One of the metrics that has developed over the last 15 years is the concept of the Functional Threshold or FTP. Originally this was tied to the power one could sustain for around 60min, and was then broadened to the power one could sustain for a 40km TT.
This metric was strongly related to performance in endurance events from a 2000m pursuit to long road races. The Gold Standard for testing was a 40km TT or a maximal hour effort. Naturally this was not appealing to many and some varieties of the testing included using a critical power model based on 2-3 maximal tests over 3min to 30min, to performing a maximal 5min effort and then after a short rest performing a maximal 20min effort and taking 95% of the 20min power as an estimate of ones FTP.
The big challenge of this was different protocols produced different results which made it hard to compare thresholds. In recent years the Power Meter Analysis Software WKO4 has used the data from training and racing to estimate FTP, and contingent on a good mix of hard efforts from 1s to hours to estimate the power for any given duration including a riders FTP. This model developed by Andy Coggan is very robust and is based on a huge volume of power files collected from riders at all levels.
Time to Exhaustion – TTE
Based on this what started to become apparent was that one could manipulate FTP by performing a shorter efforts maximally. This gave a somewhat inflated FTP. This has led to a second, and very important, concept of fatigue resistance. In WKO4 this is know as Time To Exhaustion (TTE) and is based on the duration a rider can sustain their FTP.
This allows the coach and the rider to look at their FTP and compare it to TTE and assess whether the rider has an inflated FTP. A good time to exhaustion duration is between 50-70mins. A TTE in this range would suggest an accurate FTP based on good sustained power over the intended duration of around an hour or for a 40km TT. A TTE of between 25-40min would suggest an FTP based on shorter maximal efforts of 1s to 10min. Now, this may be ideal for a track cyclist or criterium rider peaking for an event but for any event over an hour it would suggest that they will not have the stamina for the later stages of the race.
As a Coach, I am loving these new fatigue resistance metrics, which in WKO4, also apply to short and medium term power metrics for Sprint, Kilo and Pursuit performance. This is because the power at these levels in a well trained rider is very hard to develop. A ten watt improvement in FTP equals between 60-90s improvement in a 40km time trial. Linda Villumsen needed just 6 watts more to move from 6th to Gold in Rio. What can be well trained is the time you can sustain that power. This is where the bulk of training should be focused on!
For more information on FTP, TTE and WKO4 (and many more acronyms) there is a WKO4 Power Users page on Facebook and search on Youtube for WKO4 for hours and hours of excellent videos that discuss the concepts underlying power meter metrics and their application to improving your performance.
Hamish Ferguson is Canterbury Based Cycling Coach who prepares riders here and overseas for Road, Mountain Bike and Track Cycling events. In 2015 he was awarded a Master of Philosophy Degree for research on long term training metrics and their relationship with performance in road cycling events.