How long should fitness training typically keep an athlete's heart rate during conditioning?

Maintaining a heart rate of 70-85% of maximum heart rate (MHR) for 20 minutes is considered optimal for conditioning athletes. This range is known as the aerobic zone, which is effective for improving cardiovascular fitness, burning fat, and enhancing overall endurance. Training in this zone helps increase the body's ability to utilize oxygen efficiently and strengthens the heart muscle, thereby improving performance in various sports.

Staying within this intensity allows athletes to work at a challenging yet manageable level, promoting significant physiological adaptations without leading to excessive fatigue or risk of injury. This duration of 20 minutes also allows sufficient time for the body to engage in aerobic metabolism, leading to improved endurance performance over time.

The other options either set the intensity too low, which may not effectively enhance aerobic capacity, or too high, which could lead to fatigue without providing the necessary conditioning benefits.