All the advice I’ve ever had about using my back is to keep it straight.

Everytime I look at pro-riders

I can’t help think that they go against that advice.
I guess that’s what it takes to win races but is it damaging to your back to do this?

How many hour do they spend on TT’s though?

Although IRRC Armstrong had to have his lower back fused after a stress fracture? Which is what gave him an even more odd looking position.

surely if it was ‘Bad’ they would be suffereing additional stress/fatigue and wouldn’t be particularly quick as a result.

From what I can understand of bike fitting for TT/Tri bikes it’s all about how the body is supported on the bike in that ‘optimal’ position;

Riders torso is sort of suspended between your hips and sholders, ideally as flat/straight backed as possible, for a TT/aerio position upper arms supporting in as close to a vertical as practicable so weight is borne by your skeleton rather than tensed muscles/tendons, you ideally want as little wasted energy as possible which means if you can relax muscle groups in the torso, arms and shoulders you are improving efficient use of energy at the same time as reducing frontal area then its win, Win…

Sensible leg angles are also important one as well though are they not? torso to upper leg and the range of angles the knee has to move through need to be ‘Optimal’

all in theory at least, in practise there are bound to be compromises…

there was some comment on this subject IIRC by chris boardman (the open universty vids on bike tech posted recently) that they find the best aero position and then see if it can be held for the time needed.

they support their back with there arms so its not quite the same.

All about balancing power output with aerodynamics. Can be worth sacrificing a few watts if the position is much more aero

I’m not aware that pros have back problems, so probably OK.

not for them.yes for us.
read sovdal’s book on cyling anatomy.
if you’re interested.

These are elite sportsmen, they may do things in the interests of performance which are not good for longer term health and in fact they may not train extensively in quite the same position.

All the advice I’ve ever had about using my back is to keep it straight.

Which has about as much relevance to riding a bike as a jeelyfish. On that basis, any riding a bike would be bad for you. The thing is, that advice is for lifting loads – not something you’re doing when riding a bike.

I’ve recently had a Retül fit at our place, and it’s quite amazing what I found out.
Not cheap, but there are worse ways to spend £175