Watts, normalized power, efficiency, threshold, critical power, anaerobic work capacity – it all gets a bit confusing right!? As technology improves so does our capacity to measure different variables. As endurance athletes we are so often driven by the data but like many people you may struggle to break the barrier into what this terminology means.
At Premier Endurance we use Training Peaks software primarily in our day to day role so a good place to start would be going through the main workout analytics on this specific platform. This blog post has been one of the more widely requested pieces that we’ve had when chatting to athletes and coaches so let’s get going! Below you can see a snippet from the Training Peaks workout analytics.
Duration: On Training Peaks this is simply the time your head unit has been recording data for i.e. not paused/ turned off
Work: Work in Kilo Joules (Kj) is a unit of energy, in this case how much energy you’ve expended on your ride. When you use a power meter you are measuring watts – 1 Joules is 1 watt per second. Through basic math we can calculate total work in Kj for example riding at 100W for 60 seconds = 6,000 joules divided by 1000 = 6 Kj.
So, is this also your calories expenditure? Yes and no. 1 calories is equal to roughly 4.8 Kj. But luckily due to efficiency factors in cycling it is widely excepted that 1 calorie = 1 Kj give or take we can only truly be sure by measuring this in the lab.
Elevation Gain and Loss
Again, another simple one the height in metres that you have gained and lost over your ride. You can also correct this value if you think it is off by clicking the small mountain symbol above the map on Training Peak’s web platform.
The average gradient for the ride or selected time range in % terms. A flat road is 0%, downhill is minus and uphill is above 0%
BPM (Heart Rate)
A measure of your heart rate expressed in beats per minute.
How many revolutions of your crank per minute.
Power divided by your body weight in kilograms. Having up to date accurate weight is important in Training Peaks you can add this via the metrics option like a normal workout. This is a relative measure which accounts for body weight over absolute power – this is most beneficial to look at while riding uphill. On shallow gradients and flat roads aerodynamics / frontal area also plays a part and higher w/kg doesn’t necessarily mean quicker.
FTP (Functional Threshold Power)
This is looked at as the power an athlete can sustain for roughly one hour. In honesty there is so much terminology and confusion surrounding this term it’s probably a whole blog post on its own! Really all you have to know is this is the point at which exercise starts to become more “uncomfortable” and our reliance on anaerobic energy becomes higher meaning we cannot sustain it for long. Whatever you and your coach decide is the best way for measuring “threshold” then my recommendation would be to just stick to it to allow consistency and reproducibility over time. This is a core metric in Training Peaks and needs to be set accurately and regularly to ensure all other metrics are up to date.
Now that we’ve gotten the “basics” out of the way it’s time to dive more into the specific metrics associated with training!
TSS: Now we start to dig into the analytics – as a formula TSS is expressed as TSS = (sec x NP x IF )/(FTP x 3600) x 100
So, TSS accounts for time, NP or normalized power, IF or intensity factor and FTP or functional threshold power. We’ll discuss these specific terms shortly.
Simply put TSS is a measure of both how long and how intense your workout was giving us back a unit to monitor training from. This allows us to monitor the workload of a session. It is worth bearing in mind that simply achieving a desired TSS if not what training is – it is how you modify the parameters that allows adaptation.
NP (Normalized Power)
Normalized power, simply put, is a measure of what you would have done were you to ride in a steady state for the duration of your ride i.e. no downhills, freewheeling etc. It is a value derived from an algorithm which essentially accounts for the physiological costs of surges in power and our response to it. Quite often this is a true value of what you could have sustained for the given time if paced correctly. One caveat here is efforts involving multiple sprints, short recoveries etc. often give a higher NP than would have been possible in a steady state, so take it with a pinch of salt.
IF (intensity Factor)
IF is the percentage of FTP at which you rode at. It is based off NP which is discussed above, so essentially at what percentage of threshold was the NP for the ride. This is a nice metric to make sure you are loosely staying within a target zone for a ride or an interval. For example, if your interval demands 10 minutes at 85-90% than we know our IF for that period should be 0.85-0.90. For this metric to be accurate you must have up to date FTP set.
Power heart rate ratio or aerobic decoupling is a measure of heart rate response in relation to power over the course of a ride. You can read more on this here
For an aerobically fit athlete we should see stable heart rate over time while riding a constant power output, this is a nice metric to track over the base period. Generally, values under 5% are a good sign for a steady state endurance ride.
EF (Efficiency Factor)
This metric measures efficiency in terms of input (heart rate) and output (power). To calculate EF we divide normalized power by average heart rate for the given time period. As training phases prolong you should see this number rise essentially meaning you are inputting less effort for your output. Like PW:HR it’s a good metric to track over a base period. For example if we ride at 200W at 130BPM we get an EF of1.54 over time we notice a decrease in heart rate for the same power so we now ride at 200W at 125BPM giving an EF of 1.60. It is worth noting that rides where you compare these values need to be quite similar in content and fatigue levels coming into.
VI (Variability Index)
This is the ratio of NP to average power output. So, if our average power is 200W and our NP is 200W out VI will be 1.00. VI is an indicator of pacing so for steady state intervals, tests etc we’d be looking for a VI of close to 1.00. For sprint sessions and hilly routes, the VI would tend to be higher.
Velocità Ascensionale Media or, in English, how many metres per hour you are ascending. This allows us to get a measure of “climbing speed”. This metric is best for long sustained climbs at steadier gradients.
I hope the above has gone a ways into explained the differing terminology you encounter on the workout level within Training Peaks. We’ll add to this theme by discuss some more in-depth analytics along with metrics associated with the Performance Manager Chart in our next blog post!