In looking at the research, it may be concluded that the performance benefit seen in the Saunders study may have been calorie-induced, since the carbohydrate-protein solution provided a heavier calorie punch as compared to the 6% carbohydrate solution.
Therefore, research would suggest that the main focus during endurance training should be to replace approximately 30% - 50% of the total calories burned, focusing on carbohydrate calories.
Beyond 90 minutes of aerobic training or 60 minutes of anaerobic training, athletes should aim at consuming ~2 calories per pound of lean body weight each hour.
For most female athletes, this equates out to be ~200 - 250 calories per hour. For most male athletes, this equates out to be 250 - 300 calories per hour.
While there are many ways to consume these calories, I recommend that athletes focus on liquid calories to ensure proper hydration and consequent absorption and utilization of this energy.
It's well-supported scientifically that nutrition is a contributor to optimal endurance performance as well as enhanced muscle recovery. To help optimize endurance performance and enhance muscle recovery, be sure to fuel with ~2 calories per pound of body weight for every hour beyond 60-90 minutes of training.
Carbohydrates should be the focus of any endurance nutrition regimen with liquid solutions promoting quick absorption and utilization. However, remember that these nutritional strategies only play a partial role with respects to overall endurance performance; it is also essential to be smart about your training.
If you find that your resting heart rate is consistently high, you may be overtrained, which will require a longer taper period before your body is physiologically ready to put forth the effort needed for peak performance.
Kim Brown, MS, RD is a Registered Sports Dietitian and competitive endurance athlete who provides nutritional counseling and customized meal planning to athletes all around the world. More information on her services can be found at www.kbnutrition.com. She can be reached at: firstname.lastname@example.org