The change is striking. If you have not seen Zaheer Khan for a while and spot him in person, or on television, you might mistake him for an army cadet. Like a fresher at a defence academy, he is lean, lithe and sports a crew cut. Not the Zaheer with fat around the hips, whom Michael Holding called unfit after a cursory glance from a distance on the first morning of India's Test series in England in 2011.

Hips don't lie. Today Zaheer's are slimmer and more flexible as he turns to deliver the ball. Although the run-up is the same, he is now capable of accelerating without breaking sweat. The biggest change in Zaheer, who has been selected for India's Test series in South Africa, is that he doesn't have to worry about breaking down.

Before his return against West Indies A in October, Zaheer had played no first-class cricket in 2013. He pulled a hamstring in a Ranji Trophy match against Gujarat in the last week of 2012. During the IPL, he achieved tournament-best figures of 4 for 17 in a victory against Chennai Super Kings, but he spent more time in the Royal Challengers Bangalore dugout than on the field.

After numerous hours trying to rehabilitate at the frugally equipped National Cricket Academy (NCA) in Bangalore over the last couple of years, Zaheer began to get frustrated. His last Test for India had been against England in December 2012, and he desperately wanted to impose himself on batsmen again.

Yuvraj Singh and Zaheer Khan at Tim Exeter's centre Tim Exeter

Sometime in June this year, Ashish Kaushik, one of the trainers at the NCA, told Zaheer and Yuvraj Singh - who was also keen to get specialist attention on the fitness front - about Tim Exeter, an athletic and performance coach, who runs a centre in the small picturesque town of Brive-La-Gaillarde, between Bordeaux and Lyon in southern France. The place suited the pair's desire to train in an environment where they could remain anonymous.

This was the first time Exeter was working with cricketers. To him, though, the two were just athletes. "I could tell they were not as lean as they needed to be," Exeter says. "Having not worked with the guys before, I was not familiar about where they should be. But one of Zak's major goals was to get his body fat levels down and get stronger."

Originally from Scotland, Exeter, who describes himself as an athletic performance coach, moved to France five years ago along with his wife Helen and four children. He played rugby for Scotland at representative level, and once for the national team, before he broke his neck and moved on to coaching. He came to France with a couple of England rugby players - 2003 World Cup winners both - who were, like him, playing for Northampton at the time. Exeter had spent close to seven years with the club but decided to move because he was not happy with the inconsistencies in the coaching system.

"I specialise in improving performance and reducing injury risks," Exeter says. "Making athletes more robust so they don't pick up silly injuries, or help them come back from injuries better. The areas of specialty, particularly, are speed and agility, and movement efficiency. It is not about making them fast in a straight line. It is about being able to change in all directions. It is three-dimensional.

"If your movement is more efficient, you will use less energy, but you will also be more consistent, and that also allows you to generate more."

India might not have had a more skilled fast bowler, but niggles, recurring injures and inconsistent fitness habits were threatening to make Zaheer, who turned 35 this October, obsolete. He knew his chances in ODI cricket were slim, with the selectors set on the World Cup in 2015. The only way back was through Test cricket, which couldn't have been easy given its fitness demands. Her needed to make a decision about where he wanted to go.

****

The first thing Exeter worked out was a strict diet, and Zaheer bought into it without complaints. A combination of the right food and rigorous training became the routine during the six weeks he spent in France.

"Where a lot of people go wrong is, they eat too much bread and pasta and a whole lot of stuff like that," Exeter says. "But if you are not in an endurance sport like cycling or distance running, it is not good to have such food. There has been a fallacy that pasta is king, and you have got to smash carbohydrates down, but it can actually blow you up. So he reduced that a lot, and switched to more protein, like fish, and vegetables along with moderate amounts of fruit to help improve his body composition."

"Zak said that he is not the fastest bowler in the world. That is not his intention. What he wants to be able to do is bowl at a good pace, do it consistently, and do it all day" Tim Exeter, athletic and performance coach

The message was simple: if your intake of calories is more than what you expend, then you are going to put on weight. An advantage for Exeter was Zaheer knew his body well. "He is like any good professional athlete I have worked with," Exeter says. "I know what will work, but you always need the coach-athlete relationship to be working to tweak things. In that respect Zak is brilliant. He does know his body. He also knows what he wants. So we were able to develop some interesting stuff specific to him and it worked."

Other than the weight control, Exeter worked extensively on Zaheer's running technique, which increased his efficiency as a bowler and made him quicker on the field while spending less energy. "Zak said that he is not the fastest bowler in the world," Exeter says. "That is not his intention. What he wants to be able to do is bowl at a good pace, do it consistently, and do it all day. If he has bowled 120 balls a day, he wants to know that he can bowl the last one nearly as hard and fast as the first one."

According to Exeter, Zaheer has a highly demanding bowling action with a huge impact on his landing foot. "There is a massive force coming down on the leg he plants down before he delivers," he says. "He has got to have the ability to decelerate, which has mainly to do with his right leg, which is the last part of his bowling action. As he jumps up in the last part of his bowling action, he comes down very hard on his right leg because he uses that as a pivot to generate speed on the ball. That was an area we focused a lot on. That is why you start with the core, the hip area."

Apart from putting the players through a strenuous outdoor training regime, which started at six in the morning on weekdays and focused more on movements and running technique, Exeter asked Zaheer to make waves with heavy ropes - the toughest exercise - in the gym. He also had him lift dead weights while squatting on the ground, and perform vertical jumps. The physical changes started to become visible after about a month. By then Zaheer had lost 5kg, and was more flexible in his movements.

"It [the weight loss] just allows him to do better, and more often, and become consistent," Exeter says. "We worked on flexibility through his hip region, mobility of his hips, which would transfer positively into his bowling and would take a load off his lower back as well. So getting him stronger through the central part of his body would not only protect his back but also allow him to produce more powerful rotations."

When Zaheer checked in, he had failed in the deadlift from the floor. "But by the end he had started to lift some reasonable weight - around 115kg - which he could not do at the start because he had not got the strength in the core and back," Exeter says. "In that lift he is not only working his legs, he is working his glute, his hamstrings, his upper body, his core, his back, his forearms."

****

Ajit Agarkar, Zaheer's former team-mate and a good friend, could not believe the physical change. He had met Zaheer in London before he left for France. "He looked determined," Agarkar remembers. "He told me he was going to push himself to achieve the required fitness." Injuries and constant niggles pushed Agarkar into retirement this October, so he understood what Zaheer was going through. "It is about bowling with that extra weight for 20-25 overs every day," he says. "And that takes its toll."

Zaheer Khan in his delivery stride ESPNcricinfo Ltd

When Zaheer returned from France, Agarkar was amazed at the striking difference. "We could not believe how lean he had become," he says.

According to Sudhir Naik, Zaheer's long-time coach, his biggest challenge before he trained with Exeter was to last a whole Test. "It was mental, where he would worry how long he could last," Naik says. "He was always confident as a bowler. He was only worried about fitness. But so far, in the last two months, he has just built on the momentum. Especially in the three Ranji Trophy matches he has played, he has bowled extremely well, with full speed, including long eight-to-nine-over spells at a stretch."

Even though the selectors had ignored him for the home series against West Indies earlier this month, Zaheer's aim was to get match-fit. Along the way he bowled influential spells that helped Mumbai snatch crucial points. Sulakshan Kulkarni, Mumbai's coach, agrees with Naik. "In the five-odd matches he has played recently, he has bowled nearly 200 overs [147.3 in five matches] and not once did he come back to the dressing room [for a comfort break or treatment]," Kulkarni says. "You never needed to bother about his bowling. But now he looks the fittest cricketer in the team. So mentally, skill-wise, he was on top."

How can we be sure that Zaheer, who has had an injury-prone body, will last the distance, enough to take him over the last bend of his career? Training smart and focusing on the pre-season training are the key areas, Exeter says. "He told me he has played for 13 years solid. When you are younger, you can get away with murder, but as you get older it is wise to step back and have a preparation period through pre-season training. When you hit a certain age, you only need one injury, and then it just starts a chain of events, but you can definitely get it back when you are more robust. No question about that."

When Zaheer and Yuvraj arrived at Exeter's centre in the middle of a vibrant European summer, they had excess baggage. "They arrived with four to five jackets, thinking it was going to be cold," Exeter chuckles. While the summer took care of that, Exeter is satisfied he has played a part in getting rid of the excess body weight.