The main purpose of a warm-up before exercising is to prepare the body for increased physical activity. It involves increasing blood flow to muscles, enhancing flexibility, and reducing the risk of injury. A proper warm-up gradually elevates heart rate and warms up muscles, making them more pliable. It also mentally prepares individuals for the exercise session ahead, helping to improve performance. Ultimately, a good warm-up can lead to more effective workouts and contributes to long-term fitness goals.