How Hard Should You Work? What the Research Says About Exercise Intensity and Parkinson's

If you have Parkinson's disease, you have almost certainly been told to exercise. What you were probably not told is how hard. And that turns out to be one of the more interesting open questions in the field — because the evidence increasingly suggests intensity is not a minor detail.

The question researchers set out to answer

For years, the advice given to people with Parkinson's was essentially "stay active." Walk. Move. Don't sit still. Reasonable advice, but vague — and it left an important question unexamined: does exercise change the course of the disease, or does it simply help you feel better while you have it?

Those are very different claims. Feeling better matters enormously. But slowing progression would be something else entirely.

What the SPARX2 trial found

In 2018, a research team led by Margaret Schenkman published a phase 2 randomized trial in JAMA Neurology that took this question seriously. They enrolled people with newly diagnosed Parkinson's who were not yet taking Parkinson's medication — an important detail, because it meant the results wouldn't be muddied by drug effects.

Participants were assigned to one of three groups for six months:

• High-intensity treadmill walking — four days a week, 30 minutes, at 80–85% of maximum heart rate
• Moderate-intensity treadmill walking — same schedule, at 60–65% of maximum heart rate
• Usual care — no formal exercise program

Two findings came out of it. First, high-intensity exercise was safe and feasible for people with early Parkinson's — which was not a foregone conclusion, and which mattered because clinicians had been understandably cautious about pushing this population hard. Second, the results in the high-intensity group were promising enough to justify moving to a full phase 3 trial.

That second point deserves an honest caveat, because it is frequently overstated. SPARX2 was a phase 2 study. It was designed to answer "is this worth testing properly?" — not "does this definitively slow Parkinson's?" It answered the first question yes. The second question is still open.

What's still being tested

The follow-up trial, SPARX3, is a phase 3 study running at sites across the country. It randomizes participants to moderate or high-intensity treadmill exercise over 18 months, with the primary outcome being change in the MDS-UPDRS motor score. It is also tracking things like dopamine transporter binding, six-minute walk distance, cognitive function, and BDNF — a protein involved in the brain's capacity to adapt and repair itself.

Results were not yet published at the time of writing. When they arrive, they will tell us considerably more than we know today.

What this means for how you actually train

So where does that leave you, practically?

Intensity appears to matter, and "comfortable" may not be enough. The distinction being tested is not between exercising and sitting on the couch. It's between moderate and vigorous. If your current program never leaves you breathing hard, there is reason to think you may be leaving benefit on the table.

Intensity has to be earned, not assumed. Eighty-five percent of maximum heart rate is genuinely demanding work. In the trial, participants were screened, supervised, and progressed deliberately. Deciding on your own to go from sedentary to near-maximal effort is how people get hurt — and an injury will set you back further than a conservative start ever would.

Aerobic work is not the whole program. The trials above studied treadmill walking specifically, because studying one variable is how good research works. That doesn't mean treadmill walking is all you need. Balance training, resistance training, and movements that target the amplitude and speed problems characteristic of Parkinson's all have their own supporting evidence and their own role.

Consistency beats intensity you can't sustain. The protocol was four days a week for six months. A brutal program you abandon in three weeks is worth less than a challenging one you keep doing for years.

How we approach this at RSF

We've worked with people with Parkinson's in East Rochester since 2006, and our programs start with an assessment — cardiovascular status, balance, gait, strength, medication timing, and what your neurologist wants us to know. From there we build toward intensity rather than starting there, and we adjust as you change.

Some people arrive able to work hard right away. Others need weeks of foundational work first. Both are fine. What matters is that the program is aimed at a target worth reaching, and that someone is watching closely enough to keep it safe.

If you're managing Parkinson's and you're unsure whether your current routine is doing what it could, that's exactly the conversation a free assessment is for.