The anaerobic threshold: definition, physiological significance and identification

Area of Science:

• Exercise Physiology
• Metabolic Regulation
• Cardiopulmonary Function

Background:

• The anaerobic threshold (AT) signifies the exercise intensity where anaerobic metabolism supplements aerobic energy production, leading to lactate accumulation and metabolic acidosis.
• Oxygen consumption at the AT is influenced by oxygen delivery, decreasing with conditions like heart disease.
• The AT serves as a critical functional demarcation, altering physiological responses during exercise.

Purpose of the Study:

• To define the anaerobic threshold (AT) and its physiological implications during exercise.
• To explore methods for measuring the AT, focusing on lactate concentration and gas exchange.
• To elucidate the relationship between AT, metabolic acidosis, and exercise performance.

Main Methods:

• Direct measurement of lactate concentration using log-log transformation of lactate and VO2.
• Assessment of bicarbonate levels as an indicator of lactate threshold.
• Noninvasive detection of the AT using gas exchange measurements during exercise testing.

Main Results:

• The AT is characterized by a sustained increase in lactate and metabolic acidosis.
• Above the AT, exercise endurance decreases, VO2 kinetics slow, and ventilation increases disproportionately.
• Gas exchange measurements provide a convenient, noninvasive method for AT detection.

Conclusions:

• The anaerobic threshold is a key physiological marker influencing exercise performance and response.
• Lactate and bicarbonate measurements, alongside gas exchange analysis, can effectively determine the AT.
• Understanding the AT is vital for assessing functional capacity, particularly in individuals with cardiovascular limitations.