Signs of dehydration during a workout include increased thirst, dark-colored urine, fatigue, dizziness, and muscle cramps. As fluid loss continues, athletes may experience a rapid heartbeat and decreased performance. Monitoring hydration levels before, during, and after exercise is crucial, especially in hot or humid conditions. Consuming water or electrolyte-replenishing drinks can help prevent these symptoms and maintain optimal physical performance. Listening to your body and recognizing early signs can aid in avoiding serious complications.