“Guaranteed,” Cameron Moody, the club’s president, says with a smirk as he looks over at Callahan.

This time last year, as a football player at Saranac Lake High School, Callahan was gearing up to play on the gridiron of Ken Wilson Field, a few hundred yards away from Friday’s rugby pitch. He played running back, receiver and corner back.

But with his graduation last month, the days of donning football pads — something he’s done since he was 12 — are in the past. As he embarks on adulthood, Callahan is effectively trading one contact sport for another. After picking up rugby just a year ago, this weekend he will play for the Mountaineer’s social division team in the Can-Am Rugby Tournament.

In this division there are no age or weight restrictions, so the former football speedster’s acceleration may come in contact with, say, upward of 300-plus-pounds of old man mass — quite the equation for force.

Allan Knox, far right, a doctoral fellow at Rutgers University Medical School in Newark, New Jersey, observes a monitor as he and other members of the Rutgers and Western Sydney (Australia) University research teams test out a prototype shirt worn by Daniella Serrador, seated, designed to measure blood flow of rugby players who just suffered head trauma at the Can-Am Rugby Tournament in Saranac Lake. Also pictured are Dr. Gaetano Gargiulo, far left, and Dr. Paul Breen, rear. (Enterprise photo — Antonio Olivero)

It’s this basic physics equation that worries the Rutgers University and Western Sydney (Australia) University scientists who are located mere yards away from Callahan on the rugby fields. They include scientists and current and former ruggers who are spending their weekend studying the bodies and brains of banged-up guys like the Mountaineers.

“We are — unfortunately — waiting for people to get concussed,” said Jorge Serrador, the Rutgers University Medical School professor who founded this concussion-related study. It’s now in its sixth year at the Saranac Lake-Lake Placid rugby tournament.

“Part of the reason we work in the rugby community is because they are so supportive,” he continued.

“What we are finding with the concussed players,” Serrador added, “they have lower brain blood flow. So the question is: Why?”

The presence of Serrador’s concussion studies tent is a reflection of the increased awareness, knowledge and, to a degree, hysteria about concussions that has increasingly permeated the sports and pop culture worlds over the past decade.

This heightened debate about whether contact sports such as football and rugby are unhealthy to play, especially for children, reached a new fever pitch this week as the New York Times published a report that found, of 111 deceased NFL players who submitted their brains to the world’s largest brain bank, 110 were found to have C.T.E. — the degenerative disease linked to repeated blows to the head.

Information like this has resulted in an anti-football panic among many people — namely parents of hopeful football players — across the country. Moody said he’s seen it here in Saranac Lake, where he partially attributes worries about concussions in football to a steep decline in local youth partaking in the Adirondack Football League (formerly PAL Football), at which he was the commissioner between 2006 and 2011.

“Our younger group went from around 40 [players] to 20,” he said.

“We had a couple of kids who would have been the best players on the high school football team,” Moody added, “their moms didn’t want them playing football, so they moved over to soccer. We definitely know of the concern. But you don’t hear it as much in rugby.”

Concern about concussions is the entire reason why Serrador and his staff keep returning to Can-Am, where they are primarily focused on how both serious and minor head trauma affect blood flow through the brain and, in turn, the heart and the rest of the body.

This year, Dr. Paul Breen of Western Sydney University has joined Serrador in Saranac Lake. He brought eight prototype black cotton shirts with expandable bands, similar to what those studying sleep apnea use. For Serrador and the Irishman and former Gaelic football player Breen, the thought is to measure how much blood flow is coming out of the heart after injured players come off the pitch.

“It lets us see if the problem is central to the brain or heart,” Serrador said. “It helps to target treatment.”

With regard to the growing concern over concussions and C.T.E., and namely the recent New York Times report, Serrador cautions jumping too far to conclusions.

As a former concussed rugger himself, he knows that rugby, and even more so football, potentially can be detrimental. But how bad?

“It’s too early to tell,” he said.

He says, studies like his at Can-Am represent the lowest-level front lines on the battlefield that is addressing head trauma in contact sports. From his grassroots work here, it’s a long and painstaking road to diagnose what is causing these degenerative diseases.

Maybe it’s, in part, the decreased blood flow in the brains of concussed players that he is here to study. Maybe not.

“The problem is you can’t diagnose C.T.E. until someone is dead,” Serrador said. “There is no way for us to connect (whether) it’s a gradual summation of stuff or is this more related to the hardest hit they got at some point? That is a question at the moment we can’t answer.

“There could be a connection with this repeated head trauma,” he continued, “but we really don’t know. It’s kind of a big debate in the field at the moment.

“It’s hard to measure,” he added, “because the brain is only about 10 percent of your total blood vasculature. So if you take a blood sample, whatever inflammation is in the brain, it gets diluted with the rest (of the body). And if you talk to any rugby player, they are being beaten up everywhere. That’s part of the reason we started looking at the brain immediately post-[injury] on the pitch, because I am trying to figure out if the actual organ we are talking about looks a little different.”

Despite these unknown elements and his small stature, Callahan views the two sports he loves as having an almost symbiotic relationship. Maybe rugby can help football become safer.

To him, rugby is the safer sport. To illustrate, he points to something he saw on Twitter: The Seattle Seahawks, one of the National Football League’s most dominant franchises in recent years, have implemented rugby-style tackling techniques to both ensure better safety and to improve tackling efficiency.

Moody, the father of a 3-year-old and an almost 1-year-old, doesn’t have reservations about whether to let his children play football and rugby when they grow older. He hopes they will because of the fun experiences and life lessons each sport taught him. The first in his family to play rugby, he also is encouraged by the influence rugby’s safer tackling techniques is having on football. Here at home, he’s part of the effort, as he helped to institute the Heads Up Football Program’s safety courses and guidelines with local youth.

As for those not out on the gridiron or pitch? They’re missing out.

“It’s life,” Moody said. You can get hurt walking down the street. It is what it is. My mentality is you gotta go live life, enjoy it, and what happens happens.”