If you can bowl 150 or above you are express. Starc can get it there but clearly bowls more conservatively now, Archer can certainly bowl very quick but again he averages mid 140’s. Bumbra seems to be the one who maintains his pace all the time.
Akhtar had a terrible action, Thommo had the perfect fast bowling action and hence why he had no back issues.
Fast bowling is a gift, you either can or you can’t. You cannot teach someone to bowl fast without them having the fast twitch muscle fibres needed to be able to do it.
They are certainly being preserved these days, yet funny enough with all the rest they get and how well they are looked after they as a group are breaking down more than ever in history.
I think fast bowlers have always had a tendency to break down. There are plenty of examples of young quicks having issues then by about 23 or so their bodies mature and they seem to get along ok. Is it getting worse? Hard to say.
I think modern sports science, while great for most sports and good for cricket in theory may just not provide specific enough training. I have a feeling bowlers used to spend more time in the nets and less time in the gym. I mentioned this earlier in regards to batsmen and their techniques not being quite as good due to not facing enough quality fast bowling at training.
Guys like Thompson probably spent very little time in the gym and a hell of a lot of time bowling compared to the modern cricketer. Even Brett Lee probably spent a lot more time bowling than doing gym exercises.
I wouldn't call Akhtar's action terrible. It was unique and suited him and was effective in generating pace. It's a bit like calling Paul Adam's or Murili's action terrible or before that Warne's grip on the ball. Unorthodox yes but certainly effective.
The bowlers around now are all very clone like. Seem to be a lack of unique actions. I don't see any slingers getting around who bowl express pace. A lot of the spinners bowl with fairly orthodox actions. Makes you wonder how many kids have their actions changed if they have an unusual way of bowling.
A lot of the special cricketers have unique actions or styles, it's part of what makes the game interesting and puts bums on seats and I hope that is something which the game doesn't lose.