Delusions and Disingenuousness

How a legitimate pilot study became a rallying cry — and why it matters for the chiropractic profession

May 27, 2026

A few days ago I saw a video circulating on social media from a recent conference called ChiroFest. In it, Heidi Haavik, DC, told the crowd: “One single adjustment has the same effect on the central nervous system as three weeks of strength training.” This is exactly the kind of statement that energizes a room of chiropractors — and exactly the kind that deserves careful scrutiny.

The study

A 2019 study published in Scientific Reports provides the foundation for this claim. “The effects of a single session of chiropractic care on strength, cortical drive, and spinal excitability in stroke patients,” authored by Holt, Niazi, and colleagues, investigated whether a single chiropractic session could increase muscle strength in chronic stroke patients.¹ The results showed that plantar flexor muscle strength increased by an average of 64% following one chiropractic session, compared to a 26% decrease in the control group. The accompanying physiological data suggested the effect was happening in the brain, not just the muscles. It may be genuinely interesting science — but science and extraordinary claims are two very different things.

What the study actually found

The researchers recruited 12 chronic stroke patients with weakness in their lower leg muscles. Using a randomized crossover design, each participant received both the chiropractic intervention and a passive movement control on separate occasions. Three things were measured: maximum voluntary contraction force (strength), H-reflex parameters (spinal excitability), and V-waves (cortical drive — the signal the brain sends down to the muscles).

Following chiropractic care, strength increased significantly. More importantly, the V-wave/Mmax ratio increased by roughly 54%, while H-reflex parameters showed no significant changes. In plain terms: the signal from the brain to the muscles got stronger, but there was no significant change at the spinal cord level. The authors concluded that the strength gains were likely modulated at a supraspinal level — above the spinal cord, in the brain itself. They also noted that this pattern of V-wave change was similar to what has been observed following three weeks of strength training in other research. That comparison is where things get complicated.

Is the claim compelling or misleading?

The comparison originates in a 2012 paper by Vila-Chã and colleagues showing that V-wave and H-reflex changes following short-term strength training look directionally similar to what was observed here.² But the comparison is not made within this study — it is an inference drawn across two completely different studies, with two completely different populations, under two completely different conditions.

This matters for several reasons:

The comparison is between proxies, not outcomes. The V-wave is a useful neurophysiological indicator, but it is not a direct measure of strength, endurance, coordination, hypertrophy, or functional capacity. Three weeks of strength training produces a cascade of adaptations — structural, metabolic, neural, and behavioral — that a single V-wave measurement cannot capture.
The populations are fundamentally different. The Vila-Chã study used healthy individuals. This study used stroke patients whose nervous systems are damaged and reorganizing. A temporarily upregulated cortical signal in a stroke-affected nervous system is not the same biological event as progressive neural adaptation in a healthy one.
The chiropractic effect appears to be transient. A related study cited in the paper followed participants for 60 minutes post-adjustment and found that strength gains were still significant at 30 minutes but had lost significance by the 60-minute mark.³ Three weeks of strength training produces changes measurable weeks and months later. These are not equivalent phenomena, even if they briefly produce a similar signal on one measure.

The honest framing: the V-wave changes observed after a chiropractic adjustment look directionally similar, at one moment in time, to changes associated with strength training. That is an interesting observation worth investigating. Calling it equivalence is a rhetorical leap the data does not support — and where the presenter is being either purposefully misleading or extremely disingenuous.

A more nuanced picture

One instinctive response to this data is to draw a clean line: chiropractic care affects central (brain-based) mechanisms, while strength training affects peripheral (muscle-based) mechanisms. This framing has intuitive appeal and is partially right, but the reality is more nuanced.

The evidence does point toward a central mechanism for chiropractic care. The V-wave increase without significant H-reflex changes suggests the effect comes from increased cortical drive down to the motor neurons, not from changes at the spinal cord or within the muscle tissue. This fits with the broader work from Haavik and colleagues suggesting that spinal manipulation can alter sensorimotor integration in the brain.

But early-phase strength training is also predominantly centrally mediated — and this is well established in exercise physiology. In the first one to four weeks of a resistance training program, strength gains occur before any meaningful hypertrophy. They are driven by neural adaptations: increased motor unit recruitment, improved synchronization, reduced co-activation of antagonists, changes in cortical drive, and modifications in presynaptic inhibition at the spinal level. V-wave increases are a documented feature of early strength training for precisely this reason.

So when the authors compare chiropractic V-wave changes to strength training V-wave changes, they are actually comparing two predominantly central phenomena — which weakens the original comparison rather than strengthening it. The meaningful distinction between adjustment effects and training effects becomes apparent over longer timeframes: months of progressive resistance training produce dominant peripheral adaptations — hypertrophy, increased contractile protein content, connective tissue remodeling, metabolic changes — none of which would plausibly be influenced by spinal manipulation. The central-peripheral dichotomy is real and important, just not at the early-phase timeframe where the comparison is being made.

The study’s real limitations

Several methodological constraints deserve acknowledgment — most of which the authors themselves flag:

Sample size. Twelve participants, falling short of the already modest target of 15. The extraordinary variability compounds this: strength increased by an average of 64.2%, with a standard deviation of 77.7%. When the standard deviation exceeds the mean, individual responses varied enormously. Presenting the group average without this context is misleading.
Blinding limitations. Participants were told they were naïve to chiropractic care and may not have known which intervention they received — but this cannot be confirmed. The authors acknowledge that participants may simply have tried harder following the chiropractic session, a classic demand characteristics problem. No questionnaire was used to assess whether participants could distinguish between the two interventions.
Washout period. The 7-day washout between crossover sessions may have been insufficient if chiropractic effects persist beyond a week, which some cited research suggests.
Retrospective registration. The trial was registered after data collection began — a recognized methodological concern that opens the door to reporting bias.
Funding. The study was funded by multiple chiropractic industry organizations. The authors declare no competing interests, and the research was published in a legitimate peer-reviewed journal, but industry-adjacent funding in manual therapy research is a well-documented source of bias.

None of these limitations invalidate the findings. They contextualize them: this is an exploratory, hypothesis-generating pilot study, not a clinical trial establishing efficacy.

What this research actually opens up

Setting aside the overclaiming, there is something genuinely interesting at the core of this research. If spinal manipulation can acutely and transiently increase cortical drive, what happens when you immediately follow that adjustment with a strength training session? Could the temporarily upregulated neural signal improve motor unit recruitment during the training bout — and could that enhanced recruitment produce better adaptive outcomes over time?

That is the clinical question the research actually points toward, and it is a meaningful one. Chiropractic care and resistance training are not competing interventions; they may be complementary ones operating on overlapping neural pathways with different durability and depth. In the context of stroke rehabilitation, where facilitating neuroplasticity is the central goal, understanding whether spinal manipulation can serve as a primer for motor learning and strength training is a legitimate and potentially important line of inquiry.

Answering it responsibly would require at minimum: a properly powered trial with pre-registered outcomes, multiple assessment time points extending well beyond 60 minutes, functional outcomes relevant to stroke rehabilitation — not just isometric ankle force — and comparison against active rather than passive controls.

The bottom line

The 2019 Holt et al. study is real science exploring a genuinely interesting question. Its core finding — that a single chiropractic session appears to acutely increase cortical drive in stroke patients, accompanied by measurable strength gains — is worth knowing about and worth building on.

What it does not support is the claim that one adjustment equals three weeks of strength training. That comparison conflates a transient neurophysiological signal with a durable, multi-system adaptive process. It collapses the difference between a momentary increase in cortical output and the months of progressive overload that transform muscle architecture, metabolic capacity, and sustained neural function. It compares 12 stroke patients from a single hospital in Pakistan to the accumulated findings of a robust exercise science literature.

If you want my honest opinion: I think a hardcore, subluxation-based researcher wanted to justify why their singular use of manipulation has the same effects as other well-researched and medically accepted interventions. We have seen this pattern for years — traditionalist chiropractors conflating research to inflate the importance of manipulation. To me, this is delusional, and more importantly, disingenuous.

High-velocity, low-amplitude manipulation is a useful tool. We know it has meaningful effects on reducing pain and increasing segmental range of motion — and that is worth saying clearly. But by making grandiose claims instead of standing on what manipulation actually does well, we delegitimize its use and alienate the allied health professionals who might otherwise want to collaborate with us.

As chiropractors, we need to stop positioning this singular intervention as the solution to everything that walks through the clinic door. It is a tool, with a specific use, under specific circumstances. Manipulation is not a panacea for dysfunction or disease. And it most certainly does not have the same long-term effects as strength training.

The presenter took factual findings from one study, compared them to an unrelated study, and claimed the similarities as evidence of chiropractic superiority. It was a rallying cry for a room of hardliners who need to hear that what they do is better than what everyone else does — so they can continue to justify an approach the broader medical community has been skeptical of for good reason.

This is why, at times, chiropractors do not get the respect we deserve from the rest of the medical community. This is why no one takes us seriously when it matters most. I would rather be seen as a progressive human performance practitioner who thinks rigorously about load management than a hardline subluxation-based chiropractor who needs conferences to validate his clinical decisions.

If we want to take our rightful place in the integrated support team that collaborates on musculoskeletal care — we have to do better than this.

If spinal manipulation produces a transient window of increased cortical drive — even a short one — how are you currently using that window in your clinical practice? Are you pairing manipulation with loading? Or treating the adjustment as the endpoint?

The research here is messy and the claims being made from it are worse. But the underlying question — whether manipulation can serve as a neurological primer for strength work — is one worth taking seriously. If you are already doing this, or have tried and found it doesn’t hold up in practice, I want to hear about it in the comments.

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