Can Diet Manipulation During Training Benefit the Soccer Player?
Posted by Dr. Jay Williams, Virginia Tech on Aug 7, 2014 in Education
One of the hallmarks of sports nutrition is competing and training while eating a high carbohydrate diet. The rationale is that matches and training sessions rely heavily on the body’s carbohydrate stores – muscle and liver glycogen. Consuming a high carbohydrate diet is the most effective way to replenish glycogen stores after exercise and to prepare the player for the next day’s event. Years of research have established this as a sound strategy that can improve a player’s performance, especially soccer players.
For the most part, much of the emphasis on diet and training has focused on simply providing the right nutrients – proteins and amino acids for building muscle mass in strength athletes and carbohydrates for maximizing fuels stores in endurance athletes. Recently, a number of sport and nutrition scientists have suggested that the composition of the diet might also serve as a stimulus for a training effect. They propose that manipulating the carbohydrate content of the diet during training might provoke adaptations in the muscle that can benefit performance. For example, training on a low carbohydrate diet causes positive changes in aerobic muscle metabolism. These adaptations may benefit energy production when carbohydrate intake is increased during competition. This approach, called “train low, compete high”, has gained popularity with many in the cycling and distance running community. However, does it improve performance? Is there sufficient evidence to use this strategy for training the soccer player?
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"Train low, compete high" is different than the traditional method of carbohydrate loading used by endurance athletes leading up to a competition. Carbohydrate loading routines are designed to deplete the muscle of glycogen, “starve” it of carbohydrates for one or two days, and then shift to a high carbohydrate diet in the days before competition. The ultimate goal of this strategy is to maximize muscle glycogen stores for the upcoming event.
The "train low, compete high" approach is a periodization program whereby carbohydrate intake and availability is manipulated to evoke specific adaptations in muscle metabolism. This type of training is also called “low glycogen training” and “starvation training.” Using this approach, the athlete systematically trains in both low and high carbohydrate states a part of a regular routine. For example, he or she might limit carbohydrate intake during the 24 hours between training sessions. In this case, the first day’s training session would be in a high carbohydrate state and day two would be in a low state. Other examples are twice a day training that limits muscle glycogen recovery for the second session, and training after an overnight fast.
Research has shown that periodically training with low carbohydrate stores enhances the metabolic machinery associated with the aerobic energy pathways. The production of more mitochondria (the aerobic “powerhouse” of the muscle cell) seems to be stimulated as are a number of key metabolic enzymes. In addition, the ability of the muscle to use fat as an energy source is improved. This strategy could benefit endurance athletes by helping them produce more energy aerobically and by sparing muscle glycogen and blood glucose. This could allow the athlete to exercise longer and have more “gas in the tank” at the end of competition. Thus, endurance cyclists and marathon runners might benefit from this type of training regimen.
Could this strategy work for the soccer player? Would systematically altering the player’s training diet improve metabolism and performance on the pitch? This is a relatively new area of research and studies on soccer players don’t yet exist. However, there are a few red flags that might preclude a coach from recommending his or her players train low and compete high.
First, advocates for training low, competing high admit that training in a low carbohydrate state is not recommended for sports that require quality efforts. Low muscle glycogen can result in low blood glucose or hypoglycemia. This likelihood of this occurring is greater when players eat few carbohydrates. Hypoglycemia could easily impact several aspects of a training session such as reduced effort and motivation, diminished motor skills, slowed reaction and poor decision making. Thus, training low could result in poor quality of the session particular when the emphasis is on technical skills.
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Second, training low is also not recommended for hard or intense training days. Again, low muscle glycogen and the potential of hypoglycemia can limit effort. Thus, high intensity exercises designed to improve speed and short term endurance would be compromised. The quality of high-intensity training would suffer and the training effects of those types of sessions would be diminished.
Third, a high aerobic capacity is required for players to compete for 90 minutes and run 5-7 miles per match. However, soccer relies on a mix of aerobic and anaerobic metabolism. Walking, jogging and low intensity running are aerobic components of the game. High intensity running, sprinting, and accelerating require anaerobic metabolism of glycogen (glycolysis) and phosphocreatine. In short, soccer requires the muscle to shift between aerobic and anaerobic metabolism. What the research has also shown is that training low may hinder training-induced adaptations in anaerobic metabolism. Thus, while players may be able to run longer at low intensities, their ability to sustain higher intensity efforts may be compromised.
The bottom line, training low is unlikely to benefit the soccer player. While training with low carbohydrate stores may evoke some positive adaptations within the muscle, it may hinder many others. Specifically high intensity and quality efforts will likely be compromised. In short, the detriments to training low probably outweigh the benefits. Thus, players should stick with the tried and true method of high carbohydrate intake to replenish depleted muscle and liver glycogen stores as a way to maximize both the quality of training and performance during the match.
For additional information, see:
Burke LM (2010) Fueling strategies to optimize performance: training high or training low? Scandinavian Journal of Medicine and Science in Sports, 20 (supplement 2): 48-58, DOI: 10.1111/j.1600-0838.2010.01185.x
Bartlett JD, Hawley JA, Morton JP (2014) Carbohydrate availability and exercise training adaptation: Too much of a good thing? European Journal of Sport Science, in press, DOI:10.1080/17461391.2014.920926
Dr. Jay Williams, Ph. D., is a professor of Exercise Science in the Department of Human Nutrition, Foods and Exercise at Virginia Tech. His research focuses on the responses and adaptations of muscle to activity, inactivity and disease. He also has a long history of working with athletes, ranging from kindergarten soccer players to Olympic track & field athletes.