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Question:

Write a lab report on topic the lactate and ventilatory thresholds.

Answer:

Lactate threshold (LT) and ventilatory threshold (VT)

Abstract:

The concept of Lactate threshold (LT) and ventilatory threshold (VT) have been broadly applied to evaluate endurance capacity during the sports training. The study aims to establish the link between lactate and a ventilatory threshold for workload, heartbeat, VO2 %max, VCO2, and VE. For this, one physical stress test was performed on a cycle ergometer with twelve young male subjects, who performed a cycle exercise test and the work load was extended by 30kg for every 3 min up to the limit of volitional fatigue. The current study analyses the threshold changes in blood lactate, the rate of heart beat, and VO2 (volume of oxygen) during incremental exercise and significant changes in LT and VT for each parameter.

Introduction:

The term anaerobic threshold (AT) was used as an indicator of extreme exercise regimen, because of increased lactic acid in the blood and this in turn because pyruvic acid is converted to lactic acid under anaerobic condition. The AT is not appropriate since anaerobic energy is produced even at the resting level way below the threshold point. The pyruvic acid, the end product of an anaerobic system of glycolysis, is either used directly for aerobic respiration in the cell or breaks down to release lactic acid. Since the little amount of pyruvate remains, hence the term lactate is used to determine the exercise intensity. Lactic acid increases when body surpasses the anaerobic threshold. Lactate threshold (LT) and ventilatory threshold (VT) are two individual phenomenon, that takes place during a dynamic session of physical exercise and are frequently taken up as a reference for calibrating the exercise intensity.

Lactate threshold is the workload, or intensity of an exercise, at which lactic acid concentration increases in the blood (Metra et al., 1990). When a cell like a muscle cell (maximum participation in physical activity) performs mild to intense workout, the rate of glycolytic metabolism increases i.e number of glucose molecules are broken down to provide continuous energy for the functioning cell. Lactate (or lactic acid) is a product of further anaerobic breakdown of glycolysis by-product (pyruvic acid). If the production of lactic acid exceeds its removal, it begins to concentrate within the cell and ultimately diffuses into the blood. The concentration of lactate accumulation or its abrupt increase in the blood is known as the Lactate Threshold (LT) or the highest workload one can sustain without excess lactate accumulation. Potential physiological causes of lactate threshold are low muscle O2, accelerated glycolysis to meet energy demands and reduced rate of lactate removal. LT can be determined by three methods:

  1. Two‐Line Regression Model (Beaver et al., 1986)
  2.  Analysing Blood Lactate Concentrations
  3.  Individual Anaerobic Threshold

The LT determination is done by analyzing the lactate levels in arterial blood, an invasive procedure which has drawn scientist to improvise it and use non-invasive methods. VT or ventilatory threshold is a non- invasive parameter and based on the analysis of the respiratory exchange (Wyatt 1999).

Ventilatory Threshold is the inflection point for ventilation during an incremental exercise trial. When physical intensity increases gradually, the breathing rate i.e ventilation also increases in a linear fashion. However, with increasing exercise intensity, there eventually comes a point from where ventilation increment takes a non-linear curve; known as the ventilatory threshold. Oxygen consumption and ventilation increases at the same rate up to 50-70% of VO2max (aerobic capacity). Beyond the point of ventilatory threshold, ventilation increases exponentially.

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