What is the primary purpose of a warm-up before engaging in physical activity?

The primary purpose of a warm-up before engaging in physical activity is to increase the heart rate and prepare the body for exercise. A proper warm-up gradually raises the body's temperature and heart rate, which enhances blood flow to the muscles and improves flexibility. This physiological preparation reduces the risk of injury by making the muscles more pliable and reactive. Additionally, it helps to mentally prepare the individual for the upcoming physical activity, facilitating a smoother transition into the more demanding aspects of exercise.

In contrast, completing the day's workout is a goal achieved after warm-up, cooling the body down is a function performed after exercise to aid in recovery, and assessing fitness levels typically occurs in a separate evaluative context and does not directly relate to the warm-up process.