Friday, May 4, 2012

A Look Back: Diet and Soccer Performance

Nearly every week, at least one new study focused on diet and soccer performance is published. Researchers continue to learn more about specific dietary components and their effects on fitness, technical skill and mental focus. They also continue to understand the physiological, cellular and metabolic changes that link diet and performance. Back in 1973, David Muckle of the Radcliff Infirmary in Oxford published one of the first studies on how diet affects soccer performance. He found that performance was improved by drinking glucose syrup prior to the start of the match. . As they say, it’s difficult to know where you are going if you don’t know where you’ve been. In this case, it’s often helpful and quite interesting to take a look back at what was found nearly 40 years ago.

At the time of the study, researchers understood that high carbohydrate diets and glucose supplements improved work output, as well as cycle ergometer and treadmill exercise. Since soccer has an endurance component, that information suggested that glucose might also improve player performance. However, that idea had not been investigated. Thus, Dr. Muckle decided to study the relationship between carbohydrate supplementation and team performance.

Over the course of a season, a single team trained to exhaustion in Thursdays. On Fridays, training was light followed by a high carbohydrate meal. On Saturdays (match days), the glucose syrup compound containing mineral salts was consumed 30 minutes before kick off. The team played a total of 40 matches. Twenty were played after drinking the glucose syrup while the other 20 served as the control condition. For each match, the numbers of goals scored and allowed during 15-minute intervals were recorded. Also, blood samples and movement patterns of selected players were noted.

The glucose syrup solution contained 420-450 kilocalories (or calories) in a 46% solution. For comparison, a 20oz bottle of Gatorade contains 130 kilocalories in a 6% solution. So, the test drink used in this study contained a considerable amount of energy and was likely quite thick.

Dr. Muckle found that during matches when the glucose was consumed, there was a steady increase in goals scored in the second period and a decline in goals allowed (see the figure). In the final 15 minutes of the glucose matches, more than twice as many goals were scored compared to the control matches and almost zero were allowed. This probably resulted from more scoring opportunities created under the glucose condition.

As expected, glucose syrup ingestion prevented the decline in blood glucose that occurs over the course of the match.

There are a few questions about the study. Whether or not the conditions were “blinded” is not mentioned. So, the effects of the glucose syrup could be a placebo effect. Also, it is not clear if Dr. Muckle tried to insure that the quality of the opponent was randomized. That is, was the glucose provided equally for matches against both weak and strong opponents?

Despite these questions, this remains a very unique and important study. It is a very simple and straightforward look at how diet affects performance on the pitch. Clearly the most important marker of a team’s performance is the score line. In this regard, a high calorie, carbohydrate supplement provided to a team 30 minutes prior to a match, resulted in more goals scored and fewer goals conceded. Thus, it was effective.

Dr. Muckle concludes his paper with some practical suggestions for the player, suggestions that hold true today. Training should be tapered off 48 hours before the upcoming match. The athlete should rest and eat high carbohydrate meals. The pre-match meal should be light, also high in carbohydrates. Finally, before the start of the match, a carbohydrate supplement should be consumed.

Since 1973, we have learned more about the relationship between nutrition and soccer performance. We also understand the role of carbohydrate supplements in exercise. Diets high in carbohydrates lead to better technical and tactical performance as well as delay exhaustion. We also know that not only do supplements affect muscular performance but there may be a psychological improvement too. But the take home message from David Muckle’s early study remains - carbohydrates are a critical component of the player’s diet that can lead to better performance on the field.

Reference

Muckle DS (1973) Glucose syrup and team performance in soccer. British Journal of Sports Medicine, 7: 340-343.