Final answer:
The ventilatory threshold and the lactate threshold explain what happens as exercise intensity increases. The ventilatory threshold is the point where breathing rate increases disproportionately to exercise intensity, and the lactate threshold is when lactate production exceeds removal.
Step-by-step explanation:
The ventilatory threshold (VT) and the lactate threshold are used to explain what happens as exercise intensity increases. The ventilatory threshold (VT) is the point during exercise where ventilation, or breathing rate, increases disproportionately to the increase in exercise intensity. The lactate threshold is the exercise intensity at which lactate production exceeds lactate removal.
As exercise intensity increases, the body's oxygen demand also increases. Initially, the body meets this demand through aerobic metabolism, which uses oxygen to produce ATP. However, as exercise intensity continues to increase, the body may not be able to supply enough oxygen for aerobic metabolism, leading to an increased reliance on anaerobic metabolism. This anaerobic metabolism produces lactate as a byproduct, resulting in an accumulation of lactate in the blood.
The elevated lactate levels at the lactate threshold contribute to muscle fatigue and a decrease in performance. The ventilatory threshold (VT) corresponds to the lactate threshold and is a marker of the point where the body starts to rely more on anaerobic metabolism. At the ventilatory threshold, there is an increase in breathing rate and ventilation as the body tries to remove the excess carbon dioxide produced during anaerobic metabolism.