Carbohydrate drinks/powders are unnecessary if you are training for less than an hour. Carbohydrate diets may be beneficial if you are training with high-volume training performing more than 10 sets per bodypart, or who train twice a day . Being hungry before exercise can result in a decrease in performance. Carbohydrate mouth rinsing may improve performance if training for less than an hour, but more research is needed
THE COMPLETE GUIDE TO GLYCOGEN SYNTHESIS FOR PERFORMANCE AND MUSCLE GAIN SUMMARY
- This article gives a comprehensive overview of muscle glycogen synthesis and breakdown for performance.
- Carbohydrate drinks/powders are unnecessary if you are training for less than an hour.
- Carbohydrate diets may be beneficial if you are training with high-volume training performing more than 10 sets per bodypart, or who train twice a day.
- Being hungry before exercise can result in a decrease in performance.
- Carbohydrate mouth rinsing may improve performance if training for less than an hour, but more research is needed.
GLYCOGEN STRUCTURE AND GLYCOGEN SYNTHESIS
Sufficient carbohydrate intake will maximize stored carbohydrates in athletes’ muscles and supply fuel to the brain and central nervous system. The brain has a constant use of glucose, and under normal circumstances, glucose is the primary source of fuel to produce ATP in the brain. Glycogen is the storage form of glucose. The major storage sites for glycogen synthesis are the liver and muscle. The liver stores glycogen and is a reservoir to constantly supply the brain with glucose (i.e., 4 grams of glucose in the bloodstream).(1)
Most athletes will get excited when they hear about protein research and its effects on muscle growth, but if you switch the topic to the benefits of carbohydrates, their enthusiasm dwindles. Protein is critically important for athletes, but consuming more protein above a certain threshold will not have any performance-enhancing benefits and will usually come at the cost of sacrificing carbohydrates. In several studies, many athletes are not consuming the optimal number of carbohydrates for full glycogen synthesis and replenishment.(2-4)
Athletes also seem to share a disconnect between sports nutrition and its relation to body composition. In a study of college athletes, most underestimated their total calorie needs and carbohydrate requirements compared with their predictive needs for their sport. Interestingly, those with the lowest scores in sports nutrition had the highest levels of body fat.(5)
GLYCOGEN SYNTHESIS STUDIES
Similar studies have replicated these findings in which athletes consistently underestimate their daily energy requirements (-1284 kcals) and carbohydrates (-178 grams), compared to protein (-31.4 grams) and fat requirements (-27.9 grams).(6) Endurance athletes seem to be the worst for underestimating their carbohydrate needs. One study of 146 endurance athletes found that 80% of the athletes consumed the lower than recommended amounts of carbohydrates in their diet.(7)
Most athletes far exceed their protein requirements, but athletes typically fail to meet adequate, optimal carbohydrate requirements. We have all heard that there are no essential carbohydrates, which is an accurate statement, but carbohydrates are the rocket fuel to get your body moving.
WHAT HAPPENS WHEN GLYCOGEN STRUCTURE IS DEPLETED?
When glycogen stores are low, muscle cells cannot rapidly produce enough ATP to maintain high exercise intensity.(8) When muscle glycogen is depleted, it directly affects muscle function as calcium release from the sarcoplasmic reticulum is impaired, resulting in impaired force production.(9) Thus, intense muscle-damaging exercise can reduce force production after exercise regardless of high carbohydrates indicative of muscle tissue damage. (10, 11)
Compared to fats, there are relatively limited glycogen stores in the body. In the fasted state and during low-intensity exercise, a majority of the energy required by the muscle is provided by the oxidation of fats from adipose tissue. During high-intensity exercise, the contribution of fats as an energy source becomes less, and carbohydrates provide roughly two-thirds of the total energy needed.(12)
GLYCOGEN SYNTHESIS AND CARBOHYDRATE METABOLISM
Carbohydrate metabolism is the preferred source of fuel under these conditions because the rate of ATP production is two times higher than fatty acids. Carbohydrate produces more ATP per unit of oxygen than fat, so carbohydrates become an increasingly important fuel source with higher-intensity activities where more ATP is required per unit of time.
Glycogen synthesis is rapidly initiated at the onset of exercise and increases exponentially with exercise intensity.(13) Muscle contraction is a process dependent on ATP being replenished. During high-intensity exercise lasting 30 – 180 seconds, the ATP required for muscle contractions is mainly powered through glycolysis (i.e., breakdown of glycogen).(14)
For sprinting events, the last part of the race is won by the athlete who can most efficiently utilize anaerobic glycolysis. From an evolutionary perspective, carbohydrate utilization and storage promote human survival by enhancing shorts burst of high-intensity contractions to facilitate chasing prey or evading predators. However, in today’s sedentary society, excess carbohydrates have led to an increase in type II diabetes and other metabolic conditions with excess calories.
GLYCOGEN SYNTHESIS AFTER EXERCISE
Carbohydrates are recommended to facilitate enhanced performance and optimize recovery. Glycogen synthesis occurs in two phases:
a.) a rapid phase glycogen synthesis phase that does not require insulin and occurs 30- 60 minutes after exercise.
b.) slow glycogen synthesis phase is in which glycogen is synthesized over a period of hours.(15)
MUSCLE GLYCOGEN DEPLETION
Athletes involved in multi-day events and twice-a-day training are encouraged to consume carbohydrates to facilitate the rapid restoration of glycogen stores. It is recommended that carbohydrates be consumed in the first two hours after exercise to maximize glycogen re-synthesis. Delaying carbohydrate ingestion by three hours after exercise resulted in a 26% lower muscle glycogen synthesis rate than ingesting carbohydrates immediately after exercise.
A 2-hour delay in intake of a carbohydrate-rich meal had no effect when glycogen content at 8 h post-exercise.(16) Thus, it is recommended that athletes prioritize carbohydrates after exercise in the first few hours after exercise. The ISSN recommends regular ingestion of snacks or meals; providing carbohydrates and protein in a 3:1 ratio helps promote recovery and replenishment of muscle glycogen.(17)
FOODS TO REPLENISH GLYCOGEN AFTER WORKOUT
It was once thought that a majority of the carbohydrates needed to be consumed immediately after exercise, but the feeding frequency of carbohydrates is also irrelevant with extended recovery (i.e., 24 hours). Consumption of carbohydrates in four large meals or 16 small snacks had comparable effects on muscle glycogen storage by 24 hours.(18) If sessions are less than eight hours apart, it is recommended that for optimal glycogen synthesis, 1.0-1.2 g/kg of carbohydrates be consumed for the first four hours, followed by the resumption of the daily carbohydrate requirements.(16) Importantly, no additional benefit to muscle glycogen rates occurs with carbohydrates beyond 1.0-1.2 g/kg.(19)