While addressing members of The Church of Jesus Christ of Latter-day Saints from the Conference Center in Salt Lake City on Oct. 6, 2007, Elder Joseph B. Wirthlin of the Quorum of the Twelve Apostles felt his knees become locked. Despite trembling and struggling to remain standing, he stayed at the pulpit and gamely completed his remarks, steadied after a few moments by the arm of fellow apostle and longtime friend Elder Russell M. Nelson.

The vigor and cheerful determination demonstrated by that incident were typical of Wirthlin, who died in his sleep from causes incident to age at 11:30 p.m. Monday night. He was 91.

Though prior to his death he was the oldest living LDS apostle, including all three members of the faith's governing First Presidency, Wirthlin kept a full schedule. Church publicists said in a statement announcing his passing that he had continued to work in his office at the end of November right up until leaving to celebrate Thanksgiving.

His positivity shone through in his final address to church membership on Oct. 4, when Wirthlin related at length his mother's long-held philosophy, "Come what may, and love it." He encouraged his listeners to remain upbeat in whatever circumstances life might place them. "The next time you're tempted to groan," Wirthlin said, "you might try to laugh instead. It will extend your life and make the lives of all those around you more enjoyable."

A prominent figure in church leadership over the past three decades, Wirthlin was the last man asked to serve as an assistant to the Twelve (the position was subsequently discontinued), in 1975, before being assigned to the First Quorum of the Seventy the following year. He was briefly appointed to the presidency of the First Quorum of the Seventy in Aug. 1986, before being elevated to the Quorum of the Twelve a little more than five weeks later by President Ezra Taft Benson.

Wirthlin had a playful relationship with current LDS leader President Thomas S. Monson, who liked to remind church members of Wirthlin's nickname of "Swifty" from the football-playing days of his youth. (Wirthlin loved to tell football stories throughout his history of church speaking assignments.) At the time of Wirthlin's assignment to the Twelve, Monson said, "He personifies the description given by the Savior of Nathanael -- 'an Israelite indeed, in whom is no guile.' "

Brigham Young University church history professor Matthew Richardson said that his students, over the years, were drawn to Wirthlin's sense of humor and to his stories about his life. Richardson said his mother-in-law saw another side of Wirthlin when he served as bishop of her LDS ward, or congregation, and would always be the first to arrive and the last to leave ward social functions, typically staying behind to take care of chores like washing dishes.

Football and missionary service

Joseph Bitner Wirthlin was born June 11, 1917, in Salt Lake City, to Joseph L. and Madeline B. Wirthlin. He was the eldest of his parents' five children and had a variety of interests as a young man, according to church biographical sources. Blessed with a fine singing voice, he participated in vocal performances during his grade-school years, and played basketball in addition to football, once winning a free-throw shooting contest by hitting 19 of 20 attempts.

His sister Gwendolyn said in a 1986 article in Ensign magazine,, "I don't have a single memory of his ever having been unkind to me."

Wirthlin was strongly influenced by his parents. In a 1999 general conference address, he recalled that they "were hardworking. They made every penny stretch as far as possible."

Then he went on to relate a humorous consequence of his parents' frugality, recalling that they always bought him clothing and athletic equipment that was "two or three sizes too large. I was 12 years old when I received my first pair of ice skates, so large that I had to stuff a third of the toe space with cotton."

While playing in neighborhood football games, he said, his too-large football helmet would "spin 180 degrees" every time he was tackled. On one occasion, he ran full-speed into a tree.

Football continued for Wirthlin at Salt Lake City's East High School, where he played quarterback, and at the University of Utah, where he was a halfback for three seasons before foregoing his final year of eligibility to serve a church proselytizing mission to Germany, Austria and Switzerland in the late 1930s.

Midvale resident Staker Olsen, who was Wirthlin's first missionary companion, said that he and Wirthlin were serving together in Salzburg, Austria, when the armies of Adolf Hitler were preparing to invade in March 1938. After going to bed one evening, Olsen said, the two missionaries "woke up in the morning and there were swastikas hanging from every window." Olsen said that he and Wirthlin didn't leave their apartment for a week, following which time church members helped them flee the country to Switzerland.

"He was very, very spiritual," Olsen said of Wirthlin. "We had an enjoyable four months together." (Though they hadn't spoken for a number of years, Olsen, 93, had been anticipating a phone call from Wirthlin on Tuesday morning. He had contacted Wirthlin's office on Monday after reading in the weekly LDS publication Church News about a missionary experience that the two of them had shared.)

Upon returning from missionary service in late 1939, Wirthlin completed his schooling at the University of Utah, earning a bachelor's degree in business administration. He married Elisa Rogers on May 26, 1941, in the Salt Lake Temple, in a ceremony performed by David O. McKay (who became president of the church in 1951). The Wirthlins had eight children.

"Every day seemed like Sunday"

Among those touched by Wirthlin's long history of church service is former U.S. Sen. Jake Garn, who was a teenage boy in Salt Lake City's Bonneville Ward when Wirthlin was its bishop. At the time that Wirthlin began serving in the Quorum of the Twelve, during Garn's second term in the Senate, Garn said in an Ensign article that Bishop Wirthlin had always "seemed like he was one of us without being one of us," and said that Wirthlin had probably had greater influence on him than any other man.

After being sustained as a member of the Quorum of the Twelve at age 69 on Oct. 4, 1986, Wirthlin said, "I've loved every assignment I've ever had in the kingdom. And in that service, every day seemed like Sunday, because it was in the service of the Lord."

In addition to being a bishop and filling various ward and stake assignments, Wirthlin was a counselor in a stake presidency to Nelson, who would cross his path again several times as both men continued to serve in church leadership. When asked in an Ensign article to describe his former counselor, Nelson praised Wirthlin's "tremendous faith and willingness to work," adding that during their time together in the stake presidency "there was hardly ever a Sunday night when I didn't get a call from him asking if there was any more he could do for me."

Richardson said that, as a speaker, Wirthlin frequently focused on "personal discipleship," and that his addresses often reflected a strong desire to live up to his calling. "You see this urgency to live a life which was worthy of the knowledge that he possessed," said Richardson.

Those desires were reflected in a 2005 Ensign interview, in which Wirthlin was asked what he hoped for. "My number one hope," he said, "is that I may live so that I am worthy to someday be in the presence of our Heavenly Father and His beloved Son with my wife, my children, and my entire posterity, and that we shall not lose one in this respect. That would be my number one hope."

In the same interview, he was asked what advice he would offer to young adults concerned by increasing uncertainty in the world around them. "Just move forward regardless of the world," Wirthlin said. "As they read the scriptures, they will know what they should do. They shouldn't be dwelling on all of these other things. Keep busy in doing the right things.

"When I have decisions or advice to give to people, I explain that it is all laid out in the scriptures. As the Savior said, 'Peace I leave with you, my peace I give unto you: not as the world giveth, give I unto you.' Peace and hope come from knowing the Lord and our Heavenly Father and following their way of living."

Wirthlin was preceded in death by his wife, who passed away from causes incident to age on Aug. 16, 2006.

• Daily Herald reporter Joe Pyrah contributed to this story.