In October last year, Suresh Raina was picked for India's home ODI series against New Zealand. He took a late-evening flight from Delhi to Bangalore, where he was headed to the National Cricket Academy. He had just played a Ranji Trophy match for Uttar Pradesh but hadn't batted in the second innings because he wasn't fully fit.

The next morning he took a yo-yo test at the academy, and flunked it, failing to reach the minimum level set as a mandatory criterion by the Indian team management for a player to qualify for selection.

Raina missed the first two ODIs, and he was told that once fit, he would need to take the test again. He did but failed once again to attain the 16:1 mark, the minimum level set for Indian players by the team's strength and conditioning coach, Shankar Basu.

Raina was the first big-name player to have failed the test since it came into effect in mid-2016, when Anil Kumble took over as India coach. Soon he was joined in that dubious achievement by Yuvraj Singh.

The test

A yo-yo test involves a player shuttling between two cones that are set 20 metres apart on flat ground. He starts on a beep and needs to get to the cone at the other end before the second beep goes. He then turns back and returns to the starting cone before the third beep. That is one "shuttle".

A player starts at speed level 5, which consists of one shuttle. The next speed level, which is 9, also consists of one shuttle. Speed level 11, the next step up, has two shuttles, while level 12 has three and level 13 four. There are eight shuttles per level from 14 upwards. Level 23 is the highest speed level in a yo-yo test, but no one has come close to getting there yet. Each shuttle covers a distance of 40 metres, and the accumulated distance is an aggregate of distance covered at every speed level.

The player gets ten seconds to recover between shuttles. At any point if he fails to reach the cone before the beep goes, he gets a first warning. Usually a player gets a few "reminders" to keep to the pace, but three official warnings generally marks the end of the test.

As a player moves up the levels, the time available to complete each shuttle diminishes, which means he needs to run quicker to reach the next cone before the beep. The player runs until he gets his three warnings, and the level achieved at that point is the test result.

Teams have different speed levels as qualifying marks. India have set 16:1 as the qualifying speed level, which means it is mandatory for their players to finish the first shuttle of speed level 16, which in terms of accumulated distance is 1120 metres. Pakistan's minimum level is now 17:4; West Indies are at 19, and New Zealand probably have the highest level, 20:1.

ESPNcricinfo Ltd

As for "civilians", the simplest way to know if you are fit for a yo-yo test is to run two kilometres in eight minutes.

Why do cricketers need it?

The yo-yo test is mainly derived from the Leger Test, created by Luc Leger of the University of Montreal, which was popular till the turn of the century. The Leger multi-stage test, where an athlete would run non-stop 20-metre shuttles for 12 minutes, was not considered suitable for sports like cricket, which are marked by bursts of activity separated by recovery periods.

"You bowl, you throw, you hit, you run, you have about 30 seconds before the next ball starts," Andrew Leipus, who was till recently the head physiotherapist at the NCA, says. "So you've got to get your heart rate down, your breathing rate down for the next delivery."

Leipus says that the yo-yo test is not simply a fitness test, in that it also helps players improve their fitness while testing it. He used it as such when he doubled up as strength and conditioning coach at the Darren Lehmann Cricket Academy in Adelaide earlier this decade. "I used to actually run it back to back after 10-15 minutes' recovery time. Alternatively, I would get the players running at a set level."

The intention behind the yo-yo tests and the "beep tests" of old (similar to the Leger tests, where a player shuttles between cones without taking breaks), Leipus says, was and is to establish a "baseline fitness", showing the players were fitter than the common man. "It is going to mean less injuries because the guys are fitter. It is going to mean high level of performance, because guys are going to recover better out on the field. The turnaround time between matches is shorter now, so they are going to recover quick between games."

Also, once a player gets into shape to routinely pass the yo-yo test, Leipus says, "he will find it will improve his batting ability, because you recover better between runs running ones, twos, threes".

A yo-yo test also helps measure the aerobic capacity of a player. "We use it to show them how fit they are," Chris Donaldson, the New Zealand strength and conditioning coach, says. "The major physical components of cricket are based around aerobics, strength, speed, so how fit, fast and strong they are are the components we train for a cricketer so that they don't break. This way, they can play the game for longer and faster and they can do things like stop the ball, take a miracle catch or run between wickets faster."

"Like level 15 on a treadmill"

Fitness was high on Kumble's list of priorities when he took over as India coach in June 2016, and he found backing from Virat Kohli, the captain, and senior players like MS Dhoni, who supported the idea of making passing the yo-yo test a requirement for selection. Basu was asked to come up with benchmarks that players needed to be able to reach playing at the international level.

It is not only in India that the yo-yo test is mandatory. Umar Akmal was sent back home from England on the eve of the Champions Trophy this summer after he failed to attain 17:1, the PCB's qualifying mark at the time. Reportedly, Akmal could only get to 16:5.

Yo-yo tests help players recover faster between games Getty Images

Since then, Grant Luden, the Pakistan strength and conditioning coach, has raised the mark to 17:4, to motivate the players, he says. "The reason why we have come up with 17:4 is, it is not going to make you hit a cover drive or bowl faster. All it does is, it helps with the recovery." Luden says that research shows that if a player plays three matches in a week, he has the ability to not just show consistent performances but also recover a lot faster.

Luden arrived at 17:1 after sustained testing, from which he calculated averages: 17:1 was where his players showed consistent performances. "With us continually doing yo-yo testing, the standard of players started improving. That is how we moved up to 17.4." Doing a 17:4 is the equivalent of running 1580 metres, which is a touch under four times around the Gaddafi Stadium in Lahore.

Luden says that if a player who has never taken a yo-yo test is able to shuttle for 20 minutes around a cricket oval at about 16-17kph, he will be able to pass the test without breaking too much of a sweat. "That is like level 15 on a treadmill, and you have got to be able to do that for ten minutes. If you can do that for ten minutes on a treadmill, you should pass."

Yo, champions

With a level of 20:1, New Zealand's cricketers are probably the fittest in the sport. For good measure they have Donaldson, a former New Zealand Olympic sprinter, as their strength and conditioning coach.

In New Zealand, all cricketers, international and domestic, are subject to yo-yo testing. Like Luden, Donaldson too arrived at 20:1 based on the average scores of New Zealand players. Passing a yo-yo test is not a prerequisite for selection in New Zealand, however.

Still, the best New Zealand players, Donaldson reveals, have gone past 22. Not that that means they line up for the test. "They always dread it," he says. "They are always a bit scared of it, probably because they want to do well. It is a tough test because you push yourself to the absolute limit to know where you are at."

What is Donaldson's own level? "I have never done it," he admits with a chuckle. "Thankfully it wasn't around when I was running. Too hard."

Where and when you take the test matters

While it is obvious that players coming off long flights or returning after injury breaks will struggle more often than not in a yo-yo test, players who have been on the field frequently in the days leading up to a test also find it tough going.

This September, Raina was again asked to take a yo-yo test. Once again, it came on the back of a busy schedule: he had played two Duleep Trophy matches when he flew to Bangalore to take the test. He failed again.

play 5:39 The YO-YO Test The folks at ESPNcricinfo put themselves through a modified version of the YO-YO test. Let's see how they fare.

Ramji Srinivasan, one of the most senior trainers in India, a former strength and conditioning coach for India, and currently in that role for the Tamil Nadu side, says players need to be given time to prepare. "Players should also be allowed to appeal and redo the testing in ten days," he says. "They should be allowed to prepare physically and mentally for the testing."

The case of Tamil Nadu offspinner Washington Sundar illustrates his point. Ahead of selection of the squad for the New Zealand T20 series in October this year, Sundar was summoned to Bangalore for a yo-yo test in the middle of what had been a busy domestic season for him.

He was in Lucknow, playing for India Red in the Duleep Trophy final, when the call came. He had got there from Dehradun, where he was at a preparatory camp for the Ranji Trophy, only a few days earlier.

Sundar, who had never taken the test, took it immediately after the Duleep Trophy final. He missed the qualifying mark narrowly, getting to level 16, and missed out on selection for the New Zealand series.

He was clearly disappointed and did not hide it. "The next day I came back home and I woke up and saw in the newspapers that I flunked the fitness tests," Sundar told the media after hitting a century at the start of the Ranji season. "Nobody [from the management] spoke to me. I got to know the results later and did not get to know there on the same day from them."

Leipus agrees with Srinivasan that preparation time is important. "The test is both mental and physical. If you have not done it before, you don't know what to expect. There is the pacing element because the speed of the test increases as the time goes on. So you are going to probably going to go too hard too soon, as opposed to pacing yourself."

A couple of important factors that can influence the final reading are the surface the player undergoes the test on and the weather. The surface is significant due to the traction available, since the ability to pivot quickly is an important element. Turning on a natural surface like grass outdoors is not like doing so on, say, rubber matting laid over concrete indoors (as is the case at the NCA).

Leipus says that the fact that the ambient temperature is more stable indoors helps with consistency in the players' levels. "But if the variables change outdoors and if it is very hot, you will obviously be fatigued a lot quicker and the numbers will be pretty low."

Numbers aren't everything, or at least they shouldn't be

All the strength and conditioning coaches agree that age does not normally have much of a bearing on the results of yo-yo tests. Misbah-ul-Haq, Luden says, got to 18:5 without any fuss in his farewell series, at the age of 42. Ashish Nehra, who retired at 39 recently, clocked 18:4 during a yo-yo test earlier this year - reportedly better even than the likes of Virat Kohli at the time. Ravindra Jadeja, India's best fieldsman, reportedly clocked 16:1, and it is understood that Manish Pandey has set the Indian benchmark, with 19:1.

Ashish Nehra, at 39, was doing better at yo-yo tests than his younger team-mates, having been an enthusiastic runner earlier in his career AFP/Getty Images

ESPNcricinfo understands that the minimum qualification for the Indian team is to be to raised to 17 soon. According to Leipus, a major drawback of having one standard to reach is, it is not individualised. "And that is where some guys are going to be at disadvantage." Leipus and Srinivasan also agree that fitness quotient and cricketing ability are and should remain distinct. "For example, Yuvraj has had cancer, so he has reduced lung capacity, based on the treatment he received. So that is obviously going to affect his running performance in a yo-yo test, but that is not going to directly affect his cricket ability," Leipus says. "You are going to have to make those exceptions."

Indeed, there always have been exceptions. Nehra remembers: "[Sachin Tendulkar] would say: 'How many runs do I have to run?' Four. So his test was to run four in minimum time. Sachin was always quick between the wickets, even at 39."

According to Leipus, injury management is also a factor. "We never used to make Sachin do them back in the day because of his broken toe. You don't want to exacerbate injuries just for the sake of the getting a number. Yes, these benchmarks are really important, but then you do have to take them on a case-by-case basis - when the players are more established, have had some significant injuries and you have to modify your expectations somewhat."

Does fitness equal success?

Has the yo-yo test made a difference to the Indian team on the field? A BCCI official says the impact of the test is evident in the improving standards of Indian players. "Any player who covers 20 metres in less than three seconds it is hugely helpful," he says. "It helps the fielders pursue and grab difficult catches on the boundary line. Say a guy whose level is 15, and if there is a catch that is about 15 metres away, he might just get his fingertips to it. But somebody who covers 20 metres in 2.8 or 2.9 seconds, for him the same catch will be easy.

Leipus points out that the yo-yo test favours batsmen, as it emphasises the physiological and biomechanical demands of batting more than it does those of running in "linearly" for the bowlers. But he adds that players needn't be distracted by specific pros and cons. "For an elite athlete whose job is effort-recovery, whether you are a batsman or a bowler, the yo-yo test mimics that quite well. So I do not think it is unreasonable to have that as the [minimum] level."

Kumble is no more the India coach, but his fitness-first mindset is alive and strong. Kohli, for one, is uncompromising on fitness too.

"If there is one player who is putting on too much body weight, who is not doing the training, he can bring the team down. He is not being the best he can be for the team," Leipus says. "And Virat does not want that type of thinking to come into the squad. I have been waiting for this for 15 years. It is fantastic they are doing it now to change the culture."

As Nehra says, though, only a player can push his own boundaries. "When it comes to running, you have to push yourself. Virat Kohli has not become a fit athlete overnight. He has worked hard on his fitness for the last three years and that is why he is successful."