The Physical Rules
of Aerobic Metabolism Part II
Week 12. Oxygen Powered Metabolism, VO2 Max, Speed and Performance
“Oxygen powered metabolism” pushed to the max begins to top off in the world’s fastest athletes at a speeds running near 13 mph in a marathon – and then maxes out around 15 mph in the 5k and 3k races – as shown in the combined lactate and VO2 graph below.
The hard line is: Oxygen based power in muscle cells cannot boost speeds past 15 mph. This tells us aerobic metabolism is a ‘weaker’ form of metabolism relative to anaerobic glycolysis.
This lecture is a short story on aerobic metabolism, VO2 max, health and performance, but one that tells it much differently from conventional standards – particularly by:
1. Clarifying what it is not.
2. Understanding the body’s use of oxygen – first at rest. (before explaining oxygen consumption relative to exercise intensity or any physical effort whatsoever)
3. Reinterpreting aerobic exercise in terms of the physical severity of stress and damage it causes – ranging on a scale from ‘easy on the system’ to ‘stressful maximum on the heart’.
This reinterpretation expands into derivative/advanced presentations on nutrition, health, the heart, brain, and functional longevity.
I am emphasizing it is paramount to conceive how the whole body consumes oxygen at rest – especially cells of the brain and heart – in order to completely understand the positive and negative relationships between health and exercise.
The modern convention essentially ignores cells ‘working at rest’ – giving the impression aerobic metabolism (or just metabolism) is a separate function from the “exercise/performance/speed/power”.
This explains why people perceive sports nutrition as a ‘specialized’ form of eating that doesn’t pertain to their needs or lifestyle – they think ‘exercise/performance’ for athletes doesn’t apply to ‘health/everyday people’ – which couldn’t further separate their belief from the simple truth of the need to simply eat for healthy function – regardless of their level of activity.
Aerobic exercise is aerobic metabolism. Exercise = metabolism speeded up.
Conceiving rest/zero mph as part of the ‘exercise/activity’ of cells is vital if one is to more clearly understand health, nutrition, and exercise.
Clarifying Aerobic Metabolism: what it is not
Oxygen powered metabolism never produces explosive power, does not make muscles contract with great force in any type of exercise, and cannot boost speeds past 15 mph.
Aerobic power allows us to sustain a ‘high’ submaximal speed over time and distance in races like the marathon and 5k or 3k races, all of which are extremely stressful on the heart, blood, and coronary arteries.*
- Thinking in pure physical outcomes of stress/strain on tissues – specifically the overstretching of body parts such as the left ventricle and blood vessels – reveals why ‘pushing aerobically’ at high intensity levels for an hour or more (repeatedly over years) can easily damage both the heart and coronary arteries. (Covered in Week 16)
- Keep in mind for now and future presentations, the majority of negative effects, e.g. arterial calcification, heart fibrillation, muscle thickening and fibrosis – apply mainly to competitive performers who actually do perform in the high end of the ‘VO2/maximal-stress’ aerobic zone.
Reinterpreting the range of aerobic exercise into an analogous range of stress
By interpreting aerobic exercise in combined terms – of speed and stress – we see the entire range of oxygen produced power spans from ‘easy on the system’ to ‘stressful maximum on the heart’.
‘Easy on the System’ begins at the yellow dot (at rest / zero mph).
The green dot marks ‘Stressful Maximum on The Heart’ (at maximal aerobic power or where VO2 max occurs) running 15 mph.
Thus, the scale of severity of stress induced on cells, muscles, blood, the heart and its arteries ranges from ‘low to high’ – from zero mph to 15 mph.
From this standpoint – while I am preserving a conventional presentation showing muscles’ dual role in producing speed and consuming oxygen – I am introducing a more vital way to understand functional longevity of the body – especially the brain, blood, the heart and arteries.
This begins by visualizing what aerobic metabolism is – at rest.
Oxygen Consumption Visualized – at rest.
All the cells of your body use a tiny amount of oxygen. If you place your body inside a sealed airtight space as the artist did in the plaster of Paris box below – the space you inhabit becomes a single cell – and to an outsider you appear as a single gigantic cell.
Let’s look at this real life example and other scientific ones that show how this works.
Under all the conditions above a grand total Volume of Oxygen (VO2) enters the ‘space’ and a Volume of Carbon Dioxide (VCO2) exits.
When we say “oxygen is consumed”, this means O2 combines with the carbon in food to make CO2. Thus, aerobic metabolism is a slow form of combustion in cells – including the brain, heart, muscles.
Fuel + VO2 –> VCO2 + H2O + Heat
In tests such as a VO2 max test we measure the volume of O2 gas consumed collectively by all cells of the body – measured in liters or ml – indicated for now on as VO2.
Next, in a VO2 graph, we first consider the VO2 used at rest over a 1-minute period.
Then we consider how VO2 increases with exercise intensity.
Graphing Oxygen Powered Metabolism at Zero MPH (or at Rest)
Assume the astronaut, tapped artist, or scuba diver or anyone are relaxed and still.
Relaxing humans consume on average, approximately 1/3 liter of O2 per minute – as indicated by the yellow dot on the VO2 graph below.
Keep in mind, even though speed is zero – power production or aerobic metabolism in cells is active – your body is still working and consuming oxygen at rest – akin to an ‘engine at idle’ in a car.
Fuel + VO2 –> VCO2 + H2O + heat.
Note: 1 minute is the standard amount of time used to quantify a measurement of VO2 consumed.
Key Points of VO2 at Rest in a Human
- The volume of O2 used per minute by a human at rest would fill a balloon approximately the size of an orange, which is 1/3 liter. 1/3 liter = 333ml.
- At rest, VO2 per minute is called 1 MET for 1 metabolic equivalent, which = 1/3 liter.
- 1 MET is a human’s form of ‘idling’ – akin to an idling car engine using fuel and oxygen at its low point of consumption.
- Every human’s ‘idle’ point consumes either a bit more or less than 1/3L O2. This means 1 MET for all people – or their basal metabolic rate – is unique – but always fairly close to 1/3L O2 consumed per minute.
Now, forget about the graph for a moment and picture your whole body using oxygen at rest.
Feel each breath enter into your lungs; this air contains oxygen gas, which enters into your bloodstream through your lungs.
At rest muscle cells consume very little O2 – since you are not using them to move. But since only muscle cells dramatically consume more oxygen over their resting values compared to other cells – your whole body’s VO2 increases progressively and linearly – from the yellow to green dot – as speed increases.
Thus, we see actual values of VO2 in humans rise from 333 ml to nearly 3000 ml per minute – from rest to running 15mph respectively.
Comparing a horse to a human, we see speed and oxygen consumption increase similarly and the exact same leveling off – where aerobic metabolism provides no additional boost to speed.
In each case, VO2 max is the where the graph levels off and anaerobic glycolysis takes over to boost speed.
Any speed below 100% VO2 max (15mph) translates to running at a fraction of it: see the human running 7.5 mph – runs at 50% VO2 max.
85% VO2 max occurs running 13 mph (at lactate threshold – for the pace ran by World Record holder Dennis Kimetto). All speeds faster toward VO2 max/15 mph are way past lactate threshold for even elite athletes, which explains why the world world record paces and times in the 3k and 5k races can’t be sustained or ran in significantly shorter times.
There’s nothing extraordinary about testing and graphing VO2 in animals. Gradually increase running speed. Record oxygen consumption until it peaks and no longer rises – though speed may still increase. Stop the test there. Details next week when we do it in lab.
We return to the hard line:
Power production in cells of both humans and horses performing at VO2max are nowhere near maximum. Oxygen based power is ‘weak’ compared to anaerobic glycolysis.
Keep in mind, performing for short periods near maximum aerobic output – the maximum stress zone – is not necessarily harmful. It the sustaining that creates the damage – and additionally prevents recovery to cells and tissues at speeds too high and frequent over time – especially in competitive ‘athletic’ people.
What VO2 max is and is not in perspective:
When aerobic power reaches its maximum – it cannot boost speed or power past 15mph. (running)
Humans can almost double their speed over the speed where VO2 max occurs! (15 to 27.8 mph)
Only anaerobic power – specifically extreme glycolysis – boosts speed past VO2 max speed.
Increasing speed from idle – 1 MET – progressively consumes more fuel and oxygen at a fairly linear rate. (as opposed to the exponential increase with acid production.
In the world record 3k and 5k runners VO2max occurs at 15 mph – which can be sustained for only around 7.5 minutes.
The men’s 3k world record is 7:20.67 set by Daniel Komen of Kenya, in 1996.
Severity of stress on cells, muscles, blood, the heart and its arteries ranges from ‘low to high’ – from zero to 15 mph.
Comparing Other People to the World Record Marathon Runner, Dennis Kimetto
Red line/dot: Dennis Kimetto, World Champion Marathoner runs 26.4 miles averaging just under 13mph. The red dot shows where Dennis Kimetto’s ‘race pace’ acid levels are before rising exponentially – just under 13mph at 85% VO2 max.
Blue line/dot: An ‘out of shape’ person’s threshold pace is at 6.5mph or 40%VO2 max – with acid levels shifting exponentially ‘sooner’ at lower speeds.
Gold line/dot: A fit person reaches race pace or lactate threshold occurs at 10mph or 65% VO2 max.
‘Out of shape’ people shift into high rates of glycolysis at lower intensities compared to fit or trained people. Trained humans have higher lactate thresholds.
Dennis Kimetto and other endurance athletes’ higher lactate thresholds just delay the inevitable as they increase running speed – namely the unavoidable shift into ‘crazy glycolysis’. This delayed shift in a trained person occurs at a higher fraction of VO2 max compared to a detrained person – shown below.
Again, having a high VO2 max doesn’t necessarily allow a person to sustain running a competitive pace, but avoiding anaerobic gycolysis and lactate production until reaching speeds at a higher of fraction of person’s VO2 max occurs does!
Thus, VO2 max is not a predictor of race performance – but lactate threshold is.
Additionally, people who train gain the ability to run near or at lactate threshold – or put up with the pain longer. It requires sustained mental and physical effort to perform near lactate threshold. Compare the ability to sustain performing at threshold:
- Out of shape people: 30-45 minutes
- Recreational athlete: 60 minutes
- Pro-elite athletes: 90 minutes
It is uncomfortable to sustain paces near lactate threshold. This partially explains why some people never work hard enough to improve fitness or whine about ‘hard work’. This is pretty much the only time ‘no pain no gain’ should be thought as a positive.
Improving Fitness Illustrated in The Cell and by The Lactate Shift
When an out of shape person increases their fitness this means they increased lactate threshold – shown by pushing the curve to the right. This is called the lactate shift.
After a year of training it is possible that an out of shape person could shift lactate threshold from 6.5 mph to 10mph as shown in the shift from the blue to the gold line below.
Illustrated below: Color coded zones of lactate threshold training and the coaching lingo to go with it.
In a nutshell the key to increasing fitness and/or competitive race paces is to work near, at, or slightly above lactate threshold pace.
Parting Thoughts and Advancing Thoughts
Muscle’s demand for producing power is evident by the 500% increase of blood flow over their resting levels at their maximum VO2 produced power, which maxes out at 15 mph in the world’s fastest runners.
Going forward, do not forget the heart is under great strain performing running competitively. It stretches dramatically as it’s forced to expand – by filling up with up to 2x the amount of blood in order to sustain high aerobic speeds – maximized over time in the 1/2 marathon to marathon distances and maximized at the peak of the aerobic-max-stress point in the 3k and 5k races.
Additionally to the stress/strain on heart muscle tissue and arteries – cellular level fatigue leads to permanently energetic depletion of cells of the heart – resulting in mitochondrial damage, swollen/inflamed cells – beyond the damage mentioned by O’Keefe et al. in Run For Your Life. (Examined by other researchers)
I am purposely conditioning you to come to realize excessive endurance exercise can seriously damage your heart, arteries, and blood – besides your knees and feet.
Real World Graphing of VO2 – in MPH from Walking to Sprinting
ASSIGNMENT: Graph these figures above on the graph below:
Note: 1 minute is the standard amount of time used to quantify a measurement.
- A person’s VO2 at rest may be 333ml/min.
- VO2 at moderate intensity could actually be 1500 ml/min
- Max VO2 could actually be 3300 ml/min, which occurs at moderately high intensity – well before reaching very high intensity.