Exercise Physiology Flashcards
Diffusive O2 transport
Passive movement of O2 down concentration gradient across tissue barriers
Based on metabolic rate, vascular resistance, tissue O2 amt
Depends on O2 tissue gradient and diffusion distance
O2 demand
Amount of O2 required by cells for aerobic metabolism
DO2
Volume of O2 delivered to systemic vascular bed per minute
CO x (arterial O2 content)
VO2
Amount of O2 that diffuses from capillaries to mitochondria
Oxygen Extraction Ratio
OER
Tissue oxygenation is adequate when tissues receive sufficient O2 to meet their metabolic needs
VO2/DO2
CO (Q)
SV x HR
SV affected by…
Pre-load (Left Ventricular End Diastolic Volume)
Myocardial distensibility (Diastolic mm length)
Myocardial contractility
After-load (Pressure that it has to push out against)
Can be measured via cardiac cath
How we measure VO2
Arterial and venous line in patient
Measure difference to see what is truly being consumed
NOT directly measured by PTs
Indirect measurement - VO2 max test
Open circuit spirometry
Occlude the nose and force breathing in and out from mouth
Look at differences and determine O2 use
Usually in cardiac rehab
Calculating VO2
(VO2 entering) - (VO2 leaving)
Convert to mL/min
Divide by bw in kg
Final unit = mL O2/kg/min
Basal Metabolic Rate
Rate of metabolism for an individual in a completely rested state
Work of breathing
Heart, renal, and brain fx
Thermal regulation (often looks at RMR)
MET
Amount of O2 consumed while sitting at rest
1 MET = 3.5 mL O2/kg/min
Energy cost of an activity
VO2/3.5
Corrected METs
Concern about accuracy of MET level for RMR because it can OVERESTIMATE the RMR values for those that aren’t doing things that aren’t quite there
VO2 max
Often use maximal and peak VO2 interchangeable
Maximal
True max of what body could do if exercising all muscles at once
Peak
When the body has “had enough”
Peak in comparison to Max
The more mm groups working at once, the more closely Peak approximates Max
LE vs UE
Max effort from LE gets a higher VO2 peak than if you were working all your mm in you UE
How does exercise affect DO2 and VO2?
VO2 could increase 20-fold depending on exercise type
Blood flow increases to peripheral mm
Blood vessel dilation
Increases availability of O2 and extraction from blood
Increase in VO2 and DO2
If DO2 declines…
VO2 will probably stay the same
Doesn’t necessarily mean you will have a decrease in your VO2
You might see a different in a critically ill patient because it might not meet metabolic demands
O2 debt
Difference btwn O2 demand and O2 consumption
PEOC
Post Exercise O2 Consumption
Needing more O2 to recover than body has available
After STRENUOUS exercise…
Replenishment of…
ATP
Myoglobin with O2
Glycogen
Removal of…
Lactic acid
Gravitational Stress
Ability for the CV system to accommodate fluid shifts is impaired with recumbence
Must adapt to gravity to restore fluid regulation
Emotional stress
Autonomic nervous system responses
Sympathetic vs Parasympathetic
Factors that perturb O2 transport
Gravitational stress
Emotional stress
Exercise stress
Key when looking at CV and pulm fx…
Gravitational and exercise stress
They stimulate the reticular activating system, which, when dysfunctioning, inhibits O2 transport
Upright positioning?
ALWAYS
Adjust hospital beds (chair mode)
Sympathetic system
Fight or flight
Exercise Stress
GREATEST PERTURBATION TO HOMEOSTASIS AND O2 TRANSPORT IN HUMANS
All steps of O2 transport affected
Increased…
CO, ventilation, HR, SV
Enhanced…
O2 extraction
Left ventricle output
Increased by increase in HR, SV, and contractile pressure
which…
Increases systolic pressure and ejection of force
LV OUTPUT MUST EQUAL LV INPUT
Diastolic filling time relation to HR
Indirect
Diastole
Rapid and marked decrease in IV pressure
Creates a LV suction effect
Systole
Increased systole leads to increased myocardial elastic recoil
Myocyte relaxation
Acceleration of this happens because of…
Increase rate of Ca++ reuptake by sarcoplasmic reticulum
With ischemia
Lose LV distensibility
LV wall stiffness
Increase diastolic pressure
Increases pulmonary congestion
Can LV augment diastolic filling in response to exercise?
NO
O2 diffusion at tissue level
Depends on QUANTITY and RATE of blood flow
Tissue and capillary O2 pressures
Capillary surface area
Capillary permeability
Diffusion distance
What causes more rapid diffusion during exercise?
Capillary dilation…
Increases…
Surface area
Decreases…
Resistance to flow
Diffusion distance
Immediate energy
When you move from resting state and begin to exercise
Use cellular ATP and Creatine Phosphate in mm fibers
Used in first 10 seconds or so of exercise
Short-term energy
High intensity, near maximal efforts when immediate energy runs out
Anaerobic production of ATP via glycolysis
90 seconds or so
Sprinting short distances
Long-term energy
Moderate intensity activities, sustained physical activity
Aerobic production of ATP
Need O2 supply to match demand
Long distance swimming
Aerobic metabolism
Uses oxidative phosphorylation (Krebs)
Occurs in mitochondria
Requires O2
Primarily used in Type I SLOW TWITCH MM FIBERS
***Used primarily during low and mod intensity exercise
O2 should support demand needed for ATP
Uses carbs, fats, proteins
Yields 36 (skeletal) or 38 (cardiac) ATP per glucose
***Heart and CNS primarily use this
Krebs cycle
Oxidative phosphorylation
Produces a lot of ATP, but SLOWER
Glucose
Main fuel that’s used for high intensity exercise
Anaerobic Metabolism
Does NOT require O2
Anaerobic phosphorylation
Uses ONLY carbs
Occurs in cytoplasm
By-product is lactic acid
Yields 2 (skeletal) or 6 (cardiac) ATP per glucose
***Used primarily during high intensity exercise
Glycolysis
Doesn’t yield a lot of ATP, but occurs QUICKLY
Anaerobic threshold
Around 55% of peak VO2… an individual cannot produce all ATP demanded aerobically and will need SOME anaerobic work to kick in
Intensity beyond which body increases reliance on anaerobic metabolism to meet body’s energy demands
Produces lactic acid
Why SOB with this? This leads to an inefficient O2 delivery situation; more acid build-up in body
Lactate threshold
Lactic acid being produced faster that it is metabolized
Anaerobic threshold
Results from increase in blood lactate
OBLA - onset of blood lactate accumulation
Ventilatory threshold
Results from lactic acid broken down into lactate and H+
Leads to increase in CO2
Leads to increase in ventilation
SUDDEN, HEAVY VENTILATION
Metabolic respiratory quotient RQ)
(CO2 produced) / (O2 consumed)
Used in calculations of BMR when estimated by CO2 production
aka RER
Burning fat RQ
0.7
Burning pure carbohydrate RQ
1.0
Max RQ
1.15
If 1.08-1.1 shows subject gave good effort during an exercise test
Physiologic Changes with Exercise
% increase of…
Frequency = 4x
Tidal volume = 8x
Minute ventilation = 32x
Normal cardiac response to exercise
Increases in linear fashion with the work rate and O2 uptake during exercise
Increase in HR has expense of decreased diastole rather than systole
Abnormal cardiac response to exercise
Lack of linear increase in HR with increased work or VO2
Cardiac adaptation to training
Lower resting HR
HR with max exercise is the SAME of SLIGHTLY LOWER
Normal SV response to exercise
Increases curvilinearly with work
Max around 50% aerobic capacity
Causes increased EF
Abnormal SV response to exercise
Depressed SV or impaired increase in SV with work due to impaired ventricular compliance
SV adaptation to training
SV and EF will increase
How to measure SV
Pulse strength to get an idea ONLY
Normal CO response to exercise
Increases linearly with increased work from 5 L/min to a max of 20 L/min
Due to increase in HR and SV
Abnormal CO response to exercise
Failure to increase linearly with work rate
CO Adaptation to training
Max level will increase
Normal BP response to exercise
SBP increases linearly with CO during exercise
DBP should either remain constant or decrease slightly
Abnormal BP response to exercise
Sudden sharp rise in SBP or lack of increase with exercise
DBP increase > 10 mmHg OR drops sharply > 20 mmHg
Should regulate after 3 min of standing
BP adaptation to training
In healthy people SBP should remain the same
Only pt with HTN should get decrease in resting SBP with training
Rate Pressure Product
HR * SBP
Very important to monitor during exercise with patient with heard disease
Strong correlation between RPP and myocardial O2 consumption (0.9)
Normal RPP changes with exercise
RPP should increase with work rate
Abnormal RPP response to exercise
Does NOT increase with work rate
Good marker of myocardial ischemia
***If no increase, NOT tolerating ex session well and at risk for ischemia
RPP adaptation to training
Resting RPP may decrease over time…same at max effort
Abnormal A-VO2 difference during ex
Impaired ability to extract O2
A-VO2 adaptation to training
Improved ability to extract O2, so you can increase your exercise tolerance independent of central hemodynamic changes
Normal VO2 max response to exercise
Can increase resting O2 consumption 10-fold
Abnormal VO2 max response to exercise
Inability to increase O2 transport with increased energy demands
VO2 max adaptations with training
Can increase resting O2 consumption 23-fold (endurance athlete)
What reflects disability
16-18
Disabled
Anaerobic threshold and exercise
Commonly associated with the onset of significant anaerobic contribution to exercise metabolism
Blood lactate is buffered during exercise to maintain a tolerable acid-base balance
Anaerobic threshold response to training
Increased capacity to buffer and tolerate lactate
Training increases the anaerobic threshold
Peripheral changes in response to training
Increased capillary density
Increased oxidative enzymes
Increased mitochondria
Effects of bed rest and immobilization on exercise tolerance
Absence of gravitational and exercise stress
Resting tachycardia
Reduced cardiac output
Reduced VO2 max
Reduced blood volume
Reduced OE at tissue level
Pulmonary complications of bed rest
Reduced lung volumes and capacities
Decreased thoracic volume
Restricted chest wall motion
Increased thoracic blood volume
Increased blood viscosity and decreased venous flow result in INCREASED risk of embolic event
Convective O2 transport
Movement of O2 in air or blood
Determined by Hb concentration, O2 sat, and CO
Depends on active energy consuming processes
