Not only did Ryan Hall’s legs feel heavy, but his heart was heavy, too, in the autumn of 2010 when his running career seemed to have stalled.

Hall, considered the United States’ most promising marathoner, decided to do something radically unorthodox. He left behind his coach, his training partners and his home in the mountains of Mammoth Lakes, Calif., to strike out on his own.

His new coach? God.

Hall has taken a leap of faith that he hopes will lead to faster times, his first victory in a major marathon and a medal at the Olympic marathon in London this summer.

He is coming to Miami for Sunday’s ING Miami Marathon and Half Marathon — not to race but to give a Saturday seminar, sign autographs and lead students 1.2 miles in the Run for Something Better.

Hall, 29, is a devout Christian. He was raised in a religious family in the town of Big Bear, Calif. Now he is entrusting himself to a higher power. Through prayer, worship and Bible study, he determines his workouts, race tactics and goals.

“I call it faith-based coaching,” he said. “I listen to God on a daily basis. I’m learning how to hear God’s voice. It’s been an amazing adventure so far.”

Hall has also run three of his best marathons since he made the change. He finished fourth in last year’s Boston Marathon in 2:04:58, which is the fastest time ever run by a U.S. marathoner — although no records are recognized on Boston’s point-to-point course.

Hall, as usual, set a fast early pace at U.S. Olympic Marathon Trials in Houston on Jan. 14. He ran with plantar fasciitis in his left foot and an upset stomach and finished in 2:09:30, second to former teammate Meb Keflezighi.

A major alteration he has made in his regimen is incorporating more rest. He runs six days a week now as opposed to the seven. when he was piling up miles, often at a hard pace.

“I took my lead from God, who rested on the seventh day,” Hall said. “It’s working. My faith has grown through more encounters with God. Sometimes I feel He wakes me up in the morning. If I hadn’t heard from Him I might not have made the Olympic team.”

Hall knows there are skeptics in distance running circles. Some think he has gone off the deep end. They worry that he will waste his talent by relying on spiritual guidance in a sport commanded by the cold, hard numbers of the clock.

But Hall, like quarterback Tim Tebow, can’t hide his faith. He wants to set an example for other athletes, start a movement: Follow the spirit that inspires you.

You could argue that he is using religion as a crutch, that it’s a competitive copout to say his God will be happy with his devotion no matter what the results are. What if his prayers go unanswered?

But you have to admire Hall’s bravery in taking a huge risk. Most people’s lives are marked by the risks they didn’t take. He’s searching for a way to integrate spirituality and career. Even if his experiment fails he says he will have no regrets.

“It was a hard decision,” Hall said. “I’m not a coach, so that made me hungry to hear from God because I’m not sure what I’m doing. I thought of people in Africa I’ve met, how they don’t know where their next meal or their medicine is coming from. They are desperate to hear from God. I put myself in the same position.”

Hall, an All-American at Stanford who married runner Sara Hall, won the trials for the 2008 Olympics in New York City. He found out after he finished that his friend Ryan Shay had collapsed and died early in the race due to an enlarged and scarred heart.

Hall finished a disappointing 10th in 2:12:33 at the Beijing Olympics. In 2010 he withdrew from the Chicago Marathon, citing fatigue. He decided to leave coach Terrence Mahon and his training group.

“I was so fried,” Hall said. “I was trying so hard and not getting anywhere. Terrence said, ‘Maybe you don’t want it anymore,’ and that hurt. I don’t blame him because we tried different things. But I started to question my desire.”

He and Sara moved to Redding, Calif., where they attend the Bethel Church School of Supernatural Ministry. They run a foundation that fights poverty. Hall trains at altitude in Flagstaff, Ariz. Thyroid medication helped his body get back on track. He misses his teammates but likes tailoring workouts — and is often paced by neighbors on bikes.

“I view my running more as an art than a science,” he said.

Using a Bible verse — “An abundance of counselors is victory,” — he has assembled a new team: Nutritionist, strength trainer, chiropractor, massage therapist.

He’s confident of a strong American showing in London. The U.S. has come a long way since 2000, when marathon times were so weak it couldn’t send a full team to the Sydney Olympics.

“This isn’t the path for everyone and it’s not easy,” Hall said. “But for me, running keeps getting sweeter and sweeter.”