Which of the following best describes the intensity and duration of the anaerobic lactic acid system?

The anaerobic lactic acid system is characterized by its capacity to produce energy during high-intensity activities lasting from about 30 seconds to around 2 minutes. This system kicks in when the demand for energy exceeds what can be supplied by the aerobic system, particularly during sustained, high-intensity efforts.

In this context, the correct choice highlights that the intensity can be high to moderate, indicating that while the effort is strenuous (such as in sprinting or high-intensity interval training), it can also accommodate activities that are not maximal but still demanding. The duration being short to medium reflects the system's reliance on glycolysis for energy production, where the accumulation of lactic acid limits performance as time progresses, typically marking an endurance cap at around 1-2 minutes. The other options present extremes in intensity and duration that do not correspond with the operational characteristics of the anaerobic lactic acid system. For example, very high intensity and very short duration would pertain more to the phosphagen system, while moderate intensity for very long durations better describes aerobic metabolism.