Exercise Ventilation and Blood Lactate Identification of the Ventilatory and Anaerobic Thresholds

V E = f b x TV V E : volume of gas expired per minute f b : number of breaths per minute TV: volume of gas per breath (Similar to…Q = HR x SV) ↑ Ventilation …Why? Exercise

Ventilation in Progressive Exercise At light to moderate intensities (Hyperpnea)  V E increases with V O 2 (V E meets body’s metabolic demand) At higher intensity (Hyperventilation)  V E increases more per change in V O 2 (V E exceeds body’s metabolic demand)

Ventilatory Threshold Hyperpnea Hyperventilation

How Do You Increase V E ? V E = f b x TV Initial Increase Lower Intensities) ↑ VE due to… ↑ TV Further Increase Higher Intensities) ↑ VE due to… ↑ f b

Conditionfb (breaths/min) TV (L/breath) VE (L/min) Rest Moderate Exercise Vigorous Exercise

Common Belief… “You breathe more during exercise because the oxygen in your body decreases.” This (P O 2 ) is a more MINOR Consideration!

Regulation of Ventilation During Exercise ↑ Metabolism  ↑ V E Change in Ventilation is Response to Change in Metabolic Waste. Increase in Arterial P CO 2 Decrease in Blood pH (or  H + conc.)

Control of Blood pH (Buffer) Your body wants to Maintain pH at 7.4 H + + HCO 3 - H 2 O + CO 2 Non-Metabolic CO2

Control of Blood pH (Buffer) Chemical Buffer ↑ H + + HCO 3 - H 2 O + CO 2

Control of Blood pH (Buffer) Ventilatory Buffer H + + HCO 3 - H 2 O + CO 2 ↓

Where does Non-Metabolic CO 2 Come From? The transport of lactate and H + ions out of the muscle into the blood

Lactate Production and Clearance Some lactate is always produced by the body, but at lower intensities and rest the body has the ability to clear lactate (use it) at the same rate thus there is no buildup Blood lactate rises as a result of production of lactate being greater than the rate of clearance Blood lactate production increases as the body uses anaerobic metabolism

Monitoring Lactate The measurement of the blood lactate response to exercise in conjunction with heart rate and VO 2, etc is often part of a routine physiological assessment of the high-performance athlete There are three main reasons for these measures: –They serve as indicators of training adaptation –They correlate with endurance performance –They may indicate optimal training stimuli

Blood Lactate Response to Exercise A number of researchers have independently suggested that there are at least two apparent discontinuities or thresholds in the blood lactate response to incremental exercise First discontinuity: there is a sustained increase in blood lactate concentration above resting values (usually < 2 mmol/L) (called lactate threshold) Second discontinuity: representative of a shift from oxidative to partly anaerobic metabolism during constant workloads, and it refers to the upper limit of blood lactate concentration, indicating an equilibrium between lactate production and elimination (i.e. maximal lactate steady state). This second point is usually associated with blood lactate concentrations between 2.5 and 5.5 mmol/L (called anaerobic threshold) However some subjects only exhibit one discontinuity which may be termed either lactate threshold or anaerobic threshold based upon the researcher (We will call it the anaerobic threshold.

Lactate and Ventilation The increase in anaerobic metabolism at the anaerobic threshold generates H + ions H + ions combine with HCO 3 - to form H 2 O and CO 2 Increases in CO 2 and H + trigger increased ventilation Therefore anaerobic threshold should correspond with ventilatory threshold

Monitoring Lactate Shifts The closer the anaerobic threshold is to VO 2 max, the higher the % of max or workload the person can sustain while maintaining whole body aerobic metabolism Shifts in the curve to the right indicate the ability to work at higher workloads before reaching the threshold and thus maintain aerobic metabolism at greater intensities. These shifts occur from training. Shifts in the curve to the left indicate a that the subject can no longer maintain aerobic metabolism at their previous level, and thus must work at lower intensities to stay aerobic. These shifts result from detraining or from overtraining

Experimental Procedure (In Lab Today): (* The instructor will collect all blood samples) Determination of TLac (cycling) using the Lactate Pro LT 1710® analyzer Pre-exercise measurements Lactate (by finger prick) and heart rate During exercise measurements: Seven 3-minute stages starting at 70W for males and increasing 35W at the end of each 3-min stage (i.e., 70W (1 kg X 70rpm) 105W (1.5kg x 70rpm); 140W (2kg x 70 rpm, 2.5 x 70, 3 x 70, 3.5 x 70, etc). For females, starting at 60W and increasing every 30W at the end of each 3-min stage (i.e., 60W (1kg x 60rpm); 90W (1.5kg x 60rpm); 120W (2 kg x 60rpm), 2.5 x 60, 3 x 60, etc). Only take 7 blood samples. After the 7th sample, keep increasing the resistance 35W every 3 min until volitional exhaustion Lactate and heart rate at the end of each 3-min stage Post-exercise measurements Lactate and heart rate at 5 min post-exercise