A symptom of low blood sugar that athletes should recognize includes dizziness or lightheadedness, which can indicate that the body is not receiving enough glucose for energy during physical activity. Other symptoms might include fatigue, irritability, difficulty concentrating, and rapid heartbeat. It's essential for athletes to monitor their blood sugar levels and consume carbohydrate-rich foods or drinks during or after exertion to prevent hypoglycemia, which can impede performance and lead to more severe health issues if ignored.