How many carbohydrates DO I really need?
In this blog post, I review a journal article that highlighted the influence of pre race dietary carbohydrates for marathoners. More specifically, the researchers wanted to find the ‘answers’ that led to improved marathon performance in sub-elite runners. One of the answers was a greater carbohydrate intake…
Brief: carbohydrates are beneficial for sports performance. Carbohydrates permit the production of movement through muscular contraction at very high levels of intensity (where perhaps ‘fat’ as an energy source has its limitations). In addition, carbohydrates also supply Adenosine TriPhosphate for long duration, endurance sports. In activities such as the marathon, carbohydrate stores decrease in the body, and therefore must be replaced if exercise is to continue at the same intensity. Preventing excessive declines in carbohydrates stores is one way to delay fatigue, and this will allow one to perform to their best. In addition, pre race nutrition that maximises the body’s carbohydrate stores appear another way to enhance performance.
The Research Design
The research design in the article reviewed was correlational. In simple terms, the researchers collected data on a number of different factors or characteristics, and then examined the data to see if they were any ‘matching’ relationships or patterns. A suitable analogy might be: more ice creams sold as the temperature increases. The two separate ‘things’ tend to go hand in hand… So, as research goes, it’s a good place to start when trying to find things that may help to perform better (or worse for that matter). However, we must be careful not to say that one factor CAUSES another. The two may simply go together i.e. people who sing when they’re in the shower. You might find these together, but the individual is not singing to make the shower run, nor does running water cause people to sing.
Self-reported training and food diaries were also used to collect data – these unfortunately tend not to be as accurate as we’d like. So we can’t take the results as gospel. However, in this situation, it was probably the most effective means possible. The training and food diaries collected information on the 5 weeks of training leading up to the race, as well as the individuals nutrition 24 hours pre-race, the morning of the race, and lastly during the race.
What were the findings of the study?
Carbohydrate intake the day before the race was seen as a significant predictor of running speed, and accounted for a large % of the variance in performance (along with other factors like gender, training mileage and BMI – e.g. males tended to run quicker than females, greater mileage in training meant faster times).
In a nutshell, those who performed better tended to have consumed more carbohydrates the day before the race. This doesn’t mean that eating more carbs the day before GUARANTEES improved performance; for instance, the better, more ‘clued up’ runners may have also eaten more carbohydrates along with doing a whole host of performance-enhancing behaviours e.g. slept better/more or supplement with performance enhancing supplements etc. However, it demonstrates that more carbohydrates the day before a race were found in individuals who also tended to have faster running speeds, while a lower carbohydrate intake was, in most cases, found among people who had a slower running speed.
Carbohydrate intake for performance
In addition, those who consumed more than 7g per kg of carbohydrates the day before (so for a 70kg male that’s 490g carbohydrates minimum) were also found to have a shallower decline in ‘within-race’ running speed compared with runners consuming less than 7g per kg bodyweight i.e. those who had consumed more carbohydrates also tended to maintain their race running speed better, rather than displaying a large decrease in their speed as the race wore on.
Eating more carbohydrates the day before a race is a behaviour found in those people more likely to run faster. Those who consumed fewer carbohydrates tended not to run as fast. Therefore, one factor that appears to influence performance is the amount and type of pre race nutrition. Athletes would be advised to increase their carbohydrate intake significantly as part of the pre race nutrition, in order to maximise the following days performance.
Bottom line: not based solely on this study, but what we know about performance, the day before a race is the day to switch your diet to more refined/processed foods, containing high numbers of calories for not a lot of satiety, in order to maximize the body’s stores of glycogen. More specifically, increasing one’s intake of foods high in sugar or starch would be performance enhancing. With an increase in carbohydrate, it is probably wise to decrease one’s intake of fat – most individuals have HUGE fat stores, and short term fat consumption would not be necessary.
Suggestion: the day before performance, or a race, where the duration is 60 minutes or greater, consider the following:
– Remove most vegetables from your days food intake
– Include calorie containing (sugary) beverages (with each meal/between meals)
– Opt for rice, oats or cous cous as your carbohydrate source
– Add condiments like jams or honey to your meals
– Include ‘enough’ protein at each meal, without it dampening your appetite
Good luck performing!
Credits – pictures by Picjumbo