TT Position, how hard is too hard?

Please direct me to the relevant post if this has been addresses already.

I test and train on the turbo in the TT position as much as possible.

I can hold the position for long steady intervals with no problem up to an intensity of about 105% of FTP. Anything over that and I need to sit up for most or all of the intervals and I’ll just try and complete the recoveries in the TT position.

When does it become OK to accept defeat and sit up? Should I reduce the goal power to hold the position?

As a side note - Really happy with my bike fit (long distance triathlon fit so not overly aggressive).

When rested and fresh, do a new Ramp/FTP test while staying completely in aero position. Do not be too concerned about the FTP result being a little lower, as the aero position is less powerful but makes up for this by being more aerodynamic outdoors.

My $0.02… Think about your goal events and what you’ll be doing. In TT position, most people are doing longer durations at threshold or below (20 minutes or more). If you can hold this power in position then that’s great.

I would always choose to do my VO2max efforts out of position, if it means better adherence to the prescribed numbers. Reasons: physiologically my body is capable, and completing the intervals in an upright position seems better to me than failing or reducing intensity. This way I’m actually targeting my VO2max. I’m not overly concerned with holding position through multiple VO2max and above efforts on my TT bike cos that doesn’t apply to my goal events (fairly flat 10 mile and above time trials).

Thanks, I agree. If I reduce the power goal of the session when trying to hit VO2 max efforts in the TT position I feel I might not get the physiological adaptation I am looking for from the session. My aero and upright FTP are pretty close now, hopefully by boosting my upright FTP I can drag the TT position FTP up with it, If I can keep holding Z4 efforts in the TT position, which I have always been able to do.