In May of 1992, Charlie Roots and a small team of government experts summited Mount Logan to gauge to a decimal point the height of Canada’s tallest mountain.

Part of the first expedition to define Logan’s magnitude by the metre, Roots spent weeks traversing its plateaus on skis and climbing its faces with crampons and ice axe.

“For me, it was the best kind of life. Looking for rocks, walking out on ridge tops,” Roots said.

He and his colleagues from Parks Canada and the Canadian Geographic Society hauled sleds bearing heavy data-collection instruments — and gel-cells the size and weight of car batteries to power them — the whole way.

The journey took one month total, including a final eight-kilometre push through wind and whiteouts to reach the snow cone summit 6,000 metres above sea level.

Roots, now 58, still works as a research geologist with the Geological Survey of Canada after more than two decades, but has not crested any mountains recently, psychological ones excepted.

The former marathon runner and bedrock mapper has been living with ALS for more than four years.

“I have been lucky,” he said in an interview this week.

“For many, ALS starts in the feet, like tripping over things, or in the throat with difficulty swallowing and slurring of speech.

“I have been spared these.”

The condition affects only his trunk and upper limbs, making relatively light tasks like typing and cooking virtually impossible.

“To live with the disease is an ever-steepening ramp of physical difficulty,” Roots reflected in his soft baritone. "You just are becoming increasingly imprisoned physically."

He first recognized a loss of muscle strength in June 2010. In April 2011, he enjoyed his last “vigorous” use of a canoe paddle.

An avid outdoorsman, Roots had accepted by the end of 2012 that cycling and skiing were unsafe, due to the difficulty of squeezing the brakes, holding the handlebars steady and gripping the poles, as well as managing a fall in either activity.

March 2013 saw Roots drive a car for the last time, as turning the steering wheel and fastening the seatbelt were too big a challenge.

As of the past spring, dressing himself was unfeasible.

About two months ago, Roots stopped being able to raise a spoon above the dish.

“I train my focus on what I can still accomplish,” he said. “I have become a veteran of frustrating moments, more tolerant and patient with myself.

“As I can see my end more clearly than most people can see theirs, I focus on being positive and completing things simply. It is a very clarifying state of mind,” he said.

Amyotrophic lateral sclerosis, also known as Lou Gehrig’s disease, is a degenerative condition that affects motor neurons in the brain stem and spinal cord, leading eventually to paralysis of voluntary muscles. Thus far, it is incurable.

The recent social media frenzy over the ice bucket challenge, a viral campaign to raise money and awareness for ALS by dumping cold water over one’s head on camera, has drawn unprecedented attention to the affliction.

“Any publicity is good publicity,” Roots told the Star.

He pointed out that only about 3,000 people in Canada suffer from the disease. “But I’d say that it’s a good route to raise awareness about this.”

Roots is one of two Whitehorse residents diagnosed with a condition that, according to the U.S.’s ALS Association, afflicts two out of every 100,000.

While about 10 per cent of cases are genetic, most emerge from causes unknown and tend to strike active males in their late 50s.

That includes Roots.

“Once I was strong. From when I was 12 until 55, I could raise an empty 45-gallon drum over my head, or pick up a canoe to portage with a clean-and-jerk,” he said.

“Now I can no longer ... hold a sheet of paper by pinching it.”

Over the last 15 years, Roots revelled in physical activity, sojourning with his family on multi-day canoe trips down the Spatsizi, Takhini, Yukon, Swift, Rancheria, “and secret rivers too — plus ones you should never go down.”

Over the years, his annual field work led him by foot across a broad strip of central Yukon, mapping bedrock from the Alaska-Yukon border north of the Yukon River right across and into the Northwest Territories, among other areas.

Raised in the Gatineau hills north of Ottawa, Roots first came to the territory in 1966 with his father, a high-ranking government scientist who worked with Monty Alford, the late renowned mountaineer and surveyor, to organize expeditions in the St. Elias range as part of Canada’s centennial celebrations in 1967.

“I was just a little gaffer messing around Kluane Lake,” he recalled. “I got to run up and down the mountains — Sheep Mountain, Outpost Mountain — at age 10.”

An alumnus of the Ivy League Dartmouth College as well as Carleton University, where he earned his Master’s and PhD, Roots returned to the Yukon periodically for grassroots exploration as part of his graduate work throughout the 1980s.

“It’s crashing through the bush, living in tents ... I love that combination of physical challenge and mental conundrums, trying to solve things,” he said.

On one of those trips, Roots met his wife, Mary Ann Annable-Roots, a longtime dance instructor who currently works at a Montessori preschool, but at the time had signed on as a cook for a geological foray.

The couple have two children together: 18-year-old Galena, who recently graduated from F.H. Collins Secondary School and bears a name that also denotes a type of mineral ("in Spanish it means little chicken, which is good when they're small but they don't like it when they get bigger"); and 21-year-old Logan, who trains in Victoria as a middle-distance runner. (That chip off the old block won the Yukon River Trail Marathon by more than 10 minutes earlier this month, finishing in two hours, 50 minutes and 49 seconds.)

“Mary Ann went through quite a long period of anticipatory grief, thinking what’s ahead,” Roots said of the period between 2011 and January 2013, when he was finally diagnosed after tests ruled out other possible conditions.

"I think at first with our kids, you're the same old dad: 'We're teenagers, he's just getting old and doddery' kind of thing.

“I don’t think it really became truth to them until they actually went on a website and found out what ALS was, after I said, ‘That what I have.’

“The progression is slow,” he continued, “unlike with a lot of diseases, where it’s like a colossal brick wall.

"Living with ALS is constantly adapting to not doing what you once did — that’s not just years ago, but last week.”

When he first underwent tests, Roots lifted weights and ran exercises almost daily to prove to himself and others the diagnosis was not imminent. Despite the efforts and frequent IV injections, his condition did not improve.

"When diagnosed, I felt the music of my life ceasing, and I rarely hear tunes in my head anymore," he said.

Roots hasn’t been able to write legibly for two years, nor read comfortably. The muscle power necessary to hold his head up and turn the pages over a sustained period of time has weakened considerably.

“Because I loved to draw and make maps and read avidly, loss of these pleasures is a great pity,” he noted.

The resultant sense of vulnerability and dependence is difficult.

“As a healthy male, I thought I could take care of myself. No longer.”

He walks at all times with a soft helmet in case of a fall, which he could not break due to the weakness of his arms.

“I am a disaster waiting to happen.”

His colleagues in the Elijah Smith Building keep an eye out for him.

“If I’m struggling to get a book back on the book shelf or being spastic with my coat at the end of the day, they just come by and pull it on or put the book back on the shelf.

“It’s horrible to feel dependent,” he said, tears entering his eyes only when describing how his condition affects others. “It’s funny, I still get emotional about it ... I just try and fit in with the least amount of change in their own routine.”

Roots is unable to extract a wallet from his pocket, or even a card from his wallet or a bank machine, rendering him “commercially inept,” he said.

Meanwhile, the atrophy of his muscles due to a lack of motor-neuron control means less upper body insulation and hands that are almost always cold.

"I miss the physical joy of strong muscle contraction. For now my muscles are mostly flaccid — that's what paralysis is."

Because there is no known cure, Roots sees neurologists less frequently than in the lead-up to his diagnosis. He expects he’ll receive home care as his condition becomes more severe in future years.

“Anticipation of the end is....” he said, trailing off.

“Most people don’t know where their lives are going to go or how long they’re going to live, and when I accept that this is what’s going to happen to me, I have the opportunity to make much better decisions on how I spend my time, do some clearer thinking about what’s important,” he said, his voice breaking slightly.

“That’s one side, and the other is that you see humanity a different way, that I’m no longer superior or immortal, but instead when I see someone in a wheelchair or disabled, that’s me.

"I feel my cognitive ability remains strong but I ride an emotional roller coaster: feelings are more labile; tears well up unexpectedly," Roots said.

"Although the end is nearing and probably unpleasant, I look upon it as inevitable and I'm proud of what I've been able to accomplish since learning my fate. Not many are given that foreknowledge."