Lactate Threshold (MEDI221/EXSC221) PDF

Lactate Threshold MEDI221/EXSC221 Lecture Objectives Describe the techniques used to measure the anaerobic threshold LT = OBLA method Ventilatory threshold Apply the principle of anaerobic thresholds to training and exercise prescription Interpret data obtained from anaerobi...

Lactate Threshold MEDI221/EXSC221 Lecture Objectives Describe the techniques used to measure the anaerobic threshold LT = OBLA method Ventilatory threshold Apply the principle of anaerobic thresholds to training and exercise prescription Interpret data obtained from anaerobic threshold testing Revise physiology related to lactate accumulation Recommended Readings Anaerobic Threshold The phase where a greater rate of energy production is required than what can be totally met by aerobic metabolism Sustained increase in lactate (via pyruvate accumulation) and metabolic acidosis occur. Associated with the power output, VO2, or heart rate obtained at ~4mmol/L (LT2) Main concepts of improving endurance performance: Consider that you have measured VO2max and LT for each of these runners. Now they are racing in a marathon. Who is the fastest runner? The 3rd Way is economy. There are many techniques for measuring the lactate threshold There is no general consensus of what constitutes the ‘lactate threshold’ or if one even exits. ‘The point at which lactate begins to accumulate in the blood?’ ‘The exercise intensity at which it begins to increase exponentially?’ There are ~25 different LT concepts The onset of blood lactate accumulation [OBLA] is the most commonly used It is widely accepted that LTs are a criterion measure for aerobic endurance performance. Better relationship with running, than cycling performance. Lactate Threshold Terminology Blood lactate Lactate Threshold 1 and 2 (LT1 and LT2) Onset of Plasma Lactate Accumulation ( OPLA ) ( 2mM ) Aerobic and Anaerobic Threshold ( 2 and 4 mM ) Onset of Blood Lactate Accumulation ( OBLA ) ( 4mM ) Ventilatory Threshold 1 and 2 (VT1 and VT2) Lactate thresholds: Onset of Plasma Lactate Accumulation (OPLA) = the exercise intensity that elicits a blood lactate concentration of 1 mmol/L greater than baseline ~ LT1 (Aerobic Threshold) Onset of Blood Lactate Accumulation (OBLA) = the exercise intensity that blood lactate reaches a concentration of 4 mmol/L, an exponential increase is observed after this time… ~ LT2 (Anaerobic Threshold)  Overview of Glycolysis blood glucose sarcolemma Cytosol ATP Glycogen glycolysis G-6-P glycogenolysis ATP PFK 4 ATP pyruvate mitochondria lactate acetyl CoA  Fig 6.11 Text book Lactate begins to accumulate when:  Increased rate of glycolysis and production of NADH and pyruvate.  Rate to high for entry into mitochondria  Increased use of Type II fibers.  Decreased rate of lactate removal from the blood  Reduced blood flow to SKM What are some downfalls of measuring blood lactate levels at the finger? Your Turn Add your response to Weekly forum. AT’s using Lactate and VE 16 Ventilatory response to increasing exercise intensity Your Turn What would your RER be at this point? Why? Post in Weekly Forum Fig 14.5 Textbook