Which of the following best describes moderate intensity exercise?

Moderate intensity exercise is best characterized by activities that elevate the heart rate and increase breathing but still allow for conversation. Walking briskly fits this description perfectly, as it generally involves a pace of about 3 to 4.5 miles per hour, which is sufficient to enhance cardiovascular fitness without being excessively taxing. During brisk walking, an individual can still talk, indicating that the effort is moderate rather than vigorous.

In contrast, the other activities mentioned—running at a fast pace, weight lifting, and high-intensity interval training—are typically considered higher intensity. These exercises often require greater exertion, leading to a higher heart rate and reduced ability to maintain conversation due to their demanding nature. Therefore, brisk walking stands out as the quintessential example of moderate intensity exercise among the options provided.