LIVERMORE -- A police veteran, Livermore SWAT team leader and marathon runner with a love of the great outdoors, Paul Mayer is no stranger to pushing himself to the limit.

But in hiking the entire 211-mile John Muir Trail this fall in less than a week, Mayer met his match.

The 43-year-old sergeant's first experience on the "JMT" -- a rugged track snaking along the backbone of the Sierra Nevada from Yosemite National Park to Mount Whitney -- came in 2010. Younger brother Christian, an experienced mountaineer, convinced him to make the trek, mere months after Paul suffered a broken neck during a routine SWAT drill.

Livermore police Sgt. Paul Mayer, shown Dec. 4, 2013, broke his neck during SWAT training in 2010 and, after six months in recovery, hiked the entire John
Livermore police Sgt. Paul Mayer, shown Dec. 4, 2013, broke his neck during SWAT training in 2010 and, after six months in recovery, hiked the entire John Muir Trail, from Yosemite to the peak of Mount Whitney, in two weeks. (Doug Duran/Staff)

Mayer had been on his back, pushing his way up through punching bags, when "he heard something pop." Doctors diagnosed a sprain, and cleared him to work. But the pain lingered, and he underwent more tests.

"I knew I was in trouble when they told me not to move," Paul said. "I'd been walking around with (a broken neck) for five days."

He recuperated at home in Discovery Bay with a neck brace secured by metal rods. Doctors warned he might never return to the force. Not one to sit still, Mayer would walk his dog for miles in the dead of night. Within a few months, he was back working on investigations, still wearing the brace.

SWAT team member Steve Goard said he and fellow Livermore officers were shocked by their supervisor's quick recovery.

"He's intent on defying the odds," Goard said. "We thought there was no way someone would come back from that, especially in our job. ... He's just a physical fitness phenom."

Mayer -- and his neck brace -- hit the gym hard, using the planned hike as motivation. Along with Christian, sons Brandon and Cody (11 and 15 at the time) and dad Bill, 62, he completed the John Muir in two weeks.

"On the six-month anniversary of breaking my neck, I was up on Mount Whitney," Mayer said. "People didn't think I was going back to the SWAT team, let alone do that. ... I didn't take no for an answer."

Turning 40 in 2013, Christian suggested another hike. While not a record (ultrarunners Hal Koerner and Mike Wolfe recently set the mark at 3½ days), hiking the John Muir in under seven days would put the brothers in select company.

"Many people said there's no way we could do that," Christian said. "I wanted to do something that even with training, I wasn't sure if I could."

The Mayers left Yosemite's Happy Isles the morning of Sept. 7 with only the barest essentials -- water, dehydrated food, headlamps, a first-aid kit and a water pump, with empty beer cans to heat their food. Dad Bill shadowed them, hauling tents and sleeping bags to their campsites for the first few days.

The weather warm, lightning storms flashing across the Sierras, the brothers awoke at 4 each morning, and hiked as fast as their legs could carry them. Over the first two days, they clocked more than 60 miles. Planning on breaks every four hours, they pushed the pace, trudging on late into the evenings. Both men developed foot and ankle problems. By the fourth day, Christian was limping on swollen feet. Doubt crept in; fellow hikers called them crazy for trying.

"I had blisters on every toe," Christian said. "The skin was coming off my heels."

Paul wrapped his aching Achilles' heel. When he ran out of athletic tape, he used duct tape, causing painful blisters.

"When you're taping up a major muscle with duct tape and you're 70 miles from help, these are the times you doubt and feel like giving up," he said. "But you've got to keep going."

The brothers hustled ahead, ascending to the summit of Mount Whitney, at 14,505 feet, the highest point in the lower 48 states. Except for a few photographers, they were alone above the clouds.

"It was the most amazing sunset you've ever seen in your life," Paul said. "It was fitting."

But reaching the top meant the toughest part was yet to come, an extra 11 miles zigzagging brutally downhill in the dark. The brothers hiked 20 hours that final day, a total of 36 miles. They arrived at Whitney Portal just after midnight, finishing in six days, 13 hours, 18 minutes and 11 seconds.

Physically and mentally exhausted, Paul couldn't even crawl to his tent, taking pride in overcoming the obstacles.

"It's really emotional when you complete something like that with your loved one," he said, adding, "I would do it again in a minute."

Contact Jeremy Thomas at 925-847-2184. Follow him at Twitter.com/jet_bang.