ACE Personal Trainer Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Once a client surpasses the second ventilatory threshold (VT2), their ventilation is no longer sustainable due to fatigue. At this stage, the body is reaching a level of exercise intensity where the demand for oxygen exceeds the capacity for oxidative metabolism to keep up. As a result, individuals typically begin to experience significant fatigue and discomfort, leading to a point where sustaining the same level of activity becomes increasingly difficult. The physiological response includes a rapid increase in ventilation to expel carbon dioxide produced from anaerobic metabolism, yet this cannot be sustained over an extended period.

The other potential responses to this question describe different physiological phenomena that occur at varying exercise intensities or stages. For instance, ventilation may stabilize or remain constant during moderate exercise or below threshold levels, but tipping beyond VT2 results in a sharp and unsustainable increase driven by the body's urgent need to clear metabolic byproducts.