Which of the following exercises is considered to be anaerobic?

The chosen answer, interval step-ups, is classified as an anaerobic exercise because it involves short bursts of high-intensity activity that rely on immediate energy sources in the muscles rather than prolonged oxygen consumption. Anaerobic exercises typically include movements that are performed at high intensities for short durations, leading to the production of energy without the use of oxygen.

In the case of interval step-ups, this exercise requires quick, powerful movements that can elevate the heart rate significantly in a very short amount of time, making it an effective anaerobic workout. The focus is on strength and power, which aligns well with the anaerobic system of energy production.

In contrast, treadmill and elliptical workouts generally promote a steady-state form of cardiovascular exercise that primarily utilizes aerobic metabolism, which relies on oxygen and is more endurance-focused. Jumping rope can be aerobic or anaerobic depending on the intensity and duration of the effort, but it typically falls more into the aerobic category if performed for an extended duration at a consistent pace. Therefore, among the options given, interval step-ups best exemplify anaerobic exercise characteristics.