Which of the following is a benefit of strength training?

Strength training enhances metabolism by increasing muscle mass, which in turn helps the body burn more calories at rest. Muscle tissue is metabolically active, meaning it requires more energy to maintain compared to fat tissue. As you build more muscle through strength training, your body's resting metabolic rate increases, allowing you to burn more calories throughout the day. This not only aids in weight management but also has positive effects on overall health, including improved body composition and better energy levels.

Focusing on the other options: decreasing muscle mass does not align with the goals of strength training; its primary purpose is to increase muscle strength and size. Reducing bone density contradicts a significant benefit of strength training, which is to improve bone health and strength, thereby reducing the risk of osteoporosis. Lastly, strength training contributes positively to overall fitness rather than decreasing it, as it improves strength, endurance, and functional performance in daily activities.