Showing posts with label Mean maximal power. Show all posts
Showing posts with label Mean maximal power. Show all posts

Friday, November 11, 2011

Mean Maximal Power: A Unique Comparison

It's been a while since I posted. Just too busy for the most part so my apologies.  I'll do an update at some stage!

I had a long break from training due to a prosthetic leg changeover in June (had a few transition problems with that) and a lot of travel in August and September. I've been back on the bike for a few weeks now (the hardest part sometimes).  I sure have some fitness to catch up on.

For some personal motivation, I thought I'd post up a couple of charts comparing my performance before and after the leg amputation (I get asked about it occasionally, and my data is being analysed for a science write up at the moment).

So I thought I would summarise it in a neat chart known as a Mean Maximal Power (MMP) chart.

MMP charts show your best power ouput for all durations from very short periods (seconds) through to very long periods (hours). Because the horizontal axis represents durations from second to minutes to hours, we turn that into a logarithmic scale, so we can inspect best power outputs for durations covering a wide time spectrum.  Power is represented on the vertical axis.

As you would expect, one can produce higher power for short periods (seconds), and somewhat lower power over longer periods (hours), so the chart trends downwards as you move to the longer durations on the right.

By using WKO+ software, I made a comparison of my all time personal best power for the time before my accident and amputation and since then.

Two versions plotting mean maximal power to weight ratios, one for Average Power and one for Normalised Power. The blue line is before amputation, the red line is since then.

Click on the chart to see a full sized version:


The chart above shows my best W/kg for all durations.

What is very clear from that chart is the wide performance gap for very short durations but the closeness in performance over durations longer than a minute or so.  This suggests my sustainable aerobic power and my anaerobic work capacity hasn't been significantly hampered by riding with a prosthetic, however my neuromuscular power (used for sprinting and short duration hard accelerations and efforts) has been significantly compromised.

What about Normalised Power?


When plotting NP data, WKO+ restricts the output to a minimum of 5-minutes.  For most analysis and application, we really don't read too much into NP for durations shorter than about 20- to 30-minutes.  But nonetheless, the chart shows an interesting change in my power profile when viewed through the lens of Normalised Power.

NP appears to amplify the difference in performance over a wider part of the primarily aerobic duration spectrum (> 5-minutes) when compared with the Average Power chart

A reduction in my ability to perform those short high power bursts (up to ~ 30 seconds or so) definitely comes though in the NP for durations from 5- minutes to about 30-minutes.

For longer durations than half an hour though, I have been able to equal or somewhat exceed my best pre-amputation NP outputs.

This I think is reflective of the type of racing I do - which is lots of track and crit racing, some road races and only occasional time trials.  So for an apples to apples comparison, I certainly think this NP chart is pretty telling.

I no longer have that weapon of short high end power, but have instead found other ways to make up for it.

Of course this is just one way to use MMP charts. Once can plot one season over another and make comparisons as to their overall progress. Or any time periods they care to compare.

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Saturday, January 02, 2010

Power Profiling - Now and Then

Often I am asked how my cycling power ouput compares now, to before my accident and amputation.

As I progressed with my training during 2009, and as my fitness continued to improve under Ric Stern's guidance, the answer to that question kept changing, mainly as I started to close in on pre-amputation power levels.

Now that I have a full year's worth of data from 2009, I decided to take a look at my annual power profile and see how it compares to pre-amp levels.

Below is aggregate power profile data covering the past 5 years. It shows my best power to mass ratio (W/kg) for each of 4 separate durations for the years 2005 through to 2009:


The power durations shown are:
5 seconds
1 minute
5 minutes, and
95% of my 20-minute power.

Each of these power-durations represents key elements of cycling fitness, with different energy systems being the primary contributor to performance at each duration. That's why it's such a telling indicator of your overall cycling makeup, and an excellent indicator of your relative strengths and weaknesses.

This is provided of course the profile does in fact contain data from best efforts for the duration. Given it's aggregate data for whole years, then I think it's a reasonable assumption. Nevertheless, sometimes the 1-minute column can still be under stated as that usually requires dedicated efforts not often performed in training or racing.

You can read more about power profiling in this original item by Dr Andrew Coggan here:
Power Profiling


So the group of columns on the left shows my best 5-second power to mass ratio for each year from 2005 to 2009. Each group of columns moving to the right covers the other durations, with 95% of 20-minute power shown by the columns on the far right.

What matters with power profiling is the overall shape of the profile, rather than the absolute numbers. The shape in this case indicated by the lines joining the columns, which I have shown for 2006 (orange line) and for 2009 (blue line). I chose those two years as they are the two complete years representing pre-amputation and post-amputation training/racing data.

I notice a few things:
- the overall shape of each line is similar
- my short duration power has taken a large nosedive
- my longer duration power to mass ratio is actually higher than previously attained

This clearly demonstrates that it's my sprint power that has suffered the most from my lower leg amputation, yet the predominantly aerobic power durations (5-min and 20+ min) have not.

This suggests a few things to me.

One is it's an example of how we are not force (strength) limited when cycling at aerobic power levels, since even though I have lost significant leg musculature and with it strength, I have still been able to generate the longer duration power.

Another is that the lack of a lower leg muscular-skeletal system has a significant impact on sprint ability. The lower leg matters a lot more in the generation of short duration sprint power, than for longer duration aerobic power.

What can I make of this information? Well for one I no longer have the sprint I used to, yet I am as likely to be as well set up for the end of a race as I was before, since I have the engine to deliver me there. But now I lack the finishing ability. My strategy and tactics in racing may need to be modified a little as a result.

I can still work on improving my sprint of course (all track/roadie riders should) but I would say that reclaiming pre-amp sprint power levels is not going to be anywhere near as "easy" as it was for aerobic power durations, if in fact it is actually possible.

It also points to me reconsidering what events I may in fact focus on. They may change as well.

Plenty to ponder with a power profile.

What's yours look like?

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