Exercise Thresholds PDF

Exercise Thresholds KIN2230: Introduction to Exercise Physiology School of Kinesiology Learning Outcomes Learners will have the opportunity to Review the aerobic-anaerobic transition: Oxygen insufficiency Learn about the interplay between intensity and lactate pr...

Exercise Thresholds KIN2230: Introduction to Exercise Physiology School of Kinesiology Learning Outcomes Learners will have the opportunity to Review the aerobic-anaerobic transition: Oxygen insufficiency Learn about the interplay between intensity and lactate production vs lactate clearance (thresholds) Consider the implications of thresholds for training Exercise Thresholds 1 Crossing the Threshold Threshold “…is the amount, level, or limit, at which something happens or changes” 900 800 700 600 Power (W) 500 400 300 200 100 0 0 20 40 60 80 100 120 140 160 180 Time (s) Exercise Thresholds 2 Metabolic “Decisions” Picking Energy Utilization of a given energy system is dependent on: Rate of energy demand Magnitude Timeline Substrate availability Local (in the mitochondria) oxygen supply Exercise Thresholds 3 Metabolic “Decisions” Picking Energy Utilization of a given energy system is dependent on: Rate of energy demand Magnitude (Smith & Hill et al., 1991) Timeline PCr+ATP Substrate availability Lactic Local (in the mitochondria) oxygen supply Aerobic It takes time for aerobic system to supply energy ATP+PCr run out Exercise Thresholds 4 Metabolic “Decisions” Picking Energy Utilization of a given energy system is dependent on: Rate of energy demand Without substrate, we can’t do Magnitude metabolism Timeline Substrate availability (Lima-Silva et al., 2009) Local (in the mitochondria) Low CHO oxygen supply Moderate CHO TTE Low CHO Mod CHO CHO 10 65 High 18.3 ± 5.9 23.2 ± 8.8 Pro 55 15 Intensity Fat 35 20 48 hours of each diet before testing High Above LT2 (25% between Intensity LT2 and max) Exercise Thresholds 5  Metabolic “Decisions” Picking Energy Utilization of a given energy system is dependent on: Rate of energy demand Magnitude Timeline Substrate availability (Simpson et al., 2015) Local (in the mitochondria) oxygen supply Normoxia Hypoxia Normoxia Hypoxia FIO2 20.93 13.00 (%) CP (W) 172±30 134±23 22% decrease W’ (kJ) 12.0±2.6 12.5±1.4 Limits on O2 supply will limit aerobic performance VO2peak 2.82±0.37 2.30±0.30 18% decrease Exercise Thresholds 6 Metabolic “Decisions” Picking Energy Utilization of a given energy system is dependent on: Rate of energy demand Magnitude Timeline Substrate availability Local (in the mitochondria) oxygen supply Exercise Thresholds 7 Oxygen Insufficiency Oxygen Deficit Within the body oxygen (at any given time) can be: In the lungs Bound to hemoglobin within the blood Bound to myoglobin in the muscle In the mitochondria Exercise Thresholds 8 Oxygen Insufficiency Oxygen Deficit In order for oxygen to be consumed (aerobic metabolism), it has to be present in the mitochondria of the working muscle. Oxygen in the lungs or blood does the exerciser no good Oxygen bound to myoglobin in non-active muscles does the exerciser no good If oxygen is not present or present in sufficient amounts, then the muscle must utilize anaerobic sources Even at intensities less than VO2max, the local muscle can have insufficient oxygen supply for aerobic metabolism Exercise Thresholds 9 Oxygen Insufficiency Oxygen Deficit Total energy = sum of: Aerobic contribution Anaerobic contribution Even at intensities less than VO2max, the local muscle can have insufficient oxygen supply for aerobic metabolism Insufficient oxygen supply for aerobic metabolism results in anaerobic compensation Anaerobic compensation leads to fatigue Exercise Thresholds 10 Oxygen Insufficiency Oxygen Deficit Can be: Brief, quickly resolved deficiencies in oxygen supply: At onset of exercise or increase in intensity Small, brief, local Sustained deficiency in oxygen supply so anaerobic has to supplement energy supply Larger, sustained and accumulating, becomes systemic Balance between lactate (and H+): Production Clearance Exercise Thresholds 11 Oxygen Insufficiency Oxygen Deficit 2.50 Energy Cost 2.00 VO2 (L/min) 1.50 1.00 0.50 0.00 -100 0 100 200 300 400 500 600 700 200 Time (s) Power Output 100 (W) 0 -100 0 100 200 300 400 500 600 700 Exercise Thresholds 12 Time (s) Oxygen Insufficiency Oxygen Deficit 2.50 Energy Cost 2.00 Anaerobic VO2 (L/min) 1.50 1.00 0.50 Aerobic Aerobic 0.00 -100 0 100 200 300 400 500 600 700 200 Time (s) Power Output 100 (W) 0 -100 0 100 200 300 400 500 600 700 Exercise Thresholds 13 Time (s) Oxygen Insufficiency Oxygen Deficit 2.50 Energy Cost 2.00 Oxygen Deficit VO2 (L/min) 1.50 1.00 0.50 0.00 -100 0 100 200 300 400 500 600 700 200 Time (s) Power Output 100 (W) 0 -100 0 100 200 300 400 500 600 700 Exercise Thresholds 14 Time (s) Oxygen Insufficiency Oxygen Deficit Can be: Brief, quickly resolved deficiencies in oxygen supply: Transient: disappears when VO2 At onset of exercise or increase in intensity catches up and reaches steady- Small, brief, local state Sustained deficiency in oxygen supply so anaerobic has to supplement energy supply Larger, sustained and accumulating, becomes systemic Balance between lactate (and H+): Persists at steady-state and even Production continues to accumulate Clearance Exercise Thresholds 15 Oxygen Insufficiency Oxygen Deficit Can be: Brief, quickly resolved deficiencies in oxygen supply: At onset of exercise or increase in intensity Small, brief, local Sustained deficiency in oxygen supply so anaerobic has to supplement energy supply Larger, sustained and accumulating, becomes systemic Balance between lactate (and H+): Production Clearance Exercise Thresholds 16 Metabolic Thresholds Two Metabolic “Boundaries” Threshold 1: The intensity at which blood lactate can be maintained at resting levels Threshold 2: The intensity at which lactate production within muscle may be stabilized in blood Production Clearance Exercise Thresholds 17 Aerobic muscle fibre arterial capillary Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP O2 Glucose Glycogen ATP ADP RBC H+ H+ H+ H+ G-6-P ATP e- e- NAD+ ADP CO2 NADH NAD+ ADP ADP FADH2 FAD NADH x4 ATP ATP O2 Acetyl CoA PDH TCA Pyruvate ADP CO2 venous cytosol ATP mitochondria Lactate Production/Clearance muscle fibre arterial capillary Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP Glucose Glycogen ATP RBC ADP G-6-P ATP CO2 NAD+ ADP CO2 NADH ADP x4 H+ + HCO3- H+ + HCO3- NAD+ ATP H+ + lactate MCT H+ + lactate Pyruvate Production LDH venous cytosol Clearance mitochondria Lactate Balance Lactic Acid Production Byproduct of the glycolytic system Step 1 Step 2 Exercise Thresholds 20 Lactate Balance Lactic Acid Clearance H+: cleaned up using bicarbonate buffering: Bicarbonate (HCO3-) combines with H+ to form water and carbon dioxide: H+ + HCO3- → H2O + CO2 Lactate: converted back into pyruvate: In muscle of origin In the blood Clearance of lactate and H+ Transported by blood to other muscles can occur in both: Transported by blood to liver The muscle of origin The blood Exercise Thresholds 21 Metabolic Thresholds Production Clearance Two Metabolic “Boundaries” Threshold 1: The intensity at which blood lactate can be maintained at resting levels Transition from moderate to heavy intensity domains Threshold 2: The intensity at which lactate production within muscle may be stabilized in blood Transition from heavy to severe intensity domains Exercise Thresholds 22 Metabolic Thresholds Production Clearance Two Metabolic “Boundaries” Moderate Heavy Severe Lactate production in Lactate production in the Lactate clearance in the the muscle matches muscle exceeds lactate muscle exceeds lactate clearance in the clearance in muscle, but systemic lactate muscle is buffered in the blood clearance No change in blood Lactate “spilling over” Blood lactate lactate into blood accumulation accelerates Threshold 1 Threshold 2 Exercise Thresholds 23 Metabolic Thresholds Production Clearance Two Metabolic “Boundaries” Moderate Heavy Severe Mostly aerobic, More reliance on Even more reliance on whatever lactate that is anaerobic, exercising anaerobic, so much so produced gets buffered muscles produce more that much more lactate locally lactate than they can is being produced than handle so it enters can be cleared. blood. Lactate can be managed so no real accumulation Threshold 1 Threshold 2 Exercise Thresholds 24 Metabolic Thresholds Production Clearance Two Metabolic “Boundaries” Moderate Heavy Severe Lactate produced locally Too much lactate is Too much lactate is is cleared locally produced locally so it produced overall, that has to be cleared systemic clearance systemically can’t keep up Threshold 1 Threshold 2 Exercise Thresholds 25 Moderate (below Threshold 1) muscle fibre arterial capillary Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP O2 Glucose Glycogen ATP ADP RBC H+ H+ H+ H+ G-6-P ATP e- e- NAD+ ADP CO2 NADH NAD+ ADP ADP FADH2 FAD NADH x4 ATP H+ + HCO3- NAD+ ATP O2 Acetyl CoA PDH TCA MCT H+ + lactate Pyruvate ADP LDH CO2 venous cytosol ATP mitochondria Heavy (between Thresholds 1&2) muscle fibre arterial capillary Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP O2 Glucose Glycogen ATP ADP RBC H+ H+ H+ H+ G-6-P ATP e- e- CO2 NAD+ ADP CO2 NADH NAD+ ADP ADP FADH2 FAD NADH x4 ATP H+ + HCO3- H+ + HCO3- NAD+ ATP O2 Acetyl CoA PDH TCA H+ + lactate H+ + lactate Pyruvate MCT ADP LDH CO2 venous cytosol ATP mitochondria Severe (above Threshold 2) muscle fibre arterial capillary H+ + lactate H+ + lactate Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP Pi + ADP ATP H+ + lactate O2 Glucose Glycogen ATP ADP RBC H+ H+ H+ H+ G-6-P ATP e- e- NAD+ ADP CO2 CO2 NADH NAD+ ADP ADP FADH2 FAD NADH x4 ATP H+ + HCO3- H+ + HCO3- NAD+ ATP O2 Acetyl CoA PDH TCA H+ + lactate MCT H+ + lactate Pyruvate ADP LDH CO2 venous cytosol ATP mitochondria Metabolic Thresholds Two Metabolic “Boundaries” Severe Heavy Moderate Exercise Thresholds 29 Metabolic Thresholds Two Metabolic “Boundaries” ሶ 2 (L·min-1) VO Blood Lactate (mM) 4 ሶ 2max 𝐕O 12 Severe 10 Threshold 2 3 Blood Lactate (mM) 8 Heavy Threshold 1 2 6 4 1 Moderate 2 Rest 0 0 0 2 4 6 8 10 0 5 10 15 20 25 30 30 Time (min) Time (min) Metabolic Thresholds Nomenclature Threshold 1 Threshold 2 Aerobic Threshold Anaerobic Threshold Lactate Threshold Critical Power Lactate Threshold 1 Lactate Threshold 2 Ventilatory Threshold 1 Ventilatory Threshold 2 Gas Exchange Threshold Respiratory Compensation Point Maximum Lactate Steady State (MLSS) Onset of Blood Lactate Accumulation (OBLA) Exercise Thresholds 31  Performance Predicting Performance Threshold intensity describes maximum sustainable intensity during sustained exercise (Black et al., 2014) Athlete A Athlete B VO2max 50.3 55.6 (ml/kg/min) Threshold 2 175 W 165 W Perform at 170W: Athlete A will maintain without fatiguing Athlete B will fatigue and have to slow down to/below 165W Exercise Thresholds 32 Zone Training Prescribing Training Intensity Understanding intensity domains can be used to inform training zones In general: Higher intensity training is shorter in duration and requires greater recovery Lower intensity training is longer in duration but requires shorter recovery Exercise Thresholds 33 Polarized Training Zone Training (Esteve-Lanao et al., 2007) Prescribing Training Intensity Understanding intensity domains can be used to inform training zones In general: Higher intensity training is shorter in duration and requires greater recovery Lower intensity training is longer in duration but requires shorter recovery Exercise Thresholds 34 Do you feel that? It’s the winds of change Energy system activation is dependent on: rate of demand, substrate availability, and oxygen supply At the onset of exercise or an increase in intensity, anaerobic systems compensate for delays in aerobic metabolism (oxygen deficit) At higher intensities, oxygen supplies fails to meet energy demand: Intensity can be quantified based on relationship between lactate production and clearance (thresholds) Exercise Thresholds 35 Questions?