There are certain sports that put a satisfyingly large tick in 'immediately understandable' box.

Had you just beamed down from Planet Vogon and landed in the midst of a high jump event, for instance, you would pretty quickly figure out that this was all about finding out who could leap the highest (even if you did have a giggle at the humanoids' failure to invent anti-gravity devices). Same thing with a long-distance cycling race, which is clearly a means to identify the athlete who can swallow the most steroids and not fall off his bike.

Diving is obviously an activity humanoids came up with while waiting for the anti-gravity in turn to come along. Swimming is something they subsequently invented so they didn't have to call diving 'drowning' instead. And the purpose of track cycling is to see how much money can be added to Sir Bradley Wiggins' pension fund in the space of a single afternoon.

But judo is a different matter. Judo is about as easy to read as A Brief History of Time, as rich in clarity and meaning as a post-Iraq speech by Tony Blair. The word itself comes from two Japanese characters - 'ju', which means 'total', and 'do', which means 'bafflement'. Actually, they mean 'gentle' and 'way', but when the judo events got underway in the SECC yesterday morning, gentility wasn't exactly apparent.

Then again, neither was anything else. A pair of grappling judokas provide a spectacle on a par with watching two ferrets enjoy a bit of hanky-panky in a pillowcase. In other words, it's probably quite enjoyable if you happen to be in the middle of it, but all a bit puzzling to an outsider.

Fortunately, a good number of those in the SECC audience were clearly au fait with the technicalities - of judo, not the sex life of ferrets - and had a keen appreciation of what was going on. A rather larger number probably pitched up believing that a throw was something you draped over the back of a sofa, but they quickly got up to speed as well.

Just to add to the confusion, judo has evolved a complex system of penalties and an equally opaque system of semaphores to signal the exact nature of the infraction that has taken place. My favourite by a distance was the Shido, which basically translates as 'not trying hard enough'. Perish the thought that Scottish football should ever bring in a similar sanction. It's hard to think of a player who would make it past half-time.

There is also the slightly quirky format. Basically, it operates as a knockout tournament, but there is also something called the repechage, a French term meaning 'have another go'. In essence, this means you can be bounced on your head by someone and still come back and try again. Though why on earth you would want to is probably the most puzzling part of it.

The morning bouts created a cracking air of expectation, building a febrile atmosphere when the evening's finals session got underway. It was noisy enough when Australia's Amy Meyer and Onoh-Obasi Okey of Barbados kicked things off as they fought for the women's 48kg bronze at 6pm, the decibel level went through the roof -and probably halfway across the city - when Kimberley Renicks walked into the hall for her meeting with India's Sushila Likmabam.

'Make Some Noise,' exhorted the giant screen in the corner, possibly the most unnecessary plea in the entire history of sport. As Renicks made her way to her position, she wore a look of determination last seen in these parts when David Sole led his Scots out at Murrayfield in 1990 - and with similar results. Two minutes into the contest, she produced a clean ippon, stopping the fight stone dead. She had just secured Scotland's first gold medal of the Games.

In truth, nothing quite matched the eardrum-melting levels reached then, but nobody was in much danger of nodding off either. There was a wonderfully poignant moment when 38-year-old John Buchanan picked up bronze in the 60kg class, vindicating his decision to drag himself out of retirement after a decade's absence from the sport.

And then, of course, the fabulous fighting Renicks of Coatbridge seized their second gold when Louise matched the achievement of her kid sister by winning the 52kg class.

For many the subtleties of judo might still have been a mystery at the end of the evening, but there was no doubting the meaning of the Renicks' dazzling smiles.