This question is really two questions that tend to get merged into one. The first — does stretching improve flexibility? — has a fairly clear answer. The second — does having a practitioner perform the stretching add a proven benefit beyond stretching on your own? — is much less settled. Keeping them separate matters.
What Stretching Research Supports
The evidence that stretching improves flexibility and range of motion is well established. A large 2025 systematic review, meta-analysis, and meta-regression covering 189 studies and thousands of participants found that static stretching improved flexibility both immediately after a single session and, to a greater degree, following repeated stretching over time. Mayo Clinic summarizes the same general finding for a broader audience: stretching regularly — roughly two to three times a week — helps build and maintain flexibility. On this specific question, the research is not ambiguous.
What Evidence About Practitioner Assistance Does Not Yet Establish
Here's where it gets more limited. Most of the research behind that conclusion studied stretching in general — largely self-directed or lab-administered static stretching — not commercial, practitioner-led assisted stretching specifically. A systematic review focused on PNF, a stretching technique that's often delivered with a partner or practitioner, found it could improve range of motion compared with other stretching methods. But that review compared PNF against other stretching techniques — it didn't isolate having a partner involved as its own variable, so it doesn't directly tell us whether partner involvement itself adds anything beyond the technique.
Strong evidence that stretching improves flexibility does not, by itself, establish that a practitioner performing the stretching adds a proven benefit beyond what stretching on your own can achieve. That's less a finding against practitioner involvement than an absence of research that's isolated it as a variable at all — the direct comparison simply hasn't been studied nearly as thoroughly as the general stretching-flexibility link.
What This Doesn't Establish Either Way
It's also worth being direct about what stretching — assisted or otherwise — has not been shown to do. A systematic review pooling data from controlled studies found that stretching before exercise did not produce a practically useful reduction in injury risk, and research on how flexibility gains translate into outcomes like athletic performance is mixed and technique-dependent, not settled. Improved flexibility is not the same claim as fewer injuries, a lower golf handicap, or more distance off the tee, and the evidence for flexibility doesn't extend automatically to those outcomes.
The Bottom Line
Stretching, done consistently, is well supported as a way to improve and maintain flexibility. Whether a practitioner-assisted version of that stretching adds a proven benefit beyond doing it yourself is a genuinely open question — not because the idea is implausible, but because it hasn't been directly and rigorously tested the way the general flexibility question has. See Flexibility vs. Mobility: What's the Difference? for how these findings relate to broader movement and function.