The ingestion and oxidation of carbohydrate (CHO) for maximum performance potential is well-established. High-CHO foods include pasta, rice, and bread. Research has shown a high-CHO diet improves performance. This leads many to scoff their faces; but it is no excuse to go overboard. Do this and you may suffer the consequences.
Carbohydrate for Performance
Carbohydrate, like fat, is used as a substrate for oxidation during exercise. You may know this as what we ‘burn’. CHO is the predominant fuel source in the ATP-PC system (5-30 seconds) and the short-term glycolytic (STG) system ( 60 s to three-minutes) (McArdle, Katch, & Katch, 2014). These systems involve more anaerobic activity – short, sharp bursts as in powerlifting or 100 m sprint (ATP-PC) or a 400 m sprint or 100 m swim (STG). Muscle glycogen stored in your liver and muscle is used when exercising, as well as any fast-digesting CHO you eat or drink during (i.e. your CHO food or drink contains glucose that is readily available for use). CHO ingestion improves performance in endurance sports, and CHO availability increases with CHO intake before, during, and after exercise (Burke et al., 2011).
Carbohydrate loading involves eating a high-CHO diet in the run-up to an event or competition; usually around a week before. The idea is that you’ll ‘top up’ your muscle glycogen stores, maximising them if done correctly. The desired adaptation is known as supercompensation (McArdle, Katch, & Katch, 2014). This only happens if you significantly reduce the muscle glycogen stores through prolonged exercise. For the next few days, the athlete follows a low-CHO diet to keep their glycogen stores low, before switching to a high-CHO diet for three days prior to competition. Supercompensation only happens in the muscles which glycogen stores you have depleted. If you were a swimmer you would swim to deplete stores; not cycle!
Now we know the physiology and thinking behind it; let’s summarise. CHO loading isn’t simply devouring every sugary sweet or calorie-dense cake you can find. High carbohydrate intake could lead to gastrointestinal issues (de Oliveira, Burini, and Jeukendrup A ,2014) dependent on many factors such as the intestine. Conversely, undereating dampens your performance potential due to the reduced energy availability for exercise.
Carbohydrate recommendations have been discussed in a previous article, and can be seen below. Note the differentiation from light to very high activity levels, with examples, and CHO targets. A good example is concurrent training – performing strength and endurance training. Here, a low-CHO diet would be < 0.5 g/kg/bw, medium 0.5-1 g/kg/bw, and high > 1-1.5 g/kg/bw per meal based on six meals – as seen in the infographic. This works out as daily intakes of:
Low-CHO – < 3 g/kg/bw
Medium-CHO – 3-5 g/kg/bw
High-CHO – 5-9 g/kg/bw
Infographic example of periodised nutrition for concurrent training (Scott Robinson, PhD, and Daniel Owens, PhD).
To summarise, carbohydrate loading is no excuse to overeat and this could have negative consequences if you do so. Instead, it is a strategy that is relative and individual the athlete, and they should tailor it to suit. Carbohydrates are important for exercise, so find what works for you and nail your performance!
McArdle, W., Katch, F., & Katch, Victor L. (2014). Exercise physiology: Nutrition, energy and human performance (Eighth edition; International ed.).
Scott Robinson, PhD, and Daniel Owens, PhD.
Burke, L. et al. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29, 17-27.
de Oliveira EP, Burini RC, and Jeukendrup A (2014). Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Med, 79–85.
Author Credit - Liam Oliver, Performance Nutrition Student at British Diving