Dropped for the final Test in South Africa earlier this year, the country's most famous vegetarian athlete stopped pounding the pavement and hit the gym instead to replace the weight, and power, he lost through a hectic nine-month schedule.

Siddle is set to return to the Test side when Australia takes on Pakistan in Dubai, starting Wednesday, armed with the pace that had made him a mainstay of Michael Clarke's attack.

Siddle admitted he was "pretty fatigued" and "pretty shot" when his pace dropped off so much in Port Elizabeth that Brad Haddin was able to stand up to the stumps for the paceman.

When coach Lehmann declared several days later that Siddle was axed because of a lack of pace, the Victorian realised he needed to change his training regime if he was to reclaim his place in the side.

So he stopped running and went to the gym three times a week.

"If you put in more calories than you're burning then you're going to put on weight, and build muscle, it was  pretty easy," Siddle said.

"Once I got home I did stop running, it makes it a little bit easier to maintain weight.

"I think I put on nearly four-and-a-half, five kilos, it's a lot of weight since the end of South Africa. I am feeling good and the diet hasn't changed if that is going to be one of the next questions."

That diet, of course, does not include meat, much to the chagrin of card-carrying members of the ex-fast bowling cartel.

"It doesn't make any difference at all, it just shows that everyone believes you have to eat meat but I have put on five kilos without changing a thing apart from a few different training patterns and eating a bit more and watching what I eat," Siddle said.

"Everyone thinks you have to eat meat but I am the one who hasn't been injured in the last two-and-a-half years so that probably explains something."

The early indications are Siddle has rediscovered his pace.

"From the feedback from 'Hadds' [Haddin], he's always the best judge of how it's coming through, and he was feeling good with how it's going," Siddle said.

But has Siddle's extra weight and power come at the expense of his aerobic capacity and resilience? Siddle does not think so, saying his three-month stint of county cricket during the winter had preserved his fitness base.

With temperatures set to hover in the mid 30s in Dubai and Abu Dhabi, it will be asking a lot of the fast bowlers to have them bowling long spells in the oppressive heat.

"There might be stages that you have to if it is reverse-swinging or you are bowling well and have two or three wickets in a spell. You might have to push on and get a breakthrough before you finish up," Siddle said.

"You might need three- or four-over spells in that middle part of the day.

"Maybe a few more with the new ball or different stages.

"You always have to be prepared to bowl a long one, that is for sure, no matter how hot it is."

The Australians are expecting Pakistan to serve up a pitch that negates the express speed of Mitchell Johnson and suits spin - one of Australia's weaknesses in recent times.

That is likely to result in Stephen O'Keefe making his Test debut.

"We usually get dished up wickets different to other countries," Siddle said.

"It is going to be hard to say but I am guessing two spinners is going to play a big part over here. Most countries have played two spinners when they are over here and we get more spin-friendly wickets than most so that's probably going to help."