You Can't Undo the Hits

The Question I Can Never Answer

Every doctor asks how many concussions I've had. I tell them fifteen.

That number is from college, when I finally sat down and tried to write out the major ones. Fifteen is where I landed. It only covers the hits big enough that I still remembered them years later, which means it's a floor and not a total.

I started hockey in 1995. First diagnosed concussion at ten years old. Travel hockey through Midget Major AA, with lacrosse and football stacked on top of it in high school. That's about a decade of getting hit in the head on purpose, as a normal part of the sport, by design.

The ones that didn't make the list were just a Tuesday. You take a shoulder to the chin in the corner, your vision goes soft for a few seconds, you finish the shift. Nobody writes it down and there's no record anywhere that it happened.

For a long time I assumed the counted ones were the ones that mattered. That's how the question is built. How many concussions, as if the number is the injury.

The research coming out now says the number was never really the point.

What They Found in the Tissue

In September 2025, a team out of Boston University published in Nature. They examined donated brain tissue from athletes who died before age 51, mostly former football players, and compared it against people the same age who never played contact sports.

The exposed brains had 56% fewer neurons in what researchers call the sulcal depths. Those are the valleys in the folded surface of the brain. When your head gets snapped, force concentrates down in those creases, and it's the same spot where CTE shows up first.

Now the part that reframes everything. Most of those brains did not meet the criteria for CTE. No buildup of tau, which is the protein that defines the diagnosis. The neurons were gone without it.

They found other things too. The brain's resident immune cells were running hot, and the more years a person had played, the more activated those cells were. Blood vessels in the tissue showed signs of inflammation and thickening. The researchers described a signaling loop between those immune cells and the vessel walls that may be driving the whole thing early on.

So the damage starts early, it scales with how long you played, and it is well underway before a pathologist could put a name to it.

Why Counting Concussions Fails

This isn't the first crack in the concussion-count model. Back in 2023, researchers at Boston University and Harvard went through 631 deceased football players and tried to work out what actually predicted CTE.

Diagnosed concussions didn't do it. What did: how many head impacts a player absorbed across a career, and how hard those impacts were. Models built on impact count and force beat models built on years played or concussion history.

Set the two studies side by side and it's fairly plain. The injury is total load. Every hit goes into the account, including the hundreds that never got diagnosed, because a diagnosis was never what made them count in the first place.

Which means somebody who got knocked out twice across twelve years of football might be carrying less than the guy who never got knocked out once and played the line every down.

The Part Nobody Leads With

Here's where it turns, and this is the reason I wanted to write this one.

Researchers have spent years now checking in on former pro athletes to see how they're actually doing. Harvard has a long-running study following former NFL players. There's parallel work on retired rugby league players published last year. They ask about memory, concentration, finding words, the ordinary daily stuff that tells you whether someone's brain is working.

Then they look at what predicts the answers.

It isn't hit count. The factors that keep showing up as the strongest predictors of cognitive trouble in these men are:

• Chronic pain
• Depression and anxiety
• Sleep apnea
• Short sleep duration
• Carrying extra weight
• Not exercising
• Cardiovascular risk

Go back over that list. Not one item on it is a head injury. All of them are things that happen to a body across the twenty or thirty years after the playing stops.

Researchers have started folding concussion history into general brain-health risk scores, the same ones used to talk about dementia risk in people who never played a down of anything. Head impacts go in as one factor among many. They matter. They just don't sit there alone, and they are not the biggest lever available to anyone reading this.

What Training Actually Buys

I want to be careful here, because there's a version of this article that turns into a pitch and I'm not writing that one.

A trial published this year in Physical Therapy took 81 adults who were three months to two years out from a concussion and still symptomatic. Half got a structured aerobic program built to stay just under the intensity that triggers their symptoms. Half got standard care plus general advice to stay active. Twelve weeks, then a check at six months.

The structured group did not report fewer symptoms than the other group. Not at twelve weeks, not at six months. Both groups got somewhat better and the difference between them was nothing.

What the structured group did get was capacity. They lasted meaningfully longer on a treadmill test before symptoms kicked in, and that gain held at six months, though it faded some.

So training after a brain injury buys you room. More tolerance for exertion, a higher ceiling before things go sideways. On its own, over that stretch of time, it does not appear to buy you a quieter head.

That is a smaller claim than what you'll hear from most people selling recovery, and it's the one the evidence actually supports. It's still worth having. Capacity is what lets you carry weight, keep up with people, and stay in your own life.

It also loops straight back to that list. Inactivity is on it. Extra weight is on it. Poor sleep is on it. Training moves all three whether or not it ever touches the symptoms directly, and that's the mechanism worth caring about.

Assessment

The exposure is fixed. I played from 1995 through 2004, then took a dirty elbow in college that cost me a school year. No protocol reaches back and unwinds any of that. The neurons down in those folds are either there or they aren't, and no amount of sleep is regrowing them.

What isn't fixed is everything the research keeps pointing at. Whether I sleep enough, and whether that sleep is any good. Whether I'm in pain most days. What I weigh. Whether I'm depressed and ignoring it. Whether I move at all.

That's the whole reason this site exists. Not because training undoes a brain injury, because it doesn't. But study after study keeps landing on the same thing: how you're doing decades out gets decided mostly by what sits downstream of the injury, and downstream is where you still get a vote.

It's also why the training here is built the way it is. I wrote the programs around the items on that list, so pain, sleep, weight, and staying consistent are what the work is organized against instead of a number on a bar. That's a different design goal than most strength programs start from, and it came out of reading this research and recognizing my own chart in it. All of it is free on this site and it stays that way.

The hits already happened. What the next thirty years look like is still being worked out, and most of what decides it is stuff I can actually get my hands on.