Tuesday, February 5, 2013

Does Diet Affect Match Performance?

There is little doubt that it takes a tremendous amount of energy to play soccer. Professional players may run up to 12 km (7.2 miles) over the course of a 90-minute match. Most coaches and players also agree that a proper nutrition is essential to provide the calories and energy needed for peak performance. But how important is the composition of the diet? Are the types of foods eaten a key to playing well throughout the match? Researchers in Greece compared match performances of players who ate high- and low-carbohydrate diets for several days. They found that a high carbohydrate diet resulted in more running and sprinting during the match as well as a much-improved score-line. The results emphasize the critical link between proper nutrition and performance on the pitch.

Twenty-two professional male players were divided into two teams. Team A and Team B were asked to play two competitive matches separated by one week. Three and one-half days before the first match, Team A ate a high carbohydrate (CHO) diet that contained about 8 grams of CHO per kg of body weight with 79% of the total calories coming from CHO. Team B ate a low CHO diet with about 3 grams per kg and 30% CHO. Protein contents were the same and the total calories consumed in the two diets were nearly identical (2870 kcal). Prior to the second match, the diets were reversed with Team A eating the low CHO diet and Team B the high.

The effects of the high CHO diet were impressive. The first match ended with Team A winning 3-1, scoring two goals in the second period. The second match saw Team B won 2-1, scoring both goals in the second period. When viewed by diet, the team on the high CHO diet won both matches with an aggregate score of 5-2.

During the two matches, the team on the high CHO diet covered 9380 meters per match while the low CHO team covered only 8077 (a 17% difference). In fact, every field player covered more distance when eating a high-CHO diet. Some showed slight improvements (2%) while other saw dramatic increases in distance of more than 30%.

The distances covered at various running speeds were also greater on the high CHO diet. In particular, distances covered during sprinting (>15 miles/hr) and high-speed running (12-15 miles/hr) were improved by 17 and 34%.

Interestingly, exercising heart rates were slightly lower during the low-CHO diet. It is likely that less running when playing under this condition reflects fatigue and reduced effort. Thus, lower heart rates.

The results of this study clearly show the effects that diet has on soccer performance. As opposed to tightly controlled laboratory studies, this study looked at performance during a competitive match played between two teams that had been placed on diets either high in carbohydrates or high in fat. When the team was placed on a high-CHO diet, the players ran more, sprinted more, scored more goals and conceded fewer - a clear improvement on performance.

It is also interesting to note how quickly a change in diet can affect performance. With only one week between matches, Team B switched to the high CHO diet for 3.5-days. The result was vastly improved performance on the field and, most importantly, success on the scoreboard.

The bottom line is that diet can markedly affect performance during a match. Focusing on a diet that is high in carbohydrates and low in fat will help teams achieve peak performance. As this study suggests, the individual improvements can lead to a better result.

Reference

Souglis AG, Chryssanthopoulos C, Travlos AK, Zorzou AE, Gissis I, Papadopoulos C, Sotiropoulos A (2012) The effect of high vs. low carbohydrate diets on distances covered in soccer, Journal of Strength and Conditioning Research, doi: 10.1519/JSC.0b013e3182792147