An appropriate source of carbohydrates for athletes before a training session includes whole grains, such as oatmeal or whole-grain bread, as well as fruits like bananas or apples. These options provide easily digestible energy and are rich in essential nutrients. Consuming carbohydrates roughly 30-60 minutes before exercising ensures that glycogen stores are replenished, maximizing energy levels and performance during workouts. Therefore, proper pre-training nutrition is vital for endurance and intensity in athletic performance.