Looking under Froome's hood. Again.

I posted this item in December 2015 after some data on physiological testing of Chris Froome was made public in a mostly PR piece. Have a read there first if you haven't already done so.

Today I saw the published science paper was released and from the abstract I pulled out a few extra pieces of information, namely Froome's gross efficiency (23% at ambient conditions), power at blood lactate level of 4mmol/l (419W). His reported weight for the test was 71kg, which is likely above his racing weight.

So I thought I'd do up another chart, this time fixing the gross efficiency and VO2max values, and plotting the curve of aerobic power in W/kg terms versus fractional utilisation of VO2max:

The relationship between aerobic energy yield per litre of oxygen, gross efficiency, VO2max, fractional utilisation of VO2max and power output is outlined in this earlier blog post.

So what can we make of this?

1. A TdF winning cyclist has the physiology you'd expect of a TdF winning cyclist. That should be hardly surprising.

2. Froome has both high VO2max and high gross efficiency, which is a killer combo. Neither represent out of this world values. What that means is Froome's sustainable aerobic power output is then a function of his fractional utilisation of VO2max, and FUVO2max at threshold is a highly trainable aspect of one's fitness, more so than gross efficiency or VO2max.

3. The sustainable power as measured in this test was at a blood lactate level of 4mmol/litre, which is an arbitrary level for such testing. What any individual rider's BL level is at their actual "threshold" is quite variable, often somewhat higher.

4. It would seem that Froome's fractional utilisation of VO2max at this power level was ~86-87%. That's a pretty reasonable value for longer duration efforts of at least an hour for highly trained cyclists and it can quite feasibly be higher than that at threshold power, and certainly higher over shorter durations, e.g. 15-20 minutes.

5. The testing was also conducted at high humidity (60%) and temperature (30C) and somewhat interestingly Froome's gross efficiency was higher (23.6%) than when tested at ambient temperature (20C) and humidity (40%). That would add ~0.15W/kg at threshold, a very handy result for hot days. The reported his sustainable power was 429.6W at high humidity and temperature versus 419W at ambient temp and humidity. That power difference of 10.6W / 71kg = 0.15W/kg.

6. Weight. I'd expect Froome's race weight would have been a few kgs less than at the time of testing. e.g. 67kg at same power would add 0.35W/kg to threshold power.

Doping? Once again, this sort of data tells us nothing about any rider's doping status.

Read More......

Looking under Froome's hood

A little over two years ago I wrote about the relationship between four key underpinning physiological parameters that determine a rider's sustainable power output:

• VO2max
• Energy yield from aerobic metabolism
• Efficiency
• Fractional utilisation of VO2max at threshold

I don't propose to repeat myself, so go here to read that first if you'd like a more detailed explanation.

Data on some physiological testing by Chris Froome was released earlier today, so I thought I'd put a marker on one of the charts I posted in that earlier item to see where he sits.

I took the data from the cyclingnews article linked below:
http://www.cyclingnews.com/news/chris-froomes-physiological-test-data-released/

In it the key 2015 data are listed as:

Weight: Test: 69.9kg, TdF: 67kg
VO2max: Test: 84.6ml/kg/min, TdF weight adjusted: 88.2ml/kg/min
Threshold power (20-40 min): 419W
W/kg: 5.98W/kg, TdF weight adjusted: 6.25W/kg

So given we are talking 20+ minute power, a fractional utilisation of 90% of VO2max for an elite athlete is not unreasonable, so here's that particular chart, and overlayed on that is a pink box defining the area covering a range of VO2max from 75ml/kg/min to 95ml/kg/min and gross efficiency range from 19% to 25%. You'd expect elite cyclists to be somewhere in that range.

Froome's estimated TdF VO2max and 20+ minute power/mass are then shown by the green dot:

What can we infer from this?

Not a lot really, other than the data are in line with what you would expect for a rider with the performances of a grand tour winner. Certainly the physiological values are in line with historical data on plausible physiological parameters for elite aerobic endurance athletes.

As far as informing on doping status, as with power meter data and climbing power estimates, it tells us SFA. In any case I doubt it will change anyone's opinion either way.

Edit: here is a link to the lab report:
https://www.gskhpl.com/dyn/_assets/_pdfs/ChrisFroome-BodyCompositionandAerobicPhysiology.pdf

Read More......

Looking under the hood

Today I'm going to take a look under the hood of Functional Threshold Power and explore the relationship between four key underpinning physiological parameters that determine FTP:

• VO2max
• Energy yield from aerobic metabolism
• Efficiency
• Fractional utilisation of VO2max at threshold

I've prepared a chart (sample below), which I will come back to later to explore this relationship a little more. Those with an existing understanding of the relationship will likely need not look further than the various charts posted, and as normal you can click on them to reveal a larger version.

Scroll down and you will see several versions, showing the relationship between FTP, VO2max and GE at fractional utilisation of 75%, 80%, 85% and 90% of VO2max.

Our maximal sustainable aerobic power is primarily a function of our VO2max,
our gross efficiency, and our fractional utilsation of VO2max at threshold.

For everyone else, I'll introduce and explain the significance of each of these factors and then give an example of how changes affect the power we can sustain.

VO2Max

VO2max testing by the AIS
as reported by Katya Crema

VO2max is a measure of the maximal rate at which we can utilise oxygen. Normally it's also defined by how it is measured, e.g. during an incremental exercise test where the power demand is increased at a specified rate, and how long VO2max is sustained for, so that we don't rely on instantaneous peak values. Measurement of oxygen utilisation requires laboratory testing equipment that records the flow and composition of the body's respiratory gases while performing exercise.

VO2max will typically occur eventually when attempting to sustain a power output above functional threshold, and once reached is typically not sustainable for more than a handful of minutes. How quickly we attain a state of VO2max, and how long we can sustain it are determined by how far above functional threshold power we are attempting to ride, our fitness, power profile and some other individual characteristics.

VO2max is expressed in units of oxygen consumption per unit time, either absolute, i.e. litres of oxygen per minute, or relative to body mass, i.e. millilitres of oxygen per kilogram per minute.

e.g. if a 70kg rider has a VO2max of 60ml/kg/min, it means that for every kilogram of body mass, they can maximally utilise 60 millilitres of oxygen per minute, or 70kg  x  60ml/kg/min  /  1000 ml/litre = 4.2 litres of oxygen per minute.

VO2max sets the ceiling on our aerobic performance capability and as such is a reasonable determinant of our endurance performance potential, however it's not a particularly good predictor of performance. All one can really say is that to be an elite and/or professional cyclist, you will need a relatively high VO2max, typically in excess of 70ml/kg/min, however higher doesn't necessarily mean you will perform better. It just gets you a ticket to the game, but won't necessarily mean you'll be good enough to play.

That's because power output matters far more than how much oxygen we happen to use to generate it, and VO2max is not the sole factor in how much power we are capable of sustaining. And of course there are other factors beyond physiological that determine performance, but all things considered, in endurance cycling power output is a major factor.

VO2max is trainable, although it is also significantly genetically determined (perhaps half), so in a sense, you need to have chosen your parents wisely. You may not see much improvement in absolute VO2max from training, or quite a lot, or something in between. Trainability, which differs by individual and also has a sizeable genetic component, and starting fitness level are big factors. Improvements in VO2max of around 10-25%, can occur in a matter of months. Of course one can attain improvement in VO2max when expressed per unit of body mass simply through weight loss.

There have been some phenomenally high VO2max values occasionally recorded, well into the 90+ ml/kg/min range, with young Norwegian cyclist Oskar Svendsen reported to have the highest recorded VO2 max of 97.5ml/kg/min. Greg Lemond, the American professional cyclist of the 1980s and early 1990s and winner of three Tours de France, was reported to have had a VO2max of 92.5ml/kg/min, and he responded in an interview once that it was in the 92-94ml/kg/min  range. I don't vouch for the validity of these numbers, merely pointing out some of what's been reported.

Energy yield from aerobic metabolism

Citric acid cycle as per wikipedia

Without oxygen we'll die (well duh), and it's critical for sustaining our body's energy production needs, and just like many means of releasing energy through chemical reactions (e.g. rockets, campfires, internal combustion engines and many other chemical reactions), our bodies also use oxygen to help release useful energy from fuel.

Of the biochemical reactions that release energy aerobically (i.e. with oxygen), we utilise two primary fuel sources, one being glycogen and the other free fatty acids (from our body fat stores). Most of the time we obtain energy from both, but when exercising at near threshold power and above, we are heavily, if not solely, reliant on glycogen to meet the energy demand.

Using glycogen as fuel, our body can release around 21.1 kilojoules (kJ) of energy per litre of oxygen. We get a little less from aerobic fat metabolism, around 19.8kJ per litre. So in general the energy released per litre of oxygen utilised is somewhere around 20-21 kJ depending on the mix of fuel substrate used.

We do have the means to also produce energy without oxygen (i.e. anaerobically), however such energy pathways are available to us only for brief periods and are not sustainable, but are good for rapid energy demand (e.g. sprinting) and to supplement the energy provided via aerobic means when the energy demand exceeds our ability to supply via aerobic metabolism alone. Due to the limited supply of such energy though, such efforts are of short duration (seconds to minutes).

Here's a summary of the main energy pathways used by our bodies. It's a fairly complex topic (e.g. just look up the Kreb's Cycle for starters), and is one for the physiologists to chat about over a beer, beer being another key fuel substrate and one of the major food groups, along with burritos, donuts, caffeine and chocolate.

Efficiency

The basic definition of gross efficiency (GE) is the ratio of work done during the specific activity to the total energy expended and expressed as a percentage.

In the case of cycling, GE is the ratio of the energy delivered to the cranks of the bicycle to the total energy metabolised by our body. Sometimes this is referred to as gross mechanical efficiency (GME), just to emphasise the relationship between the mechanical work done at the cranks, to the total energy metabolised by the body.

There are a number of definitions of efficiency in exercise physiology and if you'd like to read about them in a little more depth, then this paper: The reliability of cycling efficiency by Lukh Moseley and Asker Jeukendrup (MSSE 0195-9131/01/3304-0621/$3.00/0 ) is a reasonable place to start and I'm sure there are others. That's just the PubMed extract which doesn't say much about the definitions, but you can find full text version online if you search, and it's a little more instructive.

As highlighted in that paper, trained cyclists typically perform with a GME of around 19-24%, meaning that of the energy metabolised, only about one-fifth to one-quarter actually ends up propelling us forward on a bike. The balance is mostly given off as waste heat, with a little energy of course needed for life support functions!

Have a quick think about that: for every watt you generate at the cranks, you are geneating around another 4 watts of heat. A rider performing longer intervals at 300W is generating somewhere in the vicinity of 1200W of heat! This is precisely why cooling is so vital for performance, as we need to dissipate that excess heat in order to continue to perform at that level.

To measure efficiency we need to measure both our energy output to the bicycle (via a power meter) and our total energy metabolised, which is done via the same respiratory gas exchange analysis equipment used to test VO2max, indeed the two factors are usually measured from the same test. Perhaps one day there will be practical and portable means to measure energy metabolised in the field but for now, the only reliable means is in the lab.

Gross mechanical efficiency can be acutely affected by things such as fatigue, hydration status, glycogen levels, environmental conditions and so on. Chronically we have an efficiency level granted to us by genetic inheritance plus however much we can manage to improve over the course of our cycling careers.

Efficiency is trainable, in particular over the long term, perhaps not to the degree of VO2max or lactate threshold, however other than by performing large volumes of training over many years, it's not totally clear whether or what specific training one can perform to achieve short term improvements. There's lots of noise from many purveyors of a fast performance gains to do with changing pedalling "techniques" or equipment choices, and while some are based on sound science and worth paying attention to, some are far more speculative, while others fall into the snake oil category.

One thought on efficiency is it's related to mix of muscle fibre types, as slower twitch fibres tend to operate with greater efficiency than their faster twitch cousins (which are better at utilising rapid energy release but less efficient metabolism), and so a fast twitch dominant sprinter is more likely to have a lower overall gross effiiency than their diesel mate. The science demonstrating the scope for chronic improvement in efficiency is a bit more limited than for VO2max and lactate threshold, and longitudinal studies are not common.

One thing efficiency is not: it isn't how you pedal, nor the way in which you apply forces to the cranks. It would really help if manufacturers of various cycle training aids would stop misusing the term - it confuses people no end.

Fractional utilisation of VO2max at threshold

This is the percentage of your VO2max you sustain when riding at your functional threshold power. It might range for example from 75% of VO2max to ~ 90% for very fit riders and is an aspect of our fitness and performance that is very trainable over the short to medium term, and can be the element of fitness we gain the greatest improvement from, but it is also something that can be developed over many years of training.

To briefly illustrate, if two riders have an FTP of say 300W, and one is doing so at 80% of their VO2max, while the other at 90% of their VO2max, the rider at 80% of VO2max has quite likely far more scope to further improve their threshold power output.

Ok, so how do all of these factors relate?

There have been suggestions VO2max and efficiency are inversely correlated, although I'm not sure how firm that relationship is, if indeed it exists across the board, or if there is a sound physiological reason why that might be the case.

The maths of the relationship is pretty straighforward though:

FTP = Energy per litre O2 (J)  x  VO2max (ml/kg/min)  x  Fractional VO2max at threshold (%)  x  GME (%)  /  60 (seconds/minute)  / 1000 (ml/litre)

e.g. 

Energy per litre of O2: 20,900 joules (say, refer above for details)
VO2max: 65ml/kg/min (say)
Fractional utilsation of VO2max at threshold: 80% (say)
Gross mechanical efficiency: 22% (say)

FTP = 20,900J  x  65ml/kg/min  x  0.80  x  0.22  /  60,000  =  3.98W/kg

So, now we can see that FTP is a function of those four variables, although we can reasonably assume the energy released per litre of oxygen at threshold is fixed, leaving us three variables to tinker with, and of course you can flip that equation around to ascertain any of the variables chosen given the other factors are known or assumed.

So back to the chart I posted earlier, see this example:

FTP W/kg for a fractional VO2max of 80%.
This rider has scope to improve threshold power by
increasing the fraction of VO2max they can sustain at FTP

On the vertical axis is gross efficiency, the horizontal axis VO2max, and plotted are curves representing various threshold power to body mass ratios, in steps of 0.5W/kg from 2.5W/kg through to 7.0W/kg, for a rider whose threshold power (FTP) occurs at 80% of their VO2max.

So for instance, if a rider has a VO2max of 65ml/kg/min and a GE of 22%, then we can see these intersect at around the 4.0W/kg curve. They could also have the same FTP with higher VO2max but lower efficiency (and vice versa).

If this rider managed to improve their fractional utilisation of VO2max at threshold from 80% up to 90%, then this is what happens with the very same GE and VO2max:

FTP W/kg for a fractional VO2max of 90%.
At same GE and VO2max, rider can sustain a far high power output

All of the W/kg curves have moved down and to the left. Now we can see that the same combination of GE and VO2max results in an FTP of ~4.5W/kg. 

Check the maths: 20,900 x 65 x 0.90 x 0.22 / 60,000 = 4.48W/kg.

To attain the same level of power improvement without increasing fractional VO2max utilisation, it would require an increase in GE from 22% to a little under 25% (not very likely in the short term), or alternatively an increase in their VO2max from 65ml/kg/min to 73.4ml/kg/min.

Of course, one can attain a power improvement via a combination of all three factors, although it's more likely that one will improve VO2max and/or their fractional utlisation of VO2max at threshold in the short to medium term, than attain any short to medium term improvments in gross efficiency.

So what's possible for the freaks exceptionally talented?

The magical troika of high VO2max, high fractional VO2max utilisation at threshold, and a high GE may well be exceptionally rare in the same individual, if it's possible at all, but given a GE of 25% is not exactly unheard of (higher GE values have been reported although some question the validity of those measurements) and we have seen VO2max values reported well beyond 90ml/kg/min, and very fit cyclists will have a fractional VO2max utilisation of ~90% at FTP (I'm not sure if or how much higher that may potentially go), then if we have another look at the above chart and see where a combination of 25% GE and a VO2max of 97.5ml/kg/min intersects, it's beyond the 7.0W/kg curve. It's actually at 7.6W/kg. Yikes.

Of course no-one we know has been measured to have an FTP near that level, certainly no-one without blood/oxygen-vector doping assistance, but just what is actually physiologically possible or plausible? Who really knows?

And what's possible for us mere mortals?

Well have a look at the chart, find a threshold power line near where you are, or would like to be, or perhaps a VO2max value if you happen to know it, and see what various combinations of W/kg, VO2max and GE are required. See what happens at different fractional VO2max utilisation levels.

I dislike setting limits on what's possible, but it's clear that if your highest VO2max is say 60ml/kg/min and there's limited scope for pushing that up much further, then I hate to be the bearer of bad news but you will never see an FTP of 6.0W/kg, but 4.0-4.5W/kg is definitely within reach. 

What does it mean for training?

Well while it's fun to occasionally look under the hood to see what elements of physiology we need to work on to improve our threshold power, one doesn't really need to get too hung up on these individual factors, as they are all inter-related and power measurement not only conveniently condenses the outcome for us but is the primary physiological measure of performance that matters. So keep training hard and smart. There's still no short cuts to improved fitness. There's also no real need to rush out and get your VO2max tested, the power meter will tell you most of what's important.

When you are the limit of  your current improvement in power, then perhaps it might be time to consolidate those gains, and then consider whether a change of tack is necessary to make the next step up. Do you need to give your VO2max a bit more attention, or have you still room to move in lifting your fractional VO2max utilisation? How well do you personally respond to such training?

We can gain some insight into these relationships though inspecting our power profile, and relationships between shorter and longer range power outputs, or for example, how our Functional Threshold Power and our Maximal Aerobic Power relate.

Of course a focus on training to improve one element can and does impact the others, but not always. Perhaps some additional weight loss is required. What one chooses to focus on may be different for a seasoned pro than a local club amateur, but the principles are the same.

OK, enough of that for now - it's time to close the hood, get back into the saddle, and rev the engine!

OK, here are the same charts for each of the fractional VO2max levels I mentiioned earlier:

75% of VO2max:

80% of VO2max:

85% of VO2max:

90% of VO2max:

Read More......

Anaerobic Stuff - Mr Peabody's WABAC Machine

Time to get into Mr Peabody's WABAC Machine. C'mon Sherman, let's wind the clock back to 2007....


This post is another take on my February 2007 Darth Vader item. Back then I wrote, with considerable assistance from Mr Peabody - er, I mean Dr Andy Coggan, an item about Maximal Accumulated Oxygen Deficit (MAOD).

Andy introduced the concept of using power meter data from a well paced individual pursuit as a means to estimate MAOD (which ordinarily would require lab based testing). He expands on it in the book, Training & Racing with a Power Meter, pp 244-248 (2nd edition).

Just to recap, MAOD is the "gold standard" measure of an athlete's anaerobic capacity. Expressed in litres of O2, it's the difference between the energy produced aerobically and the total energy demand. In an event such as the individual pursuit, a rider's total energy output is typically ~ 70-80% via aerobic means and the balance of course via anaerobic metabolism.

So I thought I'd take the analysis method from that previous post, run it on my recent events and add another twist - the points race.

In recent posts I've mentioned a few track endurance* events I've raced:
- 4km Individual Pursuit (Aussie National Championships - C4 paracycling)
- 2km Team Pursuit (Masters 150+ State champs)
- 20km Points race (Masters 45-49 State champs)

Edit: I've since updated the list to add in the 1-kilometre time trial I raced at the Paracycling nationals the day before the 4km individual pursuit.

It's all part of my comeback to competitive cycling, as these are the events I most enjoy. Well except for the individual pursuit. That's an event impossible to enjoy. But it's fun to do some analysis of pusuiting because it reveals so many things about a rider. Physiologically, technically, aerodynamically and psychologically.

In the weeks and months before my accident in 2007, I rode the same events, the only difference being the individual pursuit was 3km, not 4km and the team pursuit was 3km then vs. 2km this year (different distances for different masters age and paracycling categories).

I've been riding these events for many years but 2007 was my best season up to that point, with a win in the Team Pursuit (in a new state record time), a bronze medal in the National Masters Points race champs and two personal best times in the 3km IP. So for me, relatively speaking, they provide very sound benchmarks for how I've bounced back since then. I'm not going to go into that here though as I've already covered that a number of times.

OK, back to Mr Peabody and the analysis. Here's the chart showing cumulative O2 deficit from my recent races:


Click on the pic to enoxygenate (apologies for the Phil Plaitism).

The picture details the cumulative O2 deficit for four rides - my individual pursuit (red line), the team pursuit (blue line), the 1-km TT, and also a roughly 5-min section from my points race last weekend (the Richie Benaud cream jacket tan line). I'll get to the points race later.

Just to explain the chart - let's take the red line for the individual pursuit. You start the event from a dead stop (your bike is held in a starting gate which releases on count down to zero) and then accelerate over about 15 to 20 seconds to a high cruising pace, which you are then attempting to maintain for the balance of the event. The red line is a measure of how much oxygen "debt" I am incurring as time passes.

I incur this O2 "debt" since my power output in a pursuit is somewhat higher than my sustainable threshold power (which can be produced almost wholly via aerobic metabolism - or in a "pay as you go" sense). Once you ride above threshold, you are tapping into your limited anaerobic work capacity - and it really is limited - meaning that such efforts are by necessity going to be short lived. Harder you go, the less time you'll last. Nothing new about that.

Not only that but once you expend your limited reserve, in order to continue you will have no choice but be forced to ride under threshold in order to recover the O2 deficit. This is why pacing your effort is so crucial in timed events, and in mass start racing why dosing out the hard efforts at the right time is so important. The cost of "blowing up" is considerable in performance terms.

It's also why improving threshold power is so crucial. When you do go into the red zone in a race, you don't incur as much O2 deficit, or can last for longer at that level. And when the pace eases up again and you dip below threshold more quickly, you recover faster meaning you are ready for the next attack before someone else is. Counterattack anyone?

How do we determine this aerobic/anaerobic contribution with a power meter? Well as per the book, it's matter of looking at O2 kinetics of a well paced pursuit:


Andy showed that we can plot, along with the actual power output from a pursuit, a line representing a rider's theoretical maximal aerobic power output based on lab tests of a rider's VO2max** and efficiency***.

Except that in my case, I don't have the latter. Never mind, since the steady state part of a well paced pursuit represents power output at VO2max, we can simply adjust those VO2max and efficiency values so that they match the steady state portion of the pursuit power file. I assumed an efficiency of 22.5% and adjusted my VO2max value until it fairly represented my steady state power output in the pursuit. It came out at 58 mL/min/kg. If you change the VO2max (or efficiency) value, it moves that maximal aerobic (red) line up and down accordingly.

OK, so that's pretty funky, I can estimate my VO2max (or at least a range given that we assume efficiency is in a range typical for trained cyclists).

But by then directly comparing the difference between the maximal aerobic power, and what power I actually produced, we can then attain an estimate of the proportion of energy output from anaerobic contribution.

In my case, it estimates about 17% of my energy was from anaerobic supply. That's a little lower than typical for a pursuit, but my race time was 5:08, which is longer than the 3.5-min to 4.5-min efforts for elite riders in 3km and 4km pursuits and so it's not entirely surprising.

It also means that my MAOD was estimated at 4.16 L. We'll tag that number for now.

OK, so how about those cumulative O2 deficit lines?

In the WABAC machine we saw the way the O2 deficit would climb at different rates when riding a team pursuit as a rider alternately takes a pull on the front (O2 deficit line increases at a faster rate) and then gets back in line and recovers (where the line either rises more slowly or can even fall if the rider is quite powerful and not overly challenged by the team's pace).

If a rider exceeds their MAOD, then there is a pretty fair chance they will crack, which in a team pursuit means they are unable to continue and pull out after their turn on the front, or as sometimes can happen they cannot even maintain the pace of the rider(s) in front and they end up creating a gap in the line, which is bad news.

So I plotted the cumulative O2 deficit line from my recent individual and team pursuits and they shows the same pattern as in 2007. The team pursuit line is much shorter of course since the event is half the distance of the individual pursuit, and in a team, so it is considerably faster.

I also plotted the same line from a section of my points race on the weekend. I chose a starting point very early in the race, it was about lap 6, with 4 to go to the first sprint. My team mate was on the front at the bottom of the track, he slowed the speed down a little in the preceding half lap and then launched an attack, I was on his wheel and went with it.

I had to go pretty hard, with peak power reaching 1184W in order to cover it (he's a world class masters sprinter but not on form right now). The idea was to see what we could get from it - either get a break happening or at least pick up some early points for later strategic benefit.

Problem was, he cracked pretty quickly and I was left with about 3 laps to the sprint line. I was committed, had a gap, so went for it. The cumulative O2 deficit line shows just how deep I went. Very deep.

Once the sprint line was passed I then had to do everything I could to ensure I stayed in the race. You can see how the cumulative O2 deficit line drops away as I reduced my power output and went on the hunt for good wheels to follow. Not long later you can see the line begin to rise again as the next sprint was approaching. I sat that one out just making sure I got through unscathed and could cover any counterattacks.

When you look at the blue line tracing my cumulative O2 deficit from the team pursuit, it reaches a maximum of 4.26 L (about 2.5% higher than from my individual pursuit) and in the points race I reached 4.46L (7% higher than in the IP). What's going on there?

Well, a few things:

- firstly, there is normal day to day variability in performance.

Given that in this analysis we are keeping VO2max and VO2 kinetics**** constant, then the performance is wholly expressed as a difference in MAOD. And since anaerobic contribution to power output is still only 25% or less of total over several minutes, then it still only means a difference in performance of ~ 20-25% of 7% or less than 2% of the total power/energy.

- the next obvious difference is group versus solo efforts, and the influence of motivation/psychology

I would never discount the role that motivation can have on performance and perhaps I am capable of pulling just that little bit more out of myself in a team or a mass start event than I can in an individual pursuit. I can't imagine how I could go any harder in the IP, but it is interesting nonetheless to see if there's any more blood to get from this stone.

- thirdly, as Andy mentioned to me, lab studies indicate that MAOD is independent of the duration of the effort, although he doesn't recall any studies looking at efforts quite as long as this (~5-min). Perhaps that is a factor as well.

So there you have it.

As for the points race, well that attack was a very big risk and a large match to burn so early on. I really needed it to either form a successful break or net 5 points in the opening sprint (3 at least given the race favourite was always going to be very hard to beat). I was overhauled on the line and ended up with 1 or 2 points (I forget exactly) and so it meant I had not gained the desired return on investment. It sure wasn't through lack of trying.

It also meant that since I had gone so deep into O2 debt, I would need every ounce of craftiness to stay in the race. Perhaps in going so hard, the chase was not so easy either and everyone else had to recover too and that was just enough to keep me alive. Thereafter I just took my opportunities to collect points as I felt able. I had to gain 3 points in the final sprint to have a chance but didn't have the legs for that last lap to contest. It was enough for a 4th place finish. Had my initial salvo netted 5 points, perhaps the result may have been different and I made the podium instead.

That's bike racin'.

Edit: Since posting this the other day I also added to the chart the data from the 1-kilometre time trial. As we can see, I reached a MAOD of 4.30L, which is consistent with giving it all and with the MAOD values attained from the other efforts. Not sure if it affected the value attained in the pursuit on the next day, but does highlight the day to day variances.

Thanks again to Andy Coggan for his inspiration, Ric Stern for getting my form to such a good stage and all those team mates and competitors and supporters who help bring the best out of me.


* We call them endurance events, since even though they are about as hard as hard can be and relatively short in duration as far as cycling events go, they are still fundamentally aerobically (with oxygen) "fueled" efforts, albeit with some sizeable contribution from our anaerobic (without oxygen) energy systems.
** VO2max is the maximal rate of oxygen uptake by the body, typically occurs when exercising very hard for several minutes, although it can be induced with efforts lasting over longer periods (VO2 slow component). Expressed as litres of O2 per minute, or in relative terms as litres of O2 per minute per kilogram of body mass.

*** the proportion of mechanical energy output delivered to the bicycle crank as a ratio of total energy metabolised by the body - trained cyclists are typically around 19-24% efficient. The balance is almost all given off as heat (which is why we get so darn hot when going hard).

**** Initial VO2 assumed at 0.5 L/min and half life for VO2 assumed to be 25-seconds.

Read More......