What is the primary purpose of a warm-up before exercise?

The primary purpose of a warm-up before exercise is to prepare the body for physical activity and reduce the risk of injury. Warming up gradually increases the heart rate and blood flow to the muscles, facilitating the delivery of oxygen and nutrients while helping to improve overall muscle performance. It also increases body temperature, enhancing muscle elasticity and joint range of motion, which further decreases the likelihood of strains and sprains during the workout.

While enhancing flexibility can be a benefit of certain warm-up activities, it is not the main objective. Additionally, a warm-up is distinct from a cool-down; the latter is performed after exercise to lower the heart rate and body temperature. Increasing muscle mass is a result of training over time rather than a direct goal of warming up. Thus, option B captures the essence of the warm-up's role thoughtfully and accurately, focusing on injury prevention and readiness for physical exertion.