SCOTLAND'S medical staff admit they have no idea why Stuart Hogg, the team's full back, has suddenly started to be affected by cramp late in games. The player says the recurring problem is starting to get really frustrating – particularly since it always comes just as the match is starting to break up and the gaps for him to exploit are beginning to appear.

Hogg was again hit by the problem during the final pool game against Samoa, coming off after 71 minutes, and James Robson, the team doctor says he cannot explain what is going on. "Hoggy's cramp is doing my head in," he said. "Some people are susceptible to change in surroundings, particularly beds. For others it's the change in surface from grass to artificial. I've even seen a lot of people cramping up because we're playing on football pitches, which are slightly firmer than the ones we usually play on."

Hogg had also come off the week before, also at St James' Park in Newcastle. But as Robson pointed out, he had lasted the whole game against the USA, which was played on a football pitch at Leeds, but was taken off after 66 minutes against Japan, played on a rugby ground in Gloucester.

They have tried different salt compounds and all kinds of other treatments to try to get to the bottom of the issue. “Cramp is just one of those things we are not sure about," Robson said. "I think it is multi-factorial. Is it the boots, the surface or the bed? I don't know but we are trying to nurse Hoggy through it so next time he won't cramp. We will find it stops soon, though because he hasn't had a problem with it in the past."

Hogg himself is even more annoyed by being suddenly hit by the problem which is restricting his ability to finish games. "I don’t know what it is, but it is bloody frustrating," he said. "The game at the weekend was starting to break up but it is not about me, there are 30 other boys in this squad.

"I have worked with the physios and Doctor James [Robson]. I am not sure what is happening but we will try and get it right. We have tried lots of different things. I would love to be involved and I will work hard and change a few things, I am not sure what yet, but it was bitterly disappointing to come off.

"In the last couple of games, it has been in both calves – the lower back starts to seize up ever so slightly and then the cramp comes, which is a nightmare. The one at the weekend I chased down a kick, I was trying to steal the ball and ended up getting cramp so I had to get out of the way. I don't want to dwell on it too much; the boys had a fantastic win at the weekend and that is what we will concentrate on."

He is hoping the shift in scenery from Newcastle to London will help cure the problem and that he will get in a full 80 minutes against Australia on Sunday, an occasion where the anticipation is already starting to build. "The boys are on fire, massively excited over what is ahead," he said. "They are chuffed to bits we have got to the quarter-final. That is what we have targeted and for us this is where the hard work starts. It is a great opportunity to get one over on Australia.

"There are a number of guys who are stepping into the unknown. We have never been to the World Cup before but it is a fantastic experience and one we don’t want to end anytime soon."