MAJOR milestones on the road to Olympic and Commonwealth Games are usually occasions for excitement and anticipation. Four years out from Glasgow 2014, for example, a celebration in George Square brought together Scots hopefuls from a range of sports, and gave the city a foretaste of what was to come.

Today, exactly a year before the opening ceremony of the 2016 Olympic Games, there will be festivities in Rio. But will the rest of us feel any excitement or anticipation? Given the latest claims about widespread doping in athletics, we are more likely to feel disillusionment and revulsion.

No matter how many other sports have been added to the programme, athletics has always been, and remains, the cornerstone of the Olympics. No-one, from sponsors to broadcasters to spectators, is ever likely to say “Never mind if the credibility of track and field is irretrievably damaged, there’s always the weightlifting and the shooting”.

We need athletics to be clean, and we need the IAAF to do a lot more to ensure it is as clean as possible. The bureaucrats who run the sport’s world governing body can insist all they like that those allegations of doping are “sensationalist and confusing”. But they will find many people, from spectators with only a passing interest to professional athletes themselves, who simply do not believe them.

The direct victims of doping are those athletes who race against the cheats, and even when retrospective justice is done, some damage remains. In 2013, for example, Scottish 800-metre runner Lynsey Sharp had her European Championships silver medal from the previous summer upgraded to gold after Russia’s Yelena Arzhakova was disqualified because of irregularities in her biological passport. A wrong had been righted, but as Sharp pointed out, she had been denied her true place on the podium and her chance to hear her own anthem - not to mention the potential additional income that a gold medallist could easily earn in the wake of her success.

Doping has a seriously dispiriting effect on clean athletes, who are often all but sure that certain of their rivals are breaking the rules. But it also has a demoralising effect on spectators - not only the ones who are there in the stadium, not just those watching live on television either, but anyone who catches up on the highlights later that evening, or catches up on events via the iplayer a day or two later.

And in the long run that’s a bigger danger to sport: when we lose interest in what we are seeing because we cannot believe our eyes. We watch someone cross the line first, but do not know if they are the “real” winners or will have the gold medal denied them in doping control.

Perhaps worse still, we can see them win the race, get the gold medal, go down in the record books as the victors - only, years hence, to be stripped of their status after testing positive. It’s all a bit like those Philip K Dick novels - The Man In The High Castle being his best - in which, a couple of hundred pages in, the main characters learn that large chunks of what they have taken to be reality are in fact illusory. When you find yourself in a state like that, you tend to lose your willingness to shell out hard cash on the product in question.

Ironically, athletics is very probably cleaner now than it has ever been. The same could be said of cycling, the other sport that continues to suffer most because of doping controversies. But that probability, far from encouraging us to have faith in present performances, will just make us wonder why those sports have taken so long to become even as relatively clean as they may now be.

Of course, it would be unrealistic to expect those two sports - or indeed any other - to engage in a wholesale rewriting of the history books. No matter how systematic doping was in certain countries in the past, there needs to be a statute of limitations, for this and for other breaches of the rules.

In team sports, for example, clubs can be disqualified from a competition if they have fielded an ineligible player. A decision on such matters is invariably taken pretty quickly.

But if you discover that a number of players have been ineligible for years - as rugby union discovered in 2000, with Scotland’s David Hilton being one of the players in question - you can’t annul every result in which those players have been involved. Administrative and statistical chaos would ensue. We have to ensure that the outcome of sporting contests is by and large decided on the field of play, not in the laboratory or in the courtroom.

But, while we must draw a line under past misdemeanours, present offences still need to be dealt with as stringently as possible. What the IAAF does in that respect over the coming 12 months will determine whether, come 5 August next year, we are to watch the Rio opening ceremony with any enthusiasm at all.