Regarding the professional cyclist requiring 'bottle' for their fast descents in races, I'd say that the descending activities of the more adventurous amateur cyclists in non-racing scenarios are often even more demanding.
I, and many other amateur racing cyclists (and indeed non-racers), have made many trips to the Alps where the second principal aim of the trip is to race one's friends down the cols (the primary aim being to race up, of course).
It is no exaggeration to say that we would race each other, and other riders encountered, at the same descending speed as the professional riders going flat out on Tour de France descents. Beating one's friends (and, more importantly, the Frenchies) to the bottom was a matter of pride, and many non-professionals are extremely skilful descenders, so every single one was blitzkrieged from top to bottom - no 'recovery' time like the professionals often build in to their descents, as descending honour was always at stake. The only occasions when we might be slightly slower were on the flatter or uphill or into-strong-wind sections where pedalling is required and professional fitness and strength levels would make a difference to descending speed.
The crucial thing that made our descending far more dangerous than the Tour riders' is that we did it all on open roads, so the slightest error on a bend (whether hairpin or full-speed gradual curve) could mean piling head-on into an ascending car or truck. Plus all the countless cars that had to be overtaken on our way down. Scouting bends ahead of reaching them, to judge where ascending cars would be when you arrive at and exit them, is an inherent part of the increased concentration required over Tour riders' need for concentration - getting your exit-line right was often absolutely critical and there were many instances where the racing line was compromised by ruts/holes in the road surface (defects that often were only apparent once committed to an entry speed/line and preferred exit-line). Not to mention all the risks associated with vehicles joining the road from side roads and tracks etc without looking, or whose drivers underestimate the speed of cyclists descending compared with cars (although drivers in the Alps were generally far more aware of their surroundings than typically experienced in this country, and often facilitated our overtakes and gave a wide berth or held back when passing us uphill).
In the immortal words of
this video, the
penalty for failure, dude, is much greater in the amateur open-road scenario. But then we, and many others, judged the risks acceptable and were pretty handy at managing those risks in what is effectively an 'extreme' sport if you descend flat out. I only crashed twice, neither at high speed - once in a pitch-black tunnel on the Galibier where it was impossible to see the edge of the road, and once on either the last or penultimate hairpins at the bottom of Alpe d'Huez (wheels slid away on polished asphalt on water dropped by construction trucks ascending to the ski station, fell hard on the hip but carried on to do Les Deux-Alpes and then back up the Alpe; this one did permanently reduce the nutter-descent tendency very slightly).
Having said that, I would think that downhill skiers spend a greater proportion of their descents on the brink of losing control, and so require more concentration, but then their descents last only a couple of minutes, and they don't start them in a state of fatigue from getting up there, whereas the Cols de l'Iseran, d'Izoard, du Galibier, d'Agnel, de la Bonette, de Joux-Plane, de Granon etc etc take much much longer and really take it out of you if you ride hard up them.
On balance, I reckon the professional skiers need slightly more 'bottle' than professional road-racing cyclists, as skiers go faster and with very limited 'braking' capability, but cyclists who blitzkrieg descents on open roads require more than both. Then again, I've never skied.......
. Unbelievable respect for those crazy ladies. They've certainly got some bottle.
