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)
