Mod 3: Metabolism during Exercise Flashcards
describe energy contribution during maximal exercises of various durations
10 seconds: 75% PC, 15% anaerobic LA, 10% aerobic O2
60s: 20% PC, 50% anaerobic LA, 20% aerobic O2
2 min: 5% PC, 30% anaerobic La, 65% aerbic O2
120 min: 99% aerobic O2
determine the relative energy contribution of different athletic events :
% energy (phos/glc/oxid)
40 m dash
1500 m run
Wingate test
% energy (phos/glc/oxid)
40 m dash (5 s) 85/10/5
Wingate test (30s) 30/50/20
1500 m run (5 min) <1/20/80
marathon (3 h) <1/<1/99
explain how anaerobic exercise responses are measured in the lab
wingate test, see how much power they can generate against resistance, power drops over time due to fatigue (accumulation of H+ ions, muscle cells get acidic)
-muscle biposies: if theres a lot of muscle lactate it means theyre relying on glycolytic system (venous lactate means muscle is trying to get rid of lactate thru veins)
how do we measure total anerobic energy production from muscle biopsies?
phosphagen: change in _____ levels
glycolytic: change in ______ levels
phosphagen: change in PCr levels, atp yield: 1PCr=1 ATP
glycolytic: change in lactate levels, atp yield: 1 lactate= a.5 atp (1 glycogen=2 lac + 3 atp)
how do we measure aerobic metabolism?
-what are the 3 types?
calorimetry (quantification of energy production int he body)
3 types:
1. direct: based on measure of heat production (calorimetric chamber)
- 1 kcal = increase temp of 1 kg of water by 1 celcius
NOT PRACTICAL
2. Indirect : based on measure of oxygen utilization
-o2 uptake of 1 L = 5kcal burned
-fuel use can also be determined (if co2 production measured) see if theyre relying more on carbs or fats
how do we measure whole-body fuel use at rest or during exercise?
explain the theoretical basis of respiratory exchange ratio (RER)
measure that were able to obtain from indirect calorimetry to determine whether someone is oxidizing carbs or fat or blending
-ratio of CO2 produced to O2 consumed
-VCO2/VO2
THEORETICAL BASIS:
-amount of O2 needed to combust a given unit of food is constant BUT
-amount of O2 needed to combust a unit of CHO and fat is DIFFERENT
C6H12O6 + ^O2 –> 6CO2 + 6H2O
VCO2/VO2=6co2/6o2=1.0 (oxidizing 100% carbs)
32 ATP/6o2=5.3
ex. fatty acid: palmitate: C16H32O2 + 23O2 –> 16 CO2 + 16 H2O
VCO2(produced)/VO2(consumed)=16/23=0.7 (combusting 100% FAT)
(106 atp/23 o2=4.6)
- more carbons=more oxygens needed to metabolize it
describe the relationship between RER, CHO/fat oxidation and energy expidenture
RER is respiratory exchange ratio that allows us to estimate how much carbs or fat a person is oxidizing via a ratio of how much co2 they produce and how much o2 they consume (VCO2/VO2), 0.7 means 100% fat oxidization and )% carb oxidization, 1.0 means 100% carb and 0% fat, and 0.85 is a 50/50 split. more CHO burned=more kcal/LO2
what are the assumptions and limitations of RER?
-assumes only fats and carbs are being used for energy, ASSUMES NO PROTEIN CONTRIBUTION
-protein oxidation increases during exercise if ppl restrict carbs
-assuming ur in a steady state condition, Not like in a wingate where ur in a transition
LIMITATIONS:
-highly dependent on co2 and o2 relationship, assuming gas exchange at lungs is predictive of metabolism in muscle
-some scenarios cause excess co2 production:
1. hyperventilation (from anxiety or nervousness), expel more co2 w every breath, result in increased overestimated RER, like at beginning of vo2 max test theyre nervous and start hyperventilating and we see their RER increasing without them even exercising
- intense exercise:
increase co2 = increased RER
-produce more co2 at lungs which doesnt reflect metabolism of substrate in muscle, lactate accumulates in bloodstream which acidifies bloodstream and to counter this body produced more co2 . carbonic acid in blood converts to co2 in effort by body to clear H+ ions, so excess co2 diffusies from blood to lungs and we exhale that , not reflective of whats going on in muscle. artifically incrasing co2 production and RER of lungs which gives us an overestimate of RER over 1 which is not physilogically possible thats how u know its happening
what is the practical application of RER?
allows “fuel mix” of CHO and fat to be determined, not burning 100% of one at one time
RER %CHO burned % fat burned kcal/LO2
1.00 100% 0% 5.05
0.85 50% 50% 4.86
0.70 0% 100% 4.67
lower RER(till 0.7)=more fat burned
higher RER(till 1.0)= more carbs burned
in the middle (0.85) = 50% even split
having low carb diet-more efficient at using fats for energy = lower RER
high carb diet=more efficient at using carbs for energy
what is the RER for a person at rest?
0.78 (burning mostly fats)
how does oxygen uptake change from rest to exercise?
linear proportional relationship between increase in workload and increase on O2 consumption
-take the O2 and produce ATP aerobically
-hit plateau point where despite workload is increasing (need more ATP) , more oxygen uptake doesnt occur = THIS PLATEAU IS UR VO2 MAX
-dont see plateau in inactive individuals, usually more fit ones can push thru so we see vo2 plateau
calculate energy expidenture based on oxygen uptake data
- assume
VO2-3.5 ml O2/kg/min
ex. 70 kg person –> 245 ml/min
(3.5 x 70) = 245
1 L O2–> 5kcal
245 x 5 = 1225 kcal= 1.23 being expended each minute
=1770 kcal/day (multiply 1.23 by mins in a day (1440 min in a day)) - measured
VO2 = 250 ml O2/min –> 0.25 L/min
0.25 x 5 = 1.25
=1.25 kcal/min
=1800 kcal/day
what are the normative values of oxygen uptake at rest and during submaximal and maximal exercise?
rest: 3.5 ml O2/kg/min
what is oxygen uptake?
VO2?
the rate of O2 utilization by the body
VO2= volume of O2 consumed per minute
-L/min or ml/min (absolute quantity)
-ml/kg/min (relative amount of oxygen per kg of body mass)
what is the average resting VO2?
absolute: L/min (or ml/min)
relative: ___ ml O2/kg/min
0.2-0.3 L/min
=250 ml/min
relative: 3.5 ml O2/kg/min = 1 MET (1 metabolic equivalent)
-gardening=2 mets
-running=7 mets
what is VO2 max? its determinants? typical values?
Vo2 Max: maximal rate of O2 consumption by body
-reflects highest rate of OXIDATIVE METABOLISM
Determinants:
1. O2 delivery to muscles (CRSP system)
2. O2 utilization by muscles (mitochondrial content)
Typical values:
inactive: 2-3 L/min, 33-38 ml/kg/min
female # is lower bc females have more fat which is not as metabolically active as muscles which males have more of
active: 2.5-4 L/min, 42-50 ml/kg/min
well-trained: 3-4.5 L/min, 50-56 ml/kg/min
eliteL 4-6 L/min, 67-75 ml/kh/min
ALL FOR 60kg female(lesser value) and 80kg male
what is the criteria for determining VO2 max?
- see plateau in VO2
- reach age-predicted max HR
- high blood(lactate)-8x that of rest
- (respiratory exchange rate)RER>1.1
- voluntary exhaustion
what is the rest-work transition in terms of oxygen uptake?
going from sitting to walking at 4km/hr–> immediately increase ATP demand–> increase O2 demand, but O2 consumption lags behind
O2 demand>O2 consumed earlier in exercise
-oxygen deficit (rely on anaerobic pathways for atp production
-more than VO2 max= all anaerobic to meet ATP deficit
-EPOC=excess post-exercise oxygen consumption (O2 consumed >oxygen demand), why? helps replenish PCr stores , and muscle glycogen , and helps us clear lactic acid and expel co2, replenish oxygen stores (myo and hemoglobin)
what is the lactate threshold? how is it measured?
-what do you rely on above and below the lactate threshold?
the exercise intensity in which there is an abrupt increase in blood lactate.
- reflects ability to sustain oxidative metabolism
-above LT-rely on non oxidative sources
-below LT- use oxidative metabolism
what are the factors that influence the lactate threshold? (muscle lactate conc)
5
OEMMS
- oxygen availability
- enzyme activity
- muscle fiber types (T2=more lactate, anaerobic)
- muscle lactate transporters(take lactate from muscle and put into bloodstream) ex. repurposed like go to liver
- sympathetic Ns activity: increase norepi conc=increase lactate levels
how does lactate threshold impact athletic performance? (endurance)
what measures are impt for the performance of endurance athletes
-characteristics of successful endurance athletes
-characteristics of successful endurance athletes:
1. High vo2 max
2. high lactate threshold (as % vo2 max)
3. high economy of effort (efficiency)
4. high percentage of type 1 muscle fibers
what is exercise economy/efficiency?
greater economy of effort can be demonstrated by:
- more work performed for a given energy cost (energy in vs work output produced)
OR (in reverse)
- Lower energy cost for a given amount of work
How does exercise intensity influence fuel during exercise?
% of VO2 max % of fuel sources used
25% 15% muscle TG
50% plasma FFA
15% muscle glycogen
15% blood glucose
50% 15% muscle TG
30% plasma FFA
40% muscle glycogen
15% blood glucose
75% 15% muscle TG
15% plasma FFA
55% muscle glycogen
20% blood glucose
as exercise intensity increases, relative contribution of fat to energy decreases and contribution of carbs increases.
-burn less calories in low intensity efforts, so low intensity (VO2) might not be best for fat loss
-higher intensity=more kcal burned/min
-
What’s the difference between absolute and relative fuel use during exercise?
as exercise intensity increases, relative contribution of fat to energy decreases and contribution of carbs increases.
- as exercise intensity increases, the absolute amount of kcal/min burned is higher at higher intensities(although u burn more fat at lower intensities, they are not good for fat loss bc u dont burn as many calories)
How does exercise duration influence fuel use during exercise?
glycogen depletion increases with increased exercise intensity (higher intensity=faster glycogen depletion)
- at 50% VO2 max, as time goes on (2hrs) we can see decline of use of blood glucose as glucose stores decline, and use of muscle TG and plasma FFA increase
- as exercise duration increases, we start to progressively rely on blood borne substrates (glucose and plasma FFA ) and less on muscle sources (muscle TG and muscle glycogen)
how do researchers calculate fuel use of specific substrates?
- Measure overall rate of energy use (VO2)
- Determine % CHO and % Fat use (RER)
- Measure muscle glycogen utilization (biopsy)
(other CHO=blood glucose) - Measure muscle uptake of FFA (A-V catheters)
(other fat =muscle tg)
use indirect calorimetry(total O2 consumotion)
eg. KPE student w VO2 max of 4.0 L/min
@25% of max, VO2=1 L/min (5kcal/L O2)
=5kcal/min
@50% of VO2=2L/min=10kcal/min
what are the 4 main fuels for exercise?
- muscle glycogen
- blood glucose (from liver)
- muscle triglyceride
- blood fatty acids( from adipose tissue)
what are the key hormones in exercise metabolism? what are their roles?(hormonal regulation of fuel use during exercise)
insulin, glucagon, epi, norepi
explain the cyclic AMP” second messenger” system
-occurs w NONsteroid hormones that cant diffuse into tissue
-use 2nd messenger(cyclic AMP) that relays signal that hormone wants to come in
-hormone binds to receptor that activates enzyme Adenylate cyclase that is in cell membrane
-ATP—>cAMP
- this reaction activates protein kinase –> cellular response depends on hormone:
EPI: increases muscle glycogenolysis
EPI/NOREPI: increase lipolysis(muscle, adipose)
GLUCAGON: increase liver glycogenolysis
overall response time is FAST: less than 1 min
explain how muscle glucose uptake is regulated during exercise
blood insulin increases, blood glucose stays same and decreases only after long duration of exercise
how to maintain hormonal regulation of blood glucose concentration during exercise
- minimize glucose use by less active tissues
decrease insulin, also dec blood flow - mobilize alternative fuels to glucose
increase norepi, increase FFA from adipose - stimulate muscle glycogen use
inc epi, inc phos activity - release glucose from liver sources
inc glucogon and epi, glycogenolysis, gluconeogenesis
the combined activity of tissues which regulate hormone release and control bodily function
neuroendocrinology
hormone
-sources of hormones?
a chemical substance secreted into body fluids, with specific effects on local or distant target tissues
-sources: endocrine glands, other tissues :(kidney, secretes EPO)
what are the 2 classifications of hormones?
- NONSTEROID:
-derived from protein to peptide, or amino acids
- NOT lipid soluble –> CANNOT cross cell membrane
-released from pancreas, hypothalamus, pituitary gland, adrenal medulla - STEROID:
-derived from lipid(cholesterol)
-lipid soluble–> CAN cross cell membranes
-released from ovaries, testes, adrenal cortex
what are the major functions of hormones related to exercise?
- alter enzyme activity(nonsteroid)
- alter membrane transport( glucose uptake at muscle, insulin) (NONsteroid)
- alter protein synthesis rates (steroid and NONsteroid)
INSULIN: what is the primary action and site of release?
primary action: increase glucose/FFA/AA uptake, increase glycogen/TG and protein synthesis
decreases lipolysis
Site of release: pancreas (beta cells)
anabolic protein(builds things up, NOT breakdown)
GLUCAGON : what is the primary action and site of release?
Primary action:
increase liver glycogenolysis
increase gluconeogenesis
site of release: pancreas (alpha cells)
catabolic protein(breaks down)
EPINEPHRINE : what is the primary action and site of release?
increase muscle and liver glycogenolysis
increase lipolysis (muscle and adipose)
released from adrenal medulla
CATABOLIC
NOREPINEPHRINE : what is the primary action and site of release?
increase lipolysis (adipose)
increase cardiorespiratory function
released from SNS fibers and adrenal medulla
CATABOLIC
explain stimulation of membrane transport and glucose uptake
T2D: high blood sugar
-decreased glucose uptake in muscle –> hyperglycemia
how to increase glucose uptake? exercise, high intensities, all types
- GLUT-1 transporter
-contracting muscle pormotes other transpoters thru CA 2+ , GLUT4 transporters
-contracting muscle also increases blood flow, so more insluin going to active muscle
what determines insulin “seen” by muscle?
- blood conc
- muscle blood flow
REST: = [15 units]/L x 1L/min blood flow occurring
=15 units insulin/min coming to muscle
DURING EXERCISE:= 10 units/L x 10L/min
=100 units/min
** insulin signal directed where glucose uptake is needed
describe the primary metabolic adaptations to aerobic exercise training
MITOS
FUEL STORAGE
FUEL USE
MITOS: increased number and size, increase in oxidative enzymes like succinate dehydrogenase
FUEL STORAGE: increase in muscle glycogen
FUEL USE (@ same absolute load, like same time at 200W): decreased use of CHO, decreased lactate production –>workload feels easier
- at same absolute work intensity:
inc lipid catabolism
dec CHO catabolism (mainly glycogen )(inc lactate threshold)
^^those 2 measured by dec RER
inc aerobic use of CHO thats catabolized (inc lactate threshold)
dec RER @ given workload
incr workload @ given RER
WHY?
-less workload per mito
-inc lipid delivery to mito (HSL, CPT)
-inc enzymes for lipid oxidation
-less stimulation of CHO use (epi activates phorphorlase), lower release of epi, less reason to break down CHO
Lactate threshold:
dec LA at given workload
inc workload at given LA
WHY?
more mitos
inc in lactate clearance
inc pyruvate oxidation
dec pyruvate production
explain the influence of exercise training and fuel metabolism during exercise and aerobic performance
Direct calorimetry is based on measure of _______ _______
heat production
Indirect calorimetry is based on the measure of _________ ________
oxygen utilization
oxygen uptake refers to the _____ of ________ _______ by the body
rate of o2 utilization
VO2 max is the : __________ rate of O2 consumption by the body, and it reflects the highest rate of ________ metabolism
maximal
oxidative
the determinants of VO2 max are :
1. O2 _______ to muscles (CRSP system)
2. O2 ___________ by muscles (mito content)
delivery
utilization
the lactate threshold is the exercise intensity at which there is an abrupt increase in blood lactate.
It reflects the ability to __________ oxidative metabolism
sustain
determine rate of energy use at Vo2 at 25% and 50% of individual with VO2 max of 4L/min
at 25%, VO2=1L/min (5kcal/L O2)
1 x 5kcal/L = 5kcal/min
at 50% VO2=2L/min
2x5=10 kcal/min
what is: a chemical substance secreted into body fluids, with specific effects on local or distant target tissues
hormone
what are the BCAAs
Major AAs in exercise metabolism :
- BCAA ( leucine, isoleucine, valine)
NOT BCAA: alkaline, glutamine
what AAs take nitrogen to liver to convert to urea
alkaline and glutamine
the cyclic AMP system occurs with steroid or nonsteroid hormones?
nonsteroid
what protein does the cyclic AMP reaction (ATP–> cAMP) activate?
protein kinase
epinephrine increases _________ and ___________
glycogenolysis and lipolysis
norepinephrine increases
lipolysis
glucagon increases
muscle glycogenolysis
steroid and non steroid hormones: which is lipid soluble?
steroid hormones are lipid soluble–> derived from cholestrol(lipid), CAN CROSS CELL MEMBRANES
what alters enzyme activity? steroid or nonsteroid hormones?
nonsteroid
what alters membrane transport( glucose uptake at muscle, insulin)? steroid or nonsteroid?
NONsteroid
what alters protein synthesis rates? steroid or nonsteroid
steroid and NONsteroid
