WKO+ - I never thought that these 3 letters + could keep me so entranced! For Xmas I got two round things with something very expensive in the middle - one of them was my engagement ring and the other one a PowerTap, kindly partly sponsored by Saris (the tap, not the ring - in both senses). And since I got the PowerTap I have been fascinated with basic physics .... (oh, and I've been looking at wedding dresses too).
Anyhow, a power meter's worth really comes out at data analysis. While last year I was able to swindle my way through a drill because my heart rate stayed up, the PowerTap now tells me exactly (often to my chagrin) when I am slacking off (for my coach to clearly see). Anyhow, apart from instant power and average power, the best you can get out of the PowerTap is by using software called WKO+. I could spend hours analyzing my data (also because I still don't know my way round the software properly and it uses quite advanced training concepts). My favourite analysis is that of TSS points (Training Stress Score, it basically estimates how hard your ride was, taking into account your personal power limits and current fitness level). This means different rides for the same cyclist and the same ride for different cyclists become comparable, by comparing TSS points - so finally Ryan believes me that I had a hard spin when I tell him I had a hard spin. Recording TSS points over time, the software then creates graphs that give you an estimation of the ATL (Acute Training Load), CTL (Critical Training Load) and TSB (Training Stress Balance) (which can be very roughly translated into fitness, form and fatigue)
Here's mine for the last while:
pink = acute training load
blue = critical training load
yellow = training stress balance
Reading the graph from left to right: In the beginning I was very refreshed (yellow high) and not very fit (pink low) (Irish snowy winters apprehended me from training much) and my form (blue) was so la la. Here in Gran Canaria, I was able to put in a few long and hard training sessions, so my fitness, or acute training load (pink line) went up high, but of course it made me more tired (sending the yellow line down), but already the results are showing an increase in my form (blue line). I took two recovery days in a row, which sent the pink line down dramatically.
The long-term aim towards the racing season is to increase form (blue line up), which can only be done by doing lots of training (pink up), but doing lots of training means you become more tired (yellow down). For an actual race you want the acute training load to be low (pink low) and be refreshed (yellow up), which can be achieved by taking it easy before the race, without too much of a decrease in form.
Another great side effect of the PowerTap is that it can pretty accurately measure how many calories you burn for each ride. In detail, it shows the amount of kiloJoules needed to generate a certain wattage for a certain time (1 Joule = The work required to continuously produce one watt of power for one second; Wikipedia). And since the body looses about 3kJ to heat for each 1kJ put into the pedals (only the latter is measured by the PowerTap), your kJ burned in your ride is 4x the number it shows. BUT, since food is still measured in kiloCalories, and 1kCal is approx 4kJ, you can divide that number again by 4 to get the number of calories burnt - in effect the number of kJ shown corresponds roughly to the number of kCals burnt (which decides if I order icecream for dessert or stick to an orange).
And I finally know how hard I am supposed to really go during any drill (harder), since I've done an abbreviated test of the abbreviated functional threshold power (FTP) test (I ran out of uphill). FTP is defined as the maximum power (threshold) that one can put out over one hour. So to find out your personal FTP you ride as hard as you can for an hour - OR, you do the abbreviated test: ride 20min as hard as you can and then estimate your FTP to be 0.95 of that power number). One of the aims for endurance type sports is to improve this FTP. This number can then be used to determine your training zones by power (Active Recovery (AR), Endurance (E), Tempo (T), Threshold (TH) V02Max (VM) and Anaerobic Capacity (AC)), enabling you to plan your training even more accurately. Supposedly you get most bang for buck doing tempo training.....
Now my eyes aren't glued to the heart rate meter any more, but rather to the wattage meter. In fact, I have almost completely abandoned training by heart rate and replaced it with training by power. Long live the PowerTap!