):609-14.