What Tiger was referencing when he mentioned glute activation at Torrey Pines

After walking wincingly off the course at Torrey Pines because of back pain on Thursday, Tiger Woods cited his glutes failing to activate as a reason for his pain on nearly every full swing.

"It's just my glutes are shutting off," Woods said in the parking lot after withdrawing from the first round of the Famers Insurance Open. "Then they don't activate and then, hence, it goes into my lower back."

"So I tried to activate my glutes as best I could in between, but it just they never stayed activated."

Unless you're incredibly familiar with anatomy and physiology, there's a good chance you saw or heard Woods' comments about his injury and wondered what the heck he was talking about. And you probably made a bad joke too.

The glutes are, essentially, your butt muscles. They're the strongest muscles in your body and your power center. They're especially important for athletes, because hip extension is a primary source of explosion in many sports, including golf.

In a basic sense, glute activation (and activation of any muscle in your body) is when your brain's nervous system sends electrical signals to your muscles to fire. The stronger the signal, the stronger the muscle contraction. If you're bench pressing, your brain sends signals to your chest, shoulders and triceps to push the bar away from your chest.

Less than a year ago, Woods had a lumbar microdiscectomy. The procedure removed a disc from his lower back.

"Studies have shown that when you have a prior injury or back pain, it shuts down glute activation," Bret Contreras, a Phoenix-area personal trainer and author, said.

Woods' round on Thursday was delayed over an hour because of fog. He said that as he warmed up for his original tee time he felt good, however, as he stood and waited during the delay, he started having issues with the muscles integral to his swing.

"When you swing a club, you have hip extension and rotation, it's not just pure rotation," Contreras said.

While we don't know Woods' specific issues with his posterior chain (and since we're not doctors, we won't try to guess), we do know that overcompensation in any part the body isn't a good thing. Especially in an area that's already been surgically repaired.

Like all elite athletes, professional golfers need to not only be strong for their sport but also able to use their muscles in an efficient and synchronized manner. Think of the body as a chain; one weak link can lead to problems. And if what's supposed to be one of the strongest links is being inhibited, it's a dangerous proposition as Woods showed on Thursday.

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Nick Bromberg is the editor of From The Marbles on Yahoo Sports. Have a tip? Email him at or follow him on Twitter!