To gain the competitive advantage, multiple AFL clubs have turned to altitude training, sending their entire roster to train in the thin air of Flagstaff, Arizona.

It is the latest in the sports science insurgency, earmarked by the pursuit of even one or two percentage points improvement in performance.

Yet in the quest for an edge, these clubs may be putting their players at risk from a potentially lethal bacteria raising a silent epidemic in Arizona.

No matter where you are on Earth, be it Cottesloe beach or on top of Mt Everest, the air you breathe contains the same proportion of gases: 20.9 % oxygen, 78.09% nitrogen, and 0.1% other molecules.

But air compresses under its own weight, so it is more dense – or thicker – at sea-level, and thinner the higher one goes. That means at 8000 metres there is a third less air than in a coffee shop on Lygon Street.

Remarkably, three civilisations have evolved to flourish at high altitude: the Bolivians of the Andes, the Nepalese of the Himalayas, and Kenyans of the Rift Valley.

It has not gone unnoticed that Nepalese Sherpas are marvels of stamina, dragging unfit and unskilled American climbers through the ‘death zone’ and to the top of Everest, while the Kenyans can run at pace seemingly without limit.

Their adaptations cannot be replicated in the average person, as they are the product of thousands of years of genetic mutation. However, it has been understood for decades that the human body, if placed in a state of hypoxia – or relative oxygen starvation – is capable of making temporary physiological changes to operate more efficiently.

At high altitude most people start generating more haemoglobin, the oxygen-carrying component of red blood cells. By having more oxygen-carrying cabs on the rank, a person is able to transport more oxygen passengers – essential in enabling the body to burn the cellular glucose that provides muscles with energy.

After a period of two to four weeks at altitude, up to 8% more haemoglobin will be coursing through one’s veins.

The effects of altitude training are very similar to the benefits of injecting EPO or transfusing red blood cells, the type of blood-doping that saw Lance Armstrong banned from cycling for life. It can provide greater endurance, greater speed, and the ability to interval train at higher intensity.

Though the World Anti-Doping Agency at one point considering placing altitude training on their list of banned substances and methods, the practice remains perfectly legal, and many individuals and sporting teams have now integrated this into their pre-competition programs.

In the AFL, it was Mick Malthouse – high druid of AFL coaches – who started the current craze for altitude training.

In 2005 he took Collingwood to Arizona for a two week camp at 2100 metres above sea-level. He considered the trip so beneficial in both team bonding and performance gains that the Arizonan camp became an annual event.

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Coccidioidomycosis, or cocci as it is abbreviated, is a fungus that thrives in dry soil. When the fungus is disturbed it releases spores into the air which can then travel over one hundred kilometres.

Once inhaled by humans (and dogs, cats, even dolphins) it can cause what is commonly referred to as Valley Fever. The name comes from cocci’s prevalence around the San Joaquin Valley in California.

Typically, a bout of Valley Fever induces flu-like symptoms: headache, fever, cough, rash, fatigue, muscle and joint pain. In the same way that altitude training is about improving the body’s ability to harvest oxygen from the lungs, cocci targets the lungs’ ability to convey oxygen.

Cocci spores are so small that they reach the smallest saccules of the lung where they lodge firm, multiply and subsequently burst, causing an immune response that can lead to inflammation, disruption of blood flow in the lung, and tissue death. As a result, Valley Fever is often misdiagnosed as pneumonia or cancer.

From the lung these spores can then travel anywhere in the body, including to the skin, face, bone, and testicles. If it reaches the brain, treatment involves a shunt into the spine; at this point the infection can be lethal. Over three thousand people have died from Valley Fever since 1990.

Once inhaled, cocci is with you for life. In many people cocci spores cause no acute inflammation or adverse reaction; most of those who do experience symptoms report no cases of a second infection.

But the spores can lay dormant for decades before reviving to attack the body, and they can cause chronic illness across a person’s life. With no known cure, cocci is considered a biohazardous material, and its use in research is regulated by US anti-terrorism laws.

There is nothing, however, to stop any man, woman or child from being exposed to soil riddled with cocci, though the dangers have long been known.

During World War II the Germans complained under the Geneva Convention that a POW camp in Arizona failed the clause relating to a ‘healthy location’. In California a federal court recently ruled that placing prisoners in facilities known to be high risk for cocci amounted to ‘cruel and unusual punishment’.

Nevertheless, cocci was largely unknown outside of research labs for most of the 20th century. But with the drying-out of climate change coupled with mass migrations of people to areas rife with cocci, awareness is rising in step with an epidemic of infections.

Between 1998 and 2011 there was an eleven fold increase in reported cases of cocci in Arizona. Across the US it is estimated there are around 150 000 new cases of Valley Fever each year, Arizona accounting for two thirds of all infections, with the remainder in California, Colorado, Utah, Nevada, New Mexico, and Texas.

Those most at risk are the elderly, Filipinos, African Americans, pregnant women and people with an immune disease, but any healthy person of any age or race can contract Valley Fever.

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In the season following their first altitude training camp in Arizona, Collingwood improved from second-last to seventh. By 2010 they were on top of the ladder and went on to steamroll St Kilda in a replay of their drawn grand final match. In 2011, Malthouse’s last at Collingwood, they again finished minor premiers.

Throughout this period one change in Collingwood’s performances seemed to stand out: their strong finish in fourth quarters. For instance, nine games into the 2011 season Collingwood was gathering an average 27 more possessions than its opponent in the last quarter. In the same period they had been out-scored in the final term just once – by Geelong.

The statistics and observed performance suggested superior endurance across the entirety of a match compared to their rivals. This is the exact benefit hoped to be gained from altitude training, so the logical leap was there for other clubs to make.

Nevertheless, Malthouse has at times received criticism for taking his teams – first Collingwood, now Carlton – on a training camp that costs something shy of one million dollars, and which promises only the possibility of marginal gains.

Prior to leaving with the Blues for Arizona last December, Malthouse was curt in his response to questions about the efficacy of such a trip.

“We don’t do it to waste time, money, effort,” Malthouse said. “We do it because it’s very, very good for you. We will take those benefits and if someone else rejects them, well that’s up to them. We’re not here for anyone else, we’re here for ourselves.

“And as far as the scuttlebutt of those who choose not to use it and then condemn it, then we have scientific evidence on the contrary.”

That evidence remains under wraps at Carlton, but Collingwood has recently released their findings.

Blake McLean has been testing the blood and tracking the performance of Collingwood players in two groups: those who trained at altitude for around three weeks, and those who remained at sea-level.

His results show that within about thirteen days players training at altitude average a 4% spike in haemoglobin. Their time trial performances subsequently bettered their sea-level counterparts by 1.5%.

However, McLean’s findings and other studies’ data show that individuals vary widely in their response to altitude training. It is notable that five Collingwood players tested actually showed reductions in haemoglobin.

It is also undisputed that any gains in haemoglobin will have disappeared within one month of descent. This has provoked some parties to suggest club money is being wasted on a fad when it could be better spent on cheaper training alternatives – such as thermal stress training – or simply focusing on skills.

Dr Ian Gillam of Exercise and Sports Science Australia is critical: “The question is, does it actually increase the training response and running performance of AFL players when the season begins some three months later? Importantly, is the expense of conducting these overseas altitude training camps with a cost of at least $500 000 justified?”

According to Blake McLean, the answer is ‘yes’: “The main theory of the pre-season altitude camp is to obtain a physiological benefit which helps you train harder for the next month, which then improves your training capacity from then on.

“It’s almost like training to train. You keep building on top of what you’ve done.”

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Before taking the head coaching role with the Gold Coast Suns, Guy Mckenna was an assistant under Mick Malthouse where he took part in the Pies’ annual trip to Arizona. McKenna’s first-hand experience convinced him the training was effective, and it was soon instituted as part of the Suns’ pre-season.

“”t was a no-brainer because I could see the benefits in the playing group. Some of the scientific boffins out there say there are minimal gains, but I think that is where AFL is at,” McKenna said.

“A percentage or clearance here or there means you win games of footy.”

Like Mckenna and the Suns, many clubs are keen to harness even a marginal boost to endurance and performance. In preparation for the 2014 season, seven clubs embarked on altitude training camps during November and December of 2013. Brisbane, Carlton, and the Gold Coast sent their players to Flagstaff, Arizona. Essendon, the Bulldogs, and St Kilda sent players to Colorado. North Melbourne sent players to Utah.

Of the various locations in the US used by AFL clubs for altitude training, Flagstaff in Arizona is the favourite. It is home to the main campus of North Arizona University which, for a fee, allows professional sporting clubs to use their Skydome training facilities.

A town of just over sixty thousand residents, Flagstaff is set amidst the largest ponderosa pine forest on the American continent. The white-tipped ridges of Mount Elden and Humphreys Peak fill the horizon to the north. Under a layer of snow it is stunningly beautiful.

The scenery is, however, merely incidental. AFL clubs flock to Flagstaff because it has the facilities and, crucially, it sits at 2100 metres, considered the altitude ‘sweet spot’ – the air thin enough to increase haemoglobin production, but not so thin as to restrict the capacity for high intensity training.

A typical altitude training camp in Arizona will move between three tasks, and three locations. Weather permitting, there is a hike to the top of Humphreys Peak at 3852 metres above sea-level.

There are hikes, runs, and team-building tasks to be performed among the steep walls of the Grand Canyon ninety minutes to the north. And there is a battery of strength, fitness, and training drills to be run under the Skydome.

However, as no research exists to support the theory that altitude training results in improvements that persist across the course of a season, the camps that have become an institution at multiple clubs – including Brisbane who needed an injection of cash from the AFL just to pay for the use of Flagstaff facilities – may yet prove to be an expensive indulgence.

Collingwood President Eddie McGuire, whose players did not embark on altitude training at the end of 2013, commented: “If I was running a club that was on a handout or not being able to make a profit, I don’t think I would be blowing $500,000 on an altitude trip.”

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Because of new residential developments disturbing the soil, as well as wind storms and high soil motility from farming, the most cocci prone area in Arizona is the arid country surrounding Phoenix.

Dust storms are a common occurrence in and around the city; on 29 October 2013 a dust storm hit, the air so thick that three people were killed and twelve injured in a nineteen car pile-up.

An Arizonan dust storm is an obvious harbinger of cocci. However, the fungi’s spores are invisible, drifting undetected for many miles once disturbed.

Benjamin Park of the Centers for Disease Control and Prevention (CDC) has observed that even “people who work in office buildings have gotten it, and there’s one case of someone who just passed through the Phoenix airport.”

Director of the CDC, Tom Frieden, is spearheading efforts to educate the public about the dangers of cocci.

“Because fungus particles spread through the air, it’s nearly impossible to completely avoid exposure to this fungus in these hardest-hit states,” he stated.

“It’s important that people be aware of Valley Fever if they live in or have travelled to the south-west United States.”

In the rarefied air of Flagstaff, looking out upon a magisterial vista of mountains and coniferous forest, the last thing on an elite athlete’s mind is air-borne bacteria.

Yet with research into how cocci spreads still nascent, it is unknown whether or not the flapping of a butterfly’s wings in the Sedona desert could lead to the likes of Gary Ablett inhaling a potentially debilitating bacterial spore a few hours later.

According to the calculations of Dr John Galgiani of the Valley Fever Center for Excellence, though up to 60% of all Arizonans are likely to inhale cocci throughout their life, their annual risk of contracting Valley Fever is just 3%. A little less than half of those will develop an illness requiring hospitalisation.

Given hundreds of AFL players have visited Arizona on altitude training camps over the last decade, and a smaller number have spent periods training at the Athletes’ Performance centre in Phoenix, some of them may have inhaled cocci spores, with absolutely no ill effect.

And given the men on these camps are young, fit and predominantly Caucasian, their risk of severe illness from inhaling the fungal spores – particularly in decamping at Phoenix or just passing through to reach the more northerly town of Flagstaff – is slight.

Serious infection is surely no more than a marginal possibility. Even more marginal, perhaps, than the potential gains of altitude training.