“26.2 to Life,”a sensitive and multilayered documentary about incarcerated men at San Quentin State Prison who aremarathon runners, begins with a quote from the ancient Chinese Taoist philosopher Lao Tzu.

“The journey of 1,000 miles begins with a single step,” the wise man is said to have written. Thus the running club at San Quentin is known as the 1000 Miles Club, and for members, it is a distance measured not just in miles but years.

Fun fact: Lao Tzu’s life span likely overlapped that of Pheidippides, the Greek courier who, as legend has it, ran the first “marathon” to deliver war news. If that happened, Pheidippides would have had to cover some rough terrain from Marathon to Athens.

The terrain at San Quentin might be rougher. Physically, its marathon course is 105 laps through a prison yard with six 90-degree turns, but emotionally, it’s one path on a long road toward redemption.

Bay Area director and co-producer Christine Yoo, a volunteer at San Quentin, focuses on three of the runners — Markelle “the Gazelle” Taylor,Rahsaan “New York” Thomasand Tommy Lee Wickerd — and one of their coaches from the outside world, Franklin Ruona.

All the runners are in the midst of long prison sentences for very serious crimes. Eventually, they open up to Yoo’s camera about their offenses, their circumstances and mindsets at the time, and their growth during their decades in prison.

“Everyone’s a different man than they were 20 years ago,” one incarcerated man says.

Yoo delves into some fascinating backstories, traveling to Brooklyn, N.Y., where Taylor grew up a computer wiz, to spend time with his brother and mother; and to Palmdale (Los Angeles County), where Wickerd was a gang member and was arrested multiple times, to chat with his parents.

Wickerd is also married and has a stepson. One of the more moving scenes in “26.2 to Life” is a conversation with Tommy Jr., a young man who has traveled from his home in Nebraska to accompany his stepmother for a weekend family visit at San Quentin. It will be the first time he has seen his father without a glass screen between them since he was a young boy.

Proof that a crime creates many unintended victims, Tommy Jr. asserts, “I have a right to be mad at my dad.” But seconds later, he is in tears, and says, “I better see tears in his eyes too, or I’m gonna make some.”

All three men the film focuses on demonstrate that it is possibleto lead productive liveswhile incarcerated. Thomas, for example, is a journalist for the San Quentin News and part of the Pulitzer Prize-nominated podcast“Ear Hustle.”Wickerd began a course in American Sign Language.

Ruona, who believes that the success of those activities, as well as the running club, should lead tomore such programsand has become a strong advocate for prison reform. Yoo, who completed her film before Gov. Gavin Newsomannounced that he intends to transformSan Quentin from a maximum-security prison into arehabilitation and education facilityfocused on preparing inmates for transition back into civilian life, clearly agrees.

The film doesn’t deny that justice must be served, and those who commit crimes must pay. Its question is: How it is paid fairly to the satisfaction of victims and their families and to the benefit of society? The answers are down the road, many miles ahead.

Reach G. Allen Johnson:ajohnson@sfchronicle.com