By Neil Morrison

As this season has demonstrated, there are times in every professional rider's career when they have to grit their teeth and ignore what their injured body is telling them..

All three of this year's MotoGP rivals - Marc Marquez, Dani Pedrosa and Jorge Lorenzo - have already done just that at least once so far this season.

Lorenzo was the first to show off incredible toughness in 2013, racing at Assen less than 48 hours after breaking and then undergoing surgery on his left collarbone, finishing fifth. He then made another early comeback at Laguna Seca after re-damaging the collarbone at the Sachsenring.

Pedrosa meanwhile had fractured his collarbone in Germany, but was also back on track the following weekend in California.

Then came Marquez's Silverstone injury, in the form of a dislocated shoulder in morning warm-up. It looked like the rookie could well miss the race, and surely surrender a chunk of his championship lead.

Instead, the shoulder was painfully popped back into place at the Medical Centre and four hours later Marquez was standing on the podium, having battled Jorge Lorenzo for victory to the final turn.

To celebrate these acts we have chosen six other examples of injured premier-class riders fighting against the odds and overcoming them...

Barry Sheene - Cadwell Park 1975 - Broken left leg and thigh, broken right wrist, forearm, collarbone, broken six ribs
Barry Sheene had always shown a particularly high pain threshold. Phil Read recalls how he was astonished when Sheene revealed he'd cracked his wrist and vertebrae in his back that day while the pair were out on the town. "You wouldn't know he'd hurt himself," he said. Or the time Sheene sported sunglasses at a meeting to hide a bloodshot eye caused by internal haemorrhaging, acting like nothing had happened.

But the stories come no more famous than his recovery from the 175mph Daytona spill in 1975, the event that cemented his place in the British public's consciousness.

With a number of reasons still circulating why the incident happened, ranging from a blown Dunlop tyre to a wayward chain tensioner, 1975 looked to be over for Sheene as he suffered a plethora of injuries, most worryingly a smashed left leg and thigh.

But he wasn't to be deterred. Under the watchful eye of Thames Television, his leg was pinned and he quickly plotted his return. The images of the accident and his impish humour lying in the hospital bed made him a household name in Britain. "I lost enough skin to cover a sofa. If I'd been a racehorse, I would have been shot" said with a grin, was Sheene's typically cheeky way of describing the affair.

He returned to Cadwell Park just seven weeks later for a British championship event. After hiring the back loop of the circuit for a private test he was up to race speed after 30 laps. He managed to garner enough strength to lead the Superbike race ahead of Mick Grant but Cadwell's undulating turns and tight corners were too much for his leg.

It was still a heroic recovery considering his physical condition. In his biography A Will to Win Sheene's mechanic Don Mackay said, "His hands were blue. He couldn't pull the brakes. He was a physical wreck, just a blob of jelly." But after Cadwell he knew he could win and even the 18-inch pin in his leg wasn't going to hold him back.

Kevin Schwantz - Hungarian GP 1992 - Dislocated left hip, broken left forearm
As Kevin Schwantz was loaded into an ambulance on the outside of turn one at Assen, a furious Eddie Lawson was marching back to the pit lane, his dream of a first win with Cagiva over, mouthing off to anyone that would listen. "Schwantz is lucky he's hurt", he said.

The pair's Dutch TT had come to a dramatic end after that infamous coming together on lap six. Lawson was of course implying if Schwantz wasn't hurt, he'd soon see to that.
The Texan had dislocated his left hip and broken his left forearm in a collision with trackside bails, but with the next race in Hungary just two weeks away and Doohan injured Schwantz sniffed a championship opportunity. And Lawson's words added fire to the belly.

But even for a veteran crasher like Schwantz the dislocation hurt. In his own words, "it's a pain unlike any other because it has all the muscles, all the nerves stretched." Doctors advised him to lie on his back for ten days then get around with crutches. The Texan was up and walking freely in five.

He arrived in Hungary against several doctor's wishes and spent "three times as much time" during qualifying in the Clinica Mobile than on the bike. By his own admission he felt ok on Sunday and, aided by a rain shower just before the race, rode heroically, catching title contender Rainey after a bad start, to finish a safe fourth. Temporarily his title hopes were reignited. The downside? That pesky Lawson claimed his first win for Cagiva in that very race.

Mick Doohan - Brazilian and South African GP 1992 - Broken right leg
When Claudio Costa, the doctor who has followed and treated the MotoGP paddock for 41 years, calls your injury the worst he has encountered you know it must be serious.

Doohan and his 'big-bang' NSR blazed a trail to the top of the world standings in the first seven races of '92 and seemed to be invincible heading to Assen. His closest challenger Rainey had flown home to California himself battered and disillusioned by a practice spill at the previous round. Yet fast forward two days and Doohan was lying in a hospital ward in danger of losing his right leg after a 100mph qualifying highside.

In an attempt to get back racing as soon as possible Doohan opted to have an operation straight away to pin the leg. However the poor standard of medical care caused infection and gangrene and after a short time the leg smelt "like a bad butcher's shop."

Costa was horrified by what he saw and realised it wasn't just the leg that was in danger: "There was almost no blood getting to his foot at all. His foot started to turn black due to lack of circulation. Even worse [than losing his leg], he could have died," he said after the ordeal.

Plastic surgeons were called in to paper over a wound the size of a fist and eventually Costa decided on sewing his legs together, allowing the circulation of the left leg to aid the right.

After recuperating near Costa's home in Italy Doohan knew he had to ride in Brazil to defend his diminishing championship lead. Onlookers were worried by his yellow skin and sullen face when he showed up in the paddock seven weeks after the injury. He rode heroically to finish, albeit 12th and out of the points.

He eventually lost the championship to Rainey by four points and it took a further year for his leg to heal as it should have done. To come back from this, never mind win five titles, showed Doohan possessed no ordinary level of determination.

Wayne Rainey - British Grand Prix 1993 - Fractured vertebrae, heavy concussion
From the moment Wayne Rainey completed his first lap on Yamaha's updated YZR at the start of pre-season testing he knew retaining his title was going to be a dogged affair. Not only did the front-end chatter and engine feel underpowered, Rainey's approach to winning was bordering on obsessive, taking over everything in his life. And when his main title rival was Kevin Schwantz losing simply wasn't an option.

He entered Donington 23 points behind the Texan having beaten him only once in the previous six attempts. But importantly the Roberts team seemed to turn a corner, two races prior in Barcelona, where a switch to the year-old ROC chassis resulted in a return to the podium.

Significantly the change also aided team-mate Luca Cadalora and the mercurial Italian went to the top of the timesheets in qualifying at Donington. Rainey, never to be outdone by a team-mate, was determined to make Cadalora's stay at the top short lived when a low speed highside at Goddard's caused a compression fracture of a vertebra in his back. More worryingly, he had banged his head.

Rainey later said in his biography 'His own story', "I told the medical guys that my back was really sore, but I didn't say anything about my head. Back at the motorhome that night I found my vision was lagging. I knew I was concussed but the doctors hadn't checked, and I wanted nobody to know. Next morning I woke up and swung my head, and again my vision was behind the movement. I decided to do the morning warm-up to see how it would feel. I was two seconds off the pace, but I could choose my line. What concerned me more was I couldn't judge distance, so I couldn't pass anybody."

After a long deliberation over whether racing would be worth the risk Rainey decided he wouldn't have been able to live with himself. "Being world champion was more important than anything. I couldn't live with myself giving it away. It was terribly dangerous. There was no way I should have been racing. And I knew it."

Rainey went on to finish second and reduce the gap to Schwantz to two points. It was an astonishing feat that no one knew of at the time, demonstrating he would let nothing stand in his way.

Carlos Checa - Czech GP 1998 - Internal bleeding, ruptured spleen, minor stroke
When Carlos Checa gingerly got up and dusted himself down after a high-speed but seemingly innocuous morning practice spill at the Craner Curves at Donington Park, it seemed it would be a matter of minutes before he was back on track.

However he was soon overcome with dizzy spells and was rushed to the local intensive care. As riders began the afternoon session, Checa was lying in Nottingham's Queen's Hospital suffering from heavy internal bleeding and a ruptured spleen.

It was to get much worse. Doctors gave him a blood transfusion, which in turn caused a minor stroke. It left the Catalan without vision and the feeling in his right arm during a terrifying 20 hours, which had him fearing for his life.

The condition gradually cleared and his sight returned but left him physically destroyed. Spanish doctors advised him to sit out the rest of the season but he returned to the paddock in Brno six weeks later with his sense of humour intact, joking "Now I'm half English", referring to his six litres of transfused blood.

Doctors were perplexed by the injury, but Checa feels his elbow jabbing under his ribs as he rolled caused the internal damage.

"At first, I wanted only to live - to go home and be with my family... but now I believe... in maybe not much time I can fight for races", he said soon after his comeback.

You would think he'd have eased his way back but he suffered another violent fall in qualifying which left his Movistar NSR a heap of blazing flames. Again he dusted himself down and rode to a heroic seventh the following day. His recovery from such life threatening injuries had been miraculous.

Marco Melandri / Loris Capirossi - Dutch Grand Prix 2006 - dislocated and fractured collarbone, concussion / heavy internal bruising
To those that witnessed the first corner melee at Barcelona in 2006 (pictured) the first reaction was one of disbelief, that none of the six riders involved had been seriously injured.

While Dani Pedrosa, John Hopkins and Randy de Puniet made the restart, attention turned to Marco Melandri, whose body had been trailed into the gravel under Pedrosa's machine. It looked bad. Yet the Italian appeared at Assen four days later with nothing more than a black eye and skin abrasions. Or so it seemed.

It was to emerge three races later that Melandri had in fact dislocated and fractured his right collarbone, badly bruised his left shoulder and suffered a concussion.

Capirossi was carried to the Clinica Mobile in agony after the Barcelona pile-up and diagnosed with heavy internal bruising to his chest, hampering his breathing. With Capirossi sitting second in the standings and Melandri in fourth, neither rider was willing to go home to recover and both decided to race just six days later at Assen.

Capirossi managed 15th, having to be carried on and off the bike, while Melandri finished seventh. "In this moment I think God was looking for me," Melandri said soon afterwards.