War hero Djokovic is outstripping everyone

Robin Scott-Elliot reveals the unlikely secrets of the Grand Slam hero's extraordinary stamina

Four years ago Andy Roddick publicly mocked Novak Djokovic's physical frailty. Here, suggested the American to chuckling tennis reporters in New York, was a fine tennis player, but one too ready to raise the white flag when the going got tough.

Roddick was voicing what had been whispered in the locker rooms across the global tennis circuit, that the Serb's tendency to call for the trainer was a telling sign of a talented young man who lacked the steel to break up the Roger Federer/Rafa Nadal duopoly.

Now Djokovic looks down on the rest, with Roddick one voice among many scrambling to laud his durability in the wake of six hours of high-octane tennis that strengthened Djokovic's grip on the world game.

"Absolute war," tweeted Roddick of the men's final of the Australian Open in Melbourne that saw Djokovic defeat Nadal in a match that lasted a record five hours and 53 minutes. "The physicality of tennis has been taken to another level in the last five years."

Djokovic greeted his victory by ripping off his shirt, an astonishingly physical gesture that captured perfectly the moment of a triumph that was as much physical as it was one of sporting prowess.

Yesterday a reclothed Djokovic clutched a wombat – a toy one – in one hand and the trophy in the other for the traditional post-event press conference. "Oh man, I'm tired," he admitted.

The 24-year-old went into Sunday night's having won another sapping encounter on Friday, beating Andy Murray in four hours and 50 minutes. He is the tour weakling no longer, a transformation that has come about through an eclectic combination of hard work – Djokovic's warm-ups are notable for their intensity – a change in diet and a space-age pod that may or may not have any real benefit.

The Australian Open marks the start of the tennis year. It is when the players are at their fittest and freshest, but Djokovic's feat impressed sports scientists for his ability to produce two such marathon performances with minimal recovery time.

"It's a phenomenal effort, a phenomenal aerobic and endurance performance," said Craig Boyd of the Institute of Performance Research at Manchester Metropolitan University.

Diet is one area Mr Boyd and Dr Karl Cook, the Lawn Tennis Association's sports science manager, highlight in Djokovic's relentless advance from contender to leader of the hungriest pack the sport has seen.

In 2010 Djokovic sought the advice of Dr Igo Cetojevic, a nutrionist who, among numerous qualifications, holds a diploma from the Indian Institute of Magnetotherapy in Delhi and has studied traditional Chinese medicine. Djokovic, found Dr Cetojevic, suffered from Celiac disease and instructed him to cut gluten out of his diet. Since doing so Djokovic has won four Grand Slams.

The most controversial part of Djokovic's improvement has been his occasional use of a CVAC Pod (above right). The £50,000 device resembles something from a Spinal Tap stage set and is supposed to aid an athlete by simulating high altitude and compressing muscles at rhythmic intervals. The World Anti-doping Authority takes a dim view of such equipment, although it is not illegal. The scientific community is divided as to its effectiveness. "There is not always a lot of scientific evidence to back up what he is doing," said Dr Cook. "But he strikes me as someone who is constantly looking at any small thing that can help him last a bit longer or train harder or recover a little bit better."

This is the greatest era in men's tennis, as Nadal and Federer jostle with Djokovic for dominance, with Murray not far behind. "People are increasingly looking for those margins where they can beat their opponent," said Dr Cook.

Yesterday Djokovic reflected on his triumph. "You're going through so much suffering your toes are bleeding. It's outrageous, but you're still enjoying the pain," he said with a smile, clearly now a vastly different beast from the weakling Andy Roddick once teased for fearing a "common cold".