Since forever, I have never been great at endurance. Since being able to put a label to my body's performance - Ehlers Dandlos Syndrome (EDS), it does explain my abilities in term of being stupidly flexible for practically all my joints from my fingers, toes, knees, neck, shoulders (joint weakness) as well as it's inabilities of performance over a long period of time due to muscle fatigue. I have trained for years in endurance sports but my strength and speed has not improved. When I started with LOC and we would do individual TT along Beach Road or in Altona, I would start out great and then the muscles would just stop working.
In terms of the 20min FTP tests - they are not my friend. I can push the power for a short period of time, I can sprint at very high power (close to 1000W for 3 sec) but when it comes to endurance, my body just won't cooperate. Mentally, I can put myself through 20min FTP test but my body just doesn't want to keep up. The 20min FTP test works on the Maximal Lactate Steady State (MLSS).
I remember doing an FTP test about a year ago and my FTP was about 160W over 20min. I try to start out in a gear and cadence which is comfortable and I "think" I can hold for 20min. No matter what strategy I use, the end results is about 160-165W.
This morning was no different. The session this morning at Spin Labs was an FTP test. I started out at 190W for 5min, then worked up to 200W for the next 5min with an rpm of 85+ then the last 7min of the FTP test, I started to fatigue with my body shaking and the average went down to 165W. Frustrating. Towards the end when the instructor was pushing us to go hard for the last 2min or so, I just had nothing left...zero energy in the legs.
When the session is based on various % of the FTP, I can work with a benchmark of 180-200W as it is sometimes the lowest FTP chart available at the venues. I am comfortable when I use those benchmarks in the session as I can hold high power for a short period of time. For example, on Monday (25th Sept), the session was 4 x (1.5min 95% @ 85-95rpm, 30 easy, 1min 110% @ 85-95rpm, 30 easy, 2min 85% @ 100rpm, 1min easy, 3min 100% @ 60-65rpm, 30 sec out of the saddle, 3min recovery). I used FTP of 180W in the session and I was fine and hitting those power benchmarks or above the whole session.
My goal for the next 6 months will be to work on my endurance and increase by FTP towards 180W over 20min but work out a strategy. Do I break it down to 5min intervals where I increase and decrease my efforts over that 5min, start out strong and watch the power decrease over time or start out low and see if I can increase the power as I go along. I will have the manage my muscle fatigue and heart rate as it hovers around 175rpm during the FTP tests.
I have also heard of the short 8min FTP test which is 8-minute Power at VO2max (pVO2max) efforts. They say that the 8min test is suitable for the more experienced riders but doing the 20min FTP sets better benchmarks.