My thoughts on the recent optimal stretching dose review

Researchers at the University of South Australia in Adelaide recently published a review in the journal Sports Medicine. In it, they examined 189 earlier studies on stretching, concluding that neither time, intensity, nor frequency meaningfully affects overall flexibility. I've been asked by many people for my opinion on this paper, and the various interpretations that have been promoted on social media. The paper's conclusions have caused some people, especially fitness influencers with a strong anti-stretching slant, to declare that stretching needs no careful programming, or that it achieves nothing at all (beyond helping you stretch more). But there remain numerous shortcomings in that flawed view.

Before I share my reflections with you, I must say that I despise gatekeeping. This word describes the act of restricting access to a certain resource, often stifling growth. Flexibility Research's motto is 'sapere aude,' meaning 'Dare to know.' Thus, I insist you question everyone: friends, critics, strangers, and even myself, before shaping your own opinions. I do not want you to accept my claims at face value, because that spawns gurus and echo chambers. So, I'm giving you complete access to the entire review in question. Read it, absorb its contents, and reach your own conclusions. Then, gauge whether its core ideas clash or coincide with my words below.

Click here to get free access to the paper.

Issue #1: The review's findings do not imply that duration, intensity, or frequency are wholly irrelevant. Instead, they clearly suggest that once you surpass a certain threshold, adding more produces diminishing returns (but eventually, at more advanced levels, these factors matter again). Some influencers have oddly implied that performing one set of 30 seconds once weekly is the same as many sets done several times per week. It simply does not. The researchers found that roughly four total minutes per session per muscle group, and up to ten minutes each week per muscle group, proved most effective for the typical individual. This fact is far from astonishing, fitting well with established advice (including my own), which states that doing two sets of 1- to 2-minute stretches per muscle group, done two or three times weekly, suffice for the many with general health and fitness goals.

Issue #2: As a person reaches a degree of flexibility beyond the norm, the need to emphasise duration, intensity, and frequency naturally increases, demanding greater attention. This happens because passive stiffness becomes greater whenever muscles stretch to longer lengths, pushing them beyond their usual limits. Studies show that offsetting this increase in stiffness demands either greater stretching volume (the product of duration and frequency), higher intensity, or some mixture of the two approaches. In other words, anyone aiming for advanced flexibility must give careful regard to these specific factors in their practice. Among the studies included in the review, only a handful focused on sports or athletic groups that naturally require greater than average flexibility: 42% of these papers failed to specify participants' training histories, while of those that did, a mere 23% labelled them as “trained,” and 5% described them as “athletes.” Consequently, it appears many participants were not chasing a higher state of flexibility that demands longer, more intense, or more regular stretching routines than those typically enough for the usual individual.

Issue #3: There is a high risk of bias in the included studies. A troubling sixty-nine percent were judged as poor to moderate in quality, which ought to give us serious pause about their reliability. These significant methodological failings, such as missing concealed allocation, inadequate follow-up, and the omission of intention-to-treat analyses, are deeply alarming. We must keep these flaws in mind when drawing any conclusions from the final results

Issue #4: Most of the studies included in the review relied on broad measures of flexibility, for instance, the sit-and-reach test or a single-leg raise. These gauge only a narrow range of muscle groups (hamstrings and calves occurred in 80% of the studies). Consequently, the importance of these findings for other poses and muscle groups—such as the side split that chiefly uses the adductors—is sharply limited by the specific nature of flexibility adaptations.

Issue #5: We can't be sure if the “ideal” stretching dose proposed by the authors truly marks a fixed physiological limit, or just reveals the broader literature's preference for studies with shorter stretching times. The median duration throughout the included studies was just 2.5 minutes per session and 12.5 minutes per week. Only within the past three years have researchers begun to explore markedly extended stretching periods (up to 60 minutes daily), which seem to yield distinctly stronger gains compared to either 10 or 30 minutes each day.

Issue #6: The key struggle in judging intensity is that surprisingly few studies have squarely measured the real force placed on stretched muscles. Most researchers use only personal reports of discomfort or pain, and changing definitions of intensity across studies strengthen this doubt. Many studies in the review did not even speak of stretch intensity. As a result, we cannot form strong conclusions about optimal stretching intensity.

Issue #7: The recommendations of the authors can only be applied to improving flexibility. But some circumstances reveal that static passive stretching can boost performance, such as stretching before doing high kicks in a martial arts competition, and might reduce injury risk, particularly with hamstring strains. We remain uncertain, but we continue searching for answers. At this time, no firm evidence shows what the duration, intensity, or frequency of such stretching may accomplish in these areas.

Issue #8: Even if the authors’ conclusions were true for all stretching circumstances, that does not mean that stretching “does not work” or that its value is just to “make you better at stretching.” It’s like reading “Beware of the Dog” and then swearing it says “Pet the friendly unicorn.”

Issue #9: The review's findings bluntly contradict the bold assertions of some influencers who insist most people require only purely full-ROM weightlifting. Full-range strength work fosters mostly active flexibility, because it demands you  steer each motion with your own muscle power. But passive flexibility may still struggle to improve without static passive stretching, especially in folks notably burdened by tight tissues or high resting muscle tension. Lacking a watchful, experienced coach, lifting weights may instead produce the reverse effect: when creeping fatigue inevitably sets in, range of motion reduces, leading people to practice ever narrower arcs (thus training themselves to grow stiffer and less flexible).

What you need to know

At each stage of flexibility training, the time, intensity, and frequency of stretching have an influence on flexibility, though their overall effect changes based on your current range of motion and goals; they are less important for general health and well-being, but become crucial for advanced feats like the splits or high kicks. It is obvious that “no further advantage after a certain point” does not mean “no effect” at all whatsoever. The authors’ advice on optimal stretching routines matches the guidance that seasoned flexibility coaches have been giving for years.