Which training method focuses solely on maintaining a constant intensity?

Steady-state training is defined by its emphasis on maintaining a constant intensity throughout the exercise session. This method typically involves activities performed at a consistent pace for a prolonged duration, such as running, cycling, or swimming at a steady speed. This approach helps to improve endurance and cardiovascular fitness, as the body adapts to sustaining output over time without fluctuations in intensity.

In contrast, the other training methods involve variations in intensity. Interval training alternates between periods of high and low intensity, circuit training includes a sequence of different exercises often with varied intensities, and plyometric training focuses on explosive movements that require quick bursts of energy. Therefore, steady-state training is uniquely characterized by its constant effort level, making it the correct answer in this scenario.