Q&A: Pre-Competition Carbohydrate Loading

Q: I have a question, Do you know or have an opinion on whether or not carb loading the night before a sports match (in this case a crew regatta/race) is beneficial?

A: This is a great question and something I haven’t considered much lately. My opinion is that carb loading is unnecessary for 99.9% of the population and is most likely to lead to gastric distress, not faster race times.

However, I’m quick to admit when a question is treading upon territory I rarely visit and this area is not my specialty. So, I consulted a couple sources to see what the research is saying.

First up, a study regarding carbohydrate loading and resistance training (The effects of carbohydrate loading on repetitive jump squat power performance.):

…only few data are available on the effects of CHO loading on resistance exercise performance. Because of the repetitive use of high-threshold motor units, it was hypothesized that the power output (power-endurance) of multiple sets of jump squats would be enhanced following a high-CHO (6.5 g CHO kg body mass(-1)) diet compared to a moderate-CHO (4.4 g CHO kg body mass(-1)) diet. Eight healthy men (mean +/- SD: age 26.3 +/- 2.6 years; weight 73.0 +/- 6.3 kg; body fat 13.4 +/- 5.0%; height 178.2 +/- 6.1 cm) participated in 2 randomly assigned counterbalanced supplementation periods of 4 days after having their free-living habitual diet monitored. The resistance exercise test consisted of 4 sets of 12 repetitions of maximal-effort jump squats using a Plyometric Power System unit and a load of 30% of 1 repetition maximum (1RM). A 2-minute rest period was used between sets. Immediately before and after the exercise test, a blood sample was obtained to determine the serum glucose and blood lactate concentrations. No significant difference in power performance existed between the 2 diets. As expected, there was a significant (p </= 0.05) decrease in power performance between the repetitions in every set. Blood lactate concentrations were significantly higher postexercise with both the high-CHO and the moderate- or lower-CHO diet, but there were no differences between conditions. The results indicated that the power output during multiple sets of maximal jump squats was not enhanced following a higher-CHO diet compared to a moderate- or lower-CHO diet. These data show that elevated carbohydrate intake is not needed to optimize a repetitive power-endurance performance when it is done as the first exercise in a workout.

The second reference I’m using is the position of the International Society of Sports Nutrition and is looking at endurance performance:

• Part of all the ergogenic effect of carbohydrate loading recorded in most studies to date could be attributed to a placebo effect (endurance athletes are typically well educated and would expect a performance boost thus introducing a psychologic bias).

• The performance-enhancing effect of carbohydrate loading is small and in real-life competition most likely only significant in influencing the finishing order among top elite-level cyclists, not “back-of-the-pack” cyclists.

• Consuming adequate carbohydrate during prolonged exercise (at least non-steady events)may be more important that glycogen supersaturation via carbohydrate loading before exercise.

Another side to the above research worth pointing out is that the control groups are always consuming PLENTY of carbohydrates already! The first study has the controls at 4.4 g CHO/kg bodyweight while the second position from the ISSN is citing a study in which the control was at 6.0 g CHO/kg bodyweight!

This brings me to my own question: What happens if you purposely deplete glycogen stores and then try to resaturate them immediately prior to a race or competition?

Recently, I noted that the strength/conditioning coach for University of Maryland’s women’s basketball team imposed a period of carbohydrate depletion to quickly establish improved glycogen sensitivity to help power them through the ACC tournament. I can’t tell you for certain if this worked, but in theory I think it’s a great approach. It’s common practice among physique athletes (i.e., bodybuilding, figure, etc.) to deplete carbohydrate stores leading up to a competition only to really load up the day of the show. The goal being to “fill out” the muscles again. This doesn’t have anything to do with athletic performance, but worth noting.

To get back to your question: no, I don’t think it’s worthwhile to carbohydrate load the night before (or even three days before) a competition. My advice would be to moderately increase carbohydrate in the hours before a race. Begin with a carbohydrate dense meal at four-hours out, a well-tolerated and significant carbohydrate dense snack at two-hours out, and then sports drink from then on.

Hope this helps!