Inside features20

InsIde Football Wednesday, september 12, 2012

Hamstring injuries are the bane of football medical departments, but new research has turned up some intriguing findings, writes DR JODI RICHARDSON.

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EVERY player dreads the twang in the back of the thigh, the pain

that comes with a tear of the hamstring and the knowledge that he is destined to be off the park for at least three weeks.

Hamstring injuries have been the biggest injury problem for AFL players for years and have plagued some of the game’s greats.

Nathan Buckley, Matthew

Lloyd, Daniel Kerr and more recently Lance Franklin and Brent Guerra have suffered the pain and frustration of these injuries, which are still responsible for more missed matches than any other.

But there is some good news. Last year in the AFL, hamstring injuries hit a historical low.

A body of AFL-funded research has investigated the relationship between interchange use and

hamstring injury risk – and yielded surprising insights into an injury that has perplexed scientists for years.

The reason that hamstring injuries are metaphorically (and often literally) a pain in the backside is because there are just so many of them.

For perspective, let’s have a quick check of the stats. In 2011, there were nearly five new hamstring strains per club

and, over the past 20 years, this figure has been lower only in 2002 but not by much.

In 2011, hamstring strains resulted in nearly 300 missed AFL games across all clubs.

By comparison, the injury second in line for most new injuries per club in 2011 was ankle sprains, which kept players out of action for a bit over 155 games across all clubs.

It’s clear now why it’s such a problem for the sport and why the drop in new injuries in 2011 is great news.

In fact, the 2011 stats showed a drop in new hamstring injuries per club, fewer games missed and a lower recurrence rate.

And it just so happens that 2011 was the first year with new interchange rules.

Previously, clubs rotated four players off the bench however they liked. As of 2011, clubs had three players to rotate on and off the field and one substitute player who could come on only to permanently replace an injured player for that game.

Is this the reason for a drop in hamstring injuries? Only time will tell, it’s too early to crack open the champagne after just one season, but it looks promising.

Dr John Orchard, sports physician and co-author of the AFL Injury Report, analysed interchange use and hamstring injuries over 56,320 player matches between 2002 and 2010.

The results of this research are intriguing as they show that the risk of hamstring injury increased for a team when their opposition made 60 or more interchanges during the game.

In other words, if Geelong plays the Swans, and the Cats make 60-plus rotations, they put the Swans players at more risk of hamstring injuries than themselves. But why?

The research also showed that players who had been interchanged seven or more times in the previous three weeks were being protected against suffering a hamstring injury.

“These findings suggest that cumulative fatigue may, along with speed, be a risk factor for hamstring injuries,” Orchard reported.

Orchard adds in the research paper that “there may also be a bias in that players who interchange regularly may be less exposed because they play less total game time”.

There’s no doubt that hamstring injuries are a speed related phenomena. They occur in athletes who do repeated high intensity efforts.

Bottom line, athletes who run fast are at risk of hamstring strains and

Strung out!

marathon runners clearly are not.

“The findings of the research point towards speed and fatigue being risk factors for hamstring injury,” Orchard said.

“Speed being a risk factor more than fatigue, but they trade off against each other because the more fatigued you are, the less speed you are going to be able to produce.

“This is consistent with what we see in athletics where 100m sprinters (higher speed) are more prone to hamstring injury than 400m sprinters (more fatigue).”

In 2007, the average numer of interchanges was 58. This more than doubled by 2010.

Clubs now regularly interchange 150 times a game. More interchange has led to a much faster game.

Orchard explains that the findings of the research are consistent with the feedback the clubs are giving.

“Teams are saying that when they started

interchanging more, they were seeing improved performance and fewer hamstring injuries and so believed that more interchanges were protective against hamstring injury,” Orchard said.

“But they are only looking at their own data, and every time they ramped up their interchanges, they were increasing the risk of hamstring injuries in the opposition team.”

Orchard likens the situation to one of road safety.

“If you drive a massive 4wd, you are less likely to be injured in an accident with a smaller car but if everyone buys a 4wd, the roads get less safe as everyone is driving a bigger vehicle.”

A player has to push harder to stay with an opponent who has just had a spell on the bench.

“It makes a lot of sense that if you play on someone who has just been rested, they are going to run faster,” Orchard said.

“You’ve got to keep up with them otherwise they will get a possession on you. You might push yourself harder than you are really able to go at that time given the level of fatigue you’ve got, and that might put you at risk, but the person who has just rested isn’t at as much risk themselves.”

Surprisingly, the average number of interchanges per team per game was almost identical in 2011 as in 2010.

This means that in 2011, where only three players rotated throughout each game, the average break time for each player was reduced, compared to 2010 when four players rotated. This means more fatigue for players across the board in 2011 but fewer injuries in total – reaffirming the complexity of

TWANG: Brent Guerra.

BANG: Dylan Grimes goes down.

HAILING CAB: Easton Wood.

InsIde Football Wednesday, september 12, 2012

‘ ’I can’t remember one time on Friday night when Heath Shaw was able to springboard out of the backline. – Dermott Brereton on Crunch Time

interchange players and two substitutes have been tabled.

There are two sides to consider with regards to interchange and injury.

More interchange use rests players and enables them to return to play and perform more

sprints, generally increasing game speed and a factor that is known to put athletes at risk of hamstring injury.

The flipside is that fatigue may be a consideration with respect to these soft-tissue injuries. If we limit the number of interchanges, players will be on the ground longer and exposed to more fatigue.

Over the past decade, the AFL Research Board has put considerable funds into hamstring injury research.

Anthony Schache, physiotherapist at Richmond Football Club, explains that

‘If Geelong plays the Swans, and the Cats make 60-plus rotations, they put the Swans players at more risk of hamstring injuries.’

this issue. It was originally thought

among some in the AFL medical fraternity that the 2011 change to the interchange rules might expose players to greater fatigue levels and perhaps create greater risk for hamstring injuries but to date the opposite has been the case.

Could it be that there is some sort of threshold whereby players can cope with an optimum number of sprints over a game, and beyond that, are more at risk of a hamstring strain?

In this case, minimising the frequency of inter-change where the player freshens up for another high intensity effort would be a good thing.

But the mere fact that there is a cap on the number of sprints a player can do before he is more at risk suggests that fatigue does play a role.

What’s evident is that there is no clear relationship between speed, fatigue and hamstring injuries.

And this is not just true of the AFL; this is the case for hamstring injury research the world over.

The interchange rules were not introduced solely to address injury risk for players.

The substitute rule was also to reduce congestion and for reasons of fairness between teams if a player is injured early in game and can’t participate.

In the 2010 Grand Final between Geelong and Collingwood, James Podsiadly dislocated his shoulder in the second quarter and was out for the rest of the game. Given the sub rule, this didn’t disadvantage Geelong from the point of view of player rotation.

The capping of rotations at 80 per team per game and suggestions of changing the bench again to include two

the AFL-funded hamstring research to date has generated some important information. This includes factors that put players at more risk of a hamstring injury and recurrence, how Magnetic Resonance Imaging (MRI) can be used to make a prognosis on the time for a player to return to play after a

strain, the relationship between muscle stiffness and injury risk, as well as information about management practices of these injuries in the AFL.

Comprehensive data surrounding each hamstring strain in 2011 has been collected so that the AFL can make the best decisions on where the

funding should go for future research.

“Just about all of the hamstring injuries in 2011 were documented and we detailed the circumstances surrounding each injury,” Schache said.

“We collected information on the game where it happened, how the injury happened, MRI findings, which side, position, age, past history, how much training the player had done in the three weeks leading into the injury, where they played in the two or three games prior to the injury, the workload in the game where they got injured and the weeks preceding that.

“We also looked at game stats such as points for and against and the number of stoppages.

“This is an important piece of work to guide where we head with future injury research.”

To better understand the link between interchange use and hamstring injuries the AFL Research Board is also planning a project to use GPS data to investigate player workloads preceding hamstring injury.

“It would be nice to look at the injured player and determine how many accelerations had they done prior to injury or how much time they spent above a certain speed,” Schache said.

“We are trying to quantify the high intensity exertions of injured players.”

FOOTBALLER’S CURSE: Tadhg Kennelly.

HOBBLED: Daniel Kerr in 2010.