But a new study suggests that when it comes to preventing injuries, the obsession of many teams with those kinds of numbers may be misplaced.

"I don't necessarily think that pitch counts or innings pitched are the best way to measure the demands of pitching," Thomas Karakolis, the lead author on the study, told Reuters Health.

Karakolis, a PhD candidate at the University of Waterloo in Canada, and two colleagues looked at data from every MLB pitcher from 2002 to 2007, focusing on a given year's pitch count, innings pitched and whether the player ended up injured the following year.

In that second year, more than a quarter of major league pitchers spent time on the disabled list. That rate jumped to nearly two in five pitchers for those who tended to throw six or seven innings.

But that difference - which would seem to support the idea of using pitch counts and innings pitched to pull pitchers - was more than likely due to chance, Karakolis said.

The injuries were significant enough that disabled list players were out for an average of 78 days - more than a third of the annual baseball season.

"If we can't predict injuries based off of these metrics, how are we going to use them to prevent injuries?" asked Karakolis.

Perhaps the most famous case is Stephen Strasburg of the Washington Nationals, whose managers made it clear at the beginning of this year's season, following surgery in 2010 and less than a month of play in 2011, that he would be allowed to pitch only 160 innings.

They shut him down after 159 and a third innings, meaning he was unavailable to play in the Nationals' first-ever playoff appearance in nearly 80 years.

Strasburg did not debut in the majors until 2010, so his data are not included in the research, which is published in the Journal of Strength and Conditioning Research.

"The Karakolis study indicates that Strasburg faced very little danger from continuing to pitch," said J.C. Bradbury, of Kennesaw State University in Georgia.

The Nationals declined to comment.

Bradbury, who was not involved in the new study, published research earlier this year showing that pitch counts did seem to have a real effect on performance, but so small as not to be practically relevant.

TODAY'S PITCHERS VS. YESTERDAY'S

Because of the pitch count obsession, such numbers have been falling for more than two decades, Bradbury told Reuters Health by email.

"In the late 1980s and early 1990s, the maximum number of pitches you'd see a pitcher throw would be in the 160s. Now that maximum is normally in the 130s," Bradbury said.

Although excessive pitching can obviously lead to injury, he added: "The relevant question is, can we say that cutoffs at 90, 100, 110, etc. are safer than each other? I don't think there is any evidence (for that)."

Another factor in the mix is pitches and workouts on off days - often 30-40 pitches a few days after each start, plus strength training - which are not reflected in game-day pitch counts, said Karakolis.

One of Karakolis's co-authors, Ryan Crotin, pointed out that some of the strain on pitchers is emotional and psychological, and would not show up in typical measures.

For their stress hormone-producing adrenal glands, said Crotin, who works with the Baltimore Orioles, it's "almost like they've run a marathon".

Karakolis said that pitch counts and innings pitched were "definitely part of the future but on their own they're not going to be effective".

He suggested that teams might look into a "piggy back" system such as that used in the minor leagues, in which pitchers do not throw more than 75 pitches before being taken out of the game, and rotate between starting and relieving.

But he is clear that the data are "not conclusive yet, and I don't have any idea how that would affect performance". His study only looked at injuries.

Bradbury agreed that baseball needs better metrics.

"There have been many studies on youth pitchers that find pitches thrown are correlated with injury," he said.

"However, very little work had been done on adults or professionals, and there are many reasons to expect the impact will differ between children and adults."

(Editing by Frederik Joelving and Mark Lamport-Stokes)

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