Lecture 8 Flashcards
(25 cards)
Maximal oxygen uptake (VO2max)
Air - is inspired into the lungs - (through pulmonary circulation) - O2 flows into heart blood - (through the peripheral circulation) - O2 consumption into the Muscle - then flows into the mitochondria
Mitochondria - CO2 production occurs in the muscle - (through the peripheral circulation) - CO2 flows into and out of the heart blood - (through the pulmonary circulation) - and is expired into the lungs - and out into the air
Physiological Definition
- the highest rate at which the body can take up, transport, and utilize oxygen to perform muscle work.
Primary Criteria for Determination
- the VO2 fails to increase despite a rise in speed of locomotion or work rate (i.e. a “plateau” is observed)
Plateau - this is their max and can’t go any higher (2 dots at same level)
No plateau - not their max they gave up early (only one dot on the same level)
Secondary Criteria for Determination
- does the peak = maximum?
1. HRmax = 95% of predicted (220-age)
- ex. 20 years old with 190HR is close to max HR
2. RERpeak > 1.15
3. RCP (VT2) is evident
4. Blood lactate concentration (>8mM)
5. RPE (19-20 on 20 point scale)
6. Validation or verification trial
Measuring VO2max
Increase muscle wok —> increase VO2
“Ramp” protocol (straight line) - prof likes these more
“Step” protocol (line looks like a stair case)
O2 supply rate vs. O2 demand - muscle work rate
- determined by exercise
- positive line
Ramp-incremental exercise
1 watt every 3 sec
Almost 10 minutes of cycling till your legs just stop
- body won’t allow you to continue
VO2max is 3.6 L/min
- max is at 350 watts
Exercise protocols to identify VO2max
Can’t pass their own bodies max, even if they want to their bodies will shut down
“Ramp” incremental (30 W/min)
- POpeak = 375 W
- VO2max = 3.7 L/min
“Step” incremental (60 W every 6 min)
- POpeak = 290 W
- VO2max = 3.7 L/min
O2 demand > max O2 supply rate
VO2max and constant work rate-exercise
The longer your above your critical power the least amount of time you can stain the exercise
- 300 W (7 minutes exercising)
- 320 W (4.5 minutes exercising)
- 280 W (14 minutes exercising)
Validation trial
Heart failure patient 1
- ramp RER = 1.13
- VO2 basically the same throughout
Heart failure patient 2
- ramps RER = 1.15
- different VO2’s
105% of peak work rate from the ramp
How to express VO2max
Variable - female - male - %Difference - Range
VO2max L/min - 2.00 - 3.50 - (-43) - 2.0-4.5
VO2max mL/minxkg - 40.0 - 50.0 - (-20) - 15-60
- (taking body mass into consideration = reduces % difference by 23%
VO2max mL/kgFFMxmin - 53.3 - 58.8 - (-9.0)
Body mass, kg - 50 - 70 - (-29)
Percent body fat - 25 -15 - (+67)
FFM, kg - 37.5 - 59.5 - (-37)
VO2max and modality
Cros country skiers have the highest VO2max
- lower and upper body muscle
Activities that engage more muscle mass will result > VO2max
VO2max varies between individuals
15 females had a VO2max between 40-45
KIN students
Average: females = 46, and males = 54
Normative values for VO2max
Males - 18-19: P5 39.1, P50 48.0, P95 57.6
- 20-24: P5 36.8, P50 46.4, P95 56.9
Females - 18-19: P5 35.9, P50 41.7, P95 48.9
- 20-24: P5 34.5, P50 40.2, P95 47.1
VO2max and fitness status
Fitter individuals can exercise at intensities associated with higher O2 demand because they have a greater VO2max
Trained - max is higher oxygen uptake, faster speed
Untrained - max is lower oxygen uptake, slower speed
Importance of VO2max
A predictor of endurance exercise performance
A sensitive measure of training effectiveness
- if its a straight line the program isn’t working
A predictor of mortality in clinical populations
- study of those with heart disease, 4 year follow up
- after 500 days, 5% died
- after 1000 days, 40% died
- how many survived?
VO2 response to step-change in work rate
20W —> 120W
Tip: VO2 reflects muscle oxidative phosphorylation (OxPhos) - i.e. O2 utilized by muscle
Tip: the green line (OxPhos) reflects the circles (VO2) from the previous slide
Oxidative phosphorylation does not immediately achieve steady-state
PCr and Glycolysis/Glycogenolysis must contribute a lot at the beginning of exercise to satisfy ATP demands of 125W
- anaerobic energy sources stop contributing
Exercise intensity “domains”
VO2 response pattern changes in relation to metabolic boundaries
- moderate
- heavy
- severe
Two Metabolic Boundaries Define “Exercise Intensity”
Lactate threshold (LT)
- the highest metabolic rate (or VO2) at which blood lactate can be maintained at resting levels
- separates:
- moderate from heavy intensity exercise domains
- “comfortably sustainable” from “uncomfortable sustainable”
Critical Power (CP)
- the highest VO2 at which oxidative metabolism can provide all of the ATP resynthesis requirements
- separates
- heavy from severe intensity exercise domains
- “uncomfortably sustainable” from “uncomfortable unsustainable”
Energy systems during “all-out” exercise
Contribution of “anaerobic” systems (PCr, Gly) decline as sprint continues (power falls) until OxPhos is the only system
The “plateau” (blue —-) gives the highest power output that can be maintained solely by OxPhos (i.e. “CP” ~220W)
The LT (green —-) is below CP
Relative to maximal ATP resynthesis rate of OxPhos:
- PCr is 3.5x times greater
- Gly is 2x greater
Therefore greatest when PCr predominates
What about submaximal exercise?
What does the integrated metabolic response look like when our activity requires a low rate of ATP resynthesis that is below LT (i.e. low power output) within the green region (i.e. <160W)?
NOTE: this is an example. The power output @ LT differs between individuals and thus the range of power outputs of the moderate domain (green shaded area) will vary from person-to-person BUT the metabolic profile and perception of effort with exercise within the moderate domain will be identical.
Moderate intensity Domain (below lactate threshold)
Oxidative phosphorylation efficiently sustains all the ATP resynthesis once steady state is achieved
PCr and Glycolysis contribute very little at the beginning and not at all during state
Exercise = “easy”, “sustainable”
What about submaximal exercise? (Heavy)
Increase ATP synthesis rate increase
What does the integrated metabolic response look like when ou activity requires a rate of ATP resynthesis that is between LT and CP (i.e. 160 to 230W)?
NOTE: the power output @ CP also differs between individuals and thus the range of power outputs of the heavy domain (blue shaded area) will vary from person-to-person BUT the mtabolic profile and perception of effect with exercise within the heavy domain will be identical.
Heavy intensity domain (between lactate threshold and critical power)
360 seconds (6 minutes)
Oxidative phosphorylation sustains all the ATP resynthesis once steady state is achieved but does so less efficiently
PCr and Glycolysis contribute much more and for much longer after exercise onset but not after steady state is achieved (greater and longer contribution of both)
Exercise = “hard”, “uncomfortable” but “sustainable” (you can do it with the proper motivation
What is submaximal exercise (severe)?
What does the integrated metabolic response look like when out activity requires a rate of ATP resynthesis that is above CP (i.e. >230W)
You can’t maintain a speed above the critical power for a long time
NOTE: the power output @ CP also differs between individuals as does the time one can tolerate exercise at a given PO above CP (red arrows) BUT the metaboli profile and perception of effort with exercise in the severe domain will be identical.
Severe intensity domain
Oxidative phosphorylation cannot sustain all the ATP resynthesis requirements on its own and efficiency of this system progressively falls (no steady state)
PCr (280W, must be sustained by anaerobic) and Glycolysis contribute much, much more at exercise onset and continue to contribute as effort continues (leading to mtabolic accumulation (lactate, H+, Pi) and muscle fatigue)
Exercise = “very hard”, “exhausting”, “uncomfortable”, “unsustainable”
Exercise intensity domains
VO2 steady state - lactate steady state - energy source in steady state - exercise duration - upper boundary - training
Moderate - Yes - N/A (lactate does not change from resting concentration) - aerobic - hours - lactate threshold - distance (easy)
Heavy - yes (but greater O2 cost - i.e. reduced efficiency) - Yes - aerobic - up to 60 min or more (more if you’re well trained; depends on how far above LT the exercise work rate is) - critical power - tempo/steady (race pace)
Severe - No - No - aerobic + anaerobic - ~2-30 min (depends on how far above CP te exercise work rate is) - VO2max - intervals
Summary
All metabolic pathways work together (with goal of satisfying) and simultaneously
How the metabolic systems support exercise changes in relation to two metabolic boundaries (lactate threshold and critical intensity)
The two metabolic boundaries create three exercise intensity domains
Exercise in the different intensity domains require different contributions of the metabolic pathways to provide the needed energy
