The Determination of Anaerobic and Lactate Threshold

Methods and Materials

Subjects

Two subjects (both female students) who were physically fit for stationary cycling volunteered to participate in the study. The experimental subject 1and subject 2 weighed 55 kg and 53 kg respectively. Both the subjects were informed about the study procedures, protocol, safety measures, purpose, duration, benefits and the risk factors of the test.

Overview

Both the subjects cycled for 12 minutes at the speed of 70 rpm. The subjects were regularly encouraged to maintain the speed throughout the test with the regular increment in resistance. We measured blood lactate, total amount of oxygen consumption, carbon dioxide production and total volume of air expired.

Protocol

The cycling started with warm up phase of 3 minutes with the resistance of 60 W. The work load or resistance of the cycle was increased by 30 watts at the end of each 3 minutes and reached up to the resistance of 120 W completing the 5 stages of the test.  Before the start of the test, blood sample was taken from both the subjects by pricking a finger to measure the blood lactate at rest. Blood lactate was then measured by taking the sample within the final 30 seconds of each 3 minute workload. Expired gas sample was collected within the final 60 seconds of each 3 minutes resistance increment in the cycle to analyze the percentage of oxygen in expired air, carbon dioxide produced, and total volume of air expired.

Equipments and calculations

The cycle test was done in a Monark Stationary cycle (Ergomedic 828E). Before the start of each test, the subjects’ weights were taken by using Jadever weight machine (JPS 2030) and resting heart rates (HR) were taken by Polar FS1 Heart Rate Monitors. The subjects’ finger was pricked by using a needle of Accu-Check (Safe T-Pro Plus, 200 Serial) and the sample blood was collected in a Lactate Pro Test Slip (ARKRAY). The collected blood sample was put in to the blood lactate test meter (Lactate Pro) to find out the lactate level. O₂ Analyzer (S3A/I- AEI Technologies) was calibrated to 20.3+_– 0.5% and CO₂ Analyzer (CD 3A- AEI Technologies) was calibrated to 3.4+_– 0.5% by using Non-Hygroscopic Soda Lime VSP-NF. Gas collecting bags (Douglas bags) were well evacuated by using Dry Gas Meter (Harvard), connected to a vacuum pump. The total volume of the collected gas sample was measured by Dry Gas Meter and its temperature was recorded by K, J Thermometer (Dick Smith Electronics).

Measurement of Oxygen Consumption (VO₂):

Oxygen consumption can simply be calculated as the subtraction of the amount of oxygen exhaled (V_E O₂) to the amount of oxygen inhaled (V_I O₂), that is; VO₂ = V_I O₂– V_EO₂ (Montoye et.al. 1996).

Further,

VO₂ = (F_IO_{2 *} V_I) – (F_EO_{2 *} V_E), where F_IO­₂ & F_EO₂ are fraction of oxygen inspired and expired respectively.

Again,

V­_I is calculated by using the Haldane Transformation,

V_{I *} F_IN₂ = V_{E *} F_EN₂ (Wilmore et.al., 1994).

Measurement of Respiratory Exchange Ratio (RER):

RER is the ratio of total volume of carbon dioxide produced to the total volume of oxygen consumed.

So, RER = VCO₂/VO₂ (Wilmore et.al., 1994)

Determination of Lactate Threshold

The lactate threshold was determined non-invasively using the whole blood lactate response to increment in exercise intensity (mmol/L). L^-1 denotes the onset of blood lactate accumulation (OBLA), which normally occurs between 55%-65% of VO_2max in healthy, untrained subjects and reach up to 80% in highly trained endurance athletes, (Mc Ardle et. al., 2000). The point at which lactate began to increase by 0.25-0.30 mM above the basal levels was considered as the point of lactate threshold.

Determination of Anaerobic Threshold

The anaerobic threshold was determined by the using the measurements of sample gas analysis by;

a) an abrupt disproportionate increase in minute ventilation to the O₂ uptake

b) a systematic increase in the ventilatory equivalent for O₂ without a systematic increase in the ventilator equivalent for CO

Next: Results, Discussion and Conclusion