Average Power

Average Power is fairly straightforward – being the average of a rider’s moment by moment
power output over part or whole of a ride, usually measured by a power meter or ergometer. 
E.g. 5-minutes at 100 watts followed by 5-minutes at 200 watts equates to a 10-minute Average Power
of 150 watts.

Average Power is especially helpful as a means to assess how much work (kJ) was
performed during a ride.  This knowledge can have numerous benefits, in particular when assessing
daily energy intake requirements:
Average Power (watts) x Ride Duration (seconds) = Mechanical Work Performed (joules)
e.g. 150 watts x 600 seconds (10-minutes) = 90,000 joules (90kJ)

The Average Power a rider can maximally sustain in a well-paced steady state effort such as
during a flat time trial or on an indoor trainer (e.g. during a Threshold Power test) is one of the most
direct and objective measures of fitness.  It is usually expressed in terms of maximal average
power for various durations (e.g. 1-minute, 5-minutes, 1-hour), and in terms of watts per kilogram of
body mass (W.kg^-1).  It should come as no surprise that we can sustain a higher power output over
shorter durations.

Over the course of a training block, we seek to raise the power a rider can maximally sustain per
kilogram of body mass for longer durations, such as 20-minutes or more.  The higher the maximal
W.kg^-1 number, the faster one can ride and/or the longer a rider can sustain a given pace.

So what happens when power output is highly variable, such as typically happens when we ride
outdoors over variable terrain, or with a group, in a road, criterium or track race or over a
mountain bike course; or perform interval efforts at various power levels with rest periods
interspersed?

In these more common scenarios, Average Power can be a misleading indicator of intensity and
understate the level of difficulty of a ride (often substantially so).  That’s because:

1. the physiological responses to rapid changes in exercise intensity are not instantaneous, but
   follow a predictable time course, and
2. many critical physiological responses (e.g., glycogen utilization, lactate production, stress
   hormone levels) are curvilinearly, rather than linearly, related to exercise intensity ¹

This latter point is really important.  As power output goes up, the level of strain experienced
increases exponentially.

By way of example, let’s say a rider is capable of maximally sustaining 200 watts for about an hour.  If
we asked them to perform a 20-minute steady paced effort at 200 watts, then assuming they are not
unduly fatigued, we should expect the rider could actually complete such an effort, since by definition
they are capable of sustaining that power output for longer than 20-minutes.  It would be hard, but
do-able (indeed, over 20-minutes, a rider could maximally sustain ~ 104-109% of their 1-hour power).

But what if we asked the same rider to perform a 20-minute effort with the same average power of 200
watts, except this time the rider is asked to perform 10 x 2-minute interval repeats comprising 300
watts for 1-minute followed by 100 watts for 1-minute?

Those with any experience of this sort of effort will know the rider would be very unlikely to successfully
execute the prescribed session, despite the average power being the same.  This is because the strain
experienced during the 300 watt sections is far greater than the relative increase in power, and is not
equally matched by the reduced level of strain experienced when riding the 100 watt sections.

Normalised Power

Normalised Power is a clever means by which reported power output is adjusted to take into account
the typical and natural variability in power output.  To quote Dr Coggan:

“Normalised power provides a better measure of the true physiological demands of a
given training session - in essence, it is an estimate of the power that you could have
maintained for the same physiological "cost" if your power output had been perfectly
constant (e.g., as on a stationary cycle ergometer), rather than variable. Keeping track
of normalised power is therefore a more accurate way of quantifying the actual
intensity of training sessions, or even races.”

This is why it's very helpful to check the Normalised Power data from training sessions (or races), as it
represents a more accurate indicator of the level of difficulty and provides a means to assess changes in
fitness over the medium and longer terms despite rides/races being somewhat different.

There will be some training sessions or races where Average Power will be lower than for previous
sessions but the Normalised Power will be higher.  This would be due to the use of shorter, higher
intensity interval work coupled with correspondingly longer recovery periods necessary to ensure a
session is feasible to be completed.

In the interval example quoted earlier (the 10 x 2-min 300W / 100W intervals), the Normalised Power
for such a session would be 234 watts, meaning the equivalent physiological cost of riding at a sustained
steady state 234 watts.  Typically you would expect a rider with an FTP of 200 watts to be able to
maximally sustain ~ 104-109% of their FTP for 20-minutes, or ~ 208-218 watts.  Hence the original
prescribed session was unrealistic from the outset.

The underlying physiological principles and the mathematics of the Normalised Power algorithm are
described in more detail in an article by Dr Coggan at the following site:

Normalised Power & Intensity Factor

1. Ref: Andrew R. Coggan, PhD: Training & Racing with a Power Meter

As coaches, there are a number of fundamental principles of training we apply for improving an athlete’s
performance.  One of the most important is the need to provide an athlete with a progressive increase
in training load to maintain the stimulus required for ongoing fitness improvement in preparation for a
key race or event period.  This, along with the right doses of recovery to consolidate the gains being
made is very important for any athlete seeking a new level of performance.

So how do we achieve this progressive overload?

The simplest and most effective way is to train consistently and execute on the training plans provided.

As coaches we consider the time constraints our athletes tell us they have.  Some have nearly unlimited
time for training, others have many demands on their time (work, family, school, studies and so on) and
so time available each week can be limited.

So as an athlete, it is important to be clear with your coach what time you really can commit to your
training, and then to execute on the plan as closely as you can.  If additional training hours become
available, coach can provide suggestions on how such time should (or should not) be used.  Equally, if
for some reason unexpected interruptions to training happen, then it pays to know in what way training
could be modified.

Of course just because you might have lots of time available for training doesn’t always mean it makes
sense to use all available time – you may not be ready to take on such a training load.

So how do coaches know if you’re being consistent?

Well that’s where we need your ride files and diary notes.  Regularly!

Without them we are running blind about how your training and performance is tracking, and whether
adjustments to your plan are warranted.

One of the great things about the power meter is the ability it provides to record exactly what training
you have been doing – but the data is only one element.  It’s when that’s combined with your
comments that reveals a lot about how well an athlete is executing against a plan, whether training is
having the desired impact (improved power output) and how an athlete is coping with the training.

Since almost all RST coached riders are using power meters, and most of those are using WKO+
software, then I encourage athletes to provide commentary along with their power meter data and to
also write into their file notes both the intended/planned session and then comments on what they
actually did, how they felt, and other comments pertinent to the day (e.g. environmental conditions,
what else happened, where they rode and so on – anything that might provide help for the athlete and
the coach to assess progress).

Here is an example from my own diary:

Of course you cannot enter such information directly into the calendar page shown above but rather
that’s done in the journal page for each individual WKO+ file.  Once entered and the file saved, then all
those comments appear in the calendar page as shown. This is the place I first look to scan the training
over the past few days or week and gain a sense of what’s actually happened.

In one quick glance I can see both the planned sessions and what actually happened, both quantified by
the ride time, Intensity Factor (IF) and Training Stress Score (TSS) numbers, combined with the
comments entered into the Post-activity comments box.

From this I can tell how training is going versus plan, whether an athlete is consistently executing against
the plan and which files demand a closer inspection.  If all is good, great – if not then it’s a matter of
assessing if the reason(s) for training not going to plan are just temporary or perhaps something else
that needs follow up.

But not everyone makes such notes about how they are feeling, what they did and so on.  Of course
we can see what the power meter data suggest but the comments are just as valuable to gauge an
athlete’s response to the training.  So help your coach help you by:

• Completing the ride notes, including what the plan was, what you actually did and how you felt,
  and other information that is worth recording (e.g. bike used, weather conditions, sleep,
  recovery, mood, and so on)
• Include information that explains why things may not have gone to plan
• Send the files to coach regularly, at least weekly.

Consistency is also very well shown by the Performance Manager Chart in WKO+.  Here’s an example of
such a chart:

By charting the daily Training Stress Scores (TSS), one can quickly see how consistently a rider has
trained.  In the above chart it’s easy to see this athlete has been riding 5 or 6 days per week
consistently for the period early-May to mid-July.  And it’s this consistency that plays a very large part in
building their training loads and most importantly, improving their fitness.

The other thing to note on this chart is that over time, the height of the TSS bars gradually increases –
and this of course is because the training is steadily increasing in duration of rides as well as the relative
intensity of those rides.

If the training dose is appropriate, this will result in a pattern shown by the dark blue line (Chronic
Training Load – CTL) of gradually and consistently moving upwards, indicating the athlete is
accumulating an increasing workload – and along with that, improved fitness.  If the CTL line is not
increasing during a general preparation phase of training, then it is likely fitness development will be
marginal, plateau or even possibly decline, and further improvements are unlikely unless training gets
back on track.

Below is an example of what inconsistent training looks like in the chart.  In this case the athlete didn’t
really understand why their fitness wasn’t improving – but when faced with the stark facts that they
simply were not training with any consistency or plan in mind, their resulting poor form was not at all
that surprising.  Yet this sort of training pattern is not all that uncommon amongst many club riders.

Of course we all get interruptions to training and not everything goes exactly to plan. That’s OK, it
happens, just move onto the next day and get going again.  If an interruption is longer, then it will likely
mean the plan needs an adjustment.

The rate at which training load can increase over the medium term needs to be sufficient to ensure
stimulus for fitness development but not so much the athlete fatigues and cannot sustain the training
(and make them susceptible to illness or injury). This rate will be different for everyone (much depends
on an athlete’s prior history, other stresses in life and what opportunities for recovery an athlete has). 
This is part of what the coach works on to optimise for each individual.

So – is your training consistent?

When training– are you executing against the plan?

If not, why not – and are you communicating this with your coach?

Remember - Consistency is the key!

Safe riding.

Alex Simmons