When new missionaries open the door to walk into the Missionary Training Center here, they also open a door to a life-changing experience.

Even as approximately 350 new elders and sisters arrive each week with shiny suitcases and neatly pressed clothing, another like-sized group is leaving.The arriving group is nervous, tentative and timid.

The departing group is confident, skilled and prepared.

The difference between the two groups is made within the doors of the Missionary Training Center. The center in Provo is the largest of 14 throughout the world. The centers are highly effective in training the Church's 45,000 missionaries, according to research.

All who come to the center are profoundly changed by the experience.

Most of the missionaries come with a personal conviction of the truthfulness of the gospel and a commitment to work, but the training they receive amplifies both traits, and adds a spiritual dimension. Research conducted by the Missionary Department indicates that the changes made in the lives of the missionaries are significant in at least four areas: closeness to the Spirit, scripture study, language ability and communication skills.

However, according to recent interviews conducted randomly at the Missionary Training Center, missionaries most often spoke of the closeness to the Spirit as the most significant factor in their training.

Elder Matthew Leavitt from Cedar City, Utah, called to serve in Romania, said, "I live on the verge of tears. It has just been a great experience for me.

"The Spirit is awesome here. I've been able to recognize the Spirit more than I have before."

His companion, Elder Jayson Fugal of Provo, Utah, said, "They [Missionary Training Center staffT told us that if you don't have a testimony, you need to pay the price now. When you live as close to the Spirit as you do here, you can't help but have your testimony grow."

At the center, missionaries live by strict rules that isolate them from their previous associates. They attend classes some 10 hours a day. Those who are assigned to English-speaking missions remain three weeks while those assigned to other languages stay eight weeks. Approximately 2,100 missionaries are being trained at any one time.

What studies and interviews don't portray, however, is the obvious enthusiasm and happiness of the missionaries at the center. Typically, they arrive early to class and read scriptures and practice skills and language incessantly during their free time.

Coming into the center required a great deal of adjustment, according to the missionaries interviewed. Elder Joel Hall of Burley, Idaho, called to the California Sacramento Mission, was converted just a year ago. He explained that he changed his life after being baptized, and has changed again after arriving at the center, though he's been there less than two weeks.

"My first impression of the Missionary Training Center was that it scared me to death," he said. "All the rules and instructions took a big adjustment.

"It took about three or four days to feel comfortable.

"The change has already happened," he said. "It happens because of the way this place can bring the Spirit in; you get so pumped up."

The experience at the center is not easy, missionaries say. Elder Seth Parkinson of Grantsville, Utah, called to the Argentina Trelew Mission, said he, like most of the new missionaries, was not enthusiastic when he learned that he'd be attending classes 10 to 12 hours each day.

"I thought it would be boring but it is not," Elder Parkinson said. "We have great teachers who are about our own age. They share personal experiences and really get you excited to go out and teach.

"They tell you what mistakes they made so you won't make the same ones. That way missionaries will get better and better."

Sister Rebecca Day of North Salt Lake, Utah, called to the Ecuador Quito Mission, said, "My first impression was that I thought this was just an adventure, kind of like school. Actually, people here are a lot more focused on the work than I thought.

"We are having an adventure - a spiritual adventure."

She and her companion, Sister Mikal Lythgoe of Helena, Mont., said studying the scriptures contributes to their "spiritual adventure."

"We were talking just yesterday that we were very surprised at how much we are learning from the scriptures," said Sister Lythgoe.

"Most of the study is personal study," she said. "Teachers spend half an hour talking about the Book of Mormon and we have discussions about the doctrines.

"You have to study the scriptures for yourself to learn them. People can tell you, but you really have to find out for yourself to really understand them. We really get into the scriptures."

Communication skills - teaching and listening - are emphasized at the center. Elder Ryan Williams of Logan, Utah, called to the Canada Vancouver Mission, said, "I had a hard time when I first got here. When I was younger I was really shy.

"Here, I am doing things I never thought would be possible for me to deal with. I am a lot more confident than I used to be."

Elder Williams told of a reply he made to a friend's letter:

"He [the friend] wrote that he wasn't close to God any more, and that he was getting weaker and weaker.

"I wrote to him that he might think our Heavenly Father isn't listening to him, but that He is always listening. I bore him my testimony and tried to inspire him to serve a mission. I tried to give him something that would help him out.

"I have learned so much myself just being here."

Elder Mark Sanchez of Bakersfield, Calif., said "We develop a technique and with practice, we get better. We have really good teachers here and that helps us a lot.

"Before I came here I had a testimony but now it is a firm testimony. Now I want to go out and teach the gospel."

Teaching the gospel in another language is a skill missionaries acquire. In one class of missionaries bound for French-speaking missions, missionaries said they had learned more in six weeks than they had in years of high school or college language classes.

"I find that my desire to communicate my feelings is so strong that I don't even think about speaking," said one sister missionary, participating in a group discussion. "I don't know if I say everything correctly, or if I conjugate my verbs right, but I want so badly to express my feelings that my sincerity and desire to speak comes out. I hope that will help me communicate with the French people."

Missionaries practice French 80 percent of the time. When they do speak English, they unconsciously use French syntax, she said.

Allen C. Ostergar, director of all the Church's missionary training centers, explained: "Some missionaries come very well prepared and others come less prepared but we just use the same approach for both. They come with a great desire - they are so anxious and willing to learn."

Missionaries throughout the world follow the same standard study guides and manuals, he said. He praised the teachers, who are recently returned missionaries. "There is a lot of love developed here. There is a very close bond between teachers and students."

The teachers also convey to new missionaries the love they developed for those they served among, he added.

"It is the Lord making this succeed. People who visit us [to see the language training program in action] don't have the background. They often comment they feel something different here but they don't know what it is.

"It is hard to explain because they want a logical explanation. Sometimes our explanation is not logical to them."

While understanding the "how" of missionary training may be hard for some to understand, the "how" of missionary work is clearly explained in scripture:

"And ye shall go forth in the power of my Spirit, preaching my gospel, two by two, in my name, lifting up your voices as with the sound of a trump, declaring my word like unto angels of God." (D&C 42:6.)